Loss of power at 4000 rpm 3rd gear

[onthames]

When I hit 4k in 3rd the car doesn't wanna go anymore, kinda accelerates and then stops and then starts accelerating again and then stops by that time I've changed gear cos I don't wanna break anything.
Revving in neutral it will go to redline.

Recently replaced fuel pump, doing fuel filter now. Anything else I should check regarding this issue?

Cheers

[onthames]

engine is 2.5 m20 for reference

[onthames]

Tried again after new fuel filter. It was fine for 5 runs up to 6k rpm and then started to get stuck at 4k again. Possible vacuum leak? Will try again today and see if any different. This time I'm going to drive normally for 30 mins and then try.

[onthames]

Another update: if I go at 50% throttle I can get past 4k, it's when I'm at full throttle it won't go past

[onthames]

Right, so I've done some research and apparently this can be electrical and caused by the engine map and is intended from factory. Can anybody confirm this?

Source: https://www.justanswer.com/bmw/3bcqa-he ... Uf71K8QXRk

"or what its worth and for future reference if u should come across this issue again in future i now know what the cause was.<br /><br />it was nothing faulty or worn out, etc. it was actually the standard tune in the ECU, since asking this question i have started up a small business remapping and chip tuning these cars and when i ran a standard tune to compare with my performance tune the problem came back, looking at the full throttle ignition map there is a dip in the ignition curve right around where the problem was happening and the full throttle map takes over from approximately 75% throttle, i dont remember off hand how much throttle id give the car before the problem started to happen but it seems localised to the full throttle ignition map and at worst the last few rows of values in the high part throttle ignition map. i confirmed this was the cause by increasing ignition advance in the dipped area in small increments and the problem lessened and then disappeared all together.<br /><br />if u come across any odd issues like this in future with these cars (motronic 1.3 in particular) i now specialise in tuning these ECU's/cars, for all the help u gave me trying to figure this one out if u come across another problem that u think may be related give me an email onXXX@XXXXXX.XXX and ill try to shed some light on the problem."

[onthames]

Here is a video of the problem happening.
I did 10 runs. The first two runs went above 4000 rpm to 6000rpm no problems, this is full throttle. The remaining runs got to the following Max's: 5500, 5000, and 4000. The runs after that stayed at 4000. Interestingly, I waited 10 mins and restartedd the car after the second to last run, and I could get to 5k. So temp related maybe? Video for reference:

[onthames]

Another update. In 2nd and 3rd I can get past 4000 by using 50% throttle. In 5th gear this is not possible, no matter how light I press I cant get it over 4000. Fuel delivery?

Someone answer pretty please

[paultv]

I'd check the AFM isn't binding and that its output is clean across the full sweep.

Paul

[Lemon98]

Have you checked your distributor points and the rotor arm?

I was getting a similar but not as severe issue at high rpms and full load the engine would hesitate and almost stay at around 5k for half a second before continuing up.

Again it was only happening in 3rd and 4th.

I also can believe the quote that you put in about the dip in the ignition map because I have read my stock engine chip using a couple different definition files from TunerPro and have seen the dip.

I have since replaced my dizzy and rotor arm the car has been perfectly fine since and handled a track day at Cadwell so plenty of high revs in 3rd with no issues.

If you are going to replace your dizzy I must warn you not to go with BREMI form autodoc like I did as the black plastic cover doesn't fit properly so mine currently isn't covered. & don't go for a STARK rotor arm either as the fixing bolts are phillips head screws rather than hex which is tricky considering the lack of space between the came sprocket and the radiator.

(my engine is a 2.0 but still a motronic 1.3 from 1990)

[onthames]

Thanks for the help lads, I really want to try narrow this down before I start replacing bits because it could get costly pretty quickly. I've read some threads on other forums where guys have replaced 20 things trying to fix this. Ill have a look at the bits you've mentioned and get back to you

[Lemon98]

Thanks for the help lads, I really want to try narrow this down before I start replacing bits because it could get costly pretty quickly. I've read some threads on other forums where guys have replaced 20 things trying to fix this. Ill have a look at the bits you've mentioned and get back to you

No worries I certainly appreciate wanting to narrow down exactly the problem before splashing cash lol.

My points were all well worn on 86k miles & I think it was the factory units.

Another potential is the injectors themselves, I got mine cleaned and serviced with injector tune for £70 all in and had them back within like 4 days or something.

I know this isn't helpful in terms of tracking down a specific cause but I'm listing the things that I changed when I had similar symptoms and the car is no driving flawlessly. Honestly the difference with the cleaned injectors was the biggest I've had in my ownership of the car. I didn't think an engine could get any smoother it was incredible.

So for the money getting injectors cleaned is far cheaper than dizzy parts and had more of a noticeable affect for me

[onthames]

I tried testing for vac leaks today using smoke at 3psi. Couldn't find any. Just to check my process is right: I disconnected the rubber boot from the Maf, blew smoke in using a Jerry rigged contraption and an air compressor and kept the throttle wide open while doing this (car off). Couldn't see any leaks. I put my mouth over the rubber boot and it held my breathe, tried blowing it up like a balloon and didn't mean

[onthames]

Did find a missing relay though while cleaning connectors. Any idea what's meant to be there?

[onthames]

Thanks for the help lads, I really want to try narrow this down before I start replacing bits because it could get costly pretty quickly. I've read some threads on other forums where guys have replaced 20 things trying to fix this. Ill have a look at the bits you've mentioned and get back to you

No worries I certainly appreciate wanting to narrow down exactly the problem before splashing cash lol.

My points were all well worn on 86k miles & I think it was the factory units.

Another potential is the injectors themselves, I got mine cleaned and serviced with injector tune for £70 all in and had them back within like 4 days or something.

I know this isn't helpful in terms of tracking down a specific cause but I'm listing the things that I changed when I had similar symptoms and the car is no driving flawlessly. Honestly the difference with the cleaned injectors was the biggest I've had in my ownership of the car. I didn't think an engine could get any smoother it was incredible.

So for the money getting injectors cleaned is far cheaper than dizzy parts and had more of a noticeable affect for me

When I first start the car and do a few runs it works fine. It only has trouble after 15-20 mins of warming up. Could these symptoms still point towards a distributor problem or injector problem? I have literally no experience but the fact it starts after a certain amount of time (during that time what changes? temperature and fuel richness? someone tell me pls ) makes me think its related to something that also changes with time, which may point to it being a sensor problem. But I have no idea, am trying to use logic but I know that sometimes doesnt work with these old cars!

I may get the injectors cleaned just for the hell of it.

[mark_i]

the spare connector in your pic is for an additional relay. only used if you have a cat with lambda sensor

[Lemon98]

Thanks for the help lads, I really want to try narrow this down before I start replacing bits because it could get costly pretty quickly. I've read some threads on other forums where guys have replaced 20 things trying to fix this. Ill have a look at the bits you've mentioned and get back to you

No worries I certainly appreciate wanting to narrow down exactly the problem before splashing cash lol.

My points were all well worn on 86k miles & I think it was the factory units.

Another potential is the injectors themselves, I got mine cleaned and serviced with injector tune for £70 all in and had them back within like 4 days or something.

I know this isn't helpful in terms of tracking down a specific cause but I'm listing the things that I changed when I had similar symptoms and the car is no driving flawlessly. Honestly the difference with the cleaned injectors was the biggest I've had in my ownership of the car. I didn't think an engine could get any smoother it was incredible.

So for the money getting injectors cleaned is far cheaper than dizzy parts and had more of a noticeable affect for me

When I first start the car and do a few runs it works fine. It only has trouble after 15-20 mins of warming up. Could these symptoms still point towards a distributor problem or injector problem? I have literally no experience but the fact it starts after a certain amount of time (during that time what changes? temperature and fuel richness? someone tell me pls ) makes me think its related to something that also changes with time, which may point to it being a sensor problem. But I have no idea, am trying to use logic but I know that sometimes doesnt work with these old cars!

I may get the injectors cleaned just for the hell of it.

Yeah during that time the engine warms up so the coolant sensor will tell that to the ECU and the amount of fuel injected will reduce as you come away from the enrichment tables for low temperatures. So your thinking is correct ahaha I would always try the logical solution first as even though they're old cars they're BMWs so should work bang on if things are within spec. My thinking when going through my car was that it's occurring at high load and must therefore be spark or fuel. & I'd read about getting the injectors cleaned before so wanted to try that and I still want to replace the coil as I thought maybe the spark is a bit weak or it's not getting enough fuel.

Do you have any issue starting the car when warm/hot?

If you have a multimeter you can check whether the blue temperature sensor is good or not https://www.e30zone.net/e30wiki/index.p ... emp_Sensor

Even if you didn't have this problem I would still recommend getting the injectors cleaned because they were flowing well below what they should despite the car running what I thought was fine (after changing the dizzy and rotor arm) but the difference was huge!

[onthames]

I'd check the AFM isn't binding and that its output is clean across the full sweep.

Paul

Could you outline the basic process of testing this?

[onthames]

No worries I certainly appreciate wanting to narrow down exactly the problem before splashing cash lol.

My points were all well worn on 86k miles & I think it was the factory units.

Another potential is the injectors themselves, I got mine cleaned and serviced with injector tune for £70 all in and had them back within like 4 days or something.

I know this isn't helpful in terms of tracking down a specific cause but I'm listing the things that I changed when I had similar symptoms and the car is no driving flawlessly. Honestly the difference with the cleaned injectors was the biggest I've had in my ownership of the car. I didn't think an engine could get any smoother it was incredible.

So for the money getting injectors cleaned is far cheaper than dizzy parts and had more of a noticeable affect for me

When I first start the car and do a few runs it works fine. It only has trouble after 15-20 mins of warming up. Could these symptoms still point towards a distributor problem or injector problem? I have literally no experience but the fact it starts after a certain amount of time (during that time what changes? temperature and fuel richness? someone tell me pls ) makes me think its related to something that also changes with time, which may point to it being a sensor problem. But I have no idea, am trying to use logic but I know that sometimes doesnt work with these old cars!

I may get the injectors cleaned just for the hell of it.

Yeah during that time the engine warms up so the coolant sensor will tell that to the ECU and the amount of fuel injected will reduce as you come away from the enrichment tables for low temperatures. So your thinking is correct ahaha I would always try the logical solution first as even though they're old cars they're BMWs so should work bang on if things are within spec. My thinking when going through my car was that it's occurring at high load and must therefore be spark or fuel. & I'd read about getting the injectors cleaned before so wanted to try that and I still want to replace the coil as I thought maybe the spark is a bit weak or it's not getting enough fuel.

Do you have any issue starting the car when warm/hot?

If you have a multimeter you can check whether the blue temperature sensor is good or not https://www.e30zone.net/e30wiki/index.p ... emp_Sensor

Even if you didn't have this problem I would still recommend getting the injectors cleaned because they were flowing well below what they should despite the car running what I thought was fine (after changing the dizzy and rotor arm) but the difference was huge!

No issues starting when hot. Will test blue temp sensor and get injectors cleaned. Regarding your earlier point, what should I be looking for when inspecting the distributor points and rotor arm?
Also what ones did you finally go for when you replaced as I don't wanna buy one that doesn't fit like you did ;)
Who did you use for fuel injector cleaning?

For coil i was looking at: https://www.autodoc.co.uk/bosch/676429

I'll give it a few more days of testing and then probably go for the coil first. Then work through parts until the cost starts to become unreasonable at which point I'll head to a specialist garage I suppose.

It does occur at high load, but after a bit - do we know what temperature the enrichment tables for low temperatures stop getting used? Maybe its a case of a more general problem with fuel delivery and that its masked by the extra enrichment after a cold start. It does seem however that as I drive the car more during one session the rev limit im facing decreases - turning the car off and letting it sit for 10 mins increases the limit - and leaving the car for hours to cool down and trying again allows me to get to the normal rev limit.

[onthames]

Checked afm flap, all fine, operating smoothly. Tried driving without fuel filler cap to see if fuel venting problem, no luck

[steve_k]

i dont think anyone else as mentioned it but i'd check the CPS on the front of the engine is well within it parameters, years ago i had a similar problem on my 325i, spent ages trying to suss it out & it turned out the CPS was on it's way out.

[onthames]

i dont think anyone else as mentioned it but i'd check the CPS on the front of the engine is well within it parameters, years ago i had a similar problem on my 325i, spent ages trying to suss it out & it turned out the CPS was on it's way out.

crank or cam?

[BenHar]

crank or cam?

No cam sensors on these cars.

Ben

[Lemon98]

When I first start the car and do a few runs it works fine. It only has trouble after 15-20 mins of warming up. Could these symptoms still point towards a distributor problem or injector problem? I have literally no experience but the fact it starts after a certain amount of time (during that time what changes? temperature and fuel richness? someone tell me pls ) makes me think its related to something that also changes with time, which may point to it being a sensor problem. But I have no idea, am trying to use logic but I know that sometimes doesnt work with these old cars!

I may get the injectors cleaned just for the hell of it.

Yeah during that time the engine warms up so the coolant sensor will tell that to the ECU and the amount of fuel injected will reduce as you come away from the enrichment tables for low temperatures. So your thinking is correct ahaha I would always try the logical solution first as even though they're old cars they're BMWs so should work bang on if things are within spec. My thinking when going through my car was that it's occurring at high load and must therefore be spark or fuel. & I'd read about getting the injectors cleaned before so wanted to try that and I still want to replace the coil as I thought maybe the spark is a bit weak or it's not getting enough fuel.

Do you have any issue starting the car when warm/hot?

If you have a multimeter you can check whether the blue temperature sensor is good or not https://www.e30zone.net/e30wiki/index.p ... emp_Sensor

Even if you didn't have this problem I would still recommend getting the injectors cleaned because they were flowing well below what they should despite the car running what I thought was fine (after changing the dizzy and rotor arm) but the difference was huge!

No issues starting when hot. Will test blue temp sensor and get injectors cleaned. Regarding your earlier point, what should I be looking for when inspecting the distributor points and rotor arm?
Also what ones did you finally go for when you replaced as I don't wanna buy one that doesn't fit like you did ;)
Who did you use for fuel injector cleaning?

For coil i was looking at: https://www.autodoc.co.uk/bosch/676429

I'll give it a few more days of testing and then probably go for the coil first. Then work through parts until the cost starts to become unreasonable at which point I'll head to a specialist garage I suppose.

It does occur at high load, but after a bit - do we know what temperature the enrichment tables for low temperatures stop getting used? Maybe its a case of a more general problem with fuel delivery and that its masked by the extra enrichment after a cold start. It does seem however that as I drive the car more during one session the rev limit im facing decreases - turning the car off and letting it sit for 10 mins increases the limit - and leaving the car for hours to cool down and trying again allows me to get to the normal rev limit.

I stuck with the ones I ordered due to lack of funds lol but I really wouldn't get anything from autodoc anymore. I ordered some trailing arm bushes and they didn't fit either.

Get everything from BMW if you can.

& with regards to checking the points you're looking for deep wear/corrosion on the points. They start off as like complete cylinders and then get a kind of groove warn through the middle of them over time. The more they wear the further the spark has to travel and result in a weak spark at the plugs.

For the injectors call InjectorTune and let him know that you're form the forum https://injectortune.co.uk/

Regarding checking the crank sensor that is actually a very good idea!! Costs nothing too lol. I had forgotten until seeing that post but I once had a problem where the car wouldn't rev over 2/3000rpm and one of the things I checked and cleaned with some brake clean was the crank sensor and all the teeth which fixed the problem.

[onthames]

Yeah during that time the engine warms up so the coolant sensor will tell that to the ECU and the amount of fuel injected will reduce as you come away from the enrichment tables for low temperatures. So your thinking is correct ahaha I would always try the logical solution first as even though they're old cars they're BMWs so should work bang on if things are within spec. My thinking when going through my car was that it's occurring at high load and must therefore be spark or fuel. & I'd read about getting the injectors cleaned before so wanted to try that and I still want to replace the coil as I thought maybe the spark is a bit weak or it's not getting enough fuel.

Do you have any issue starting the car when warm/hot?

If you have a multimeter you can check whether the blue temperature sensor is good or not https://www.e30zone.net/e30wiki/index.p ... emp_Sensor

Even if you didn't have this problem I would still recommend getting the injectors cleaned because they were flowing well below what they should despite the car running what I thought was fine (after changing the dizzy and rotor arm) but the difference was huge!

No issues starting when hot. Will test blue temp sensor and get injectors cleaned. Regarding your earlier point, what should I be looking for when inspecting the distributor points and rotor arm?
Also what ones did you finally go for when you replaced as I don't wanna buy one that doesn't fit like you did ;)
Who did you use for fuel injector cleaning?

For coil i was looking at: https://www.autodoc.co.uk/bosch/676429

I'll give it a few more days of testing and then probably go for the coil first. Then work through parts until the cost starts to become unreasonable at which point I'll head to a specialist garage I suppose.

It does occur at high load, but after a bit - do we know what temperature the enrichment tables for low temperatures stop getting used? Maybe its a case of a more general problem with fuel delivery and that its masked by the extra enrichment after a cold start. It does seem however that as I drive the car more during one session the rev limit im facing decreases - turning the car off and letting it sit for 10 mins increases the limit - and leaving the car for hours to cool down and trying again allows me to get to the normal rev limit.

I stuck with the ones I ordered due to lack of funds lol but I really wouldn't get anything from autodoc anymore. I ordered some trailing arm bushes and they didn't fit either.

Get everything from BMW if you can.

& with regards to checking the points you're looking for deep wear/corrosion on the points. They start off as like complete cylinders and then get a kind of groove warn through the middle of them over time. The more they wear the further the spark has to travel and result in a weak spark at the plugs.

For the injectors call InjectorTune and let him know that you're form the forum https://injectortune.co.uk/

Regarding checking the crank sensor that is actually a very good idea!! Costs nothing too lol. I had forgotten until seeing that post but I once had a problem where the car wouldn't rev over 2/3000rpm and one of the things I checked and cleaned with some brake clean was the crank sensor and all the teeth which fixed the problem.

Working on checking the "dizzy" now and crank sensor. Getting the distributor cap off is a ballache! I almost have the bolts out but fuck knows how I'm gonna get them back in

[Lemon98]

Take the radiator fan shroud out it helps with the clearance

[onthames]

Cars going into BMR in a couple of weeks as I couldn't figure out the problem with my limited knowledge. If they solve it I'll post the solution here for anyone who has a similar issue in the future

[Lemon98]

Cars going into BMR in a couple of weeks as I couldn't figure out the problem with my limited knowledge. If they solve it I'll post the solution here for anyone who has a similar issue in the future

Awesome good choice of garage!! I'm interested to hear what they come back with

[onthames]

Drilled a hole in the bottom of the TPS today as was full of oil. Will see if it helps. Fingers crossed. Had to push back BMR visit as had other commitments

[onthames]

This made it take much longer for the RPM issue to start happening. Anyone reckon I should get a new TPS? Drilling seemd to help. Maybe need a new one to fix compltely?

[onthames]

Fixed. I took the cover off the afm and cleaned all contacts with electrical contact spray and bent the arm ever so slightly to make contact with a new area of the carbon rail

[fixedwheelnut]

Fixed. I took the cover off the afm and cleaned all contacts with electrical contact spray and bent the arm ever so slightly to make contact with a new area of the carbon rail

Well done, I was about to add what @Steve_k said the CPS sensor can cause this fault at high rpm especially if the air gap is too big either by having been knocked out of line or tooth damage on the pulley.

[onthames]

Yeah during that time the engine warms up so the coolant sensor will tell that to the ECU and the amount of fuel injected will reduce as you come away from the enrichment tables for low temperatures. So your thinking is correct ahaha I would always try the logical solution first as even though they're old cars they're BMWs so should work bang on if things are within spec. My thinking when going through my car was that it's occurring at high load and must therefore be spark or fuel. & I'd read about getting the injectors cleaned before so wanted to try that and I still want to replace the coil as I thought maybe the spark is a bit weak or it's not getting enough fuel.

Do you have any issue starting the car when warm/hot?

If you have a multimeter you can check whether the blue temperature sensor is good or not https://www.e30zone.net/e30wiki/index.p ... emp_Sensor

Even if you didn't have this problem I would still recommend getting the injectors cleaned because they were flowing well below what they should despite the car running what I thought was fine (after changing the dizzy and rotor arm) but the difference was huge!

No issues starting when hot. Will test blue temp sensor and get injectors cleaned. Regarding your earlier point, what should I be looking for when inspecting the distributor points and rotor arm?
Also what ones did you finally go for when you replaced as I don't wanna buy one that doesn't fit like you did ;)
Who did you use for fuel injector cleaning?

For coil i was looking at: https://www.autodoc.co.uk/bosch/676429

I'll give it a few more days of testing and then probably go for the coil first. Then work through parts until the cost starts to become unreasonable at which point I'll head to a specialist garage I suppose.

It does occur at high load, but after a bit - do we know what temperature the enrichment tables for low temperatures stop getting used? Maybe its a case of a more general problem with fuel delivery and that its masked by the extra enrichment after a cold start. It does seem however that as I drive the car more during one session the rev limit im facing decreases - turning the car off and letting it sit for 10 mins increases the limit - and leaving the car for hours to cool down and trying again allows me to get to the normal rev limit.

I stuck with the ones I ordered due to lack of funds lol but I really wouldn't get anything from autodoc anymore. I ordered some trailing arm bushes and they didn't fit either.

Get everything from BMW if you can.

& with regards to checking the points you're looking for deep wear/corrosion on the points. They start off as like complete cylinders and then get a kind of groove warn through the middle of them over time. The more they wear the further the spark has to travel and result in a weak spark at the plugs.

For the injectors call InjectorTune and let him know that you're form the forum https://injectortune.co.uk/

Regarding checking the crank sensor that is actually a very good idea!! Costs nothing too lol. I had forgotten until seeing that post but I once had a problem where the car wouldn't rev over 2/3000rpm and one of the things I checked and cleaned with some brake clean was the crank sensor and all the teeth which fixed the problem.

Hi mate I'm trying to get in touch with injector tune but their webform doesn't seem to show up? Was wondering if you had an email or something
Cheers

[rix313]

This is James' email address sales@injectortune.co.uk

I had a similar issue on my race car which wa svery dull during a race. That turned out to be a TPS.

[Lemon98]

Hi mate I'm trying to get in touch with injector tune but their webform doesn't seem to show up? Was wondering if you had an email or something
Cheers

Sorry I didn't get back to you sooner, sold my E30 a month or so ago so haven't been checking the forum. Got myself a manual E46 330ci instead as is way cheaper on insurance.

But yeah that sales@injectortune.co.uk is how I contacted James and he replied to me through that so hopefully you'll get a better running car soon!