E30 Zone

Speedtouch wrote: ↑
Thu Jan 15, 2026 10:14 pm
Have you carried out a compression test?

Unfortunately I haven't. I don't have the kit. I'm gonna try next week to send the car for a repair shop. And let the guys have some fun

Hmm, new engine time, perhaps? How many miles has it done? There is no way to know the milage of an E30 😅 The cluster always fails. This one was busted 7 years ago but I fixed. It have now 155000 km on the cluster. 3 or 4 months ago this engine was open to change a failed headgasket. The engine was...

Been chatting with my pal again………. ⸻ AFM failure (why it matches perfectly) When AFM signal drops out at a certain flap angle: • ECU suddenly “loses” load info • Injector pulse collapses • Spark is momentarily invalid ➡️ That causes an instant, clean cut at a specific RPM, regardless of load. ⸻ Bo...

Is it possible that the ignition coil has developed a fault, even though you replaced it last year? Also worth measuring the resistance of the HT leads to ensure they're within spec. Do you have the CID lead fitted? https://www.e30zone.net/e30wiki/index.php?title=CID It's also worth checking out th...

Hi, thanks for your help. The ICM on Bosch Motronic Systems is a transistor inside the ECU that is controled by the CPU depending on the signals from diferent sensors, mainlythe CPS sensor. It's not an external module. I've tried 3 different ECUs already, they all work on another e30s. About the TPS...

Yes, quite possibly. "An engine backfire happens when the air-fuel mixture ignites at the wrong time, either too early (in the intake manifold, blowing back through the intake) or too late (in the exhaust system, creating flames out the tailpipe). Common causes include incorrect ignition timing, ri...

Speedtouch wrote: ↑
Wed Dec 31, 2025 6:00 pm
Well, it would if there's a temporary leak then it somehow re-seals itself. Does it have a steady idle speed?

The idle is fine.
Also a vacuum leak would cause this engine to backfire ?

In that case, it would all tend to point to a vacuum/air leak somewhere on the intake manifold/AFM side of things, upsetting the mixture strength. What do the spark plugs look like after a run? They should all be a nice even tan colour. Another possibility is a failing or incorrect heat range set o...

Well, it seems to rev quite well, until it hits around 4,000rpm. Could it be a typical M40 worn camshaft causing the problem - do you notice any ticking sound at all? "The cam is the known weak spot of the M40 engine, and is more susceptible to lobe wear than any other E30 engine, usually caused by...

Another update. I've wire Brusched the trigger wheel and clean it with brake cleaner.
I also disconnected the 2 wires from the alternator. The problem pressists.

Another update. I've wire Brusched the trigger wheel and clean it with brake cleaner.
I also disconnected the 2 wires from the alternator. The problem pressists.

Speedtouch wrote: ↑
Tue Dec 30, 2025 11:16 pm
You could test this theory by directly wiring the ECU +12V feed to the car battery +12V terminal, then taking it for a drive...

I will definitely do that, it's the only way. I'm not sure if I'm gonna feed the 12v through the ignition switch or through the DME relay. Maybe I'll try both.

UPDATE. I've installed a brand new genunine CPS sensor from BMW. The problem pressists. I tried with the TPS, AFM and IVC disconnected and have the same issue. The problem happens both with the car stoped and driving the car. I jiggled the car key while maintaining constant acelerador pedal and felt...

For sure, it is not cool rock steady! Perhaps you have a faulty rectifier in the alternator that is causing the voltage glitches? You could try temporarily disconnecting the alternator and try the test again... I was going to disconnect the alternator several days ago. But the big wire was starting...

Have you checked the notorious green wire that runs behind the dashboard to the ECU? The Wiki guide provides more info: https://www.e30zone.net/e30wiki/index.php?title=Engines_Troubleshoot This is awesome stuff. I tried the light bulb on several locations. I have here a video with the bulb conected...

I'm wondering if it's a possibility your exhaust system is blocked somewhere - have you tried revving the car right up to the red line with it stationary? Alternatively, it could be a blocked fuel filler cap breather causing a restriction... If I apply light throttle I can rev the car. If I apply m...

Have you tried cleaning out/replacing the idle control valve? I see what you mean, I had that problem before. When acelerating the engine cuts because of the ICV. I disconnected to see if it made any difference. But the rev counter drops below the actual revs the engine is producing and some pops a...

UPDATE. I used a timing light pointing to the trigger wheel marking compared with the arrow. It advances and retards timing depending on the rpm and engine load. When the cut happens the light goes off. So I can't see what happens. I guess it retards timing or advances to mutch. I also put a ground ...

I would also try adding an extra engine-to-body earth strap, if only temporarily, to see if it makes any difference... Im defennatly going to try to earth to chassis today. Yesterday I tried different used CPS sensors and got the issue even worse. I also tested the tps sensor that it's working grea...

So it's 'bogging' down when you try to accelerate? In that case, there's probably an inlet manifold vacuum air leak somewhere. I would carefully check any hoses, couplings, etc, for cracks/splits, and try spraying starting spray or brake cleaner around the inlet manifold with the engine warmed up a...

Yes. If the ignition switch has worn contacts, you won't be getting a reliable power feed to the DME/ECU. You could try bypassing it altogether, and running a direct +12V feed to the ECU, obviously ensuring you are feeding the power to the correct terminal(s). You mentioned it only dies under load,...

I would start with checking the basics, such as engine-to-body earth strap(s), and that you have a decent DME (ECU) relay. Also verify that the ignition switch is giving a reliable supply to the engine electrics. Thanks for your reply. I had a friend with his e30 here at home and i swapped his ECU,...

Hi everyone :D I'm having an pain in the ass issue with a 316i m40b16 engine :cry: If I apply any engine load on the car, it cuts power on what it looks like it's an ignition issue. The rev counter drops to zero and then goes back to normal. I changed all the ignition system last year. Plugs, ht lea...

Hi, I wonder if anyone has a clue why resetting the ECU the car performs a lot better. And passing some days it starts to loose power. If I reset the ECU again it performs better again. This is a very weird behavior for an 1990 E30 316i with no O2 sensor. I wonder if fuel trims are activated even wi...

I finally did it, it was the bottom wire that i had to intercept the signal, probably its the one that sends voltage to the DME. Now i have full control of the voltage sent to the DME. I set the maximum tension i could get on the AFM to became leaner, now with the flick of a switch i can enrich the ...

gonna review the Fuel Pressure Regulator, probably its still the same from factory :mad: It probably is, and non the worse for it - one of the most reliable part on the car. They can be damaged by someone connecting the two fuel hoses the wrong way around, although this is rare, but apart from that...

Without injectors working to spec., you are chasing unicorns by playing around with the AFM signal. At best you will end up with fuel mixture control no better than that offered by carburetors - correct at two points at the most. The thing about having the injectors rebuilt is that it is an investm...

Without an O2 sensor, the ECU doesn't know how much the injector flows will have reduced by now, and so will be making no attempt to compensate. The mixture will almost certainly be weaker than it should, which is consistent with what you were trying to achieve in your OP. Full injector rebuilds, r...

Most (UK) E30s do not have lambda sensors to determine if the average fuel mixture across all the cylinders is weak or rich. The ECU just assumes that the injectors are within spec., and applies pulses to them of the length that should give the correct mixture. The later systems on the VW and Honda...

OK, so your saying that a best engine management on VW and Honda are compensation possible bad injectors than BMW ones?

In that case, getting them professionally rebuilt and balanced would be the first thing to do. Their flow rates will be way down on what they should be, some will be injecting more fuel than others, their spray patterns are likely to be far from ideal, and one or more may still be dribbling fuel wh...

Brianmoooore wrote: ↑
Sat Sep 28, 2019 7:39 pm
How many miles has the car done on the current set of injectors?

100000 miles, its a 1990 316i btw

The carbon track in the AFM is laser trimmed to provide the correct air/fuel ratio at all engine revs and loads, with the actual ratios modified for power/emissions/economy by the throttle position switch. Without a full engine dyno. and air/fuel ratio measuring equipment you are not going to match...

The main idea doing this is to fool the ecu, making to change to the full throttle ignition and fuel maps earlier than the standard 4500 rpm. If i lighten the spring tension 4 clicks, i think i'm getting this effect, since i notice more go at 3800rpm. The idea is to make that happen with the flick ...

Search found 51 matches

Re: M40b16 engine cutting on aceleration

Re: M40b16 engine cutting on aceleration

Re: M40b16 engine cutting on aceleration

Re: M40b16 engine cutting on aceleration

Re: M40b16 engine cutting on aceleration

Re: M40b16 engine cutting on aceleration

Re: M40b16 engine cutting on aceleration

Re: M40b16 engine cutting on aceleration

Re: M40b16 engine cutting on aceleration

Re: M40b16 engine cutting on aceleration

Re: M40b16 engine cutting on aceleration

Re: M40b16 engine cutting on aceleration

Re: M40b16 engine cutting on aceleration

Re: M40b16 engine cutting on aceleration

Re: M40b16 engine cutting on aceleration

Re: M40b16 engine cutting on aceleration

Re: M40b16 engine cutting on aceleration

Re: M40b16 engine cutting on aceleration

Re: M40b16 engine cutting on aceleration

Re: M40b16 engine cutting on aceleration

Re: M40b16 engine cutting on aceleration

Re: M40b16 engine cutting on aceleration

Re: M40b16 engine cutting on aceleration

M40b16 engine cutting on aceleration

ECU/DME weird behavior.

Re: AIR Flow Meter, Motronic 1.3 signal change

Re: AIR Flow Meter, Motronic 1.3 signal change

Re: AIR Flow Meter, Motronic 1.3 signal change

Re: AIR Flow Meter, Motronic 1.3 signal change

Re: AIR Flow Meter, Motronic 1.3 signal change

Re: AIR Flow Meter, Motronic 1.3 signal change

Re: AIR Flow Meter, Motronic 1.3 signal change

Re: AIR Flow Meter, Motronic 1.3 signal change

Re: AIR Flow Meter, Motronic 1.3 signal change

Re: AIR Flow Meter, Motronic 1.3 signal change