Car skips a beat randomnly at high rev range!!!STARTED AGAIN

[siddiqi1]

Dear All,

Car: M20B25 SPORT

Recently the car has developed a new and very randomn problem.

Whilst driving and giving it some beans...id say in third gear at appx 4.5k the car jerks and misses a beat...almost like a loss of spark or fuel.....then when a regain power(pretty instaantly) and give it beans again....i hear a pop from my exhaust and the same jerk appears????

Now if i drive in normal behavior after this occurs, its fine through all the gears, idles perfectly too

Its very randomn, and i have had 1/2 tank of fuel so i cant see that its a starvation of fuel.

Its due for a service in a month, but the HT leads are fine, dizzy looks new, coil maybe suspect but thats just a guess, i dont know the conditon of the sparks, but as i have no lack of performance otherwise i doubt these are the cause??//.

Otherwise it pulls very hard, so im not really lacking performance.....so Im a bit bewildred by this one

Also, this may help, but it is very hard to start from cold....from hot start its fine.

Could it be my fuel pressure regulator?

Regards

Saboor

[bam2002]

Could be alot of things..

To much fuel pressure.

Spark related..

Or I had a similar problem and it turned out to be the plug on the bottom of the throttle body was loose, so when I was accelerating it would miss or if i hit bump it would wiggle and Id missfire.

so check all the connectors. Put a fuel pressure gauge on the fuel line and test the pressure.

Then check rotor cap etc..

[siddiqi1]

To much fuel pressure, is that possible, well i assume that would occur if the regulator failed?!

Spark related: You think? I have ordered new sparks as a precautionary, but then it wouldnt start, it wouldnt idle perfectly either!!Stumbled

Ah the switch you are talking about is the TPS! Well ive checked that to the best of my knowledge, theres no dirt or debri around any of the pins, and it clicks on full close so i assume its operating fine, otherwise again the car wouldnt be idling well as it would think the throtlle was open

Rotar cap...it could be that.....how do i check it, do i just pull the leads out or........?

thanks so much for your input

Regards

Saboor

[e30-320i]

Take it off and check the points inside the cap i ended up removing the rad to get mine off though as i couldn't get to one of the bolts with my limited tool selection.

[siddiqi1]

update:

just had the car serviced, oil, oil filter, fuel filter,air filter and PAS fluid.

Still finds ti difficult to start but the skipping has not yet come back, though i strongly belive it is still there!!

Could it be the AFM?

Regards

Saboor

ps rotar hasnt been checked, though it would be missing if something was wrong with that at idle

[jaydub]

sounds like over fueling , sticky injector possibly ?

[maxfield]

I would of though rotor arm. Not very common for H/T leads to fail.

Can't see why too much fuel pressure would make it misfire

AFM is another option.

[Gwynleym10]

I think it could well be a worn rotor / cap. Take it off and have a look.

Is it taking a while to start? The loss of power at randomly could also be the fuel pump slowly dieing!

[siddiqi1]

Guys,

is there any chance it could be the coil??

It did it again today whilst i was going through the gears and it did it roughly at the same rpm ranger and in the same gear (3rd gear)

Is it the fuel pump, how hard are these to change?

Saboor

[siddiqi1]

i went to the dealers today and purchased a new FUEL PUMP RELAY.

the old was in bad conditon, well i thought so anyway, all the pins looked burnt to me....had all black soot over them as if they had burnt out.

Anyhooo changed those, butthe starting problem was still there, am goingo t get the rotor and cap checked tmrw, seewhat results!!

Saboor

[siddiqi1]

Urgent help Please

Just changed my fuel pump for a used working one.......and stil have the same problem, however it doesnt do it as often.

Ive got some what improvment to the drive now, but it still skips as iff thefuel pump is dying.....could it be my fuel pressure regulator

How do you change one of those?

Saboor

[DaveD]

its part no 6 just at the front end of the inlet manifold

http://www.realoem.com/bmw/showparts.do ... g=13&fg=15

got a spare if you need it...just pull the fuel pipes off ( unscrew and replace

but it could be as said before rotor or cap..they are old cars and the caps can wear.......

[siddiqi1]

see i do agree that it could be the rotor,but when i floor it and all is well it pulls like a train,i could be at 2k or 6k and it will randomnly jerk

One thing is certain,new coil,jst serviced with new sparks,fuel filter and what not. It is always a git to start in the morning after having left it overnight,shakes violently,but giving it a lot of gas,it then setles aftr a minute and idles perfectly!

Thank you for the offer of the regulator,ive just ordered a new one!wish id asked earlier.thanks.

I cant see it being anything else

[DaveD]

if it doesn't work ...its got to be electrical ..i know everyone says it can't be but have a look at the ht leads...you never know...............................

[AndyTouring]

My '89 320i Cab has a similar problem. Slight hesitation from 2500 - 3000rpm up.

Checked dizzy & rotor (aren't they a PITA to get at?) - cleaned contacts, looked in good condition.

Plugs look ok.

Took quite a bit of churning over to start after I'd been away for a few days. By comparison, 316 started first turn of the key.

Couple of times it has refused to start without some throttle juggling - cold start not working?

Car has spent a lot of it's life doing very little mileage which never helps.

[siddiqi1]

Andy,

The only reason i doubt the dizzy and rototr, and please do correct me on this, is that when i put my foot down its goes alright, pulls and accelrates immediately, no hesistation, but then on an off day say im acclerating and then suddenly asi f ive hit the limiter it hops n skips, i let go of the gas, and its ok....but then i drive slowly and it hop skips asi f the fuel pump is going.

But i changed the fuel pump, and am awaitng a fuel pressure regulator at the mo, Im hoping its that, because it splutters when it starts from hot and then is ok, as if the pressure regualtir is waiting forthe pressure to build!!!

However, after the fuel pressure regulator has gone in, if it still does it, then i will check the dizzy and rotor thia Friday........is something i can do myslef?

Saboor

[Dan318-is]

Coolant temp sensor?

[siddiqi1]

The blue one buddy, changed that when i first purchased thecar 8 months ago, im not saying it may have failed again, but was a BMW PART so doubt it failed, have been getting good MPG so i dont think so

It wouldnt cause the car to randomnly hop and skip like a kangaroo, or would it?

Saboor

[Dan318-is]

Well if it was intermitanly failing it could cause fueling problems. Sounds more like a sparking issue to me mate. Maybe replace the rotor for good measure anyway?

[Simon13]

more likey a dicky coil playing up, they take a while to start when the coil isn't at it's best

[siddiqi1]

Well if it was intermitanly failing it could cause fueling problems. Sounds more like a sparking issue to me mate. Maybe replace the rotor for good measure anyway?

Isi t hardo t do, something an amatuer is able to do?

Hows your car runnig by the way?

Sabs

[siddiqi1]

more likey a dicky coil playing up, they take a while to start when the coil isn't at it's best

I thought that too buddy, so i thought i shouldchange it, so i did for another Bosch unit i purchased from Gareth, same old starting problem!!! So itsn otthe coil!!!

thanks

Sabs

[Brianmoooore]

Just looked down through this thread, and there's no mention of one of the first things that should be checked on a six pot - the plug and socket and the wiring under the rubber boots, for the injector loom under the centre of the inlet manifold.

[abelai]

It sounds like an connector or wiring fault like Brianmoooore said, temporary electrical problem PITA get a can of contact cleaner clean all the connectors and pull back the rubber boots to check the wires aren't damaged.

[siddiqi1]

brain,

Thanks for looking through the thread.

Lucky you mention this part of the engine. Now i did take it apart,i.e. Unscsewed and saw no corossion,however i did not take the rubber apart to see the connections to the terminals, do you think this will make a diff.

How do i separate the whole thing from the rail its on.

Whats in this part of the loom that would affect starting and randomn jerking?

[abelai]

You unscrew the connector apart and then you can also remove the other part off the metal bracket by unscrewing a collar. The connect carries the injector signals and CTS signal.

[Brianmoooore]

Wires often corrode through under the rubber boot of the lower part. Plug and socket comes apart, and is held in place like a miniature version of the diagnostic connector.
ECU temp sender signal and temp gauge signal go through this connector, as well as the fuel injector signals.

[siddiqi1]

ah fuel injector signals,now that is something to thnk about!

Could i start the car from cold whilst fidling with the injector loom plug!

Do you think the ecu thinks one of the injectors is not working?

[Brianmoooore]

!Do you think the ecu thinks one of the injectors is not working?

E30 ECU isn't clever enough to think anything. There's no feedback loop for it to check like newer stuff.
You can try a wiggle test I suppose, bot it would be better to dismantle and check. Can be accessed by removing the air filter assembly.

[siddiqi1]

thanks Brian.

Will have a wiggle and a shake at it!!!!

Contact cleaner wouldnt go amiss either i think whilst im there any way!!!

Sabs

[siddiqi1]

UPDATE:

Well after having changed the AFM for a known working one from Chris-W, along with having checked the rotor and dizzy cap, i can report the problem solved as for now.

Firstly, the rotor was slightly burnt, i scratched it on a wall to get the shine back i.e. contact surface, and check the cap, which was in good conditon.

Will replace the rotor tommorow and will report back.

Also adjusted the tappets which werent out that much, but certainly gone a lot more quieter..............thank the lord its over with

THANKS ALL SO MUCH

Saboor

[siddiqi1]

UPDATE:

Having previously said that the problem had been solbved, it returned with a vengance!!!!!

Clearly it wasnt the AFM or the rotor, but no harm in changing them.......i then changed the CRANK POS SENSOR.

Now, ith asnt done anything as of yet, but i do beleive that my TPS is either FAULTY or my ICV is!!!

Im a rTPS this Friday for a new part, and will report back on the findings........

So for now, it looks as of the CPS has solved the problem, as it was theadered near the actual sensor, has made a MASSIVE diff in performance, sound and accleraiton in my opinion!!

[gareth]

[sam325is]

my girlfriends dad had the exact same problem on a 1994 merc of his. he tried allsorts. threw money at it left right and center. in the end mercedes found out it was the actual ecu at fault. so he bought a new one and it has never happened again.

sometimes the problem disappeared for as long as a month...just thought it was worth a mention.

[siddiqi1]

hmm i was thinking the ecu to,might try a swap and see what that results in!

Thanks for the idea,it could be overheating or something...but as for now it hasnt done anything yet,seems ok