Bad idle and hesitation

[singhters]

BMW 1992 BMW 32OI M50

My car has been suffering from bad idle, bouncy revs and power underload I have changed all kinds of parts under the sun to no avail.

I fixed the bouncy rev part by reattaching the earth cable for the injectors which was sheard.

But the hesitation and bad idle remain, but once I drove the car and for three days their wasnt a problem it did not hesitate and had loads of power, only to notice an injector was leaking from the top part of the hole it goes in the fuel rail, Im now thinking that the fuel pressure regulator was supplying too much pressure to the unjectors and that this leak released that pressure hence making the car run like it should, can anyone back me up on this theory cos when I put a new O ring back on the injector to stop the leak the car went back to the way it was.

appreciate your help.

 

[Kirby]

Possibly the idle control valve is bad/dirty. Read these articles and see if this describes your problem:

http://www.unitedbimmer.com/kb-e36-icvcleaning.php

http://www.ee.udel.edu/~xuan/auto/DIY-ICV.html

 

[singhters]

Nah mate cant be that tbh ive had 2 icvs and its deffo not that, I have changed many parts on the car everything except the Fuel pressure regulator, fuel pump and 5 coils ive even tried 4 injectors 2nd hand and still its the same.

I would really like for someone more experienced to answer the question posted about the fuel pressure being too high cos thats the only explanation I can give as to why it was not hesitating when the injector was leaking.

Am i right in my theory that when the injector was leaking it was releasing that excess pressure that the rail was recieving.

 

[ThatOneGuy]

There are quite a few recent threads on this subject on the M3 forums. Most likely culprit... bad gas.

http://www.m3forum.net/m3forum/showthread.php?t=114721

 

[singhters]

Sorry but thats not what im looking for i want to know if my theory is correct as to the question I asked.

 

[Kirby]

In theory, yes, excessive pressure could prevent the injectors from opening.

BUT - how bad was the fuel leak? It would have to be a GUSHER to significantly lower the fuel pressure. If the leak was just a few drops a second, that would NOT be enough to significantly lower the pressure.

 

[singhters]

Well when it leaked on the first occasion it gushed like hell and the car was powerful as hell as well on this occasion it was a tiny leak to say the least the car was running and pulling like a train again but eventually went into limp mode, so I would say yes it was a gusher and when I took the injectors bhoy petrol gushed out the top of the rail.

So when its leaking it pulls from 1k in any gear even in 3rd it pulls from 1k like a train, in 1st it seems to fly.

But when its not leaking it blips in all gears until the higher rev range only really starts to pull when it hits around 3k, in this state the 1st gear is the worst it totally misses 1000rpm and 2000rpm and starts to pull at around 2500 3000rpm.

Also the idle seems to go an and off the cylinder like its overfuelling its like 3secs of smooth vmmmmmm and then 3secs of chugging off and on like that.

So do I need a new pressure regulator ?.

thanks for the advice.

 

[Kirby]

With that info, a failed fuel regulator is a good educated guess, but nothing more. If it were mine, depending on the price of the regulator, I would replace it if it's cheap --- or first attach a pressure gauge to the fuel rail and actually measure the pressure.

 

[singhters]

Well the regulator I can get for £48.79 and hav already ordered but instead of picking it up and putting it on im gonna do as you say and do a pressure check using a gauge, I will post the results when I have done this.

thanks for the advice you have been most helpful.

 

[singhters]

Ive done the test but dont understand the readings, on the gauge in the picture below you will see what options their are for the reads.

Engine idel condition was in the red which is bad.

INS hg was readin 15psi

When holding the throttle down or pressing it further on the fuel pump inlet section it would not go past 0.7 bar and if i pressed it further it would jus bounce back and go the other way.

So I think that the fuel pressure regulator is bad and is either not holding the pressure where it should because the higher the revs the leaner it gets so on that note I think im gonna buy a new regulator.#

 

[singhters]

well i replaced the regulator and still their is hesitation and bad idle.

any other suggestions as to what it could be.