My M5-90 is jerking when I have a constant pressure on accelerator (just to maintain constant speed), only at low rpm(1500-2000). Does anywone have a clue where I should begin to search the problem.
This topic has been covered nicely in the old board, if you care to look back a month or two...someone described it as a 'fish bite' feeling. There were a number of answers, one of which seemed to be a cure in the throttle cable adjustment (unless I'm totally misunderstanding it). I meant to print it out for future reference.
This is common with the E34 motor it seems. I found it annoying when I bought my '92 last summer. I later installed a JC chip only to discover that it already had the Dinan chip there. The fish nibble feeling pretty much stopped after I installed the chip. It seems the factory chip has the same feeling to it, but I can't say that because I've never driven one with it in.
Do you know if your car has an aftermarket chip in it? In any case it isn't a serious 'problem' and also you may be able to fix it.
Good luck,
Bill
My M5 -95 was also jerking exactly like you describe it!
After installation of an UNICHIP ( http://www.dastek.co.za/ ) it is not jerking at all any longer!
If you change the chip and the problem goes away, that means there's something wrong with the existing chip or the DME I would think. No matter, if changing the chip fixes the problem, hey cool.
With a UNICHIP you don't really "change the chip"! Acually you don't even get into the ECU at all! As DASTEC describes it:
"The UNICHIP is much more than just a "chip". In actual fact it is a fully functioning computer which is added to the vehicle’s existing engine control unit (ECU). Apart from controlling general timing and mixtures it can do idling control, drive extra injectors, take full control over timing functions, eliminate road speed governors etc. It can be accurately described as a "Piggyback" computer.
The UNICHIP gets wired into the existing ECU harness. If it is removed the vehicle is back to standard. Unlike other after-market units if the UNICHIP is programmed with zeros the vehicle will be standard. Only areas where the vehicle isn’t perfect need to be altered.
The main difference between other after-market "chips" and the UNICHIP is that with the UNICHIP every individual vehicle is optimised. It is not just a chip that was made on one particular vehicle and then gets used on other similar vehicles."
From what I have read and heard many M5:s are jerking and obviously is adjusting the car on a rolling road one way to eliminate this problem (as long as you don't have other problems with your engine)!
Two more advanatges are:
1) The car is no longer hesitating when accelerating on part throttle from low and medium revs and probably as a result from this
2) The engine feels much more powerful specially from medium and low revs (even from revs under 1000 rpm)
I have the same problem and it is annoying to say the least - two shops have replaced 4 parts to no avail so be careful - 02 sensor, air flow meter, fuel pressure regulator and throttle switch. seemed to work fine after air flow meter, but problem is back full throttle - pun intended. let me know if you find the old message board posts and if someone finds the problem - i will do the same. I have a Dinan chip (but they were one of the shops that mis-diagnosed)
higher octane gas (through booster since 91 is only thing around) and the jerking has either completely or mostly disappeared. a few more miles and I will know for sure - Dinan chip must not like the low octane
Linear Mode
