rough idle stumble acceleration intermittant [Archive] - Bimmerfest - BMW Forums

: rough idle stumble acceleration intermittant

11-07-2008, 11:36 AM
Greetings everyone,

I'm hoping someone can give me some advice as I'm growing frustrated tracking the problem down with my 1992 e34 535.

Ok so my vehicle will seem to idle smoothly but after I take off and am at a stop it will slowly begin to idle rough and feel as if the pistons aren't firing. I can rev it and it sputters in sound and after I take off it will sometimes smooth out and sometimes it stays firing on what feels like 4 or 5 cylinders instead of all six.

So I recently in hopes of fixing the problem replaced all six injectors with remans. They are the bosch yellow "ford" ones. I also changed all spark plugs with stock replacements. and replaced wires with stock bosch parts. Right after I did all this it appeared to be fine and ran smooth as a new car. then after a few stop lights it got worse and worse.

Initially the #1 injector appeared to be not operating hence I replaced all six. I check all them for voltage and they all came toalmost 12v with key at on position.

Can someone tell me what else to check. This all started after the car sat for about 2 weeks. Everything was fine prior to that. It feels as if the cylinder/s are flooding or the car is running rich .I really don't have the money take it to the stealer and dont want to have to junk the car.

Cali Love (e34)
11-07-2008, 03:17 PM
perhaps the idle control valve... you get a check engine light at all? try a stomp test to see if you have any codes stored in the computer memory... you can post the codes here.

11-09-2008, 09:15 AM
Ok guys,
Thanks for the advice... There are no CELs being displayed. Heres an update I go to thinking about the Fuel Pressure Regulator not opening up and the excess fuel having to be dumped into the cylinders. So while the car was running and warmed up I disconeccted the vacum line to the FPR and the motor performed the same, I thought that it was suppose to surge or something to that effect. There is suction on the line I can def. confirm that when I place my finger over the hole. I then took it for a spin around the neighbor hood and to a few stop lights and same problem even with the vacuum line disconnected. I noticed the majority of my problem is at idle and the longer I'm at idle the worse it gets when I take off it will sputter till it gets caught up wether its burning off excess fuel or whatever.

How can I further test my Fuel Pressure Regulaotr FPR ?

bimmer dot info
11-10-2008, 09:52 AM
Clean the ICV first.

To test the fuel pressure you will need to find a service port or splice a T into the fuel line to attach a fuel pressure gauge.

11-10-2008, 10:26 AM
Thank you for the great advice and I appreciate you guys taking time to reply. I want to check the ICV but am having trouble locating it. I follow the vacum line attached to the FPR and it disappears through a hole on the intake manifold. It looks as if I will have to renove the fuek rail again to gain access. Does this sound right or am I looking in the wrong area? Also How would I go about cleaning the ICV once removed?

Another quick question. When I disconnect the vacum line and drive with the FPR detached from a vacum source ... shouldn't that make a difference wether it be worse or better? Currently nothing changes in engine performance.

bimmer dot info
11-10-2008, 01:13 PM
Part 17

11-10-2008, 01:56 PM
Thank You Bimmer dot,
That diagram is really good but my car is a bit different. Part 17 I can't find. coming out of the head/valve cover is the tube and that goes to a "t" one side goes to the intake boot between the AFM and intake throttle Body, the other side goes to the intake manifold. prior to the manifold it passes through a large hard piece of plastic just below the wire harness/fuel rail. This does not have any wires attached but appears that it could be a valve of sort.

Now coming out of the intake manifold, is a medium sized hose that goes to a sensor but on the other side of that sensor is a hose that goes to a resevoir tank behing the left headlight.

Any ideas or advice. Sucking on the FPR vacum hose leaves a strong gas odor taste in my mouth. Does that sound defective? Any other descriptions of what the ICV might look like or where to look I feel like an idiot at this point but need advice.

11-10-2008, 02:03 PM

I found this picture and this is my setup. I dont have a #12 it goes directly into the boot. If 14 is stuck closed or opended could that cause a rich condition?

11-20-2008, 05:09 PM
Thank you all for your help. Since I hate finding post with info. unresolved I wanted to share with everyone how I fixed/what fixed my problem.

To recap, My car sat for a week or two and upon starting I had avery rough idle. I thought it just need to warm up and took it for a drive and fresh gas. When I got to the gas station the car was warmed up but very very rough running. I filled her up and while filling up I noticed a classic rotten egg smell. I drove approx. 10 miles on the hwy and burned through about 3-4 gallons of gas! My car was sputtering while driving and idling very rough at stops long I sat the worse it got. I had no check engine lights and the car never died on me. Didn't even through any codes on the stomp test. I thought the problem was bad injectors dropping in and out and flood the cylinders. I replaced all six with the Bosch/Ford upgraded injectors. Still had the same problem. I chenged the wires and plugs, still had the problem. I checked fuel pressure and replaced the fuel pressure regulator FPR. Still had the problem. I finally check the distributor cap and discovered that my old one was cracked in half! I also replaced my ICS/Pulse Generator. After these items were replaced my car now runs better than ever. Like new with no miss fires and better gas milage than ever. I also did a throttle body cleaning using Amsoil PowerFoam ( Awesome STuff) and clean out the injectors with Redline SI-1 (Also great stuff).

I hope this helps others. I was experiencing a rough idle with misfires on random cylinders and sustained no fires sometimes. I was also getting a good idle every once in a while for a split second only to return to the violent shaking like sitting in a drag car ready to launch "glub glub glub glub"