IDLE PROBLEM, please help!!

[liljos]

ill add pictures if requested*

my e34 (m20) has an idle problem and misfire. the car was running great till about this week. last week it wasn't running due to a slave cylinder failure. I replaced that and got the clutch working. at first the car wouldn't start and after having a BMW specialist diagnose it and removing/testing the fuel pump, he swapped the fuel relay with another similar(blue) relay under the hood. the specialist told me I had a bad fp relay. after the car got started, it idled fine. but then it would jump to 2k or 2500 and just stay there. *when the idle goes back to normal (700-900) the check engine light comes on. when the revs increase, the check engine light goes off. when driving; it takes off from 1st pretty rough and jumps. in any other gear if I go wide open throttle it stutters, especially in 5th. sometimes it will even completely just shut down.*

what I think: I'm not looking at any vacuum leaks but there are a few things I'll point out. there are 2 in/outlets (not sure) that are to the left of the tb. they look like they would have hoses attached to them but don't have any.*
when the tech was working on my car and the idle climbed, he tapped on the ICV and it started to idle normal.*
my car tells me: the oil level sensor*
there are 2 plugs. one on each side with orange housing that I can't seem to find where they go or are for.*
there's a plug right above the alternator that isn't connected?(possible oil level sensor?)*
I'm trying to get help and figure out the idle problem and why it randomly shut down.*
and I also recently discovered my car has Bosch platinum 4+ spark plugs.*

[vpilarrt]

Don't have answers for all your questions but:

2 outlet/inlets on side of tb - you talking about #4 on attached pic? If so, they connect to coolant hoses and are there to prevent the tb from icing up in cold (very cold) weather. A PO must have bypassed it + ypu don't need it in Fla. http://bmwfans.info/parts/catalog/E3...sing_assembly/
If tapping the ICV effects idle, I would supsect its bad or at least need cleaning. You can clean it by removing the vaccum hoses and spraying the inside with carb/choke cleaner.

[liljos]

Don't have answers for all your questions but:

2 outlet/inlets on side of tb - you talking about #4 on attached pic? If so, they connect to coolant hoses and are there to prevent the tb from icing up in cold (very cold) weather. A PO must have bypassed it + ypu don't need it in Fla. http://bmwfans.info/parts/catalog/E3...sing_assembly/
If tapping the ICV effects idle, I would supsect its bad or at least need cleaning. You can clean it by removing the vaccum hoses and spraying the inside with carb/choke cleaner.

thank you for the reply. it's tough being the new guy -___- but I'm gonna do that and see if it helps the idle. but would that stop the 2k-2500 rpm spike when it warms up and remains as I'm driving?

[e30newbie1212]

If the problem is mainly at start up, I would look to the 02 sensor. I had that problem and it turned out to be the 02 sensor. And once it warms up it idles fine. So look at that, and the stuttering, I would look at fpr. try one that is known to work. I had all sorts of issues with cutout and stutter, and trouble starting out because the fpr was done. Replaced it and she runs like a raped ape. Hope that helps!

Sent from my Ally using Tapatalk

[liljos]

If the problem is mainly at start up, I would look to the 02 sensor. I had that problem and it turned out to be the 02 sensor. And once it warms up it idles fine. So look at that, and the stuttering, I would look at fpr. try one that is known to work. I had all sorts of issues with cutout and stutter, and trouble starting out because the fpr was done. Replaced it and she runs like a raped ape. Hope that helps!

Sent from my Ally using Tapatalk

thanks for the reply. but you kinda got it backwards. the problem is after warm up. it just spikes and it's never made sense why. idk if it's the spark plugs, a sensor, a dizzy, or the ivc /: I need help but something new I found out, if I take a drive while it's warming up; Ill Be in 5th gear step on the gas and it stutters to catch speed, as soon as I press the clutch, it turns right off.

[harold30]

I have fixed this problem recently to my 89 e30 325i but we have a reverse scenario. Mine was on cold start and yours is when the engine is warm. Idle problem has a lot of factors to consider as it will do a chain reaction. most common is the vacuum leak, icv (my car rev up to the extent 3K without pressing the gas pedal) trying cleaning it with carb cleaner, if it doesn't help replace it with a used good one or better yet new, i would strongly suggest to change your o2 sensor (is responsible to take reading for air/fuel ratio and it will last roughly 50K-60K miles), clean your injectors and replace seals (clogged injectors will cause this problem too and its commonly unsought)

[liljos]

a vacuum leak where? and what i'm thinking of doing is cleaning out my injectors. any recommendations on a solution to use or how to go about doing so? my car also revs to 3k sometimes without the pedal pressed. what did you change on your car to fix the problem?

[jlevie]

Idle or hard starting problems are most commonly caused by intake leaks and/or
a sticky or defective Idle Control Valve (ICV). The only reliable method of
locating intake leaks is to have a smoke test run on the intake and crank case
and to test the brake booster with a gage and vacuum pump. The complete list
of possible causes of an intake leak is:

Intake boot
Throttle body gasket
ICV hoses & connections
Brake booster, hoses, and connections
Crank case breather hose
Evaporative control hoses, valve, and expansion tank
Fuel pressure regulator & hose
Injector seals
Valve cover gaskets & bungs
Oil filler cap
Dip stick o-rings
Oil return tube o-rings

While leaks in some of those can be found by inspection or by spraying carb
cleaner on suspect areas, not finding leaks that way doesn't eliminate the
possibility. Only a smoke test will really work.

Once the possibility of intake leaks is eliminated, the ICV needs to be
removed and cleaned with carb cleaner until the vane inside moves freely. When
the ignition is switched on you should be able to feel vibration from the
ICV. If no vibration the ICV is bad, there's a problem with its wiring or
connector, there's a problem with the TPS, or the DME (or Idle Control Module
(ICM) on an ETA car) is faulty.

For the DME (or ICM) to control idle, the idle switch in the TPS must work
correctly. The switch should close when the throttle stop is 0.030-0.060" off
the idle stop screw.

The fuel system should be tested via the suite of tests in the Bentley manual
as invalid rail pressure can be a contributor to idle and starting problems. A
simple injector check is to pull the injectors, jumper the fuel relay to run
the pump, and see if the injectors are leaking. You can also point the
injectors into a towel, remove the coil wire, and crank the engine to see if
all of the injectors appear to be spraying in a similar fashion. The best
approach to possible injector problems is to have the injectors cleaned and
flow tested. Since raw fuel can or will be released in these tests, have a
fire extinguisher handy.

While a bad check valve in the high pressure pump can result in longer than
normal cranking, if the fuel system is working as it is supposed to the rail
will reach normal pressure in a few turns of the engine. A weak pump, clogged
filter or leaking FPR in conjunction with a failed check valve can result in
longer cranking.

The O2 sensor can be a contributor to idle problems. The O2 sensor is a
scheduled maintenance item with a useful life of no more than 100k. If the
sensor has that mileage or more (or is of unknown age), replace it.

The AFM can be a contributor. If the vane doesn't move freely or the
resistance track is worn the DME may be receiving invalid data from the
AFM. And if someone has fiddled with the bypass air adjustment the DME may be
unable to stabilize idle. The bypass air adjustment should only be adjusted
per the procedure in the Bentley and with an exhaust gas analyzer. And even
then everything else associated with engine management has to first be
operating properly. If the AFM becomes a suspect, replacement with a good used
unit is the best approach.

Improperly adjusted or malfunctioning valves will affect idle and starting. As
can compression issues from ring or cylinder wear. A valve adjustment is
called for every 15k. A useful diagnostic is to run compression (dry and wet)
and leak down tests on the engine. Aged ignition wires, plugs, distributor
cap, or rotor can cause problems. Insulation does break down with time and
heat. And since the youngest E30 is going on 20 years old, if the ignition
system is original or the plugs are old replacement is indicated.

Although not usually a problem, a bad DME temp sensor is a possibility. That
generally won't cause an unstable idle, but can cause hard cold or hard hot
starts and/or a rough idle. As can problems with the timing reference
sensors. Although not commonly encountered, a bad harmonic balancer on an
M20B25 or M30 engine will cause problems.

When all other possibilities have been eliminated and idle or starting
problems persist, replacement of the DME, or if applicable the ICM, is
indicated.

[liljos]

wow that was a lot thank you. I've got an update. I figured out why I had a miss fire. it's in cylinder 6 and it's because the spark plug is bad. I tested them all and it was the only one with 0 resistance. I also did a manual choke while spraying carb cleaner into the intake and it starts. I got a few questions: does this mean there's no fuel going into the engine? and could the miss fire be the reason why it's not starting up? I was also spraying the ICV with carb cleaner while the key was in the on position. it wasn't moving but I felt the light vibration. when I go to empty out the ICV of carb cleaner the outcome is orange/brown ish. is the ICV supposed to spin around or something or does it stay in one position till the car is moving?