1987 325 terrible idle

[craiggroves91]

Okay guys, so my "Piece" DD 87 325e has always had a crap idle since I got it.
It's lumpy and the car shakes. It also cuts out sometimes when accelerating.
It does rev pretty happily and smoothly. I changed out the cap and rotor and this helped get rid of the cutting out problem a little I think, but the thing still idles terrible. I adjusted the valves and this didn't help at all.
I also changed the plugs right after I bought it not too long ago.
What cheap things can I try to help it?
I really don't want to throw money at it, after all its "the piece"

It does have an exhaust leak at the muffler inlet, but this can't make the car idle crappy can it?

thanks
-Craig

[dnguyen1963]

The cheapest thing and probably the best is to do a smoke test. >90% of rough idle is due to vacuum leak.

[jlevie]

For the complete trouble shooting list:

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.

[craiggroves91]

So So I took off the intake boot and airbox and I have oil throughout the whole thing.
Is this a problem with CCV?

[jlevie]

This engine doesn't have a CCV. It has a hose from the valve cover directly to the throttle body. Some oil in the intake is normal, but if the engine/head has a lot of miles on it or there are intake leaks into the crank case the oil quantity will increase.

[craiggroves91]

This engine doesn't have a CCV. It has a hose from the valve cover directly to the throttle body. Some oil in the intake is normal, but if the engine/head has a lot of miles on it or there are intake leaks into the crank case the oil quantity will increase.

Yeah, thats what I figured.

I can't seem to find a vac leak with carb cleaner. I wish I could do a smoke test.

Do you know what resistance spark plug wires should have?

[pantelones]

That leak is directly related to the "bitch tube" or the crank case breather. If that isn't sealed and working properly than the motor will spit oil through the valve cover breather at higher RPM's into your intake. Intake leaks will contribute, but the main cause is the crank case breather.

[craiggroves91]

That leak is directly related to the "bitch tube" or the crank case breather. If that isn't sealed and working properly than the motor will spit oil through the valve cover breather at higher RPM's into your intake. Intake leaks will contribute, but the main cause is the crank case breather.

By crank case breather you mean the hose from the valve cover to the throttle body right?

It seems to be fine. I took it off its not plugged or anything.

I could inspect the bitch tube the best i can while its on the car. Maybe I should just by some various gaskets and replace them

[pantelones]

^^^ No, by crank case breather i mean this.....


IMG_3929 by Los Pantelones!, on Flickr

[craiggroves91]

^^^ No, by crank case breather i mean this.....


IMG_3929 by Los Pantelones!, on Flickr

Thats the bitch tube, got it!

That could also be a source of a vac leak right?

[pantelones]

That could also be a source of a vac leak right?

Yes, my car had a terrible idle prior to pulling to motor. The bitch tube was leaking horendiously, and my intake was full of oil. Actually, now that I think of it check your TPS if you haven't already. If you are leaking that much oil into the intake there is a good chance that your TPS is full of oil and not working properly. You can drain it, and drill a small hole into the bottom where the TB shaft sits and see if that fixes your idle. Or try a new sensor if you don't want to trust it.

[craiggroves91]

Yes, my car had a terrible idle prior to pulling to motor. The bitch tube was leaking horendiously, and my intake was full of oil. Actually, now that I think of it check your TPS if you haven't already. If you are leaking that much oil into the intake there is a good chance that your TPS is full of oil and not working properly. You can drain it, and drill a small hole into the bottom where the TB shaft sits and see if that fixes your idle. Or try a new sensor if you don't want to trust it.

Well I took of the TB and cleaned it to the airbox and cleaned everything out. Didn't make a difference. Ill look into the TPS.

I'll check it out more right now.

[craiggroves91]

My water pump seems to be leaking also



FACEPALM!

[craiggroves91]

Alright guys.
So I did a headgasket replacement and pretty much every other top end gasket.

So if there is vac leak its coming from a hose. All of them seem to be fine.

The idle is still choppy. I ordered another set of plugs and I'm going to see what that does.

I hear spark when I pull the wire a little. So its either the plugs or a fueling issue?

[craiggroves91]

Spark plugs were fine that I pulled out, put the new ones in anyway. Still shaky at idle.

Any ideas?

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