Yes, An idle question. SORRY!! But please help. (PayPal gift for answer)

[ct3155]

Alright guys. I have searched here quite a bit and read my Bentley book as if it were the bible.... And I'm still stumped on this one.

I have an idle issue that I have completely run out of ideas on. First off I'll list the problem and then the car, and what has been done to it.

The problem, very shitty low idle when cold and warming up. Most of the time to start cold I have to give it a little bit of throttle until she stables out... Or else it will die. While on the gas during cold start, it feels to not be running on all cylinders.. Very lumpy! It will smooth out in ten seconds or less.. Then I can proceed to drive. It will continue to lope around at idle bouncing from 450-550 while warming up. Then once at operating temp it will idle at a healthy 6-700.

It runs and drives normally once at normal temp. Plenty of power as it should! It will occasionally dip down to low idle but come back. But this whole cold start issue is getting old. I've been battling this bitch for two weeks!

1988 325is m20 with mark d chip
Always run 93 or 91 if I can't find the earlier...
As far as internals on the motor go, stock.

REPLACED:
-Spark plugs - today, no change
-Re-man AFM from advance, still no change. So I guess mine is still good
-Cleaned idle control motor, no change
-Made sure idle and full throttle switch was adjusted and functioning right, it is. No change
-I have three ecu's and alllllll of them run the same way. Ruled that out.
-Fuel pump and filter was new last summer as well.
-All new gaskets everywhere and rubber. No air leaks. See below.
-Coolant switch has been replaced as well. Less than one year ago.

I havent yet done a smoke test, no access to machine yet. I know most of these idle issues with the e30 are air leaks. But I have done a cruel test... While idling I sprayed starting fluid anywhere and everywhere there could be unmetered air entering. No beans.. Idle speed was solid. I doubted it would be that anyways as I had the motor out last summer and replaced every gasket known to man In it. Couldn't have gone bad yet...

My last hope is bad injectors? I am ordering them new 17lb ones as I type, from a member on here. Or maybe cap and rotor? It's two years old...

Anybody have any other ideas? I thought I had my bases covered well here, but the car doesn't want to give up the secret yet.

I have one 20 dollar PayPal gift for the person that tells me my answer!!! I just want to drive.��

If i have left anything else out that is needed info, let me know!!! I should have the answer. I thought i knew this bad boy inside and out!

Thanks for the help people!

[5Toes]

Sounds like a coolant temp switch, since it is temperature dependent. Replace that, about $12 for a new one.

Also check your tps cold AND warm. My buddy had a tps that tested good cold but once warm would not work and it was a headache for a while until he figured it out.

let me know

[ct3155]

Well sir,

You have come across one of things i forgot to mention.... I do know the temp switch is good! I replaced that less than a year ago as well.. I did ohm test it out just to be double sure. I will edit my post. Thanks though!

I will deff test the switch cold and warm. Never thought of that!

[5Toes]

Okay, yeah I was surprised you didnt give it a plug since this issue is temp related!

Also I would go ahead and replace your oxygen sensor if you dont know the last time it was replaced. MPGs may go up!

I have a DIY in how to do it for $45 using a NGK ford sensor.

[jlevie]

I havent yet done a smoke test, no access to machine yet. I know most of these idle issues with the e30 are air leaks. But I have done a cruel test... While idling I sprayed starting fluid anywhere and everywhere there could be unmetered air entering. No beans.. Idle speed was solid. I doubted it would be that anyways as I had the motor out last summer and replaced every gasket known to man In it. Couldn't have gone bad yet...

All you probved by spraying carb cleaner around is that that isn't a big leak in a place that carb cleaner will work. The only way to tell if there are intake leaks is to have a shop run a smoke test.

My last hope is bad injectors? I am ordering them new 17lb ones as I type, from a member on here. Or maybe cap and rotor? It's two years old...

Installing 17lb injectors at this point would likely be a big mistake. Having the stock injectors professionally cleaned an flow tested would be a good idea. But I doubt they are causing this problem.

[K1CKBAC]

I've had the exact problem. Changed my throttle position switch located on the bottom side of the throttle body. Made sure its got a click when the throttle opens from idle. Starts up like a champ now. Good Luck.

[ct3155]

Thanks guys!! I'll look into all this advice more tomorrow when its light out again.

I'll update with what i find tomorrow!! :)

[Bretts85E30]

its not just a matter of making sure the tps has that click actually follow the bentley and measure resistance to make sure the switch closes at the points its supposed to and make sure the throttle stop hasnt been tampered with cuz that can have an impact on the tps operation too.

the idle switch should close at 0.20-0.60mm then just go full throttle to see if the switch closes there too 0 ohms should be measured at both when they close.

but the fact that it happens most at cold tells me that it might be IAT/CTS related since the dme doesnt factor in the o2 sensor until at operating temperature.

also just for shits and giggles check ur distributor cap/rotor, cps, and wires follow all inspection measurements from bentley.

and fyi vacuum leaks dont make themselves well known until warmed up unless ur hoses are totally trashed but every vacuum leak ive had didnt cause me any problems until at operating temperature when the metal expanded to the point where the leak opened wide to raise the idle high to the tune of 2k rpms at idle.

ive had a good cts that went bad in no time. take it out and check to see if it has excessive corrosion or even if the connector is corroded.

all the little things will add up and make u much more proud of the car in the end it just takes proper diagnostics and time lol the bentley is bible when it comes to diagnosing these cars but there are some things it doesnt cover that u have to figure out for yourself

have fun and hope ill be keeping track of your progress cuz im curious to see the outcome

[mrgraphics]

I have a similar problem. I have new CPS, temp sensors, and new O2 sensor.

Something I'm pursuing is the possibility that the injectors themselves are introducing air when cold. When the seals leak on the fuel rail, you'll get obvious fuel. But if they are leaking where they go into the intake, that's just air.

My theory is that when cold, the rubber is a tad bit smaller and allows air to pass. As it warms up the rubber expands and makes a better seal.

Purely hypothetical through . . . no proof that is is true. If this isn't it I'm going down K1CKBAC's rabbit hole.

[hendrixvodu]

i had this problem chased it for a long time and it ended up being my dme i had a 153 and apparently they are problematic, if you have a buddy with an e30 or something try pulling it to try, or upgrade to the 173 if you have a 153 they can be had for around $50-60 and you get the stop test so its an upgrade even if that wasnt the problem, also check your intake boot and the vac line under the throttle body with the "check valve" in it mine wasnt seperated but cracked very very badly, even oil dip sticks and oil caps can cause a vac leak

[E30-325iS]

You need to check the resistance of the temp sensor at the DME connector. Corrosion or a broken wire will significantly affect the temp reading that the DME.
Check C191 if you do not get the same reading at the DME and the sensor.

[Northern]

'88 should have a 173 dme anyways.

[ct3155]

Quick update,

I have ruled out throttle position switch. So temp didn't have any effect on that. This is what i did:

Since Bentley says there should be continuity at terminals 2 and 18 when the car is at idle, I just took the liberty to make sure there was. I unplugged the switch and put a jumper wire on the cars connector side on terminals 2 and 18, thus completing the circuit telling the car its at idle.

Turned the key, no luck. Problem was still there. Bad idle, so low.

But what i did find out is if i removed this jumper, it would idle at about 1200 with no stumbles.

End result of today:

-Runs great at warm idle - still, this wasnt the problem
-Runs great just off idle - Confirmed with jumper wire procedure, and just normal driving

Smoke test will take place tomorrow.


Also checked the O2 sensor according to Bentley. No fluctuating current until after a few minutes of running... Check out perfect, as it should! It is about two years old.


More ideas guys?

[ct3155]

Since Bentley says there should be continuity at terminals 2 and 18 when the car is at idle, I just took the liberty to make sure there was. I unplugged the switch and put a jumper wire on the cars connector side on terminals 2 and 18, thus completing the circuit telling the car its at idle.

Turned the key, no luck. Problem was still there. Bad idle, so low.

But what i did find out is if i removed this jumper, it would idle at about 1200 with no stumbles.


More ideas guys?

So this means the car only has the problem when the ECU is being told to idle.

Is this correct?

What could it mean?

[5Toes]

Sounds like your ICV is broken perhaps?

take a dime and drill a hole in it. Like a 3/16" inch hole. Place in your ICV (idle control valve) and try to start the car. Make sure the ICV is unplugged and open when you try this.

Also, my car had bad wiring for the coolant temp sensor. All it did was cause a high idle and rich running.. the DME thought the motor was super cold all the time. Everything else was really good condition and it idled like 1100 maybe 1200.

At this point sounds like an intake problem (ICV or vac leaks)