M20 high idle ~1200 rpm

[bmwguy325is]

Okay I have looked and searched through all the threads with idle in them.
Okay 1987 325is miller maf kit and chip. I have repleced the IAC the hoses on the intake new intake boot new breather hose new O2 sensor checked the O2 relay(works).
So when the car is cold in the morning it idles where it should then after driving around it starts to idle at 1200. It doesnt hunt up and down its pretty steady. any ideas???

[matt0300]

Chip? Or maf?

[bmwguy325is]

I have the miller kit with the chip that makes it work

[Sagaris]

Four things

1) Does the throttle close completely at idle, or has the idle stop screw been tampered with? Verify this by removing the intake boot and visually checking it.

2) Check that the idle switch on the throttle position sensor works.

3) Check the voltage on the idle control valve harness

4) Check for intake leaks that could be giving the engine extra air.

[bmwguy325is]

Four things

1) Does the throttle close completely at idle, or has the idle stop screw been tampered with? Verify this by removing the intake boot and visually checking it.

2) Check that the idle switch on the throttle position sensor works.

3) Check the voltage on the idle control valve harness

4) Check for intake leaks that could be giving the engine extra air.

1. checked
2.yes did the continuity tests works
3.checked and all is what it should be
4.the intake itself has been resealed as in all new gaskets.
It idles where it should until the car warms up.
I am going to check the coolant temp sensor today

[bmwguy325is]

Checked TPS again. Checked the O2 sensore ohms and voltage all was good. Replaced the vacuum hose for the fuel pressure reg. Check and redid a few things on the intake piping.
Checked the Coolant temp sensor and it was not to far off of the ohms it should be. However starting the car without it it ran just fine. Then plugging it back in the car started to idle @1200. HMM
???????

[Sagaris]

The coolant temp. sensor will provide some cold running enrichment up to around 120 F after which the enrichment is pretty negligible. I would try disconnecting the battery and letting the ECU reset to see if things improve as the ECU gets a fair chance to re-learn the fuel trim.

[bmwguy325is]

The coolant temp. sensor will provide some cold running enrichment up to around 120 F after which the enrichment is pretty negligible. I would try disconnecting the battery and letting the ECU reset to see if things improve as the ECU gets a fair chance to re-learn the fuel trim.

I will do that. I can easliy unplug the ECU in the glove compartment. Thanks didnt think of that. Here goes!

[bmwguy325is]

Well that sure didnt work. The only thing that disconecting the battery did was make it steadily idle at 1300 now.
SO anymore ideas out there? Any mysterious vacuum lines I could have missed??

[jlevie]

In addition to the hoses you have replaced intake leaks are possible at:

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

A properly conducted smoke test will pretty quickly tell if there are any intake leaks.

[bmwguy325is]

In addition to the hoses you have replaced intake leaks are possible at:

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

A properly conducted smoke test will pretty quickly tell if there are any intake leaks.

Have not checked the throttle body gasket
I did put a new hose clamp on the brake booster but did not change to grommet going into booster.
crank case hose is new
check the evap hoses
new valve cover gasket the old one had an obvious leak LOL
I got a new o ring for the oil cap but not a new cap
I ussed a rubber cork to see if it was the sip stick tube
oil return I have no clue
Right now I am calling around to shops. Most wont touch it cause its modified. Even though all I want is a smoke check.

[bmwguy325is]

So as a test I tried this:
I unplugged the AF meter and started the car. Did the normal 1200 rpm idle.
I then plugged in a 153 ECU with the AF meter still unpluged and the car idle normally.
The miller chip is for the 525 ecu I have. Which I was told is the same as a 173 just it came from a California emissions car.
So maybe I have a bad ECU?

[bmwguy325is]

Come to the conclusion that the car has a software issue.