Trouble-shooting bad idle. Here's where I'm at...

[Warren N.CA]

Removed, inspected, cleaned ICV. It seems to move freely and looks good. It buzzes and vibtates satisfyingly when the ignition is on. Resistance across its terminals exactly as specified by Bentley. The voltage at the Harness connector seems OK, although one of the outer terminals measures only 5 Volts, as compared with 10 Volts on the other. I have discounted this difference as insignificant, am I wrong about this?

The throttle idle switch operates perfectly, and its applied voltage is as specified. (The full throttle switch operates, but has a resistance of around 100 Ohms, in the closed position, cometimes dropping as low as 25. This is not good, but I'm not having problems that I know of at full throttle.)

Next I plan to test the coolant temperature sensor for correct resistance. (Don't know how I'll get the connector off with the fuel rail in the way.)

Also, Im going to try to determine if it is running rich or lean by observing the behavior per Bentley.

Funny, just after starting, it idles fine for several seconds, then suddenly the idle speed drops way down and it tries to die, unless I catch it with the throttle.

Car is '90 325is

Any insights?

[western99]

Removed, inspected, cleaned ICV. It seems to move freely and looks good. It buzzes and vibtates satisfyingly when the ignition is on. Resistance across its terminals exactly as specified by Bentley. The voltage at the Harness connector seems OK, although one of the outer terminals measures only 5 Volts, as compared with 10 Volts on the other. I have discounted this difference as insignificant, am I wrong about this?

The throttle idle switch operates perfectly, and its applied voltage is as specified. (The full throttle switch operates, but has a resistance of around 100 Ohms, in the closed position, cometimes dropping as low as 25. This is not good, but I'm not having problems that I know of at full throttle.)

Next I plan to test the coolant temperature sensor for correct resistance. (Don't know how I'll get the connector off with the fuel rail in the way.)

Also, Im going to try to determine if it is running rich or lean by observing the behavior per Bentley.

Funny, just after starting, it idles fine for several seconds, then suddenly the idle speed drops way down and it tries to die, unless I catch it with the throttle.

Car is '90 325is

Any insights?

[Warren N.CA]

I believe they are one and the same.

[western99]

I once had a similar problem and it turned out that my fuel pump was going. The pressure would flucutate ever so often, making my idle inconsistent at times. May want to check that out.

Removed, inspected, cleaned ICV. It seems to move freely and looks good. It buzzes and vibtates satisfyingly when the ignition is on. Resistance across its terminals exactly as specified by Bentley. The voltage at the Harness connector seems OK, although one of the outer terminals measures only 5 Volts, as compared with 10 Volts on the other. I have discounted this difference as insignificant, am I wrong about this?

The throttle idle switch operates perfectly, and its applied voltage is as specified. (The full throttle switch operates, but has a resistance of around 100 Ohms, in the closed position, cometimes dropping as low as 25. This is not good, but I'm not having problems that I know of at full throttle.)

Next I plan to test the coolant temperature sensor for correct resistance. (Don't know how I'll get the connector off with the fuel rail in the way.)

Also, Im going to try to determine if it is running rich or lean by observing the behavior per Bentley.

Funny, just after starting, it idles fine for several seconds, then suddenly the idle speed drops way down and it tries to die, unless I catch it with the throttle.

Car is '90 325is

Any insights?

[Warren N.CA]

And the winner is... RICH. When the idle drops, it catches itself at about 300 RPM and come back up to around 1K RPM, and the strong smell of fuel is in the air.

Removed, inspected, cleaned ICV. It seems to move freely and looks good. It buzzes and vibtates satisfyingly when the ignition is on. Resistance across its terminals exactly as specified by Bentley. The voltage at the Harness connector seems OK, although one of the outer terminals measures only 5 Volts, as compared with 10 Volts on the other. I have discounted this difference as insignificant, am I wrong about this?

The throttle idle switch operates perfectly, and its applied voltage is as specified. (The full throttle switch operates, but has a resistance of around 100 Ohms, in the closed position, cometimes dropping as low as 25. This is not good, but I'm not having problems that I know of at full throttle.)

Next I plan to test the coolant temperature sensor for correct resistance. (Don't know how I'll get the connector off with the fuel rail in the way.)

Also, Im going to try to determine if it is running rich or lean by observing the behavior per Bentley.

Funny, just after starting, it idles fine for several seconds, then suddenly the idle speed drops way down and it tries to die, unless I catch it with the throttle.

Car is '90 325is

Any insights?

[Warren N.CA]

it would seem that the fuel pump is OK.

I once had a similar problem and it turned out that my fuel pump was going. The pressure would flucutate ever so often, making my idle inconsistent at times. May want to check that out.

[western99]

May want to check that out as well.

[Warren N.CA]

Vacuum leak would cause a LEAN condition, and I appear to be running RICH.

May want to check that out as well.

[Warren N.CA]

Tests good on cold engine 2300 Ohms, conforms to Bentley's spec.

Any hints from the fact that it runs fine for the first 5 or 10 seconds, and only after that the idle falls and then goes up, accompanied by fuel odors?

Bentley's table for rich cold idle also points to- Injectors, cold start system (I don't think this applies to i cars), fuel pressure too high, intake air flow restricted, ignition timing incorrect or weak spark. Where should I look first?

Removed, inspected, cleaned ICV. It seems to move freely and looks good. It buzzes and vibtates satisfyingly when the ignition is on. Resistance across its terminals exactly as specified by Bentley. The voltage at the Harness connector seems OK, although one of the outer terminals measures only 5 Volts, as compared with 10 Volts on the other. I have discounted this difference as insignificant, am I wrong about this?

The throttle idle switch operates perfectly, and its applied voltage is as specified. (The full throttle switch operates, but has a resistance of around 100 Ohms, in the closed position, cometimes dropping as low as 25. This is not good, but I'm not having problems that I know of at full throttle.)

Next I plan to test the coolant temperature sensor for correct resistance. (Don't know how I'll get the connector off with the fuel rail in the way.)

Also, Im going to try to determine if it is running rich or lean by observing the behavior per Bentley.

Funny, just after starting, it idles fine for several seconds, then suddenly the idle speed drops way down and it tries to die, unless I catch it with the throttle.

Car is '90 325is

Any insights?

[western99]

I am running out of options here..... Not sure what could be causing this? Are the injectors spraying correctly???

Removed, inspected, cleaned ICV. It seems to move freely and looks good. It buzzes and vibtates satisfyingly when the ignition is on. Resistance across its terminals exactly as specified by Bentley. The voltage at the Harness connector seems OK, although one of the outer terminals measures only 5 Volts, as compared with 10 Volts on the other. I have discounted this difference as insignificant, am I wrong about this?

The throttle idle switch operates perfectly, and its applied voltage is as specified. (The full throttle switch operates, but has a resistance of around 100 Ohms, in the closed position, cometimes dropping as low as 25. This is not good, but I'm not having problems that I know of at full throttle.)

Next I plan to test the coolant temperature sensor for correct resistance. (Don't know how I'll get the connector off with the fuel rail in the way.)

Also, Im going to try to determine if it is running rich or lean by observing the behavior per Bentley.

Funny, just after starting, it idles fine for several seconds, then suddenly the idle speed drops way down and it tries to die, unless I catch it with the throttle.

Car is '90 325is

Any insights?