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?

[Warren N.CA]

Looks like I'll be having the opportunity to learn how to test injectors, soon.




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

[ryan roopnarine]

have you taken a gander at this? perhaps its FPR related, rich doesn't automatically mean that fuel supply is "proper" If i were you, and I really wanted to get this car straightened out, post haste, I'd build a 10 or 15 dollar fuel pressure gauge. here's something from our good friends sean and johan that you might be able to adapt to your application.

http://bmwe32.student.utwente.nl/sean750/fuel_pressure_regulators/FuelPressureRegulators.htm

[Warren N.CA]

the most logical next step out of the five items remaining on the table. Fuel pressure could be too high. I'll look at the URL. i made my own pressure bleeder for the hydraulics, so why not.



have you taken a gander at this? perhaps its FPR related, rich doesn't automatically mean that fuel supply is "proper" If i were you, and I really wanted to get this car straightened out, post haste, I'd build a 10 or 15 dollar fuel pressure gauge. here's something from our good friends sean and johan that you might be able to adapt to your application.

http://bmwe32.student.utwente.nl/sean750/fuel_pressure_regulators/FuelPressureRegulators.htm

[ryan roopnarine]

the url doesn't have any information about building one. paul shovestul (sp?) showed me his home made one, and i bastardized it to make it as cheap as possible....you might actually be able to buy a fuel pressure gauge for $15, which i'm sure would be the preferrable solution. Go to lowes/home depot. Ask for somebody that deals in well equipment and irrigation, and tell them that you want a water intended pressure gauge that goes to 100 psi, with the npt/aircompressor style fittings. find the cheapest one. walk over to the air compressor section. Look at the bins of fittings they have. take the gauge out of the box, and start trying out fittings until you find one size that fits. I used two nipples, one in each side of the gauge, some hose clamps, and the existing hose on the fuel system. This cost me about $9. was going to buy a proper one, but there were no busses running by discount auto parts or autozone on saturday, and both were at least 5 miles away.


the most logical next step out of the five items remaining on the table. Fuel pressure could be too high. I'll look at the URL. i made my own pressure bleeder for the hydraulics, so why not.

[Warren N.CA]

saving $6. Guess I'll pick one up at AutoZone, tonight. That was a good URL, and showed me how to change the pressure regulator.


the url doesn't have any information about building one. paul shovestul (sp?) showed me his home made one, and i bastardized it to make it as cheap as possible....you might actually be able to buy a fuel pressure gauge for $15, which i'm sure would be the preferrable solution. Go to lowes/home depot. Ask for somebody that deals in well equipment and irrigation, and tell them that you want a water intended pressure gauge that goes to 100 psi, with the npt/aircompressor style fittings. find the cheapest one. walk over to the air compressor section. Look at the bins of fittings they have. take the gauge out of the box, and start trying out fittings until you find one size that fits. I used two nipples, one in each side of the gauge, some hose clamps, and the existing hose on the fuel system. This cost me about $9. was going to buy a proper one, but there were no busses running by discount auto parts or autozone on saturday, and both were at least 5 miles away.

[Bill R.]

make an adapter for use with your car. no big deal... For what its worth i'll bet you that you don't have too much fuel pressure.. I haven't seen it yet on a bmw






saving $6. Guess I'll pick one up at AutoZone, tonight. That was a good URL, and showed me how to change the pressure regulator.

[Warren N.CA]

Vacuum leak. Even though I thought I had looked at everything carefully, I missed something. Found it when I started nosing around the pressure regulator. The hose from the manifold to the FPR came off the manifold end when I pulled it, and looked good. But when I tried to get it off the FPR, it was bonded in place by heat from the cooling system just below it, I think. Putting a little downward pressure on the hose, at the nipple revealed a lateral crack on top. Slightly more downward pressure and the crack got bigger. So I tore it off, cleaned up the nozzle, and went to Kragen for a piece of hose. When I first started it up, it was better- no more hunting, but still a pretty crappy idle. But the longer it ran the better it got. Then I remebered that whenever I change the chip, the idle is bad for about 30 minutes, until the DME adapts. So I took it for a drive, and in a few minutes everything was back to normal. Could still have a cold idle problem tomorrow, but I really think not.

Thanks to all who helped with advice and hand-holding.




make an adapter for use with your car. no big deal... For what its worth i'll bet you that you don't have too much fuel pressure.. I haven't seen it yet on a bmw