Cold Idle

[jsloden]

Hey guys, having a real problem with the cold idle. In order for the car to idle when it's cold you have to keep your foot on the gas. If you don't it will die. This usually takes a couple of minutes. As soon as the temp needle starts to come up it's like a switch is tripped and it idles perfectly. I was leaning towards cold start valve? This was replaced within the last year though.

Thanks,
Justin

[dmcnc]

Cold start valve doesn't affect your idle while cold; It would flood your car if it stays open or a closed one would require an extended crank.
Check your Idle Speed Regulator operation by pulling the Idle ECU plug facing the center of the car. If your rev's jump significantly, then you're ISM is good. If it doesn't make a difference in RPMs, we'll keep troubleshooting from there.

[David T]

Cold start valve doesn't affect your idle while cold; It would flood your car if it stays open or a closed one would require an extended crank.
Check your Idle Speed Regulator operation by pulling the Idle ECU plug facing the center of the car. If your rev's jump significantly, then you're ISM is good. If it doesn't make a difference in RPMs, we'll keep troubleshooting from there.

During cold start-up the one thing that has the biggest effect is the Control Pressure Regulator aka warm-up regulator. It acts like the choke on a carbureated car and rich-ens the Air/Fuel ratio till the motor warms up. You test the CPR by hooking up a pressure gauge and watching it as the motor warms up to confirm proper operation of the CPR. If necessary they can be rebuilt.

[jsloden]

Ok, pulled the plug on the isr. Didn't make a difference. The car starts up easily the first time when cold. If you kill it before it warms up then you you have to give it a lot of gas to get it to restart. As soon as the needle temp needle it's like a switch is flipped and it idles perfectly. Both the isr and the warm up regulator are only a few months old. They were both replaced by dmch back in the summer. how would I check to see if they're getting voltage. Would the key have to be on, car running, etc...?

Thanks

[dmcnc]

Ok, pulled the plug on the isr. Didn't make a difference.
- just to make sure, you pulled the plug on the ECU computer - right?
Screen Shot 2018-01-07 at 12.29.11 PM.jpg
If you pull this plug with the car running, your idle should spike significantly (and confirms your idle speed reg is good).

The car starts up easily the first time when cold. If you kill it before it warms up then you you have to give it a lot of gas to get it to restart.

- The 12Vs from the start-up circuit (during crank) will warm up the thermotime switch (TTS) and shut the Cold Start Valve shortly after the first crank.This prevents you car from "flooding."

Both the isr and the warm up regulator are only a few months old.
- My first DMCH ISR came from a bad batch of Chinese sourced units, and failed within a few months. Should you have to replace this one, consider getting an OEM Bosch replacement or something like this - http://www.ebay.com/itm/like/152587819390?ul_noapp=true. Otherwise it should still be on 1-year warranty?

how would I check to see if they're getting voltage.


- Both plugs should get 12V with the key on run.

[jsloden]

Okay, got 12 volts at the idle control valve but nothing at the warm up regulator. Do you know which pin I could check at the computer and where I could check it at the bulkhead connectors?

Thanks

[DMC5180]

Turn the key to Run without starting and put your hand on the ISM. Does it vibrate?


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[jsloden]

Okay, turned the key to run and nothing vibrates. I was tracing the yellow/red wire that goes to the warm up regulator. It goes back through the bulkhead in the blue connector. I unplugged the blue connector and that pin is not getting any voltage. I went back to the fuse box to check the number one fuse which is the one that the warm up regulator in on. The fuse is good. I then noticed that it looks like that yellow/red wire runs through the rpm relay. Does the rpm relay turn the warm up regulator on and off? If so, this could be a problem. I checked for voltage at the rpm relay with the key on and it isn't supplying any voltage to the yellow and red wire.

[dmcnc]

With the relay plugged in, can you confirm the RPM relay is getting power (green cable) with key on Run and nothing is coming out the WUR cable pin (yellow/red). Do you have an extra RPM relay for testing?

Okay, turned the key to run and nothing vibrates. I was tracing the yellow/red wire that goes to the warm up regulator. It goes back through the bulkhead in the blue connector. I unplugged the blue connector and that pin is not getting any voltage. I went back to the fuse box to check the number one fuse which is the one that the warm up regulator in on. The fuse is good. I then noticed that it looks like that yellow/red wire runs through the rpm relay. Does the rpm relay turn the warm up regulator on and off? If so, this could be a problem. I checked for voltage at the rpm relay with the key on and it isn't supplying any voltage to the yellow and red wire.

[jsloden]

Yes, with the key on the rpm relay gets voltage, the green wire. But there is nothing at the yellow and red wire. Unfortunately I don't have another rpm relay.