Stumbling/Stalling during Idle

[Mattglas]

Up until last month my car ran perfectly, it idled at 750 and never stumbled. However, out of nowhere it started to stumble and then stall whenever it idles (hot or cold). I've thrown everything I can think of at it and nothing has worked. Does anyone have any sugestions?

Here's a list of the things I've done:

• New gaskets/o-rings on top end of engine
• Readjusted the valves
• Adjusted the timing
• Checked the spark plugs
• Checked the dwell swing
• Checked compression (115psi cold on everyone)
• Checked voltage to idle motor (11v)
• Checked idle ecu and motor by removing the plug closest to the center of the car and having the idle spike to 2200
• Checked battery voltage at idle (13.5

to 14.5)

This is what happens when the car idles:
https://drive.google.com/file/d/0B2N...w?usp=drivesdk

Don't know if its related but is this amount of smoke coming out of the oil filler normal?
https://drive.google.com/file/d/0B2N...w?usp=drivesdk

[Bitsyncmaster]

Does it just the idle problem? Does it run normal when driving?

I would do a fuel pressure check.

Sudden problems could be the fuel pump but that would also show a problem when driving.

[Mattglas]

Does it just the idle problem? Does it run normal when driving?

I would do a fuel pressure check.

Sudden problems could be the fuel pump but that would also show a problem when driving.

It runs fine while driving, doesn't misfire or hesitate at all. I replaced the fuel pump a few months ago with the updated combo one. Relating to fuel, I have 93 octane in the tank. Not sure if that makes a difference. I just recently found out that it requires 87.

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[Bitsyncmaster]

It runs fine while driving, doesn't misfire or hesitate at all. I replaced the fuel pump a few months ago with the updated combo one. Relating to fuel, I have 93 octane in the tank. Not sure if that makes a difference. I just recently found out that it requires 87.

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Now I don't think the fuel is the problem. What voltage does your car hold at idle speed?

[Mattglas]

Now I don't think the fuel is the problem. What voltage does your car hold at idle speed?

It starts at 14.5v and slowly decreases to 13.5v and then goes back up to 14.5v. I have specialtautos 120 alternator.

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[Bitsyncmaster]

Does the voltage drop to 13.5 because the RPM is dropping? Just looking for clues to help find your problem. Seems odd it starts out at 14.5 volts unless your engine RPM is higher during that time.

[Mattglas]

Does the voltage drop to 13.5 because the RPM is dropping? Just looking for clues to help find your problem. Seems odd it starts out at 14.5 volts unless your engine RPM is higher during that time.

The rpm stayed between 600 and 725 the whole time I was testing. I don't really remember if it was related to the rpm droping. I think the voltage was just decreasing and increasing

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[Bitsyncmaster]

I looked back at your video and it looked like the oil pressure gauge was jumping without the RPM changing much. How old is your battery? I'm still just guessing at what may be the problem. An idle only problem like you have is strange since you have verified the mixture (dwell) is good.

One thing I just thought of is I have seen some RPM relays have marginal connections on the second output which drives the lambda system. But that problem is only with RPM relays that have the twin contacts on the relay. I would just jumper the RPM relay (three pin jumper) to test if the problem goes away. That problem may not show up at higher engine RPM.

[Mattglas]

I looked back at your video and it looked like the oil pressure gauge was jumping without the RPM changing much. How old is your battery? I'm still just guessing at what may be the problem. An idle only problem like you have is strange since you have verified the mixture (dwell) is good.

One thing I just thought of is I have seen some RPM relays have marginal connections on the second output which drives the lambda system. But that problem is only with RPM relays that have the twin contacts on the relay. I would just jumper the RPM relay (three pin jumper) to test if the problem goes away. That problem may not show up at higher engine RPM.

The battery is around a year old. The jumping oil pressure is also a new occurrence, started around the same time. Though, I thought it was due to the original oil pressure sender that my car has. For jumping the rpm relay I would jump pins 30, 87, and 87b right?


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[Bitsyncmaster]

The battery is around a year old. The jumping oil pressure is also a new occurrence, started around the same time. Though, I thought it was due to the original oil pressure sender that my car has. For jumping the rpm relay I would jump pins 30, 87, and 87b right?


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You would jump the large brown wire (+12 volts) to the white/purple (pump) and the double yellow/red (lambda).

I don't look at pin numbers much anymore.