Need help with rough idle - Please

[MMiller]

Bump please.. On poor low rpm running

[JohnJL]

Check your timing, coil and plug condition?

[scarceller]

Have you tested the AFM 5vdc output signal? The AFM may have a bad carbon track. With engine not running measure the AFM output signal (0-5vdc) while you are pushing the barn door open. With door closed it should be down near 0vdc then push the door slowly open and look for a clean sweep from 0-5vdc. Test the 0.7 - 3.0vdc area real well as the AFM spends a lot of time in this area and it's here where the carbon track becomes compromised. 0.9-1.1vdc is the idle area.

Also, have you disconnected the O2 sensor to be sure the issue is not a bad O2 sensor?

[MMiller]

Originally Posted by JohnJL

Check your timing, coil and plug condition?

New plugs, Wires good, new coil ,cap,rotor....timing may need to look into.

Originally Posted by scarceller

Have you tested the AFM 5vdc output signal? The AFM may have a bad carbon track. With engine not running measure the AFM output signal (0-5vdc) while you are pushing the barn door open. With door closed it should be down near 0vdc then push the door slowly open and look for a clean sweep from 0-5vdc. Test the 0.7 - 3.0vdc area real well as the AFM spends a lot of time in this area and it's here where the carbon track becomes compromised. 0.9-1.1vdc is the idle area.

Also, have you disconnected the O2 sensor to be sure the issue is not a bad O2 sensor?

Good stuff Sal....I'm beginning to suspect the AFM so I will do as you discribe to check it. As far as the 02 sensor I don't think my 3.2 is currently running one. The PO put SSI on it and the bung one might use is capped and I have not find one so far anywhere else. Plus if I'm correct the plug on the left side of the motor where I think the O2 sensor plugs up is empty. How would you set up a 3.2 to work around not having a O2 sensor? The car has a history of performing well.

Thank you Guys for your input

Mike

[scarceller]

You don't need to do anything if the O2 sensor is gone. The DME program code simply runs in open loop mode just like the ROW (none O2 Sensor) cars. Just be sure those loose connectors especially the big round one is NOT touching ground, I'd ty-wrap it to a secure location so it does not bounce around.

I suspect you may have a faulty carbon track in the AFM. Do the 0-5vdc test with key in run engine not running. With the harness connected poke these lines and put the dmv across the ground and signal lines:


The Timing is NOT adjustable, it's built into the DME code and the distributor has no adjustment. I doubt it's a timing issue.

[MMiller]

Originally Posted by scarceller

You don't need to do anything if the O2 sensor is gone. The DME program code simply runs in open loop mode just like the ROW (none O2 Sensor) cars. Just be sure those loose connectors especially the big round one is NOT touching ground, I'd ty-wrap it to a secure location so it does not bounce around.

I suspect you may have a faulty carbon track in the AFM. Do the 0-5vdc test with key in run engine not running. With the harness connected poke these lines and put the dmv across the ground and signal lines:.

Will do and thank you.....really appreciate your help

Can you clarify this instruction please - With the harness connected poke these lines and put the dmv across the ground and signal lines.

Mike

[scarceller]

Originally Posted by Panerai

Will do and thank you.....really appreciate your help

Can you clarify this instruction please - With the harness connected poke these lines and put the dmv across the ground and signal lines.

Mike

Mike,

What I mean is leave the AFM harness connected as in the photo. Pull back the rubber boot but leave it connected. Then insert the '-' test lead into the back of the connector so that it makes contact with the ground pin inside the connector. Then do the same with the '+' lead on the signal line. You simply want to read the voltage across the ground and signal line right at the back side of the connector with the connector connected to the AFM. Remember key must be in 'RUN' engine off.

[MMiller]

I wanted to follow up and bring closer to this thread...

The high idle was indeed caused by the micro switch, once set correctly this fixed the high idle problem.

I however also had a very rich condition which was cause for the rough idle, poor performance at low speed and popping in tail pipe. This was due to a bad # 4 injector that was dumping fuel into the cylinder. In my first post I stated that I had sent the injectors out for refurbish so I was slow to suspect them as the source of the problem.

regards,