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-   -   Need help with rough idle - Please (http://forums.pelicanparts.com/porsche-911-technical-forum/733666-need-help-rough-idle-please.html)

MMiller 03-11-2013 05:58 PM

Bump please.. On poor low rpm running

JohnJL 03-11-2013 07:44 PM

Check your timing, coil and plug condition?

scarceller 03-12-2013 03:58 AM

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 03-12-2013 07:08 AM

Quote:

Originally Posted by JohnJL (Post 7323292)
Check your timing, coil and plug condition?

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

Quote:

Originally Posted by scarceller (Post 7323624)
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 03-12-2013 07:35 AM

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:
http://forums.pelicanparts.com/uploa...1363102506.jpg

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 03-12-2013 08:11 AM

Quote:

Originally Posted by scarceller (Post 7323914)
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 03-12-2013 09:10 AM

Quote:

Originally Posted by Panerai (Post 7323983)
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 05-20-2013 05:12 AM

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,


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