AT wits end- 85 3.2 rough idle - Page 3

mackskibum · 04-24-2008, 06:55 PM

oil cap is new.

stlrj · 04-25-2008, 04:42 AM

Assuming it was not like this earlier. When did this condition first appear?

DRACO A5OG · DRACO A5OG's Garage

Well Mack..,

I had taken my baby into my Wrench for a DDD I did on her and "WIIT" asked him to adjust my Air/Fuel Mixture.

He stated something was wrong with my Air Flow Meter it was not functioning properly, he failed to adjust while I was watching him.

Does anyone know if the AFM can be serviced?

Lately, I have been adjusting by feel by watching for any sub-dips and/or drops in idle to increase richness but if my AFM is malfunctioning this is just futile.

mackskibum · 04-25-2008, 11:41 AM

stlrj- this appeared before my top end job a year and a half ago. I was convinced that the issue was more mechanical since I was using a pile of oil and the leakdown was for s**t. Since re-installation I have been nipping at this trying to nail down the problem.

Draco- its hard to tell what the issue is with the AFM except that the possibility exists that the resistance trace on the inside of the meter has some wear. There are a couple of threads about how to manage a move of the wiper inside the AFM to correct. On mine, I only have an issue at idle- everywhere else in the power band I am fine and on the money mixture wise.

DRACO A5OG · DRACO A5OG's Garage

Quote:

Originally Posted by mackskibum

Draco- its hard to tell what the issue is with the AFM except that the possibility exists that the resistance trace on the inside of the meter has some wear. There are a couple of threads about how to manage a move of the wiper inside the AFM to correct. On mine, I only have an issue at idle- everywhere else in the power band I am fine and on the money mixture wise.

Mine too, only at idle it is rough fluctuating at 820-880 RPMs but runs like a bat out of hell. Normally at this RPM's it should be smooth a purr but it seems so lean.

craigyirush · 04-25-2008, 02:59 PM

FWIW I had a long-term (lasted over a year) rough idle problem - usually when the engine was warm.

This lasted through two tune-ups and one new ICV valve.

Finally, when I took it back to my shop complaining of bad gas mileage, they put the sniffer on it and adjusted the DME unit - not sure what they did but it involved putting a tool of some sort in the back of it.

Once this adjustment was made, the idle smoothed right out and the fuel consumption improved.

Again, I have no idea what was done to the DME!

burgermeister · burgermeister's Garage

i think the DME has some kind of rotary fuel quality switch that dials back the timing and / or changes base mixture ... I either read about it in the Bentley or in one of the informative and entertaining SteveW / Loren posts ...

db_cooper · db_cooper's Garage

Yes, there is a switch in the control unit. See the site:

http://www.911chips.com/fuelsys.html

Adjustments should be done with care. Most positions retard the timing and lean out the mixture. You best would want to confirm it is in the US spec. It might have been mis adjusted somewhere else too.

craigyirush · 04-26-2008, 04:49 PM

Thanks for the link.

The mechanic did it with the car running and there was an immediate improvement in the idle and the various readings (CO, etc). The improvement in the idle and the fuel consumption has lasted for a few months now.

DRACO A5OG · DRACO A5OG's Garage

Update:

Today I rasied teh idle to keep her at 880RPMs and leaned her out to keep from sub-dipping. I hope it works.

mthomas58 · 05-29-2009, 05:21 AM

I am having a similar rough idle following my recent engine swap. Engine idles at approx 900 RPMs but there is a distinct rough idle pulse that you can feel by putting your hand at the exhaust pipe. Engine runs fine otherwise and pulls strong. Engine does want to die when oil cap is removed. Have appt Monday at the Dealership to troubleshoot - tech says that he will start with the fuel mixture.

mthomas58 · 06-01-2009, 08:15 AM

Quote:

Originally Posted by mthomas58

I am having a similar rough idle following my recent engine swap. Engine idles at approx 900 RPMs but there is a distinct rough idle pulse that you can feel by putting your hand at the exhaust pipe. Engine runs fine otherwise and pulls strong. Engine does want to die when oil cap is removed. Have appt Monday at the Dealership to troubleshoot - tech says that he will start with the fuel mixture.

Problem diagnosed at cyl #2. Orig though to be a bad plug or plug wire. Tech replaced my new NGK with a Bosch but no change. (He doesn't like NGK....says it stands for No Good Kind) Turns out I have a slight intake leak at #2 as RPM would increase with throttle cleaner spray. He suggested replacing the gaskets on 1, 2 & 3.