3.2 DME - idle adjusting - per Sept Pano

[larrym]

OK - it was a great September Pano article by Alan Caldwell on getting stable idle on 3.2 dme cars

- but - we guys with 3.2 conversions REALLY need to know - - the rest of last paragraph

what are those secret jumper settings that allow us to bypass the O2 sensor requirement?

- where is that info besides in the nearly unobtanium factory manual which most of us conversion guys do not posess or have access to ?

[86 911 Targa]

Originally Posted by larrym

OK - it was a great September Pano article by Alan Caldwell on getting stable idle on 3.2 dme cars

- but - we guys with 3.2 conversions REALLY need to know - - the rest of last paragraph

what are those secret jumper settings that allow us to bypass the O2 sensor requirement?

- where is that info besides in the nearly unobtanium factory manual which most of us conversion guys do not posess or have access to ?

Here ya go............

Inside the engine compartment relay cover.

And, check my thread of 10/3/2010. "Another Idle Issue"

Good luck,

Gerry

[MH911]

Hmmm. I didn't get my September issue. I'm very interested in this article.

[88911coupe]

What is that socket used for normally? I've always looked at it and thought something needs to be plugged in there.

[rusnak]

The jumper only disables the icv, which would compensate for the idle screw adjustment by letting more or less air past the throttle. To disable the O2, you merely disconnect it, as when adjusting CO%.

[MH911]

Well, my Sept. issue arrived yesterday. I read through the article and it seems simple enough to do for a very low experienced wrench like my self. So, where can I locate one of these exhaust system analyzer and am I going to pay an arm and a leg for one? Is it something one can rent? Is there another way to take this reading?

Why am I looking into this?

I have a idle surging issue when engine is hot. When I disconnect the O2 Sensor, then the engine will idle just fine. My mechanic said that the O2 sensor I replaced in April was defective. I have the old one installed now ( still surging ) and waiting for a replacement for the defective one. I would like to get a proper adjustment after the replacement O2 sensor is in place.

Thanks everyone for any help on this issue.

[rusnak]

Hot surging can be a vacuum leak.

You might want to rent or borrow a co% meter. The mixture adjustment only applies to cold startup. Once in closed loop, really there is no adjustment.

[RSM-M491]

I did the idle adjustment today, question, when I put the jumper in place the car started to idle roughly. Is that normal? I also had to turn the screw a good amount to get the idle to change!

(Counter clockwise)

Thanks!

Rod

[MH911]

I'll start looking for a leak when I get the replacement O2 sensor installed.
In the mean time, I'll be using my search button on how to find leaks. :-)

[rusnak]

I would try to find the leak first. The reason is that if you find and seal off vacuum leaks, then the surging will go away, and you'll find that the O2 sensor is good. The reason surging stops when you disconnect the O2 sensor is that it's running in open loop, on a preloaded map. No surging because the dme is not measuring false air.

[RSM-M491]

I tried to adjust the idle this weekend, waited for the car to warm up, put the jumper in, and turned the screw counter clock wise, I gotta tell you, not sure it really worked! Could there be another issue? Also, when I put the jumper in place it started to idle even rougher! SHould it do that when I hook in the jumper?

Also, my throttle cable seems to be sticking sometimes, lubed everything under the rear deck, any other suggestions? Or do I need a new cable?

THANKS!

Rod

[rusnak]

See if the icv is resting in the half open position.

[RSM-M491]

Ok, HOW do I do that? I am new at this, so I apologize. I am great on British cars, but learning my away around on the 911.


Thanks!

Rod

[martyk]

The article in Pano on the idle adjustment was good as far as it went. It did not emphasize the following though.

A very basic assumption prior to setting the idle (i.e.making final idle adjustments) is that all other aspects of your engine and related systems are operating correctly, within acceptable ranges.

For example:

The state of tune should be good, including valves properly adjusted and cam timing correct and of course, reasonable compression and low cylinder leakage.

Other fuel injection components functioning correctly - especially, not to overlook the head temperature sensor and be on the lookout for vacuum leaks. System fuel pressure is also critical.

The explanations contained in this article are fairly good, as far as they go. The big problem I see is that idle problems are not always related to idle adjustments.

[rusnak]

I think it might help to post excerpts from the article at this point for clarity. Too much clouding of the issues going on here.

[RSM-M491]

Any idea as to why when I put the jumper in, the idle got more rough?

Thanks!

Rod

[davidbrain]

Hi. I have a 3.2 ,I live in Australia. My car starts first time every time. But idle surges approx 10-15 times when started, I assume until it gets warm, then it settles to around 1000rpm. After driving for some time it seems to do the same thing when I stop at traffic lights. Most of the time I give the accelerator a rev and the engine settles to around 1000 revs . I have changed the O2 sensor and fiddled witht the idle but no change. I am going to change the head temp sensor as well (just arrived from Pelican) but I don't think this will work as most of what I read says that if this unit is faulty it usually only affects cold starts, engine won't start ? Anyway I will give it a go and let you know what happens.

[Rot 911]

I suspect there are going to be a few 3.2's then end up running worse then they did before people read this article.

[kodioneill]

The air flow meter can cause problems. Do a search for adjusting the AFM. There is a potentiometer inside that can wear out and a small adjustment that can be made to correct it . Also to check for vacuum leaks, spray small spurts of brake clean around the intake manifolds and see if the idle changes. My injectors were bad and I replaced them it made a world of difference.

[rusnak]

Originally Posted by davidbrain

Hi. I have a 3.2 ,I live in Australia. My car starts first time every time. But idle surges approx 10-15 times when started, I assume until it gets warm, then it settles to around 1000rpm. After driving for some time it seems to do the same thing when I stop at traffic lights. Most of the time I give the accelerator a rev and the engine settles to around 1000 revs . I have changed the O2 sensor and fiddled witht the idle but no change. I am going to change the head temp sensor as well (just arrived from Pelican) but I don't think this will work as most of what I read says that if this unit is faulty it usually only affects cold starts, engine won't start ? Anyway I will give it a go and let you know what happens.

Could be a vacuum leak. Check the hoses and intake gaskets.