3.2 Problem

[sf911]

Here's one for the Brain Trust . My 84 3.2 has developed a strange problem . When crusing at 2200 RPM with very little throttle my car starts to buck violently . To stop the bucking all I have to do is add a hair of throttle or let my foot of the gas . I have changed both flywheel sensors as well as the CHT sensor . The car idles great , starts great , and pulls very strong . It almost feels like the electrical signal to the DME is interupted at 2200 RPM because I see the gauges jump around . The only thing that I haven't checked is the Throttle Position Sensor on the right side of Throttle Body . Any help is appreciated .

[bickyd]

Originally Posted by sf911

Here's one for the Brain Trust . My 84 3.2 has developed a strange problem . When crusing at 2200 RPM with very little throttle my car starts to buck violently . To stop the bucking all I have to do is add a hair of throttle or let my foot of the gas . I have changed both flywheel sensors as well as the CHT sensor . The car idles great , starts great , and pulls very strong . It almost feels like the electrical signal to the DME is interupted at 2200 RPM because I see the gauges jump around . The only thing that I haven't checked is the Throttle Position Sensor on the side of Throttle Body . Any help is appreciated .

Air fuel meter wiper arm. Change your path.

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[sf911]

Sorry that I didn't mention it in my post but that was the first thing I tried .

[Goth]

Check the idle micro switch on the back of the throttle body. It should click at the slightest crack of the throttle.

[old man neri]

Originally Posted by sf911

Sorry that I didn't mention it in my post but that was the first thing I tried .

You opened up your air flow meter and looked at the little wiper arm path? What did it look like?

[911obgyn]

Throttle position sensor is just a switch for wide open throttle, doesn’t affect cruise. Check plug gap if you haven’t in awhile, I have found running issues because of worn electrodes, NGK plugs, don’t seem to last long. I switched to Bosch recently and time will tell.

[fiminod]

Thats the Porsche gods telling you to stop cruising at 2200rpm...

[sf911]

Idle switch was adjusted - no change to problem , wiper path changed - no change to problem , I can't see it being a spark plug problem but I will check . I 'll put on a new cap and rotor today and see what happens .

[proporsche]

Hi sf911 how old are your spark plugs and what kind do you use?
Ivan

[sf911]

I'm using Bosch plugs and they are about a year old .

[Rodsrsr]

DME realy could be beginning to fail. My car had a similar problem and it was the relay. Often overlooked if the car starts and runs, many assume the relay is fine, but they can cause intermittent, even temperature related problems. Pick up one of the new solid state units.

[proporsche]

ok on the spark plugs, what numbers? Have you check them lately and how many miles on them.
For example wr5dc..??

[john walker's workshop]

Unplug the O2 sensor and try it. Pop the distributor cap and see if everything is clean in there, as in not full of black dust, or carbon tracks.

[Lake Guy]

+1 Mr Walker

I had a similar problem. When I checked my distributor cap it was cracked. I replaced it and the issue was sort of resolved. I say sort of because the car really has never liked to run low RPM much. I was planning to do the air flow meter part next if I kept it as it was. But, it’s out for a full rebuild now so no point.

[DRACO A5OG]

After all the above. Find a fellow 3.2 and place your DME into donor car and try to repeat the symptoms.

DO NOT PLACE DONOR DME into your car!

If it repeats then send into Steve Wong for service.

[pete3799]

Check your motor and trans. mounts too.

[steely]

Originally Posted by fiminod

Thats the Porsche gods telling you to stop cruising at 2200rpm...

what gear were you in?

Agreed you can ignore idle micro and WOT switches since you weren't in either.

[sf911]

Today I changed the cap & rotor - No change to problem ,
replaced DME relay - no change to problem ,
disconnected idle switch - idle went up a little - no change to problem
disconnected throttle position switch - no change to problem
un-pluged O2 sensor - no change to problem

I'll try to find a donor DME on Monday and give that a try .

[Tea Tray]

Take a look at your engine electrical connections. This is my 87 3.2 connector. Also check engine grounds. RPM specific issues can also be caused by vibration and junky connections.

[sf911]

Will any DME work ? I have a friend with a 87 . mine is a 84 .