'84 3.2 sputters sporadically

[ruby911]

About a week ago, my 3.2 began showing a slight hesitation sporadically as I ran up through the RPMs. It did not do it every time, only sporadically. Well, it appears to be getting worse and the slight hesitation has turned into a slight sputter above 3500 RPMS. The car still feels like it pulls reasonable well and the power seems OK.

I tried searching the forum and have been reading some recent threads about what seems like similar problems, but seem to be more unclear as to what the problem could be. I removed the AFM and cleaned a nice layer of black oily gunk out of the airway and adjusted the contactors to have a clean contact patch. This helped responsiveness, but not my problem.

Is this as simple as 'go ahead and do a tune up" (rotor, cap, wires, plugs etc)? Also, I though the Motronic maintained lean/rich and there was no way to adjust this - am I way off here?

I am trying to go after the higher probability issues first rather than the shotgun approach of throw everything at it - Thanks for any guidance you may have.

Farrell

[daber88]

I would try cap, rotor, and plugs if they haven't been done in a while. My 87 3.2 started having a slight hesitation mostly under load on my trip home from buying it. I replaced the cap, rotor, and plugs as well as fuel filter which solved my hesitation.

Also, which may pertain to you since you are in Marietta, my car started to have a little miss and sputter earlier in the week. Noticed it after it sat in the rain all afternoon one day. I took off the cap and there was moisture in there! Dried it all up and put it back on and the car ran great! So, you might just want to take a look under your cap if the car has been out in the rain this week.

Derek

[aston@ultrasw.c]

Start with the basics: plugs, wires, coil, distributor, fuel filter, fuel pressure, air filter etc....

Then the fun starts!

You were correct to take a look at the AFM they are notorious for causing probs.

Also think about:

Vacuum leaks, rubber elbow, manifold gaskets

Injectors: flow rate and weeping

Idle control valve

Throttle position micro switches

O2 sensor

Injector wiring

crankshaft speed and position sensors

CHT sensor

DME, cold solder joints, damaged components

I spent 6 months and a whole pile of parts to figure out why my 3.2 was hesitating. It was very frustrating but I learned a lot!

[ruby911]

Thanks for the feedback guys, off I go to begin my tune up.

[ischmitz]

Sounds like you are getting good advice already. In addition to what aston said I would try to classify the behavior more:

If the frequency of the event gets higher it could be something like a boken solder joint that gets worse over time, broken wire in one of the sensors, bad connector, etc. I'd call this case #1 and these are the hardest to track down.

If the events gets more pronounced with time this points more to a mixture-related cause such as: The vacuum leak is getting bigger, the O2 sensor is getting more unresponsive with time, etc.

The main difference is that case #1 happens sporadically with perfect running reriods in between while case #2 usually is something that gets progressivly worse with time but never gets better again.

Just to give you an example: I had something very similar where my 3.6 all of a sudden had a very slight hesitation. It happened for a split second the first time and then again about a month later. The first time I didn't think much of it. Well eventually it became so bad that it almost left me stranded a 100 miles away from home. At the time I was 100% convinced it was something where the entire DME stopped working. The car lost all power while crusing on the highway and it felt like I had turned the engine off.

It turned out to be a loose/poor connector for the O2 sensor and a poor connector to the AFM. I found it by having the Bosch diagnostics tool in the passenger seat for several month. When it happened I saw the O2 signal went to 0. It caused the mixture to go so much out of spec that the engine acted like there was no fuel or no spark.

Good luck,
Ingo

[aston@ultrasw.c]

We should really start a wiki for - my 3.2 isn't running right.

In my case the engine would hesitate under full load...sometimes. It would heal itself only to fall sick again a couple of weeks later. Sometimes it almost felt like it was oscillating: cutting in and out as the car tried to accelerate.

When I finally figured it out, it was the harness powering the injectors. The harness had been folded in half and squashed into a clamp. It may have been done at the factory. Over enough time the insulation broke down. At high torque loads it would pull on the wiring and create a short.

This would be a case #1 prob above.

A couple of months later I was looking through the big stack of receipts from the PO and guess what, he had replaced all the same ****e I had trying to fix the same prob.

[ruby911]

All fixed now, and runs like mad. New Magnecor wires, rotor, cap plugs, cleaned and lubed the ICV and AFM. Thanks for the feedback - another project marked off the list.

Thanks to all, Farrell

[kidrock]

Great news, Farrell. It always seems a bit sweeter when you do it yerself...a true Labor of Love.

I hope you purchased a spare DME relay with all the other stuff

[scarceller]

Try this simple test first: disconnect the O2 sensor and see if this helps. I have seen bad O2 sensors cause your issue and it's very easy to rule this out, just unplug the O2 and run it.

The O2 sensor is not required for these cars to run, it simply fine tunes the mixture to help maintain a 14.7AirFuelRatio but if the sensor goes bad it can really wreak havoc on the mixture.

[ruby911]

Thanks Sal, but the probem has been cured.