1983 944 Running rich, stumbling, hesitation.

[sdcali]

1983 944 stumbles, hesitation, rich-Update-She is running again! Problem solved.
1983 Porsche 944---140k miles

UPDATE
Scenario- Car started to run a little rough. Heard what sounded like a backfire, no noticeable power loss. Parked car and restarted, idles fine but when given gas, its stumbles, sputters, hesitates and has no power. Exhaust smells extremely rich at idle, yet engine does not miss at idle. Instead at 5% throttle, engine stumbles, sputters wont take gas. However at 20%, engine picks up gas and revs clean. Towed car.

Things that were done-
Gas change and treatment added.
New fuel filter.
New plug wire, cap & button
New spark plugs.
New O2 sensor.
New TPS
New Coolant Temperature Sensor
New DME relay
No discernable vacum leaks, checked with pressure using 10psi into manifold.
Tested with another Mass Airflow Sensor (MAS), no change. Adjusted wiper arm on current MAS, no change.
Tested with another DME engine control unit ECU, no change.
Ohm meter test on- Coil/wires, Injectors, Aux air valve, Throttle position open/closed, Engin cool sensor, all within range. Test were done at the ECU unit.
Checked engine timing, fine.
Fuel pressure is fine.
1983 Porsche 944- Hesitation, stumbling, running rich - YouTube

Solution to the problem-Checked reference sensor and it appeared ok other then a small crack on the connection(top). After I removed, I noticed the bottom (not visible from the top) was cracked, melted and missing a small piece. I replaced this reference sensor with one I picked up from AutoBahn used parts here in San Diego. Plugged it in and connected. Car started right up and the stumbling, hesitation was gone immediately. Fantastic!!!! After all the changes, replacements and adjustments that were made to the car prior to solving the initial problem, the Porsche now runs like a raped ape!!!! Please note- before I started this process of trying to fix the car, I had absolutely no experience in working with cars, much less an 83 944 Porsche. About a month of reading posts and finding time to work on the car, using what I have read from so many helpful individuals, I got her going straight. Everything listed above only cost me $420 (out of pocket, all Bosch).

[Chunkerz]

Are there any grooves in the AFM wiper strip? I had similar problems with my car and upon inspecting the AFM I found deep grooves in the strip. I bent the arm in a little bit and it ran much better after that.

[sdcali]

Tested w/new MAS-no change in problem.

[mikepellegrini]

The backfire then running bad sounds like one of the vacuum lines blew off. I don't know that the way you tested it would be conclusive. A vacuum gauge would provide more reliable results.

John's favorite vacuum gauge diagnosis site: How to Use and Interpret a Vacuum Gauge

Another potential would be a bad TPS. I know you replaced that but I've seen new parts that are defective.

A quick easy test is to disconnect the TPS and see if it revs normally.

[sdcali]

mikepellegrini- Thank you for the suggestions. Im going to take your advice and purchase a vacuum gauge. The link you forwarded to me is great!. Also, I will disconnect the TPS this afternoon and see if the revs returns to normal. Thanks again!

[Slam]

Disconnecting TPS was suggested in your other thread, too. Hmmm... How about checking your vac line routing? I thought something looked funny when I watched your vid. Check the lines coming off the throttle body. And put the cover back on the AFM and seal it up. If that was my car I'd see if raising the idle helped. That would give me a clue - is your AAV stuck?

[Ederd]

before
after

my 84 was having a similar problem, however i had to replace plugs and wires with Bosch parts and fixed my probs. I also at the same time flushed and reversed flushed my injectors as well as rotor cap and the prob went away.

[sdcali]

Slam----Got her running!!!! Reference sensor was cracked/damaged on the bottom side (not visible from the top). Thank you very much for your direction/help.

[Kevin.]

Awesome .. love it when a 'fix' is posted!

[sdcali]

Kevin-yea, Im so stoked!!

[Ederd]

Glad to hear it!

[Slam]

Cheers!

[mike leborgne]

Everyone, I have a 1987 924S with similar problems as mentioned in the orginal thread and have replaced many of the same parts. Can anyone help me with: What is a reference sensor ?? and where is it located on my car. Sorry for being so dumb, but eager to learn more about doing my own work. thanks in advance you guys are great.
Frenchy

[sdcali]

FRENCHY- Im not exactly sure where the Reference Sensor is located on an 87 924s, however Im guessing it's in the same or similar spot as the 944s. It is located on the back wall of the engine compartment, right under the windshield. Look at the place were you add oil to the car. The Reference Sensor should be behind (little to the right) and bellow the oil additive spout. They are connected to a wire and bracket that is attached to the back of the manifold. Follow them up to the plug in connections that are attached to the manifold. NOTE- There are 2 sensors. The One that is the easiest to remove is the reference sensor. The one that is behind (look exactly the same) and harder to remove is the speed sensor. Try the easy one first, thats what I did and it worked!
Click on the like bellow, it will show you what to look for.
Any special considerations for replacing the DME relay?

[sdcali]

SLAM-Thanks for all your help, really.

[mike leborgne]

sdcali,thanks for helping to locate the sensor, found it. WOW it the space limited. Thanks for the link it will help when I get the new sensor.
Frenchy

[Rowan]

I am also having a similar issue, my 87 p924s. runs fine at idle but when I put it in gear and drive there is a lot of hesitation. I out my foot in it and then it slowly, very slowly, gains speed. also around 2k rpm it starts to stumble and backfire it doesnt really clean up as it revs higher no power and it still backfires. I recently rebuilt the top end after braking the timing belt and have been chasing problems to get it back to what it used to be: all new vacuum lines, new cap rotor . I ordered new wires and plugs because they are ****ty plugs and the wires are also crapped out. there is also a sensor of some kind that is all melted (the car had a small engine fire) I cant find anything that it would connect to Ill upload a picture of the melted part.

[Rasta Monsta]

Rowan, recommend starting a new thread for help with your problem

[16again2009]

Rowan, the 1988 924S has a plug in near the back of the intake manifold that the wire you mentioned plugs into. The 1987 924S does not have it but it does have the wire. Your plug has no where to go. Don't worry about it.