82/3 944 with annoying stutter

[Kiwi944]

My 82-build 944 has an annoying stutter at 2800 rpm and above when on a partial throttle opening, but only when it is warm, and if I give it full throttle.

When the engine is first stated it's fine for the first couple of minutes, and if I switch it off when it is hot, and restart after a minute or so, when everything is still warm, again, for the first couple of minutes it is fine, then the hesitation reappears.

So far I have tried 3 airflow meters (and the one which on it has been tested using the Clarks Garage instructions with a 9v battery and a multimeter and appears perfect).

I have replaced spark plugs, fuel filter, reference sensors, temperature sensor, J-boot and put some injector cleaner through the fuel system, and none of this has made a bit of difference...

I am not sure where to go to next, and the thing which has me baffled is that on full throttle, it is perfect.

Have I missed something blindingly obvious?

[dgcantrell]

Check the plug wires. Especially the resistance of those damned resistor "ends" that fit down over the spark plugs. I had a slight miss every so often on my 928 one time and it was one of those. I eliminated them from the 944 by going with Magnecor wires. Never had an issue since. That was 1998ish.

[JD159]

Not too familiar with the older models, does it have an o2 sensor?

Doesn't the DME skip the o2 sensor when on WOT and only use the input on partial throttle? That info was given to me by Russel Berry

[Kiwi944]

Originally Posted by JD159

Not too familiar with the older models, does it have an o2 sensor?

Doesn't the DME skip the o2 sensor when on WOT and only use the input on partial throttle? That info was given to me by Russel Berry

I don't think so. If it does, i can't find it!

[J1NX3D]

RoW cars dont have O2 sensors. I clarified that with Russel when I got my 944max chip.

[Project560]

I am no expert but I am working through a number of things on my own 1984 944 project. A few items that seem to come up quite often on forums are the DME temperature sensor and throttle position switch. I haven't had a problem with the DME temperature sensor myself, but I wonder if this may not be providing the right temperature signal to the DME/ECU. Others with more experience with this may be able to weigh in with better information.

My other thought is the throttle position switch. I just found that mine is full of oil residue and is not providing the right readings. If this is not operating properly on your car, then it could also be misleading your DME/ECU.

Clark's has good troubleshooting information to check both of these. It doesn't cost anything to check them. Good luck!

[Kiwi944]

Originally Posted by Project560

I am no expert but I am working through a number of things on my own 1984 944 project. A few items that seem to come up quite often on forums are the DME temperature sensor and throttle position switch. I haven't had a problem with the DME temperature sensor myself, but I wonder if this may not be providing the right temperature signal to the DME/ECU. Others with more experience with this may be able to weigh in with better information.

My other thought is the throttle position switch. I just found that mine is full of oil residue and is not providing the right readings. If this is not operating properly on your car, then it could also be misleading your DME/ECU.

Clark's has good troubleshooting information to check both of these. It doesn't cost anything to check them. Good luck!

Thanks for this. I have replaced the temp sensor, will have a look at throttle position sensor .

[djnolan]

Originally Posted by Kiwi944

Thanks for this. I have replaced the temp sensor, will have a look at throttle position sensor .

Another thing that gets overlooked is the fuel system throughput. Clogged filters or injector screens or spray nozzles will rob performance. Fuel injector cleaner just moves the problem further downstream. Look at Witch Hunter for how to refurb injectors. WitchHunter Performance - Injector Cleaning & Flow Testing Services

[John_AZ]

FYI, FRWilk, "The944" covered early car "stutter" very thoroughly with detailed instructions.

A couple of weeks ago his web site went down. I do not have any of his historical information saved.

There may be an archive ---somewhere on the web.

J_AZ

[Kiwi944]

Originally Posted by JD159

Not too familiar with the older models, does it have an o2 sensor?

Doesn't the DME skip the o2 sensor when on WOT and only use the input on partial throttle? That info was given to me by Russel Berry

It is USA spec and it DOES have an o2 sensor. Something else to check out...

[Swennydawg]

It sounds as if somethings overheating. Fuel pump,fuel pump relay,gas lines
or maybe the ignition coil.

[Kiwi944]

To cut a very long story short, I've fixed it!!!!

Thanks to JD159 - it was the oxygen sensor. It turns out the car runs the three wire sensor. In desperation I unplugged the twin-wire connection and took the car around my usual test circuit.

No more hesitiation, spluttering or missing. In short, it was perfect.

Since then (3 weeks ago) I have done around 4000km in it. Fuel consumption has gone from awful, to 37mpg, the engine is running much cooler and the car is now fun to drive.

[AKCJ]

Glad you got it working better. I was going to suggest that air could be leaking from one or more of the hose connections under the intake manifold. I pulled my manifold and replaced all those old hoses and it helped. Also, TPS.
My car is also an early build - looks like a clone to yours.

[Kiwi944]

Originally Posted by AKCJ

Glad you got it working better. I was going to suggest that air could be leaking from one or more of the hose connections under the intake manifold. I pulled my manifold and replaced all those old hoses and it helped. Also, TPS.
My car is also an early build - looks like a clone to yours.

So far, so good! What is your build date/VIN?

[M. Murphy]

Another clone. 83 NA

[Kiwi944]

Originally Posted by M. Murphy

Another clone. 83 NA

Great looking car!

[Bukowski]

Originally Posted by John_AZ

FYI, FRWilk, "The944" covered early car "stutter" very thoroughly with detailed instructions.

A couple of weeks ago his web site went down. I do not have any of his historical information saved.

There may be an archive ---somewhere on the web.

J_AZ

Off the top of my head - maybe the Wayback Machine has something. I might try punching it into Google later...

[djnolan]

Priceless info, can it be recovered? What happened to the owner?

[Project560]

I found this webarchive, but it may not have all of the information. Does anyone know the story on the infamous FR Wilks?

https://web.archive.org/web/20111230151755/http://www.the944.com/index.htm

https://web.archive.org/web/20111230151324/http://www.the944.com/shudder.htm

[djnolan]

Originally Posted by Project560

I found this webarchive, but it may not have all of the information. Does anyone know the story on the infamous FR Wilks?

https://web.archive.org/web/20111230151755/http://www.the944.com/index.htm

https://web.archive.org/web/20111230151324/http://www.the944.com/shudder.htm

Amazing to find most of the site is archived but archives to the second level links seem to be missing.