What do you all make of this?.....Help needed

[Kliminati456]

Please any help/advise in this matter will be greatly appreciated.....

1990 CQ 7A

Problem started last week and has come and gone but is getting worse. When i push the throttle enough to open the second butterfly in the throttle body the engine stutters and threatens to stall. It happens from idle to about 4000 rpm or when the rpms fall down into that range when slowing down it sputters and threatens to stall. If I raise the rpms slowly it doesn't happen. Shifting from a stop into 1st and 2nd are the worst. When the rpms are high like on the high way it doesn't stutter. Pulling away from each stop light I have to rev it up to like 4000 or 5000 rpms as I let the clutch out. The problem seems to get worse as the engine gets hotter.

If it does stall it will not just start back up. It struggles and wants to but wont until I find the perfect amount of gas to give it. Too much or too little and it just tumbles over and dies. Eventually (usually 20 mins later) I can get it started but it continues to act up. There were no issues like this before a week ago and its getting worse.

I have checked/fixed any vacuum leaks, checked all connections, played, with idle switch, and inspected both the maf and isv which appear to be clean. Something about the air/fuel mixture doesn't seem to be correct.Can a maf just stop working all the sudden or cause these symptoms?

Heres a couple videos to show you what I mean (not the best sound/video quality)

http://www.youtube.com/watch?v=lLGRgzN9hCI

http://www.youtube.com/watch?v=pPwK8Dqi198

[UrS4boy]

Definitely struggling. Sounds choked, either at the intake or the exhaust (plugged cats)? However the hard restart makes me think that the fuel pump is tired.

Is the timing off a few teeth at the distributor or are the camshafts a couple of teeth off?

[Error404]

fooked / blocked injector(s), big vacuum leak maybe, timing as suggest above

[Tonks4x4]

All above possible but could also be just fuel feed. For example, silt in the tank, blocked pipe, tired fuel filter,

[mcandmar]

Check the throttle position sensor, i see your running with no heat shield on the tubular manifold, that = melted TPS sensor in my experience.

[UrS4boy]

Check the throttle position sensor, i see your running with no heat shield on the tubular manifold, that = melted TPS sensor in my experience.

Oooo...Good call. Exact symptoms: idle is not so bad and wide open is not so bad, however, in between, not much if anything = bad throttle position info = ECU is confused.

Here is a link to some AAN, ABY and ADU throttle potentiometer info that might help:
http://forums.quattroworld.com/s4s6/msgs/20405.phtml

Here is a diagram showing the PN of the 7A throttle potentiometer and its location on the bottom (hot side) of the 7A two stage throttle body.

[Kliminati456]

Okay I just pulled the codes and got 2232, 2242, 2212, 4431 so definitely intake related, A few of those codes are probably from me disconcerting things to try and weed out the problem...


2232=Air mass sensor

Symptom....
- Limp home mode
- Poor fuel intake
- Engine dies

Possible Cause...
-Output voltage too low or too high in relation to RPM

2242=CO potentiometer

Symptom...
- Poor acceleration
- Poor fuel intake

Possible Cause...
-Output voltage too high

2212=Throttle valve potentiometer

Symptoms...
-Power loss

Possible cause...
-Output voltage too low or too high in relation to air mass


4431=Idle stabilizer valve

Symptoms...
- Engine might die when cold
- Engine surges Fault in sensor wiring

Possible cause...
-Fault in sensor wiring

[UrS4boy]

You can find out more info about most of those codes here
(click on the labels to go to more info and follow the hyperlinks):

http://members.shaw.ca/speedtek/UrS%...ice%20Map.html

However, I do not know what the 2242 CO Potentiometer Code is, unless it is VAG speak for the Lamba sensor, aka "O2" (oxygen) sensor. Paul? prj? Wanna school me?

[prj]

It's 7A so it's possibly not even a Bosch ECU.

Things to check:
* Fuel pressure, injectors
* MAF
* Exhaust blockage
* Wiring

[Error404]

no 7A is 5hitachi

[mcandmar]

The CO Potentiometer is on the MAF sensor, used to adjust idle fuel mixture. If you have been unplugging stuff clear those codes and see if any of them come back.

It could just as easy be a faulty maf sensor, unusual on a 7A as they dont have any thin wires to break like an S2 maf and usually dont give any trouble. But the symptoms sound right.

[madpugger]

Its because your screen wash is low

This is kinda similar to my symptoms which turned out to be a broken woodruff key on the cam pulley. Timing had slipped a bit, really lazy engine but not so bad high up...

[UrS4boy]

This is kinda similar to my symptoms which turned out to be a broken woodruff key on the cam pulley. Timing had slipped a bit, really lazy engine but not so bad high up...

That could make sense. Some of my early thoughts on this were the timing off a few teeth (at the cam sprocket OR crank sprocket (same)). Pretty easy to check the woodruff "key" (actually part of the sprocket) on the cam shaft. Just need to pull the top timing belt cover, zap strap the belt to the sprocket and give the bolt a quick wrap with a 24 mm box end wrench (to loose the bolt). Hints for the sprocket removal are in this G40 cam positions sensor DIY:

http://picasaweb.google.com/persing/...orReplacement#

[UrS4boy]

The CO Potentiometer is on the MAF sensor, used to adjust idle fuel mixture.

Is that unique to the 7A? I don't find a listing for that function on the AAN (ABY/ADU) ECU (pins 7/55, 25/55 and 26/55):

http://forums.quattroworld.com/s4s6/msgs/21009.phtml

[WidowmakerS2]

My bet is timing, happened to my 7A, cam side had slipped a few teeth.