LI Steve

Hi everyone here on the 944 side of rennlist! I've had a 928 for the last few years and just picked up a 91 944S2 Cab (and love it)!

I am having one problem with it - at around 5400 RPM, only at WOT, there is a severe misfire / stumble. I don't think it is happening when the car is in 1st gear, but does happen every time in 2nd and 3rd (haven't tried 4th or 5th!). Again, it is only at full throttle. At 3/4 throttle, it pulls just fine all the way to redline.

The car has 51k miles on it. I have replaced the cap/rotor/wires/plugs and the air filter. I have also tested the TPS according to the write up on Clarks, and the TPS seems to test out fine.

Does anyone have any other ideas? Could it be the DME?

Thanks in advance.

V2Rocket

id check the AFM

LI Steve

Does the AFM come into play at full throttle? I thought the AFM reading was ignored during full-throttle

I searched without success for a procedure on testing the AFM - if you know of a thread or url, could you post it?

Thanks again.

V2Rocket

http://www.clarks-garage.com/pdf-manual/elect-22.pdf

LI Steve

Thanks again Spencer - that is exactly what I needed. I will test the AFM when I get some time.

Does anyone know if the AFM signal is taken into account by the DME when the car is at WOT? I remember reading somewhere that at WOT, the AFM is ignored, but I haven't been able to validate that.

M758

Broken valve spring.

I know this often the case onthe 8valve cars and I believe the smae on the 16 valve cars. There are two valve springs per valve and often times one spring can fail and the car will run fine at low RPM. At higher RPM the one spring alone can't keep up and as such the car stumbles.

LI Steve

Thanks M758 - I had read a few threads on that, and considered it. If that is the case, wouldn't the problem happen at any throttle position? I only have the problem when the pedal is to the floor - at any less than 100% throttle, the car revs past 5400, right to redline, without any problem.

I can hold the car at > 5400 rpm with no problem... as long as the throttle is not wide open.

Maybe I am just trying to convince myself that this is not the problem???

If this is the case, do I have to pull the head to replace the spring (if the valve/piston are not damaged)?

V2Rocket

assuming there's no damage you can just pull the cam tower off and replace the spring

M758

Do the electrical stuff first, but if it does resolve it go after the springs. I have seen 3-4 944 spec car suffer from high rpm miss that came from bad valve springs. The WOT thing is a bit odd, but the only thing to remember is WOT means no reading the O2 sensor. It just pulls off the map in the chip. You could pull the O2 sensor and see what happens. The car should still run, but may idle funny.

LI Steve

On the S2, is it easy to remove the valve cover? I know it is a PITA on the non-S2 models, but mine looks like it should just pop off after taking out 13 bolts...

If I get the cover off, will it be easy to tell if one of the springs are broken? If so, maybe I will try that before I pull the AFM and O2 sensor.

Thanks again!!!

Campeck

could be....

injector trouble, FPR, fuel pump, fuel filter. what plugs are in it?

LI Steve

They are Bosch Super WR5DC Coppers - gapped to .7mm - just replaced (the previous ones were the same type and looked fine when removed).

Would any of your suggestions be more likely considering I only have the problem at WOT? I would think if it is fuel related that the problem would be more 'intermittent' instead of only happening at 5400rpm and full throttle, but as you can see, I am quite a newbie.

Thanks.

eman930

The DME ignores the the 02 sensors at full throttle, The afm is always in play from what I understand but I may be wrong. I would def check the AFM first

Catfood

My 944S is doing this as well, when I goose it in 2nd gear to 6000 rpm it stutters and even if I keep my foot to the floor it will not rev up any more. And then if I try it again it will go to redline just fine. Is this a broken valve?

LI Steve

Thanks for clearing this up for me. I will check the AFM this weekend and let everyone know how I make out.