Any ideas on why my car will only accelerate to 5200-5500 RPM? It sorta' feels like the rev limiter is kicking in, and sticks under hard load. It will occationally eventually pull through to redline if I keep my foot in it.

As of now, I have tried a new coil and cleaned the AFM and neither have cured the issue. By the way, it is an '87 if that makes any difference at all.

This is a real issue as this is a SPEC 944 and the entire field pulls away from me significantly during acceleration.

 

I'm having this problem with my 86 NA. I think it's the sparkplug wires either arcing out , crossfiring or just too high of resistance at higher revs. I have not replaced them yet, it does not miss at all and runs smooth to this point, and yes, if I stay in it for a sec or two, it will pull to the actual revlimiter. I know my wires are shot for a fact, I just need to swap them out to see if it helps.

 

Thanks for the tip. It does run smooth up until 5200-5500. I will see if I can borrow a set to swap and give it a go.

Note that this problem is getting progressively worse. It used to only happen occationally and would go away after the first couple of laps.

 

Perhaps AFM?

 

AFM was on my list of possibilities. I cleaned it, now I may want to swap or try bending the arm inside to see if the tracks are pitted. I would rather swap first though.

 

TPS?

 

TPS on an NA only reads idle, WOT and nothing for mid throttle. I notice it all the time and don't always go WOT, I'll pay attention to it tomorrow.

 

Maybe something is stuck in your throttle cam?

 

Check you're coil, mine was stuttering., back-firing at anything over 4K+ and felt like cutting out at ~5.5Krpm

 

IF the problem happens when the car is warmed up then you might want to look into maybe your 02 sensor.

 

I was having this problem a while back and it turned out to be a rotten fuel line. the line from the tank was collapsing when too strong of a load was placed on it. And the fuel pump had been rebuilt using orange putty.

Keith

 

Wow, looks like alot of different possibilities:

Coil(already checked that), AFM(cleaned,but not replaced),throttle cam,fuel lines, and spark plug wires...I was also told to try swapping the brain by someone not on Rennlist.

 

David...
You got some good advice and some not so good advice.

Coil and plug wires. Definite thinks to check out. Their funtion is RPM dependant meaning that higher RPM's can cause a problem.

AFM is not linked to RPM at all. Only air flow. Same with TPS and the entire throttle system.

If you were having WOT issues then look there. If it occurs at a set RPM not matter the throttle position then it is not throttle related.

I think Coil & plugs and plug wires are good check. The DME can also fail. Doubt it is fuel pressure related or injectors as there behavior is driven by throttle position not so much by RPM.

Note there is also a speed and reference sensor. These are the two plugs on the bell housing behind the intake. labled BG and DG. These tell teh DME engine speed and have TDC pick-up. Maybe they are failing and the higher speeds are not being red properly.

PS... I did have wiper track problems on my AFM and this probelm was not the result. It was RPM independant.

Hope this helps!

 

Non Porsche but I had a similar problem everytime I would get to about 5800 rpm on an Acura. it would act real funny and kind of bog...turned out there was a big chunk of my rotor gone off the counterweight area. It would be semi balanced and run fine below 5800 until it started to wobble and couldn't keep up with the demand.

 

I checked mine a little while driving to and from work today...

I did notice it in both mid and WOT positions. Actually slightly wore but not much in mid throttle. I also compared it cold and up to temp. When cold or up to half warmed(about half to the first white line) if I got it to do it before warmed, it looses a cylinder for a few seconds then clears up. I'm thinking a bad wire or bad wires. I'm due for an oil change and plan to do the wires then. They are used wires that I beleive are good, my attempt may just be a toss. I should also check the plugs to try to read them and find the violating cylinder. I also noticed that the rpm on my car that it does it is aprx. 5500-5700. It could be just the tach variance or maybe doing it at a different speed on mine. I hope it is not a DME issue, being two cars, same deal and pretty much the same revs, it could be.