dmalo810

Okay, just about run out of solutions to solve my 3800 - 4K power cut.
Replaced: Cap, rotor, wires, fuel regulator, damper, vacuum lines, BOV.

Here is a more discriptive view of the issue. Only in 4th and 5th gear, under acceleration, hard or soft, the engin will just cough, sputter and sometime backfire around 3800 to 4200 rpms. Replace all the above with new and still a problem. Anything I'm missing to do? Cycling valve, wastegate, HELP!!!

Thanks,
Don

dmalo810

Oh yeah, it's an 86/951... duh, sorry I forgot to mention that...

fast951

Which chip are you running? How much boost are you running when it happens. Does it happen if you are not on boost?

PorscheDoc

I had a big cutout issue on a 951S this week, but it was only under a simulated heavy load (simulating a hill) on the dyno. Normal run was fine. Turned out to a bad coil. It cut out at 4800 rpms every loaded run.

Hall951

mine was my wastegate switch to a dual port

reno808

yes coil coud do that. wasgate wont cause a cut off like that. it could also be a vac leak EX: IC connectors, vac lines, cycling valve (use clarks garage web site to test it), chips will do it to..

Perry 951

I'm diagnosing the same thing and have checked/replaced almost everything. I'm hooking up with John later this week for some testing. I'll post the results.

BTW.. I'm leaning towards a failed coil as noted above. Sucks cuz the coil has a whopping 12,000 miles on it. I'm also thinking the KLR may have issues as well since it wont output codes.

Jfrahm

Could be a cracked intake tube or a bad AFM also I think.

-Joel.

Jimbo951

Check the pressure pipes between the turbo, intercooler & throttle.

I've had hoses tear or work loose. When I was under full boost, the hose would open up and dump the boost. The ECU didn't know what to make of this and turned off the engine for a second or so.

PS: How fast are you going to see 3800 RPM in 4th or 5th?

aventari

I don't see spark plugs in your list, did you replace them?

dmalo810

Hey everyone, thanks. I've got a spare coil sitting around and I'll give that a try first. Spark plugs I did not replace, I pulled them and they look brand new. Also, I'll check on chips, I don't even know if they are stock or some aftermarket. I have no others so that would have to be a purchase if the coil side of things don't work.
Jimbo, I did that and continue to check it. I did have that problem but it happened under any boost. I fixed that problem... I hope for good.
Reno, could be and I'll check that again using Clark's Garage info. Jfra, hope not, but I'll check.
Occasionly, it will not lose power, but that is very rare. It's just a bit frustrating, especially when you get a chance to hit it on the on ramp of the freeway or some rice burner wants to test you, ahhhhh!!!
Okay, again thanks for the messages and I'll give all input a try or try again.
Don

reno808

it could also be the J-Boot. It was giving me problems.

dmalo810

Just a little of an update. I installed another coil from a 87 n/a 944. I think we've got it close to a fix. I wasn't able to duplicate the sputter yesterday but 1 out of 5 times. And only then the one time was under heavy load, about 14# of boost in 5th gear at about 3k rpms.
Still going to do a chip review.
Something that might be related, the car "surges" under mild boost, not a smooth accelaration. Thoughts?
Thanks again everyone for the help!

JET951

throttle position sensor

Perry 951

I just got back from testing a KLR with John, all is the same. We agree my issue appears to be ingition related. I'm going to gap my plugs a little closer and see what happens. If that does not work, I'm off to dig up my old coil or buy a new one.

No idea on your part throttle surge... I have a somewhat similar surge at very low throttle input that I'll investigate next.