Stumbling over 4000
 

Let's say I'm racing someone and through just about every gear (but not always), when it gets above 4000rpm, the engine starts stumbling. You can see the tach needle jumping, as if something's missing. I've changed and/or checked vacuum hoses, fuel filter, spark plugs, plug wires, and TPS (and cleaned out TB with STP fuel injection TB cleaner) and all of those are fine. Any other ideas as to why the car does this? Every once in a while, it surprises me and pulls through the gears fine without any stumbling, but most of the time you can count on it.

Check the ignition coil. It may be crapping out on you at higher rpms resulting in a miss.

--nathan

Cool, thanks. I'll see if I can switch out one with a friend and see what happens.


Any other ideas???

Thats not fair he stole my answer... Seriously I'd start there.

I have a similar problem at 2100 rpm. It sometimes starts to stumble or hesitate, but the problem quits at 2200 rpm. Did all the same things you did with no change. I then bought a msd coil, but that didn't help either. I'm starting to think it could be an injector problem. Does your stumbling problem continue through 4k or does it go away after a certain rpm?

It continues through 4k. Sunday, gonna get a coil and see if that helps...

Check your coil and TFI module.

I was thinking of changing the tfi module before going after the injectors. Mine was never in for the recall about 6yrs ago.

had a very similar issue w/my car
 

I had a similar problem with my car. Loss of power above 4000 rpm's turned into stubling and bucking and just plain heartache when driving the car. The longer i put up with it the worse it got. I replaced almost all of the sensors for the FI and it turned out to be the mass air meter. The minute I put the new one in my car came back to life, never been happier. I hope this helps you. wish someone could have given me the same advice for my car! Let us know how it goes.

Re: had a very similar issue w/my car
 

Thanks for chiming in. I forgot to mention, though, a friend of mine let me use his MAF and the car did the same thing. Now, it is possible (highly unlikely, though) that his was bad too, but he said it worked fine in the car it use to be in.
Mmmm. I never have weird, hard-to-trace problems like this in my '79...:D

Man...:rolleyes: seems like I was too quick to start complaining .... Seems like it was the coil. Simple. I just put a new one in and the car is doing fine over 4000, smooth all the way to 5000+. Gonna drive it around today and make sure. Thanks.

WOOOO WHOOOO!! SCORE! :D

Glad you got it tracked down. Hopefully that will take care of it.

--nathan