i have a 90 sixspeed and it dies at 3000 rpm everytime i drive it i replace the ignition coil and the ignition module and pick up coil still have the same problem. its like u turn the key off at 3000 rpms anybody else ever seen this? it will start right bck up run smooth till 3000 rpms

 

1) check fuel pressure at 3000 rpm UNDER LOAD (revving it up in the driveway does not req same fuel input as when loaded)...low pressure may be due to dirty filter or a dying fuel pump (in-tank GM fuel pumps are only good for 10 yr or 100k miles, whichever comes first)

2) check backpressure in the exhaust system (see Service Manual for simple test procedure) for possible plugged cat or mouse nest in muffler.

 

ohm check your injectors, you might have a couple of dead ones.

 

i reparted the fuel filter too the injectors are fine i had them tested the car died no running rough or anything it just dies

 

Did that year have a "valet key" option? Could this be a valet key he's driving with?

 

Hmm...really sounds like it coud be a restriction in the exhaust, but it would usually struggle and spit at that point, not just stall out.

 

i tried my other key didnt help any im running a h pipes and muffler ele. dont see how it could be clogged up its like u turn the key off a 3000 the radio cuts out and everything

 

It happens at 3K even if you come up on 3K slowly?

For example, if you cruise at 2,800 is it perfectly fine? And, can you drive steadily without problem at 2,900?

Did you say whether it would happen with the car in park/neutral?

 

What codes is it throwing (easy to check)? That would go a long way toward figuring out what's wrong.

 

no codes and its a 6 speed i can drive all day at 2800

 

A couple of thoughts. You just might have to get a scan tool or a laptop with the cable and software, so you can watch what's going on. Though I've never used one, a lot of people here have.

Sounds like a very frustrating problem. Do you have the Factory Service Manual? I'm also thinking out loud here too. Have you checked the throttle position sensor? At a certain RPM range, certain conditions have to exist. It could be as crazy as the throttle linkage between the pedal and the throttle body pushing against a wire harness and causing a short. I'd sure be examining all the wiring, especially because the car just goes 'dead' at 3K.

Does it easily go over 3K in the driveway? Or only when it's in 'Drive'? Could it be related to a shift? Tell us more.

 

The radio going dead almost guarantees some kind of electrical problem. The car goes 'electrically' dead at 3K rpm. Either it's a short or something is pulling or diverting all the current. How is the battery? Does the whole dash go dead too?

 

i have it at a gm shop now they have the scan tool hooked up and nothing looks bad. im outta ideas

 

it revs fine in the driveway

 

Makes me wonder, what the car would do on a dyno. If the shop has a dyno (all smog test here in CA has a dyno by law), why not put it on the dyno and see what it does? I'm still betting on an electrical problem.

Finally, when the car quit, did the gauges go completely off, or were they on? Black or all the usual pre-turn-the-key lights on for oil pressure, water temp and SES light?

 

the lights go out but all the gauges work fine

 

Wait 'til it gets dark then pop the hood and look at the sparkplug wires and other wires. Watch for arching as someone revs the engine @ 3K +

 

No illuminating lights to the gauges! Your 90 came out with the analog gauges, versus the digital readouts on the earlier C4's. But the gauges are still working, meaning that the temp and oil pressure are still reading with the engine off?

Wow. Primary cause, I'd still have to say chassis electrical . Second cause, might be something in the interface between the transmission and the ECM, but there can't be a lot, with a manual. Worth thinking about.

Put the car on a dyno and run it up and see what happens. It doesn't do it standing still, only when you're rolling it. Does it happen in any gear, or just between 1st & Second? You have to narrow down what happens and what conditions occur. While it's running still, I'd be wiggling all the harnesses while someone else had it running at 3K rpm. Maybe it's possible when the car hits a bump, there's a short or open circuit that activates in the main wire harness.

Tough problem! My little bro is a master mechanic at a Ford Dealership and he's certified on Ford GT's (not the Mustang GT, but the GT and we've had many a phone con about bizarre problems on cars. We've done quite a few together, so this is where this is coming from.

At a Dodge dealership many years ago, he once had a very tough intermittent and by wiggling the harnesses carefully, he found the culprit harness on the right fenderwell. Apparently, the car had been in a serious accident and everything was repaired, but nobody caught the broken wire inside the harness that had been stretched to the breaking point, unseen during the accident.

Keep us informed!

 

That's a good one too!

 

When you replaced the HEI coil did you make sure to transfer over the ground bar from the old coil/cap?

The only other "crazy problem" I can think of, but have never heard of, is that the starter is staying engaged with the flywheel somehow and throwing current back into the electrical system......but that is a guess and I'd think you'd hear that!

If the gages work.....watch the "voltage" gauge when your problem occurs.

Good Luck!