I just recently purchased a 89 IROC-Z with TPI 350 engine, what i was told it was rebuilt around 15,000 miles ago along with the transmission. But the problem is that, when i go 0-30 seems alright but not quite fast as i expected it.. it lack of hard acceleration, and at 40-50 mph it starts to chug like a train pulling a trailer like bouncing forward/back/forward/ back.. then as i reach 85-100 mph it rattles the insides, any idea whats goin on w/ the tpi?
Thanks

 

Check your catalytic converter, also do you have a break hanging up? Sounds like you may have a caliper sticking a bit on a warped rotor.

 

85-100 is an balance issue. If you have a steel driveshaft then swap it for an aluminum one. I'd find out how long since routine matainence- plugs, wires, etc.

 

Thats a possibility a guy swapped driveshafts in his 91 and it made a huge difference.

 

I've had this problem before. I'm not saying it couldn't be all of the other things people have listed... But you can check to see if the exhaust is clogged for free.

Just disconnect the exhaust after the Y-pipe, wire the rest of the exhuast up so it doesn't drag and drive around. Yes is will be loud but that's the fun part, just don't don't do it at night if the people that live around you complain alot. I did it on my car and the difference was night and day. If you don't notice a difference then the only thing you've lost is your own time but you haven't spent a dime.

 

Thats why I mentioned the catalytic converter. My buddies LT1 car was acting kind of sluggish especially above 4500rpm. We gutted the cat and lets just say it woke it up a bit

 

Disconnecting the exhaust is misleading, even a fully functional car is gonna run much better without the cat, I-pipe, and muffler.

 

Your right any car will run better, but if your exhaust is clogged and you un-bolt it the difference is night and day, at least both times I've had to do it. Also if you plug a scanner into your computer a clogged exhaust will also make a lot of the readings out of wack. I've seen a mechanic chase what was thought to be a bad O2 sensor or MAP senser, they'll spend a bunch of money still have the problem and in the end they'll un-bolt the exhaust and all of the readings will be in the range they should be.

Plus if he takes the car out with no exhaust and the problem is still there then it is clear you can scratch the exhaust off your list of possible causes. One thing the "The Freak" didn't say was how hot is the car runnning I've also noticed that a clogged exhaust will make a car get up to temp much faster.

In the end I just hate to spend money if I don't need to. Unless he's got a drive shaft laying around, or all the parts for a tune-up already in his garage, this is something he can do tonight if he wants to, for free. If it's not the exhaust then at least you had a reason to drive around with "open headers" which in my book is never wasted time.

 

First of all Thanks to everyone who replied to help me out, ive looked at what everyone has said beside driveshaft..

I checked on the underenth of the car, and there was no cat converter, and there was a leak of oil one of the support for the part on the right side opposite of the alternator didnt have two screws connected on to it, but that probably is the reason why its shaking, tommorrow will take the front tires off to take a look at the brakes to see if its hanging which's causing that chugging part during 40-50 mph, but its just strange because as i start from 0-30 power accelration doesnt work.. i floor it like crazy and it goes slow then as it hit 30-35 mph the power accel works, then 35-50 it rides but when i let go of the acceleration it chugs if i hold on to it.. it keeps going w/out chugging. then 50-80 mph it doesnt chug like around 35-50 mph but over 80 it startts to rattle... i wldve pulled the whole thing out and check it out but i dont have a place to do it so trying to find the specific thing to fix on the spot

ps, i dont know if its the driveshaft, since there were certain mph it start screwing up.. and since going any mph between 0-100 i shifted it to neutral and the chugging/vibration and all stops it was like all smooth

 

Could be a few burnt spark plug wires. It's an engine vibration if it stops shaking in neutral.

 

hey was a soulution ever found for ya, i have vertually the same problems, with the same car. if you found a good solution i would be interested in hearing it. i have done the full tune up and it helped but it did not solve the problems.