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89 Corvette TPI 350 Rough idle. Won't rev up.

6K views 14 replies 8 participants last post by  Kodiak450r 
#1 ·
I've been trying to get this car running for a friend and haven't had much luck as of yet. My father in law has been working on it but he doesn't know much, if anything, about cars except kind of how to drive them.

The car has been sitting for almost a year now because the battery was always dead and it wasn't reliable so the lady that owns it didn't want to drive it. The gas tank had a bunch of water in it but it's been drained and dry gas has been added to the tank, along with new gas.

It's an 89 Corvette, auto trans, TPI 350. The car will usually start fine but idles rough most of the time. Actually I haven't seen it run right. I've checked the fuel pressure and it's within spec. I just changed the plugs, wires, distributer cap and rotor. I'm not sure if it's a spark issue or a fuel issue.

Keep in mind that it's bad enough that the car is not drivable. I changed the TPS because a friend suggested that might be the issue but I haven't been able to adjust it yet since it got dark out while I was switching it but I'm preparing for it to not solve the problem tomorrow when I get back to it.

Any suggestions or things I should test? Thanks in advance.
 
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#4 ·
whats it doing exactly and what happens when you try and rev it up? is it blowing black smoke? if so check the cold start injector. it's located on the back of the intake manifold and is very prone to sticking.
 
#5 ·
That is the same engine I'm running in my jeep, and I had a TON of problems to get it up and running. It took me a long long long time to realize that even though I had awesome fuel pressure and perfect injector pulse voltage, my injectors were fubared. After spending about 30 minutes on the phone with http://www.fiveomotorsport.com the guy set me up with some plug and play injectors that are for mustangs but they fit perfectly. Stock injectors were just under 20#, and I ended up with 23# injectors which was fixed by having my PCM remapped.

For the hell of it, I brought my old injectors down to a local shop that cleans them and they put them in a machine to show me the spray pattern, and they were definitely at fault. they all "clicked" but only two had a usable spray.

If I were you I would hook that thing up to a real time scanner, if you'd like you can borrow mine, I also have a program to hook that up to my laptop for graphing data. I also had to replace a density sensor... If you need my scanner, I can also loan you my noid light that plugs into the injector harness to test it.
 
#7 ·
what is it the engine everyone wants ? I have two one with the cold injector and one after they took out the cold injector . The one Iam having problems with is the one with the 9th injector and thats been programed out I have a howell computer and harness in my CJ7 and its kinda doing the samething.
 
#8 ·
just did one in the shop, needed injectors. gm has them discontinued so we bought a set from napa. We replaced them to find that 3 of those were no good. a job is always better when you get them twice. not to mention the tune port set up goes together like a jig saw puzzle. i hate that car.
 
#9 ·
There is no black smoke. There is spark, I actually checked it today. Then tried to start it on ether. It didn't work earlier today. So I changed the ignition control module and the coil. It started again, which it wouldn't before I changed them.

Later on in the day after talking to a guy at a local shop I tried unplugging the temp sensor on the front of the engine. It ran much better but still not right.

After replacing the sensor and plugging the new one in, I started it and it ran the same as it did with the old one. I tried starting it with Ether again and it did fire. I unplugged the sensor again and it fired right up but still didn't run right.

The fuel pressure tests about 45 psi and doesn't change significantly weather its running, good or bad.

Thanks for the offer CC but I'm in Alabama for the week and that's where the car is. I actually have a scanner at home in my garage that I should have brought but it's borrowed and I didn't want to bring it all the way to Alabama. Since I left my truck in a parking structure in Mobile for a week while I was on a cruise.

I really don't want to change the injectors because it looks like a huge pain in the butt not to mention they are $45 dollars a piece so it's a huge investment for a guess.
 
#11 ·
cleaning them wont do anything. they loose resistance like a duramax diesel. for what its worth the vette we had did the same thing, kind of a crap shoot if it would run or not, had its days. also if one injector is bad it will shut down all of them - they work together. you need to check the resistance on the injectors that will answer your question. get an ohm meter and get crazy.
 
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