91 Z28 Trouble starting and won't rev
Thread Starter
Junior Member
Joined: Nov 2010
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91 Z28 Trouble starting and won't rev
Hey everyone,
I just picked up a great looking, but not running 91 z28 with a TPI 305 and automatic a few days ago for and found this awesome website slam packed full of useful information. However after searching for hours I am still unable to find anyone who seems to have the same issue as me. When we got the car, the guy said that sometimes it would start, sometimes it wouldn't. Well we were not able to get the car to start at all until replacing the fuel filter, and spraying carb cleaner in the intake, and adding a few gallons of mid grade with STP fuel system cleaner. Once we did get it to start it would sound like it was misfire, and we could not get it to run above 2500 rpm. After replacing the spark plugs the misfire problem went away. So now I am stumped with a car that only starts with carb cleaner and won't go over 2,500 rpm. What I know as of now is...
-Fuel pressure is around 42psi when running, lower when priming before starting. Not 100% sure on these numbers, the loaner gauge I used was pretty crappy
-Check engine light is not on when car is running
-TPS voltage is at .58-4.30 (is this to far off of recommended voltages?)
-Fuel pump does prime when key is turned
-Nothing will surprise me on this car. I pulled a rats nest of an old alarm system out before even beginning the project.
UPDATE!
-Replaced distributor and coil
-Replaced spark plugs
-Vacuum pressure is at about 7.5psi at idol
The car will now start with carb cleaner, but will not go above idol after I left it sit for a few weeks. Anyone else have any ideas? Im just sitting here browsing the web looking for more idea.s
Any help would be greatly appreciated, I am young and trying to learn more about chevys the best way I know how. And here is a picture of the car as she sits now (front ground effects are in the garage, had to take it off to get on the dolly, and we are going to get it painted before putting it back on again)
I just picked up a great looking, but not running 91 z28 with a TPI 305 and automatic a few days ago for and found this awesome website slam packed full of useful information. However after searching for hours I am still unable to find anyone who seems to have the same issue as me. When we got the car, the guy said that sometimes it would start, sometimes it wouldn't. Well we were not able to get the car to start at all until replacing the fuel filter, and spraying carb cleaner in the intake, and adding a few gallons of mid grade with STP fuel system cleaner. Once we did get it to start it would sound like it was misfire, and we could not get it to run above 2500 rpm. After replacing the spark plugs the misfire problem went away. So now I am stumped with a car that only starts with carb cleaner and won't go over 2,500 rpm. What I know as of now is...
-Fuel pressure is around 42psi when running, lower when priming before starting. Not 100% sure on these numbers, the loaner gauge I used was pretty crappy
-Check engine light is not on when car is running
-TPS voltage is at .58-4.30 (is this to far off of recommended voltages?)
-Fuel pump does prime when key is turned
-Nothing will surprise me on this car. I pulled a rats nest of an old alarm system out before even beginning the project.
UPDATE!
-Replaced distributor and coil
-Replaced spark plugs
-Vacuum pressure is at about 7.5psi at idol
The car will now start with carb cleaner, but will not go above idol after I left it sit for a few weeks. Anyone else have any ideas? Im just sitting here browsing the web looking for more idea.s
Any help would be greatly appreciated, I am young and trying to learn more about chevys the best way I know how. And here is a picture of the car as she sits now (front ground effects are in the garage, had to take it off to get on the dolly, and we are going to get it painted before putting it back on again)
Last edited by gc11090; Sep 6, 2012 at 08:44 PM.
Joined: Oct 2001
Posts: 12,214
Likes: 1,140
From: Il
Car: 1989-92 FORMULA350 305 92 Hawkclone
Engine: 4++,350 & 305 CIs
Transmission: 700R4 4800 vig 18th700R4 t56 ZF6 T5
Axle/Gears: 3.70 9"ford alum chunk,dana44,9bolt
Re: 91 Z28 Trouble starting and won't rev
You need to buy a factory service manual from Helm. Its loaded with answers for about everything you'll need to know.
If the injs are stock, OHM test them. They could also just be stuck/sticking. Vendors here can sell you new ones if needed.
Your cat(s) or muffler could be plugged up. Do a back psi test on your exhaust system.
Could also be something simple like a huge mouse nest in front of the air filters.
With a limited idea of whats going on with your car we can only guess.
That looks to be a nice car, keep it that way!! good luck.
If the injs are stock, OHM test them. They could also just be stuck/sticking. Vendors here can sell you new ones if needed.
Your cat(s) or muffler could be plugged up. Do a back psi test on your exhaust system.
Could also be something simple like a huge mouse nest in front of the air filters.
With a limited idea of whats going on with your car we can only guess.
That looks to be a nice car, keep it that way!! good luck.
Thread Starter
Junior Member
Joined: Nov 2010
Posts: 8
Likes: 0
Re: 91 Z28 Trouble starting and won't rev
I gutted the cat, I'll disconnect the muffler and see if that helps. Manual is on the way, intake is fine, will check injectors tonight. Thank you for your reply, it is greatly appreciated.
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