87 GTA 5.7 Rough idle, hesitation, progressive problem, injectors???
08-08-2012, 02:31 PM
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87 GTA 5.7 Rough idle, hesitation, progressive problem, injectors???
Ok I have a 1987 GTA 5.7L TPI 145,000 miles. I have a hard start problem, bad hesitation on acceleration and really rough idle. This is a progressive problem that has slowly gotten worse and worse over the years. To bypass the hard start I have to give it gas like its carburated. In RPMs above 2500 it runs better.
Here is what myself and a few of my friends have diagnosed in good working order. Triple checked all of the below.
TPS
EGR
CAP, ROTOR, WIRES, PLUGS
MAF
INTAKE GASKET
PLENUM GASKET
NO MAJOR VACUUM LEAKS BUT SLIGHTLY LOW VACUUM
FUEL PUMP
FUEL PRESSURE REGULATOR
IGNITION COIL
FUEL FILTER
Other things to mention:
No check engine light on
Ran several cans of Seaform through the gas tank
Cleaned the throttle plate
It has run this way for years
Sprayed carb cleaner in the valve covers to verify no bent valves
Has a Hypertech chip installed
K&N Filter installed
My question, is it possible that the injectors are fouled bad enough to cause this problem. ALLDATA and several web sites suggest it is but I want to hear from you guys. Nobody else seems convinced but me that this is the problem. I have the injectors but I hesitate to put them in because its $100.00 down the drain if I am wrong. I have ohmed the originals in the vehicle and they ohm out to normal specs. But of course this would not matter if the issue is plugged injectors. When we hook up a fuel pressure tester to the fuel rail the pressure drops pretty fast (within 5 mins to 20lbs from 42lbs) which I read is a indication that the injectors are in fact stuck open. Has anyone replaced injectors for these symptoms and if not what else should I try? I am running out of options and hope.
Here is what myself and a few of my friends have diagnosed in good working order. Triple checked all of the below.
TPS
EGR
CAP, ROTOR, WIRES, PLUGS
MAF
INTAKE GASKET
PLENUM GASKET
NO MAJOR VACUUM LEAKS BUT SLIGHTLY LOW VACUUM
FUEL PUMP
FUEL PRESSURE REGULATOR
IGNITION COIL
FUEL FILTER
Other things to mention:
No check engine light on
Ran several cans of Seaform through the gas tank
Cleaned the throttle plate
It has run this way for years
Sprayed carb cleaner in the valve covers to verify no bent valves
Has a Hypertech chip installed
K&N Filter installed
My question, is it possible that the injectors are fouled bad enough to cause this problem. ALLDATA and several web sites suggest it is but I want to hear from you guys. Nobody else seems convinced but me that this is the problem. I have the injectors but I hesitate to put them in because its $100.00 down the drain if I am wrong. I have ohmed the originals in the vehicle and they ohm out to normal specs. But of course this would not matter if the issue is plugged injectors. When we hook up a fuel pressure tester to the fuel rail the pressure drops pretty fast (within 5 mins to 20lbs from 42lbs) which I read is a indication that the injectors are in fact stuck open. Has anyone replaced injectors for these symptoms and if not what else should I try? I am running out of options and hope.
Last edited by jtapoling; 08-08-2012 at 02:42 PM.
08-09-2012, 06:10 PM
#2
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Re: 87 GTA 5.7 Rough idle, hesitation, progressive problem, injectors???
When you checked the resistance on the injectors did you test them when they
were hot and cold? The coils typially shut down/fail when they get hot.
You may also have a leaky injector. After you run the engine for a couple of minutes,
pull the plugs, if you have any wet cylinders then you have a leaky injector.
Let us know
were hot and cold? The coils typially shut down/fail when they get hot.
You may also have a leaky injector. After you run the engine for a couple of minutes,
pull the plugs, if you have any wet cylinders then you have a leaky injector.
Let us know
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