1989 Corvette Sputters When Warmed Up
09-15-2016, 11:33 PM
#1
1989 Corvette Sputters When Warmed Up
Hey guys i ran into a problem in my corvette that i cant figure out.
my friend gifted me his 89 corvette, it wasn't running when i got it.
changed the battery, changed the oil and filter, air filter, fuel pump, fuel filter, spark plugs, coil pack, and 02 sensor and i used a fuel cleaner to help remove gunk and stuff from the combustion system. problem is the car starts to sputter when it starts to warm up. when its cold it'll start just fine but after like 3-5 minutes the car starts to hesitate and wanting to turn off. fuel pressure is fine just recently tested, spark is good. the only theory i have is that maybe the new 02 sensor may have been faulty. additional details is that the car has been sitting for a couple of years. my friend turned it on once in a while so the oil wouldn't sit there for too long.
any theories? i have no clue about what to do now.
my friend gifted me his 89 corvette, it wasn't running when i got it.
changed the battery, changed the oil and filter, air filter, fuel pump, fuel filter, spark plugs, coil pack, and 02 sensor and i used a fuel cleaner to help remove gunk and stuff from the combustion system. problem is the car starts to sputter when it starts to warm up. when its cold it'll start just fine but after like 3-5 minutes the car starts to hesitate and wanting to turn off. fuel pressure is fine just recently tested, spark is good. the only theory i have is that maybe the new 02 sensor may have been faulty. additional details is that the car has been sitting for a couple of years. my friend turned it on once in a while so the oil wouldn't sit there for too long.
any theories? i have no clue about what to do now.
09-15-2016, 11:53 PM
#2
Could be but I would test the ignition module and don't forget the thermal grease.
09-16-2016, 12:09 AM
#3
Team Owner
changed the battery, changed the oil and filter, air filter, fuel pump, fuel filter, spark plugs, coil pack, and 02 sensor and i used a fuel cleaner to help remove gunk and stuff from the combustion system.
problem is the car starts to sputter when it starts to warm up. when its cold it'll start just fine but after like 3-5 minutes the car starts to hesitate and wanting to turn off.
fuel pressure is fine just recently tested, spark is good.
problem is the car starts to sputter when it starts to warm up. when its cold it'll start just fine but after like 3-5 minutes the car starts to hesitate and wanting to turn off.
fuel pressure is fine just recently tested, spark is good.
Check this first. Disconnect the MAF sensor and see if it runs better. Also, did you clean the entire throttle body by removing the IAC and the IAC housing and clean the passages?
What did you do to test fuel pressure? Did you test it while it was turned to run but engine off and did the pressure hold? Did you test it with the engine running in idle and the fuel pressure regulator hose off? Did you do a WOT run?
Spark is good? Did you check the wires? Do you know if the harmonic balancer is good? What was the timing?
09-16-2016, 08:15 PM
#4
09-16-2016, 08:24 PM
#5
Why did you change the fuel pump and coil? What made you think they were bad? Fuel cleaner? Good joke but until they can prove something, you bought a can of snake oil.
Check this first. Disconnect the MAF sensor and see if it runs better. Also, did you clean the entire throttle body by removing the IAC and the IAC housing and clean the passages?
What did you do to test fuel pressure? Did you test it while it was turned to run but engine off and did the pressure hold? Did you test it with the engine running in idle and the fuel pressure regulator hose off? Did you do a WOT run?
Spark is good? Did you check the wires? Do you know if the harmonic balancer is good? What was the timing?
Check this first. Disconnect the MAF sensor and see if it runs better. Also, did you clean the entire throttle body by removing the IAC and the IAC housing and clean the passages?
What did you do to test fuel pressure? Did you test it while it was turned to run but engine off and did the pressure hold? Did you test it with the engine running in idle and the fuel pressure regulator hose off? Did you do a WOT run?
Spark is good? Did you check the wires? Do you know if the harmonic balancer is good? What was the timing?
im not familiar with WOT.. what test is that? i googled it and it gave me world of tanks.
havent checked the harmonic balancer yet.
i'll get back to you guys when i do these tests
09-16-2016, 09:33 PM
#7
09-16-2016, 09:51 PM
#8
Sounds like it could be a o2 did you use a universal?
09-16-2016, 10:39 PM
#9
Team Owner
That doesn't say much. The reason we do a WOT run is to see what the pump delivers under load. Especially useful when things get up to temp so you can see if the electronic part works ok when cold and not so good when hot.
09-17-2016, 01:34 AM
#11
Team Owner
09-17-2016, 06:48 PM
#13
i tried that when the car was running cold and the psi would jump up into the correct range for the corvette, but when it started sputtering the psi maintained the pressure as if it wasnt under load.
09-17-2016, 06:50 PM
#14
the psi reads the correct pressure for the car which was like 45 i believe. once it warmed up though the the psi maintained the pressure as if the car wasnt under load.
09-17-2016, 07:05 PM
#15
09-17-2016, 10:50 PM
#16
Team Owner
All that is good but we still don't know if it can maintain 45 psi when it is under load which needs more fuel than when it is not. AFAIK, 5000 rpm under load take more fuel than 5000 rpm with the gear in neutral or park. If you know it works under extreme conditions, we can rule out the pump. So it is good to know what the fuel pressure is doing a WOT run. Leaks show up more under load. Without load, the pump might be able to keep up.
09-18-2016, 05:56 AM
#17
Le Mans Master
Member Since: Oct 2004
Location: South-central Missouri
Posts: 6,314
Received 500 Likes
on
395 Posts
"Runs fine when cold...but after it warms up" is classic for electrical "stuff". I'm thinking injectors succumbing to alcohol.
(Prior to 93, OE injectors were susceptible to alcohol - the insulation of the internal coil windings would fail and the windings would come in contact with one another - shorting out. As the situation progresses, more of the windings short, indicated by the lower resistance. But, as the windings short to one another, the magnetic field that is generated to act upon the (valve) is diminished and the fuel flow is reduced and eventually cut off.)
Once the car is warmed up, and the idle "sputtering" has begun, measure the resistance of each injector. They should all be within an ohm across the lot (most read 14 ohms, but some center around 12 ohms).
IF ANY of them reading exceptionally low, e.g., close (say) to 10, that is an injector that is going bad. By the time one gets to 8 ohms or less, the injector is in serious trouble - passing little if any fuel at all.
If you do find an injector(s) displaying low resistance (again...they may first need to be up to operating temp), replace the entire set with new, alcohol-tolerant injectors. (Jon at FIC can set you up with NEW STAINLESS injectors. Don't be tempted to buy any so-called reconditioned ones, unless you just love repeating this rough-running scenario...over and over.
)
FYI, I had an injector go bad, and also one of the intake valves in that same cylinder was also burnt. I suspect the excessive lean condition was the cause. My theory seems to be borne out, as the motor had under 40k miles at the time, and now has just over 60k with NO problems.*
Anyway... Test 'em (while HOT) first. IF you have even ONE that is bad, that's the signal to change 'em ALL.
(Prior to 93, OE injectors were susceptible to alcohol - the insulation of the internal coil windings would fail and the windings would come in contact with one another - shorting out. As the situation progresses, more of the windings short, indicated by the lower resistance. But, as the windings short to one another, the magnetic field that is generated to act upon the (valve) is diminished and the fuel flow is reduced and eventually cut off.)
Once the car is warmed up, and the idle "sputtering" has begun, measure the resistance of each injector. They should all be within an ohm across the lot (most read 14 ohms, but some center around 12 ohms).
IF ANY of them reading exceptionally low, e.g., close (say) to 10, that is an injector that is going bad. By the time one gets to 8 ohms or less, the injector is in serious trouble - passing little if any fuel at all.
If you do find an injector(s) displaying low resistance (again...they may first need to be up to operating temp), replace the entire set with new, alcohol-tolerant injectors. (Jon at FIC can set you up with NEW STAINLESS injectors. Don't be tempted to buy any so-called reconditioned ones, unless you just love repeating this rough-running scenario...over and over.
)FYI, I had an injector go bad, and also one of the intake valves in that same cylinder was also burnt. I suspect the excessive lean condition was the cause. My theory seems to be borne out, as the motor had under 40k miles at the time, and now has just over 60k with NO problems.*
*The injectors were replaced by a Chevy dealer before I bought the car - a ZR-1. It only took a couple years before they went bad again. Turns out the dealer installed new old stock (NOS) injectors - and they were doomed from the start: just a matter of tine.
Anyway... Test 'em (while HOT) first. IF you have even ONE that is bad, that's the signal to change 'em ALL.
The following users liked this post:
Greasemonky8 (09-18-2016)
09-18-2016, 01:24 PM
#18
"Runs fine when cold...but after it warms up" is classic for electrical "stuff". I'm thinking injectors succumbing to alcohol.
(Prior to 93, OE injectors were susceptible to alcohol - the insulation of the internal coil windings would fail and the windings would come in contact with one another - shorting out. As the situation progresses, more of the windings short, indicated by the lower resistance. But, as the windings short to one another, the magnetic field that is generated to act upon the (valve) is diminished and the fuel flow is reduced and eventually cut off.)
Once the car is warmed up, and the idle "sputtering" has begun, measure the resistance of each injector. They should all be within an ohm across the lot (most read 14 ohms, but some center around 12 ohms).
IF ANY of them reading exceptionally low, e.g., close (say) to 10, that is an injector that is going bad. By the time one gets to 8 ohms or less, the injector is in serious trouble - passing little if any fuel at all.
If you do find an injector(s) displaying low resistance (again...they may first need to be up to operating temp), replace the entire set with new, alcohol-tolerant injectors. (Jon at FIC can set you up with NEW STAINLESS injectors. Don't be tempted to buy any so-called reconditioned ones, unless you just love repeating this rough-running scenario...over and over.)
FYI, I had an injector go bad, and also one of the intake valves in that same cylinder was also burnt. I suspect the excessive lean condition was the cause. My theory seems to be borne out, as the motor had under 40k miles at the time, and now has just over 60k with NO problems.*
Anyway... Test 'em (while HOT) first. IF you have even ONE that is bad, that's the signal to change 'em ALL.
(Prior to 93, OE injectors were susceptible to alcohol - the insulation of the internal coil windings would fail and the windings would come in contact with one another - shorting out. As the situation progresses, more of the windings short, indicated by the lower resistance. But, as the windings short to one another, the magnetic field that is generated to act upon the (valve) is diminished and the fuel flow is reduced and eventually cut off.)
Once the car is warmed up, and the idle "sputtering" has begun, measure the resistance of each injector. They should all be within an ohm across the lot (most read 14 ohms, but some center around 12 ohms).
IF ANY of them reading exceptionally low, e.g., close (say) to 10, that is an injector that is going bad. By the time one gets to 8 ohms or less, the injector is in serious trouble - passing little if any fuel at all.
If you do find an injector(s) displaying low resistance (again...they may first need to be up to operating temp), replace the entire set with new, alcohol-tolerant injectors. (Jon at FIC can set you up with NEW STAINLESS injectors. Don't be tempted to buy any so-called reconditioned ones, unless you just love repeating this rough-running scenario...over and over.
)FYI, I had an injector go bad, and also one of the intake valves in that same cylinder was also burnt. I suspect the excessive lean condition was the cause. My theory seems to be borne out, as the motor had under 40k miles at the time, and now has just over 60k with NO problems.*
*The injectors were replaced by a Chevy dealer before I bought the car - a ZR-1. It only took a couple years before they went bad again. Turns out the dealer installed new old stock (NOS) injectors - and they were doomed from the start: just a matter of tine.
Anyway... Test 'em (while HOT) first. IF you have even ONE that is bad, that's the signal to change 'em ALL.
09-18-2016, 01:36 PM
#19
Team Owner
"Runs fine when cold...but after it warms up" is classic for electrical "stuff". I'm thinking injectors succumbing to alcohol.
(Prior to 93, OE injectors were susceptible to alcohol - the insulation of the internal coil windings would fail and the windings would come in contact with one another - shorting out. As the situation progresses, more of the windings short, indicated by the lower resistance. But, as the windings short to one another, the magnetic field that is generated to act upon the (valve) is diminished and the fuel flow is reduced and eventually cut off.)
Once the car is warmed up, and the idle "sputtering" has begun, measure the resistance of each injector. They should all be within an ohm across the lot (most read 14 ohms, but some center around 12 ohms).
IF ANY of them reading exceptionally low, e.g., close (say) to 10, that is an injector that is going bad. By the time one gets to 8 ohms or less, the injector is in serious trouble - passing little if any fuel at all.
If you do find an injector(s) displaying low resistance (again...they may first need to be up to operating temp), replace the entire set with new, alcohol-tolerant injectors. (Jon at FIC can set you up with NEW STAINLESS injectors. Don't be tempted to buy any so-called reconditioned ones, unless you just love repeating this rough-running scenario...over and over.)
FYI, I had an injector go bad, and also one of the intake valves in that same cylinder was also burnt. I suspect the excessive lean condition was the cause. My theory seems to be borne out, as the motor had under 40k miles at the time, and now has just over 60k with NO problems.*
Anyway... Test 'em (while HOT) first. IF you have even ONE that is bad, that's the signal to change 'em ALL.
(Prior to 93, OE injectors were susceptible to alcohol - the insulation of the internal coil windings would fail and the windings would come in contact with one another - shorting out. As the situation progresses, more of the windings short, indicated by the lower resistance. But, as the windings short to one another, the magnetic field that is generated to act upon the (valve) is diminished and the fuel flow is reduced and eventually cut off.)
Once the car is warmed up, and the idle "sputtering" has begun, measure the resistance of each injector. They should all be within an ohm across the lot (most read 14 ohms, but some center around 12 ohms).
IF ANY of them reading exceptionally low, e.g., close (say) to 10, that is an injector that is going bad. By the time one gets to 8 ohms or less, the injector is in serious trouble - passing little if any fuel at all.
If you do find an injector(s) displaying low resistance (again...they may first need to be up to operating temp), replace the entire set with new, alcohol-tolerant injectors. (Jon at FIC can set you up with NEW STAINLESS injectors. Don't be tempted to buy any so-called reconditioned ones, unless you just love repeating this rough-running scenario...over and over.
)FYI, I had an injector go bad, and also one of the intake valves in that same cylinder was also burnt. I suspect the excessive lean condition was the cause. My theory seems to be borne out, as the motor had under 40k miles at the time, and now has just over 60k with NO problems.*
*The injectors were replaced by a Chevy dealer before I bought the car - a ZR-1. It only took a couple years before they went bad again. Turns out the dealer installed new old stock (NOS) injectors - and they were doomed from the start: just a matter of tine.
Anyway... Test 'em (while HOT) first. IF you have even ONE that is bad, that's the signal to change 'em ALL.
09-18-2016, 02:20 PM
#20
Racer
Check eBay for deal on reman injectors that are Bosch 3's.
https://fuelinjectorconnection.com
Here is a series of videos to help you diagnose.
When I rebuilt my 1989 I immediately tossed the old injectors.
https://fuelinjectorconnection.com
Here is a series of videos to help you diagnose.
When I rebuilt my 1989 I immediately tossed the old injectors.