I got a few questions
Thread Starter
Junior Member
Joined: Aug 1999
Posts: 80
Likes: 0
From: Metairie, LA. USA
Car: '87 Firebird
Engine: '89 Corvette L98, unstock
Transmission: 700R4
Axle/Gears: 3.23 posi
I got a few questions
Or subtitled "I friggin give up!"
I have an '85 vette that's giving me fits.
I'll give a little background on the problem and ya'll tell me what ya think.
Shortly after the car was purchased it developed a miss, figuring it needed a tune up, we changed the plugs, wires, cap, rotor, and even the coil(MSD). It cured it for a while, then it started again.
The car smokes a little on start up(153K miles), so we figured it was fouling plugs. After changing the plugs several times, the problem seemed to get more frequent and more persistant. It got so bad that we could change the plugs and it would emmediatly still miss.
After reading a Chilton manual under "troubleshooting" one of the cures for a miss at driving speeds was changing the fuel filter. This sounded silly, but we did it anyway. It fixed it!
Now, after running the tank empty because the fuel sending unit went bad, the problem has returned. I obviously replaced the sending unit, and changed the filter again(it worked once
). I checked fire on all the wires and they're good.
I don't know what else to try!
Any help would be appreciated
------------------
Redbird
Bayou Motorsports
87 Firebird
Modified for Autocross
I have an '85 vette that's giving me fits.
I'll give a little background on the problem and ya'll tell me what ya think.
Shortly after the car was purchased it developed a miss, figuring it needed a tune up, we changed the plugs, wires, cap, rotor, and even the coil(MSD). It cured it for a while, then it started again.
The car smokes a little on start up(153K miles), so we figured it was fouling plugs. After changing the plugs several times, the problem seemed to get more frequent and more persistant. It got so bad that we could change the plugs and it would emmediatly still miss.
After reading a Chilton manual under "troubleshooting" one of the cures for a miss at driving speeds was changing the fuel filter. This sounded silly, but we did it anyway. It fixed it!
Now, after running the tank empty because the fuel sending unit went bad, the problem has returned. I obviously replaced the sending unit, and changed the filter again(it worked once
). I checked fire on all the wires and they're good.I don't know what else to try!
Any help would be appreciated
------------------
Redbird
Bayou Motorsports
87 Firebird
Modified for Autocross
Member
Joined: Jul 1999
Posts: 223
Likes: 0
From: Oklahoma City, USA
Car: 89 IROC
Engine: Yes
Transmission: That, too.
There's a chance you might have a bad injector. Does the problem always occur on the same cylinders every time? Injectors can go bad, like anything else on the motor. You can check the injectors by measuring the resistance of the solenoid coil with an ohmeter, but I can't remember off the top of my head what the resistance measurement is supposed to be. In addition to a solenoid going bad, injectors can also fail by sticking in the wide open position, or by failing to close completely. This will make that cylinder run terribly rich all the time.
To see if an injector may be sticking open, check the fuel pressure while you shut off the engine. On a TPI system, after you shut off the motor the system should still hold pressure for a very long time, at least an hour or two. If you see the fuel pressure dropping rapidly after you shut off the engine, the fuel pressure is bleeding off somewhere. That somewhere could be a stuck injector.
To see if an injector may be sticking open, check the fuel pressure while you shut off the engine. On a TPI system, after you shut off the motor the system should still hold pressure for a very long time, at least an hour or two. If you see the fuel pressure dropping rapidly after you shut off the engine, the fuel pressure is bleeding off somewhere. That somewhere could be a stuck injector.
Member
Joined: Apr 2000
Posts: 213
Likes: 0
From: Ok, USA
Definately check your injectors. Then see if there is a place locally that will be able to clean them. I have heard that if you buy one injector it is better to buy a whole set because you will have an uneven distribution of fuel(let me know if anyone else has or hasn't heard of this). There are a couple places here where I live that clean those injectors so I am sure they are in your area as well. Good Luck!!!
------------------
TPI 305,
Gutted airboxes,
gutted MAF,
K&N filters,
Corvette Servo.
14.9@93mph
"Speed kills, wanna live forever, drive a Ford."
------------------
TPI 305,
Gutted airboxes,
gutted MAF,
K&N filters,
Corvette Servo.
14.9@93mph
"Speed kills, wanna live forever, drive a Ford."
Thread Starter
Junior Member
Joined: Aug 1999
Posts: 80
Likes: 0
From: Metairie, LA. USA
Car: '87 Firebird
Engine: '89 Corvette L98, unstock
Transmission: 700R4
Axle/Gears: 3.23 posi
Thanks Guys,
I was hoping it wasn't the injectors, mainly because I know nothing about fuel injection. But that doesn't sound too difficult to check. When checking the resistance should a bad one have more or less resistance? (I figure I'll check all of them, the good ones should give me an idea of what the resistance is supposed to be) Also, can an injector stick closed? And, I noticed that when it runs right(on all 8) it would be hard to start and smell like raw fuel(like a flooded carb), but now it starts real easy but misses, Does that make any more sense or help any?
Thanks again, and I'm going to check the resistance and put the pressure regulator to it.
------------------
Redbird
Bayou Motorsports
87 Firebird
Modified for Autocross
I was hoping it wasn't the injectors, mainly because I know nothing about fuel injection. But that doesn't sound too difficult to check. When checking the resistance should a bad one have more or less resistance? (I figure I'll check all of them, the good ones should give me an idea of what the resistance is supposed to be) Also, can an injector stick closed? And, I noticed that when it runs right(on all 8) it would be hard to start and smell like raw fuel(like a flooded carb), but now it starts real easy but misses, Does that make any more sense or help any?
Thanks again, and I'm going to check the resistance and put the pressure regulator to it.
------------------
Redbird
Bayou Motorsports
87 Firebird
Modified for Autocross
the OHM check on the injectors goes like this...
Warm up car to operating temp
shut off car
remove harness from each injector
use digital ohmmeter and place one probe on each terminal of injector
Reading should be around 16 ohms (it was on mine) any deviation should be okay.. UNLESS one is more than say 1 or 1.5 ohms less than the rest.
you will see what the "average" is and if one or two are much lower or higer than the "average" you will know what is going on!!
Happy hunting!!
Warm up car to operating temp
shut off car
remove harness from each injector
use digital ohmmeter and place one probe on each terminal of injector
Reading should be around 16 ohms (it was on mine) any deviation should be okay.. UNLESS one is more than say 1 or 1.5 ohms less than the rest.
you will see what the "average" is and if one or two are much lower or higer than the "average" you will know what is going on!!
Happy hunting!!
Member
Joined: Sep 2000
Posts: 160
Likes: 0
From: Pocono Pa
get a fuel gauge and do a fuel pres drop test on each injector..it is discribed in every repair manual i have seen and will tell you if you have an injector problem,Also try hooking up the fuel pres gauge and comparing your readings to the manual..........I had a 87z305TPI drive me nuts with a similar problem....turned out to be a spark plug wire shorting out in the wire loom
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Joined: Nov 2008
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From: Rockville Centre, NY
Re: I got a few questions
There's a chance you might have a bad injector. Does the problem always occur on the same cylinders every time? Injectors can go bad, like anything else on the motor. You can check the injectors by measuring the resistance of the solenoid coil with an ohmeter, but I can't remember off the top of my head what the resistance measurement is supposed to be. In addition to a solenoid going bad, injectors can also fail by sticking in the wide open position, or by failing to close completely. This will make that cylinder run terribly rich all the time.
To see if an injector may be sticking open, check the fuel pressure while you shut off the engine. On a TPI system, after you shut off the motor the system should still hold pressure for a very long time, at least an hour or two. If you see the fuel pressure dropping rapidly after you shut off the engine, the fuel pressure is bleeding off somewhere. That somewhere could be a stuck injector.
To see if an injector may be sticking open, check the fuel pressure while you shut off the engine. On a TPI system, after you shut off the motor the system should still hold pressure for a very long time, at least an hour or two. If you see the fuel pressure dropping rapidly after you shut off the engine, the fuel pressure is bleeding off somewhere. That somewhere could be a stuck injector.
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