Do these symptoms sound like a bad injector?
07-19-2017, 12:19 PM
#1
Do these symptoms sound like a bad injector?
Stock LB9, 117,000 miles
Factory Multec Injectors
Ran fine for first 1,000 miles after major tune up:
(plugs, wires, cap, rotor, module, pickup, coolant, all sensors replaced, idle set, vacuum leaks checked, fuel pressure/regulator checked, echlin fuel rail injector cleaner treatment)
Then did a system cleaner (Gumout multi-system tune up) into the intake and soak, and the gas tank.
Symptoms started soon after
I just changed the fuel filter (as a precaution)
Symptoms:
Cylinder(s) missing shortly after startup. Cold, no apparent miss but starts within a minute of driving.
Miss gets worse with warm up.
Car idles high and has trouble with low idle
Can hear small backfiring (muffled popping) in exhaust
Miss remains at low RPM and high RPM but much less apparent at high RPM
Miss remains and gets worse at heavier throttle (low and higher RPM)
Engine has less power (but still some).
Seems to shift harder into second at mid throttle.
I suspect a stuck/clogged injector.
A fouled plug or vacuum leak would clear up with higher RPM.
Thoughts?
Factory Multec Injectors
Ran fine for first 1,000 miles after major tune up:
(plugs, wires, cap, rotor, module, pickup, coolant, all sensors replaced, idle set, vacuum leaks checked, fuel pressure/regulator checked, echlin fuel rail injector cleaner treatment)
Then did a system cleaner (Gumout multi-system tune up) into the intake and soak, and the gas tank.
Symptoms started soon after
I just changed the fuel filter (as a precaution)
Symptoms:
Cylinder(s) missing shortly after startup. Cold, no apparent miss but starts within a minute of driving.
Miss gets worse with warm up.
Car idles high and has trouble with low idle
Can hear small backfiring (muffled popping) in exhaust
Miss remains at low RPM and high RPM but much less apparent at high RPM
Miss remains and gets worse at heavier throttle (low and higher RPM)
Engine has less power (but still some).
Seems to shift harder into second at mid throttle.
I suspect a stuck/clogged injector.
A fouled plug or vacuum leak would clear up with higher RPM.
Thoughts?
Last edited by Tootie Pang; 07-19-2017 at 01:59 PM.
07-19-2017, 12:54 PM
#2
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Car: 88GTA
Engine: 5.7TPI
Transmission: Auto
Axle/Gears: 3.27
Re: Do these symptoms sound like a bad injector?
"Then did a system cleaner (Gumout multi-system tune up) into the intake and soak, and the gas tank."
Welcome to my world. Now order some new Bosch III's!
I did the same thing on my 85. Ran fine till I loosened all the crap everywhere and in the injectors.
Replaced with new injectors and filter, runs like a champ!
Welcome to my world. Now order some new Bosch III's!
I did the same thing on my 85. Ran fine till I loosened all the crap everywhere and in the injectors.
Replaced with new injectors and filter, runs like a champ!
07-26-2017, 01:47 AM
#4
Re: Do these symptoms sound like a bad injector?
Well I got the Bosch D3's in and... that wasn't the problem. Doh! Oh well, I went through the upper engine stuff and made sure it was all good. Fresh gaskets, cleaned electrical connections, throttle body cleaning. That sort of stuff.
So I started it up and it started missing and backfiring again at idle after a little warming. I immediately thought back to when I first got the car and the No.2 plug was particularly fouled. So I unplugged the No. 2 injector and the backfiring stopped and the engine smoothed out. Damn. Time to pull that plug and prepare for valve stem seals.
Either way, I think after 30 years and 117,000 miles, the Multecs were probably due.
On to the plug. I am narrowing it down I hope. I suppose that system cleaner could have loaded up the weak plug.
So I started it up and it started missing and backfiring again at idle after a little warming. I immediately thought back to when I first got the car and the No.2 plug was particularly fouled. So I unplugged the No. 2 injector and the backfiring stopped and the engine smoothed out. Damn. Time to pull that plug and prepare for valve stem seals.
Either way, I think after 30 years and 117,000 miles, the Multecs were probably due.
On to the plug. I am narrowing it down I hope. I suppose that system cleaner could have loaded up the weak plug.