Fuel Injector question testing
Thread Starter
Safety Car
Joined: Jul 2006
Posts: 3,696
Likes: 1
From: MA
Fuel Injector question testing
Hello forum.
I have a 93 Corvette with stock LT1.
When car gets hot (warmed up) the car has a slight miss or popping sound in exhaust that you can hear.
So far i have replaced the Spark plugs,Wires and ICM (All OEM ) and last coil with MSD street fire. and still have this miss.
So now I test ohms tested the fuel injectors and they all tested at 12.5 ohms cold.
I read that they should test at 16 ohms or better.
Does 12.5 seem low and this could be the problem causing miss?
I heard if its a optispark problem it would be running rough at start up and pretty much all the time.
Thanks for any help
Repzard
I have a 93 Corvette with stock LT1.
When car gets hot (warmed up) the car has a slight miss or popping sound in exhaust that you can hear.
So far i have replaced the Spark plugs,Wires and ICM (All OEM ) and last coil with MSD street fire. and still have this miss.
So now I test ohms tested the fuel injectors and they all tested at 12.5 ohms cold.
I read that they should test at 16 ohms or better.
Does 12.5 seem low and this could be the problem causing miss?
I heard if its a optispark problem it would be running rough at start up and pretty much all the time.
Thanks for any help
Repzard
Le Mans Master
Joined: Jun 2006
Posts: 5,642
Likes: 5
From: One day you're a Comet...the next day you're dust... Arkansas
It depends on which injectors you have. 12.5 is still considered a high impedance injector. Check them hot and cold and if they are consistent with each other within each heat range they are probably OK.
Race Director
Joined: Jun 1999
Posts: 14,924
Likes: 9
From: Merritt Ils Fl
Not an LT1 guy but agree with BADDuck, injectors should be checked hot and cold. Something to think about: Only when warm, is something happening when the system goes into closed loop? Sounds like it. Have you attempted to pull codes? Can you have a scan run to document changes?
Intermediate
Joined: May 2003
Posts: 28
Likes: 0
If it helps, I HAD the same exact problem. It even blew the Injector 2 fuse. I too changed the optispark (due), Plugs, and wires. I checked the other known suspects. It turned out I had one injector testing really really low.
How did your plugs look? I ended up changing to the Bosch III, and the car feels new again
But what prompted my response was a slight miss, and a slight popping at idle in the right exhaust bank.
Hope that helps.
How did your plugs look? I ended up changing to the Bosch III, and the car feels new again
But what prompted my response was a slight miss, and a slight popping at idle in the right exhaust bank.
Hope that helps.
Thread Starter
Safety Car
Joined: Jul 2006
Posts: 3,696
Likes: 1
From: MA
Well I just tested them hot all injectors test at 12-13 ohms except for 1 tested 10.2 ohms (last injector on pass side toward fire wall ) so I think I may have found the issue.
1 bad injector .???
Ps..did check codes..none just 12
So I think i will be ordering some Bosch III
1 bad injector .???
Ps..did check codes..none just 12
So I think i will be ordering some Bosch III
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Safety Car
Joined: Jun 2006
Posts: 3,629
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From: FL
The GM part number is 17015094, but it comes up as discontinued. Rock Auto shows several brands but a single new one (not remanufactured) is almost half the cost of a set of 8 Bosch III's from Jon at FIC.
Your call of course, but I know what I would choose.
Your call of course, but I know what I would choose.
Le Mans Master
Joined: Jun 2006
Posts: 5,642
Likes: 5
From: One day you're a Comet...the next day you're dust... Arkansas
Team Owner
Joined: Jul 2004
Posts: 28,462
Likes: 3,288
From: Hartford WI
Thread Starter
Safety Car
Joined: Jul 2006
Posts: 3,696
Likes: 1
From: MA
Update: Well i called up Jon @ F.I.C and left a message.
These are the injectors im looking at to buy. http://fuelinjectorconnection.com/sh...&productId=197
If Jon say they will be fine..Its a sale
I want to Thank "ALL" for your input and help , again the forum comes to the rescue
These are the injectors im looking at to buy. http://fuelinjectorconnection.com/sh...&productId=197
If Jon say they will be fine..Its a sale
I want to Thank "ALL" for your input and help , again the forum comes to the rescue
Le Mans Master
Joined: Mar 2001
Posts: 7,999
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From: Life is just one big track event. Everything before and after is prep and warm-up and cool-down laps
Cruise-In III Veteran
Cruise-In IV Veteran
St. Jude Donor '12
The Bosch 3's are very good. And Jon is d'man for injectors.
Team Owner
Joined: Mar 2001
Posts: 54,124
Likes: 30
From: Cincinnati, Oh USA
An ohmeter will only find gross injector coil failures. The defining electrical test for injector coils can be done with an imedance bridge which measures the coil inductance and Q. I had a bad injector in my 87 which measured the same d.c. resistance as all the other injectors but my impedance bridge showed 1/2 the inductance and 1/2 the Q. An ohmeter will not find a turn to turn short in the coil, but an impedance bridge will easily find this fault.
Melting Slicks
Joined: Nov 2008
Posts: 2,765
Likes: 5
An ohmeter will only find gross injector coil failures. The defining electrical test for injector coils can be done with an imedance bridge which measures the coil inductance and Q. I had a bad injector in my 87 which measured the same d.c. resistance as all the other injectors but my impedance bridge showed 1/2 the inductance and 1/2 the Q. An ohmeter will not find a turn to turn short in the coil, but an impedance bridge will easily find this fault.
I know what it is.
My father has one for Antique vacuum tube radio repair in his basement workshop.
He uses it for the IF cans & " Litz wire wound oscillator coils.
You are an Electrical Engineer I know.
BR
Last edited by 87 vette 81 big girl; Jun 1, 2011 at 10:33 PM.
Team Owner
Joined: Mar 2001
Posts: 54,124
Likes: 30
From: Cincinnati, Oh USA
You have to explain what an Impedance Bridge is to others here on C4(show a picture.)
I know what it is.
My father has one for Antique vacuum tube radio repair in his basement workshop.
He uses it for the IF cans & " Litz wire wound oscillator coils.
You are an Electrical Engineer I know.
BR
I know what it is.
My father has one for Antique vacuum tube radio repair in his basement workshop.
He uses it for the IF cans & " Litz wire wound oscillator coils.
You are an Electrical Engineer I know.
BR
I have been thinking about showing how to make a simple impedance bridge yourself, but even simple ones require an audio oscillator circuit and headphones.
Team Owner
Joined: Jul 2004
Posts: 28,462
Likes: 3,288
From: Hartford WI
An ohmeter will only find gross injector coil failures. The defining electrical test for injector coils can be done with an imedance bridge which measures the coil inductance and Q. I had a bad injector in my 87 which measured the same d.c. resistance as all the other injectors but my impedance bridge showed 1/2 the inductance and 1/2 the Q. An ohmeter will not find a turn to turn short in the coil, but an impedance bridge will easily find this fault.
Melting Slicks
Joined: Nov 2008
Posts: 2,765
Likes: 5
My father would "Kill" if I took his Impedance Bridge and claimed it as my own.
LOL
My temper came from somewhere.
I appreciate your input & vast electrical experience always here on C4.
Brian