03 ZO6 replaced fuel injectors, still misfiring/bogging down /hesitating/bucking - CorvetteForum - Chevrolet Corvette Forum Discussion



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03 ZO6 replaced fuel injectors, still misfiring/bogging down /hesitating/bucking

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Old 06-13-2018, 06:18 PM   #1  
ZO6_Dom
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Default 03 ZO6 replaced fuel injectors, still misfiring/bogging down /hesitating/bucking

Hey guys made a thread a few weeks ago trying to diagnose my car. Thought it was fuel injectors so I replaced all of them. Still having the same issue.

LS2 motor with less than 5k miles on it. Fresh head job, perfect compression.

Scanned it with my friends GM scanner, even with it plugged in while driving, giving live info during a misfire episode it wouldnt throw a code other than p0300

As of two weeks ago only after start up, while crusing at a steady pace around 1.5-2K rpm the car will start misfiring/bogging down /hesitating/bucking if I just keep my foot on the pedal giving it gas it will continue to misfire for 10-30 seconds then "kick back on" to normal power again.
When it has started doing this and I got caught at a red light I had to rev it up and give it gas or else it will flood itself and die. I say flood because when it does this I can smell a strong fuel odor burning in my exhaust.

Any ideas what to swap next? Coil packs, Plug wires, new spark plugs (again), 02 sensors, vaccum leaks?

Thanks....
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Old 06-13-2018, 07:09 PM   #2  
evolmotorsprt
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What fuel injectors and size did you install? Was the LS2 tuned for the original or current injectors? When you say flood I think of bigger injectors on a stock tune.

Also so check your plugs and wires and the condition of where the coil packs and injectors connect to the harness.

Last edited by evolmotorsprt; 06-13-2018 at 07:10 PM.
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Old 06-13-2018, 08:03 PM   #3  
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Originally Posted by evolmotorsprt View Post
Also so check your plugs and wires and the condition of where the coil packs and injectors connect to the harness.
I would suspect loss of spark/spark breakdown before fuel based on your description of the symptoms. Check per evolmotorsprt directions and see what you find.
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Old 06-13-2018, 08:43 PM   #4  
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Hello Mr. Dom !!
What data PIDS were you looking at with your friends Tech 2 ??...I'd be looking at your your O2 sensors and long and short fuel trims...also MAF gm/sec at idle and under load...also Baro and ECT PIDS...were you able to do this ??...you said you were looking at live data driving...if you can post these here I probably give you some direction (numbers at idle and 3000 RPM)..now you said you changed injectors...did you check the injectors for feed and signal ??...if either were no good new injectors won't help ya !!...now as far as vacuum leaks the car will run better under load but crappy at idle...vacuum leak fuel trim numbers are high at idle and more normal at high RPM...you don't have a vacuum leak !!...you can check your fuel trims with that Tech 2...a bad MAF sensor or low fuel pressure will have good trim numbers at idle and high fuel trim numbers at high RPM. I don't know if you know how to read Mode 6 data but I'd look there (A2 -A9)...you most likely will find your cylinder that is misfiring there...maybe your friend that owns the Tech 2 is familiar with mode 6. You can probably do a cylinder balance test with that Tech 2...or just pull each plug wire and see if you notice a change in RPM...with 8 cylinders it's a little more difficult to tell...I don't know what else to tell you...if you want to just fire the "parts cannon" go for plug wires, coil packs, O2 sensors, MAF sensor, fuel pump...if you need direction on how to check some things let me know.

p.s. Fuel pressure KOEO is 55-62...with key off less than 5 psi drop in 1 minute !!...with engine running fuel pressure should NOT drop when you snap the throttle !!

Last edited by rwobs777; 06-14-2018 at 12:33 PM.
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Old 06-14-2018, 02:19 PM   #5  
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Quote:
Originally Posted by evolmotorsprt View Post
What fuel injectors and size did you install? Was the LS2 tuned for the original or current injectors? When you say flood I think of bigger injectors on a stock tune.

Also so check your plugs and wires and the condition of where the coil packs and injectors connect to the harness.
I used OEM replacements, I also double checked wires for any burning and their connections. And yes the car was tuned with the OEM sized injectors, put a few thousand miles on since with zero issues until now.

Last edited by ZO6_Dom; 06-14-2018 at 02:21 PM.
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Old Today, 10:18 AM   #6  
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I had a similar problem in my Mustang. It turned out to be the MAF. I would look into that next
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Old Today, 09:15 PM   #7  
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Just replaced spark plug wires. Spark plugs. Header gaskets. Still did its usual cold start misfire before I even got down the street. 02 sensors and coil packs next?
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