New to forms with missfire issue
Thread Starter
Intermediate
Joined: Apr 2018
Posts: 31
Likes: 0
New to forms with missfire issue
Hey guys I just picked up a 96 Vette CE lt4. The car sat for many years and only has 70k miles. The previous owner had cleaned the tank, replaced the plugs, filters and a few other things to get it going again. When I bought it it ran decently but had some misfireing and codes p300 and p304
So I decided to change out the Opti, water pump, theromastate, plug wires and coil. Drained all fluids and replaced. I inspected the plugs and they looked brand new. The issue was still there. So finally I dug into the fuel injectors where cyl 4 was clogged. So I removed and cleaned all the injectors while I was at it I bought a new FPR. Now the car feels smooth and runs strong. Except at high load under low rpms. In 5th or 6th gear at WOT the car studderes a bit it's really bad with the AC on. I can also hear an ever so faint miss at idle. What are your thoughts? I thought I had replaced all the important probimatic parts.
Thanks in advanced.
So I decided to change out the Opti, water pump, theromastate, plug wires and coil. Drained all fluids and replaced. I inspected the plugs and they looked brand new. The issue was still there. So finally I dug into the fuel injectors where cyl 4 was clogged. So I removed and cleaned all the injectors while I was at it I bought a new FPR. Now the car feels smooth and runs strong. Except at high load under low rpms. In 5th or 6th gear at WOT the car studderes a bit it's really bad with the AC on. I can also hear an ever so faint miss at idle. What are your thoughts? I thought I had replaced all the important probimatic parts.
Thanks in advanced.
Racer
Joined: Apr 2018
Posts: 349
Likes: 55
Hey guys I just picked up a 96 Vette CE lt4. The car sat for many years and only has 70k miles. The previous owner had cleaned the tank, replaced the plugs, filters and a few other things to get it going again. When I bought it it ran decently but had some misfireing and codes p300 and p304
So I decided to change out the Opti, water pump, theromastate, plug wires and coil. Drained all fluids and replaced. I inspected the plugs and they looked brand new. The issue was still there. So finally I dug into the fuel injectors where cyl 4 was clogged. So I removed and cleaned all the injectors while I was at it I bought a new FPR. Now the car feels smooth and runs strong. Except at high load under low rpms. In 5th or 6th gear at WOT the car studderes a bit it's really bad with the AC on. I can also hear an ever so faint miss at idle. What are your thoughts? I thought I had replaced all the important probimatic parts.
Thanks in advanced.
So I decided to change out the Opti, water pump, theromastate, plug wires and coil. Drained all fluids and replaced. I inspected the plugs and they looked brand new. The issue was still there. So finally I dug into the fuel injectors where cyl 4 was clogged. So I removed and cleaned all the injectors while I was at it I bought a new FPR. Now the car feels smooth and runs strong. Except at high load under low rpms. In 5th or 6th gear at WOT the car studderes a bit it's really bad with the AC on. I can also hear an ever so faint miss at idle. What are your thoughts? I thought I had replaced all the important probimatic parts.
Thanks in advanced.
Le Mans Master
Joined: Sep 2013
Posts: 6,192
Likes: 750
From: near the thumb in the mitten
Misfire counter is a parameter in some scanners that displays the number of misfires per cylinder. It helps with P0300 and what may feel like a misfire with no codes. With a "clogged" injector it's strange only one would have the condition. Injector drop test could indicate if other injectors are effected.
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Le Mans Master
Joined: Sep 2013
Posts: 6,192
Likes: 750
From: near the thumb in the mitten
If you can get access to a tech2 you can monitor misfires. fuel trim can indicate if engine is lean due to injector or rich from losing spark. I'm guessing you have replaced spark plugs what brand is in it? Maf is film clean if it's oily it can cause rough run.
Thread Starter
Intermediate
Joined: Apr 2018
Posts: 31
Likes: 0
Yes. It has ngk. I have access to hptuner which I believe is not supporteda dn if course I have an odb2 scanner. I'll try cleaning the maf that's a good idea
Thread Starter
Intermediate
Joined: Apr 2018
Posts: 31
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Well I cleaned the maf and no luck there. Actually I noticed the missfire is possibly getting worst as it warms up.... Is that even possible or am I imaging it? While peaking around I noticed the new water pump I just replaced is leaking from the leak hole. Man am I mad. So I called summit racing and told them I think both parts are bad. So they are sending me 2 new ones. Maybe it's possible I got a defective Opti right out of the box? Ill keep updated.
Update: I got a P0303 code
Update: I got a P0303 code
Last edited by v33sonata@gmail.com; Apr 14, 2018 at 01:05 AM.
