Misfire under boost
11-09-2009, 04:12 PM
#1
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Thread Starter
Join Date: Oct 2006
Location: Southaven, Ms.
Posts: 218
Misfire under boost
Car misfires under boost. Mild "popping" in the exhaust, sometimes gets worse, the occasional backfire, not loud.
spark or fuel must be the problem, which?
I have installed:
NGK Iridium IX BPR6EIX-11, spark plugs? Is this the problem?
Accel 8.8mm. plug wires.
Is Turbo blowing out spark? Started out at factory gap, then lowered it to 0.20. Is this the problem? Wrong plug?
Is engine running out of fuel?
Plug color is red/rust, indicates normal. Used fouled NGK plugs from the 81'NA I have, running them cleaned up the plugs, still ran with the missfire. Running lean? Air fuel gauge given to me appears not to work.
Runs great until you get into boost.
Stock FPR. Stock fuel lines.
Stock ignition.
JWT upgrade.
3" mandrel bent exhaust, Magnaflow muffler..sounds great! until misfire....
spark or fuel must be the problem, which?
I have installed:
NGK Iridium IX BPR6EIX-11, spark plugs? Is this the problem?
Accel 8.8mm. plug wires.
Is Turbo blowing out spark? Started out at factory gap, then lowered it to 0.20. Is this the problem? Wrong plug?
Is engine running out of fuel?
Plug color is red/rust, indicates normal. Used fouled NGK plugs from the 81'NA I have, running them cleaned up the plugs, still ran with the missfire. Running lean? Air fuel gauge given to me appears not to work.
Runs great until you get into boost.
Stock FPR. Stock fuel lines.
Stock ignition.
JWT upgrade.
3" mandrel bent exhaust, Magnaflow muffler..sounds great! until misfire....
Last edited by captken; 11-09-2009 at 04:53 PM.
11-09-2009, 04:58 PM
#2
How much boost are you running?
What octane fuel?
Are you using the JWT 260hp upgrade or 400hp upgrade?
Have you checked all the sensors and connections?
Ecu connections?
You really need to get the a/f gauge working... that will tell you what's going on in the fuel department.
What octane fuel?
Are you using the JWT 260hp upgrade or 400hp upgrade?
Have you checked all the sensors and connections?
Ecu connections?
You really need to get the a/f gauge working... that will tell you what's going on in the fuel department.
11-09-2009, 07:18 PM
#3
Registered User
Thread Starter
Join Date: Oct 2006
Location: Southaven, Ms.
Posts: 218
boost
10psi. Misfire occurs at indicated 5psi, autometer phantom gauge.
Manual boost controler I built, diy home depot.
93 octane with octane boost, I have tried 104 Octane boost and NOS octane booster/racing formula to up the rating a couple points, cannot see any difference between using pump gas or the octane supliment.
JWT 450hp upgrade.
89 ecu plugs soldered in.
New sensors and upgraded plugs.
Manual boost controler I built, diy home depot.
93 octane with octane boost, I have tried 104 Octane boost and NOS octane booster/racing formula to up the rating a couple points, cannot see any difference between using pump gas or the octane supliment.
JWT 450hp upgrade.
89 ecu plugs soldered in.
New sensors and upgraded plugs.
11-09-2009, 09:09 PM
#4
i felld offa mai trike
Join Date: Nov 2008
Posts: 827
does it make alot of black smoke out the exhaust when you're boosting? You could be fouling them under boost and running lean at low rpm's/light load would un-foul a plug... long shot I know, but still lol
Also, my car had fouled a plug and would still idle fine and would actually run normally until I got into it, I'll bet it's the spark plugs causing your problems...
I took my plugs out today and cleaned them off, they were a nice brown color, and it still helped majorly the way my car ran.
Also, my car had fouled a plug and would still idle fine and would actually run normally until I got into it, I'll bet it's the spark plugs causing your problems...
I took my plugs out today and cleaned them off, they were a nice brown color, and it still helped majorly the way my car ran.
11-11-2009, 04:08 PM
#6
Registered User
Thread Starter
Join Date: Oct 2006
Location: Southaven, Ms.
Posts: 218
P90a head
No black smoke on acceleration. Observed, following the car.
Tried NGK non irridium, same result.
I wonder if the hydraulic head could be leaking down?
Installed new timing set.
Car ran way better before I set cam timing and ignition timing to spec.
Roughly twice as fast.
I have heard you need to adjust the valves on the hydro head...hmmm
Ideas?
Tried NGK non irridium, same result.
I wonder if the hydraulic head could be leaking down?
Installed new timing set.
Car ran way better before I set cam timing and ignition timing to spec.
Roughly twice as fast.
I have heard you need to adjust the valves on the hydro head...hmmm
Ideas?
11-11-2009, 06:04 PM
#7
At this point you really need to get your a/f gauge working to see if / when it's running too lean.
If I remember correctly, the ecu got fried by rain water, so it got shipped off to JWT to be rebuilt?
Is the timing set to ~20* BTDC?
Have you checked the fuel pressure?
Do all 6 spark plug tips look the same when removed? Any that are fouled or fried more than the others?
All ecu & sensor connections are correct and tight?
I would re-gap the plugs to ~.041 in.
If all else fails, I say something is wrong w/ the JWT ecu.
If I remember correctly, the ecu got fried by rain water, so it got shipped off to JWT to be rebuilt?
Is the timing set to ~20* BTDC?
Have you checked the fuel pressure?
Do all 6 spark plug tips look the same when removed? Any that are fouled or fried more than the others?
All ecu & sensor connections are correct and tight?
I would re-gap the plugs to ~.041 in.
If all else fails, I say something is wrong w/ the JWT ecu.
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