Got everyone stumped on my setup
Thread Starter
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iTrader: (25)
Joined: Dec 2004
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From: Kannapolis, NC
Got everyone stumped on my setup I will give as much info as possible. The problem is a dead misfire between 2800-3200 rpm. The car spits and pops very badly. Replaced PCM, been thru SD tune and now are running a 100 mm Lingenfelter MAF. Nothing we do will change the characteristics of the problem. The motor is a LS7 with ported L92 heads and a 257/266 248/222 110 cam advanced 4 ivo-22.5 ivc-54.5
evo-67.5 evc-19
Open exhaust with kooks 1 7/8 headers.
.040 gasket with a .035 quench
heads milled to achieve 68cc
SCR: 11.99:1
DCR: 8.27:1
The problem is not in the tune has been looked at by different reputable tuners and nothing has changed. Some thoughts are that there is something wrong with the cam (how it was built) or the crank reluctor wheel is bent (would think this would cause issue at all times??) Have you guys come across anything that was acting like this before? Thanks for any help.
evo-67.5 evc-19
Open exhaust with kooks 1 7/8 headers.
.040 gasket with a .035 quench
heads milled to achieve 68cc
SCR: 11.99:1
DCR: 8.27:1
The problem is not in the tune has been looked at by different reputable tuners and nothing has changed. Some thoughts are that there is something wrong with the cam (how it was built) or the crank reluctor wheel is bent (would think this would cause issue at all times??) Have you guys come across anything that was acting like this before? Thanks for any help.
Thread Starter
10 Second Club
iTrader: (25)
Joined: Dec 2004
Posts: 2,554
Likes: 1
From: Kannapolis, NC
TECH Enthusiast
Joined: Apr 2005
Posts: 540
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Well you could verify your cam timing with a degree wheel to check that
check the plugs to see if there is a fine crack (probably already did)
Double check timing with the light (probably did that too)
Start unplugging injectors to figure out if its a single cylinder or all of them
I had an issue that sounds almost identical to a friends car.. he was running an AEM and had the senstivity set wrong on the crank sensor..
Whats the timing doing when it occurs (you have HP tuners or efi live?), is there knock?, AFR?
check the plugs to see if there is a fine crack (probably already did)
Double check timing with the light (probably did that too)
Start unplugging injectors to figure out if its a single cylinder or all of them
I had an issue that sounds almost identical to a friends car.. he was running an AEM and had the senstivity set wrong on the crank sensor..
Whats the timing doing when it occurs (you have HP tuners or efi live?), is there knock?, AFR?
For sure dont over look the simple things either.
Try unplugging your 02's, one side, test it. Other side, test it, both sides, test it.
I had a simular problem a year ago. Just because someone is reputable doesnt mean they are worth a lick. It ended up being an 02 and took 5 months to track down. Started with my SES light flashing while cruising down highway. Later developed into a hard miss between 1300-4500.
Did the tuners check your sensors at idle or while the car was malfunctioning? If they did it at idle or when it wasnt malfunctioning odds are it wont show up. Data log it during the malfunction and see what its doing electronics wise.
Try unplugging your 02's, one side, test it. Other side, test it, both sides, test it.
I had a simular problem a year ago. Just because someone is reputable doesnt mean they are worth a lick. It ended up being an 02 and took 5 months to track down. Started with my SES light flashing while cruising down highway. Later developed into a hard miss between 1300-4500.
Did the tuners check your sensors at idle or while the car was malfunctioning? If they did it at idle or when it wasnt malfunctioning odds are it wont show up. Data log it during the malfunction and see what its doing electronics wise.
I recently had a problem similar to this. I had a misfire at 2800 to 3200 rpm at light acceleration. If I gave it more gas during that rpm it would clear up. missed at light accel. any other time the car ran great. Try to narrow down the cylinder that is affected. I used a genesis scanner and looked at the misfire counts. #7 showing miss counts. ended up being a broke valve spring on #7. Thank god for dual springs.
Maybe this will help. may not
Maybe this will help. may not
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