Engine Missing After Prolonged Downtime
Thread Starter
Le Mans Master
Joined: Aug 2002
Posts: 8,472
Likes: 38
From: Houston TX
St. Jude Donor '11
Engine Missing After Prolonged Downtime
I tried starting my car today after it had been down without battery power for some weeks. It has been down because I upgraded blower head units from a Novi 1200 to a 1500. This required some different brackets and different air bridge from ECS so I had them send me an LS3 intercooler to throttle body pipe so I could eliminate the MAF housing since I was using the POWRMAF 100mm housing and card style LS3 MAF sensor.
Anyway, I got everything all back together and started it up and it ran like garbage; missing badly and randomly, not being able to maintain a steady RPM and when I gave it throttle it almost dies. The new pipe that that the MAF is in is slightly larger so I tried playing with the MAF tables but it didn't change anything. I switched to VE mode and it got a little better but not much. There was a misfire DTC that I cleared and it has not come back. To me it seems ignition related and I got to thinking that it may need a crank relearn from being without power for so long?
I'm stumped so any unput is appreciated. I know the smart thing to do would be to put the old pipe and MAF housing back in to get it back to how it was but I am not at that point yet.
Anyway, I got everything all back together and started it up and it ran like garbage; missing badly and randomly, not being able to maintain a steady RPM and when I gave it throttle it almost dies. The new pipe that that the MAF is in is slightly larger so I tried playing with the MAF tables but it didn't change anything. I switched to VE mode and it got a little better but not much. There was a misfire DTC that I cleared and it has not come back. To me it seems ignition related and I got to thinking that it may need a crank relearn from being without power for so long?
I'm stumped so any unput is appreciated. I know the smart thing to do would be to put the old pipe and MAF housing back in to get it back to how it was but I am not at that point yet.
Thread Starter
Le Mans Master
Joined: Aug 2002
Posts: 8,472
Likes: 38
From: Houston TX
St. Jude Donor '11
There's HPT logs and a screenshow of two stumbles here: http://www.hptuners.com/forum/showthread.php?t=20132
Tech Contributor
Joined: Jul 2002
Posts: 14,950
Likes: 264
From: St. Louis, MO
St. Jude Donor '08
Sure sounds like unmetered air to me too...
GTODoug just installed one of these MAF's, might want to shoot him a PM to see if he had any specific problems tune wise when he did so. His car is running great with it, not sure what all he had to do to get it that way.
GTODoug just installed one of these MAF's, might want to shoot him a PM to see if he had any specific problems tune wise when he did so. His car is running great with it, not sure what all he had to do to get it that way.
Safety Car
Joined: Sep 2008
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Anyway, I got everything all back together and started it up and it ran like garbage; missing badly and randomly, not being able to maintain a steady RPM and when I gave it throttle it almost dies.
classic symptom for unmetered air like has been said before. When you gas it the ecm sees a tps increase but the main sensor it looks at is maf to add fuel. Either the MAF is whacked out or there is air getting to the engine and the ecm isnt seeing it. I would first watch tps while your gassing it (can be done with KOEO) then look at maf and see if it changes while you gas it. Good luck
classic symptom for unmetered air like has been said before. When you gas it the ecm sees a tps increase but the main sensor it looks at is maf to add fuel. Either the MAF is whacked out or there is air getting to the engine and the ecm isnt seeing it. I would first watch tps while your gassing it (can be done with KOEO) then look at maf and see if it changes while you gas it. Good luck
Thread Starter
Le Mans Master
Joined: Aug 2002
Posts: 8,472
Likes: 38
From: Houston TX
St. Jude Donor '11
Thanks for the input guys. There's not much after the MAF with the current setup to let unmetered in air. I'll look at my catch can setup too. I'll take a look and likely change back to the LS2 pipe and POWRMAF to see if that changes anything.
Thread Starter
Le Mans Master
Joined: Aug 2002
Posts: 8,472
Likes: 38
From: Houston TX
St. Jude Donor '11
Well I played with it last night. I could not see any obvious air leaks so I changed back to the POWRMAF housing and LS2 pipe and edited the tune back to how it was before the car went down for the head unit swap. It ran much better but the miss is still there, it's just less pronounced. Whats worse is my brand new head unit is leaking like a seive!
So I doubt I'll have time to troubleshoot the miss anytime soon as the unit may have to go back to Paxton AGAIN, or maybe in the dumpster.
So I doubt I'll have time to troubleshoot the miss anytime soon as the unit may have to go back to Paxton AGAIN, or maybe in the dumpster.
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Thread Starter
Le Mans Master
Joined: Aug 2002
Posts: 8,472
Likes: 38
From: Houston TX
St. Jude Donor '11
I tried new plugs and wires last week and it didn't help. Today I swapped my stock LS2 MAF back in and re-dialed in my MAF tables. Problem solved. Idle is solid, cruising is smooth, no stuttering, and WOT is back to Holy $h1t! I don't know what happened to the card style MAF because it was trouble free when I first put it in but I'm just glad to have a nicely running car again.
Oh, any my latest Paxton leak was because it was overfilled from the factory. Took ~2 oz or oil out and it has been trouble free for a while.
Oh, any my latest Paxton leak was because it was overfilled from the factory. Took ~2 oz or oil out and it has been trouble free for a while.
