L-EATER

iTrader: (2)

My LS1 powered truck has developed a strange problem. It runs fine when you start it up cold and will usually run fine until you shut it off and let it sit for a while after say a 10 or 15 minute trip or more. Upon re-starting it runs like total ***-sputtering and missing and wont hardly pull itself. Its like heat-soak is a factor. I have determined that, when its doing this, I can unplug the harness connector that goes to the passenger side coils and nothing seems to change. If I unplug the driver side coils harness, it dies or sometimes runs as if its on maybe 1 cylinder. So when its having this problem the passenger side coils are contributing a little not much-the problem is definitely on the 2,4,6,8 coils. One thing thats weird is that it doesnt set any codes.

Another thing that is strange is, when its doing this crap if I go full throttle it will straighten up and run like a bat outta hell within 1 to 2 seconds of putting it on the mat. Sometimes after I lift and go back to part throttle cruising it stays running fine, sometimes it goes back to running on 4 cylinders. But everytime I go full throttle it clears up.

I have searched on here and it seems some people have had trouble with the harness connector. I have looked at mine and it looks ok. I scraped the blades a little just in case there was some kinda corrosion film on it but that didnt help any. I have traced the power and ground wires back thru the harness and they are fine. I am thinking it either has to be all 4 coils on the pass side gone bad, the harness that ties the 4 coils to the engine harness, or the connector on the engine harness. What do you guys think?? I am planning on swapping the coils side to side first thing tomorrow morning to see if the problem moves or stays.

HELP PLEASE !!!

BOTTLEFED383

check intake gaskets for a leak or restricted converter if they are still on the vehicle

L-EATER

iTrader: (2)

No converters on vehicle. I hadn't thought about the intake-thats something to consider, thanks.

What about the PCM? Can it be freaking out and causing this? I have another one on my Blazer thats the same yr, I could flash it with the trucks file and see if that changes anything.

Keep the ideas coming.....

eseibel67

iTrader: (10)

Too much co-incidence for 4 coils to come and go in unison. Swapping the coils is a lot of work for nothing.

Those 4 coils do however share a common power source and ground. My bet is a ground problem since the condition changes with temperature. And when you go WOT, the engine is twisting on the mounts just enough to reconnect the bad ground.

XGthArO86X

iTrader: (1)

my car does the same exact thing to the key..

my car pulls o2 codes both went at sametime? ive replaced nthem bout 6 months ago i dnt want to spend another 160 lol

horsepower_junkie

iTrader: (4)

If I was in your shoes I would be checkin the injector harness for a bare wire, if you have access to a good code reader watch pids on maf and tp sensor you might be surprised. Could also be an iac problem? just a few to think about

cody161

iTrader: (18)

also see if you can find out where all those coils are grounded. I had a similar problem with coils 1,3,5,7 misifiring and there was a ground on the back side of the drivers side head for all of those coils that was loose.

L-EATER

iTrader: (2)

Ok, I re-checked and re-cleaned the terminals on the coil harness connector and put some electrical grease on it. Nothing changed so I traced the ground thru the harness to a place where 3 grounds hook to 4 grounds. Couldnt see what was under the factory shrink wrap there so I cut that out and re-soldered it and added a wire which I took to the firewall. Nothing changed so I tapped into the power wire and checked the volts while it was missing and it had full battery voltage (13.94) I went ahead and jumpered a wire straight from the battery to the pink wire going to the pass side coils while it was missing and still no change.

I am on my way outside to swap the coils side to side, just to see.....I really dont expect that to change anything but its bugging me not knowing.

Keep the suggestions coming.

Ryanmgaspard

iTrader: (6)

Mine did the same thing and same cyclinder misfire but I never threw a code. I had my tuner read the computer while running and the passenger o2 was dead and the driver side was very slow. I spent the $80 for the Denso ones (which is what you will get if you order ac delco's) and the problem is solved.

L-EATER

iTrader: (2)

Ok, I swapped the coils side to side and its still acting like a fool. I checked the injector harness and found a questionable splice on # 7 so I repaired that. Still acts up.

A couple replies mention 02's......can the 02 really cause all 4 cylinders on one side to cut out at the same time? I should have some time to hook the laptop to it tomorrow and do some scans. I am going to study the wiring diagrams tonight to see if there are any common threads.........

GRRRRRRRR !!!!! I hate oddball problems.

35th camaro

i work as mecanic and probleme like that sound verry much like 02 sensor before caths. on same side of 2 4 6 8, seen this many times. wrong output from 02 making computore to send to much fuel to that bank of cylindres, thats why you are getting misfires, but at full trottle you can burn the fuel. dont wait to fix or you will ruin your cath if you have any.

XGthArO86X

iTrader: (1)

Changed my o2s today. Haven't had a problem since. It did the same exact things your does. I connected the modus to it and read all misfires and everything. Changed o2 on pass side and not a single one. And before it missed 2,4,6,8 like 456 times ha

ViaBellator

iTrader: (2)

+1 on the O2's. What happens is that the bad O2 reads really rich on that bank and causes your LTFT's to read -20 or so. At idle/cruise the ECM ends up pulling so much fuel it runs lean and misfires. When you go WOT it goes into PE mode, runs in open loop, and doesn't read the sensor so no more lean condition and no more misfires.

Happened on my 04 GTO exactly as you described. New O2. No more problem. Figured out the LTFT issue via HP Tuners and forced the car into Open Loop at Idle and the problem went away. Back in closed loop and the longer it sat the worse it got. You could literally watch the fuel trims go really negative.

thunderstruck507

iTrader: (18)

if it were the coils I would expect backfires when the excess fuel did get lit

check the injectors and the o2 sensors as mentioned

L-EATER

iTrader: (2)

Well I ran out of time to mess with it-had to go back to work for a couple days but I am off tomorrow-will swap the O2 and see what happens. I hope this fixes it so I can move forward with my plans to turbo it