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Misfire cylinder 2(actually 1) only under load



dont think a bad cat can bend a valve but it can cause misfires, random too. care would not feel like its got full power when wot tho if the cat was clogged up. they feel real gutless and sound like a vacuum cleaner with a full bag.

i guess you tried coil swap and icm already.

but then theres that damn crank sensor harness. mine was rather torn up baked and missing insulation. that harness caused 4 different codes to pop up over time.
 
Took ICM, coils, wires and plugs from other ssei.

No help.

Car is definitely gutless. It studders under boost from all the misfires.

Runs best with no SC belt.
 
only thing left is a bad wire some where, to the icm, or the injectors maybe. f ing gremlins. that wire holder loop on the d/s dog bone, wires get chafed there, and off the pcm plugs harness if its just laying around.
 
I swapped injector 6 and 4 wire pigtails. So 4 plugged into 6 and etc... Still puts out fuel but timing wrong. Figured it would show bad wiring. Didn't move the Problem. Actually couldn't tell a difference.

I swapped injectors, moved the injectors, checked the compression, checked the fuel pressure.

I'm at Pcm, catalytic converter, or something else.

I'm running P-log front and ported rear stock on ssei. Think i will get a H-body down pipe. I hate speed daddy headers.
 


take the up stream o2 sensor out, go for a ride, see if it still misses. the hole will let any back pressure from a clogged cat escape and let it run better, sounds like crap, but maybe run better.
 
From a cold start, does each exhaust port get warm equally? Kinda sounds like my problem when 2 injectors weren't firing because bad wiring. You said you swapped injector plugs, and it sounded no different. On my bad injector wires (actually zzp adapters) if I pulled them off the injector nothing changed. That's when I felt those cylinders exhaust exit pipe things (primaries?) And they were ice cold. Car also had serious hesitation under load and crazy misfires of course.
 


Temp gun would be a better idea. Would have saved the 2nd degree buns on my finger tips. Who knew that the primaries only took about 5 seconds to get hot enough to melt flesh?
 
I've got the temperature gun. No misfires at idle but I can see any temperature differences at idle and then run it up the street and check again.
 
Really hard to get a good reading on the back cylinders. Does not appear as if I have a cold cylinder. Front manifold is stainless and seems to read different than the cross over temperature. I think shiny stuff reads low with temperature gun.

Still kind of at a loss.
 
still fighting misfire only under boost. Ported heads I put on somehow bent a valve. Just did a compression test all cylinders with plugs removed, bypass open, and TB open. 170 - 175 psi all cylinders. I'm at the end of my rope. I own two running Bonnevilles and I have switched coil packs, plugs, ICM, wires, ........etc..... Nothing left to swap but the PCM. Runes fine without boost (no belt), Misfires cylinders 2 and 5 mostly 5. couple of 3 and 4 if I hold it. It will actually backfire or poop out the exhuast.

Will the PCM from my running 03 SSEI run in my 02 SSEI? (both stock)


Problem car is 02 SSEi with 53,000 miles. My intercooler with Yellow Terra 1.9 rockers, ported rear exhaust manifold, p-log front, 2-1/4 intercooler(mine).


Any advice?
 


How do the plugs look? Does the misfiring cyl plugs look any different?

Also any vac leaks? Check with a can of carb cleaner or propane torch and listen for idle speed changes.
 
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