SSmokin 01

iTrader: (14)

Well here we go(long). I've had the car set-up the way it's been on my '01 for 19k miles and on the '02 for about 10k(currently 13k miles). I haven't had any problems. I know the whole fmu deal is not optimal but with the maft(base 10% rich wot 0) my o2's at wot have been in the rich low to mid .90's. Just recently the car would drop on its face at anything above 4700 rpm.

I a-tapped it and found the #3 cylinder miss-firing anywhere from 20-100 times. This only happens once rpms cross this point. TPS % or load has no effect on when the missfire starts.

My ltrims fluctuate anywhere from + 9-25%(I know not optimal).Maft doesn't greatly effect them.

No knock is present during the missfire.

o2's on B1 jump .02-.03 when the missfire starts.

Fuel pressure is 66psi at idle and 63psi during part throttle. During wot the pressure will gradually drop to 55 psi because the fmu is garbage. However the o2's never drop below .90's and no signs of detonation are present.

During the missfire timing is at 17.5-18.5 and once dropped to 9.

ECT(no fluctuations) and IAT do not effect the missfire on-set.

19-20 inches of vacuum at idle.

Voltmeter slightly past midpoint.

Oil pressure at 40-50 psi.

Smooth idle and runs normally under the 4700 rpm threshold.

Rich smell from exhaust.


Now this is what I've done to trouble-shoot the problem:

Swapped wires- no change
swapped coil- no change
changed plug- no change
changed plug gap from .35-.33- no change
plug inspection- all plugs normal with #3 showing signs of missfire only after repeated runs during diagnostics
swapped injector- no change
inspected fuel rail- no obstructions
compression tested cyls- all at 183-185psi
pulled rockers and pushrods on #3- straight
inspected valve springs- no visible break or fatigue
swapped o2's- no change
pcm re-set- no change
removed maft- picked up SES light: fuel trim lean banks 1&2
and got 2-3 degrees of knock retard along with the ever present missfire and caught 20 misses on #1 cyl
re-installed maft at 10%rich base and 6%rich wot- no SES but no change in missfire
visually inspected all visible vacuum lines- no breaks


Whats left?:

disconnect blower
change fuel filter
crank sensor check- where and how to????
propane test for vacuum leak
check coolant for contamination
inspect head gasket
inspect valves
up-grade fuel system: duel in-tank,CAS fpr,delphi 42.5lb/hr injectors,-8 feed -6 return,LS1 edit
wideband

I'm about to lose my mind on this. Everything is centered on the #3 cyl and just recently the #1 cyl(maybe head gasket?). This rules out some of what I checked since it's isolated to only one cyl but I figured I'd check everything.
Anymore suggestions??
Any help is welcome.Thanks

Danny2tek

iTrader: (1)

I'm gonna have to say head gasket

SSmokin 01

iTrader: (14)

I'm leaning that way to based on the #1 cyl picking up more frequent missfires at the same time as #3. I'll be checking coolant and a few other things tomorrow.

SSmokin 01

iTrader: (14)

Well I checked the coolant in the radiator and there wasn't a drop missing. Then I checked the overflow and it was right up to the proper level. Could such a small un-noticed amount be passing the gasket and causing the missfire. The symptons have just started and I "get out of it" whenever the miss starts.

Now here's where I tell you how it all went to poop tonight on the way to my girlfriends. I was coming off of an on ramp in 3rd gear at maybe 65% throttle. I took it up to 65mph,shifted to 5th and started coasting back to 55mph. Thats when I noticed the new stumble.

Whatever has been on the fritz has finally let go totally. The car managed to limp the 1 mile to my girlfriends. I tapped it and found:

#1 cyl missfire 20-65 times at idle and part throttle
#3 cyl missfire 20-80 under load but not at idle
#5 cyl random missfire 2-10 times
#7 cyl missfire 20-65 times at idle and part throttle
ltrims b1 pegged at +25%
ltrims b2 0.0%
tps .4%
780rpm constant with a rough idle
maf- 1.00 lb/min
ect- 207
iat- 75
timing- 22.5
fp- 66psi
vacuum- dropped to 16 inches from the normal 19-21
flashing SES
DTC's: P0174 fuel trim system lean bank 2
P0101 mass air flow sensor performance (poor)
P0300 engine miss

This has got to be the head gasket,right? I mean there's no misses on b2 just b1.Is there any thing else(besides the gasket) b1 specific that I haven't checked? I'm just trying to eliminate everything else before pulling the head.

As far as the maf dtc goes, I couldn't tell you. I've got a couple laying around anyway(1 from my '01 and the 1 from my girlfriends '02) that I can swap in if there's a problem.

So what do you think??

landlords2

So did you ever find the problem to this?