Project101

ok guys I hope this is the place to figure this out


vehicle 91 Jeep Wrangler 04 5.3/4l60 c6 exhaust manifolds and vats turned off

symptoms:
vehicle fires right up runs great then right around operating temp it starts to miss intermittently on random cyclinders. once above idle it drives fine. just at stop lights and at home in my garage in park it will do it.

TECH2 at idle
st fuel trim 0-2%
long term fuel trim 20-25% both cylinders, while driving goes down to 4%
tp angle 4%
map 32kpa
maf 4.8ish grams/always close to commend
02 seem to be cycling properly.

failed attempts:
1.ac delco plugs/wires/tired moving coils around with no luck
2.compression test(185-190) /leak down was unable to hear and leaks
3. replace both up stream o2s (from another problem I made )
4. found crossed injector wiring my fault (late night drunken wiring)
5. checked fuel pressure
6.swapped out fuel filter'
7. swapped known good fuel rail and injectors/intake reseal with gm teal color seals
8. swapped know good maf/map/tb

I know I'm forgetting something .
I try to use my head to fix mown problem and not cry out for help for everything I do but I'm genuinely stumped.

any help would be great thanks guy

I have hp tunners but just got it.
I know my grammar and spelling suck. lol

DT69cam

This may be too easy but what is your idle speed set at ?

kingtal0n

iTrader: (1)

I have the same or similar problem. I've noticed it only happens when the engine bay really heats up. Cold engine everything is fine. Then gradually it will miss- only at idle, in gear more than in park, but never when I touch the gas/driving. Engine runs perfect besides this one thing.

Pretty sure its just my coilpacks or crank trigger wire getting too hot under the stock nissan hood I have (in a swap) and its all near the downpipe kind of. Too hot to touch for sure over there. I will be making some shields pretty soon, but thats not going to stop the heat "soaking" just radiated IR, to fully fix this issue I will need some kind of vent or duct so the high temp air near the top of the engine can escape. I'll probably put a very small, rain-friendly vent in the hood.

Pop N Wood

iTrader: (1)

Had a similar problem in my DD and was dirty injectors and possible bad injector O rings. Stuff like that doesn't throw codes so don't forget basic mechanics when chasing a problem.

Project101

Tech 2 is saying target idle is 550
once up to temp.
on start up tgt idle is 675 I belive .

today I recorded known good o2 data in my wife’s Tahoe and compared it to my rig.
the o2s are cycling but the pattern looks rough in comparison. I got a wide ban o2 today so tomorrow eve I’m going to try and set it up and see if my engine is actually lean Or just reading lean.

not sure what my next move is.
oh and in regards to injector o rings I swapped in a known good fuel rail with injectors and no change (wife’s Tahoe)

pdsq98gt

The high ltft at idle and fine at cruise screams vacuum leak to me.

Project101

I agree.

when I pinch off the pcv (fixed orifice) long terms come down to about 6%
I have resealed the intake with no changes . but I will try the old propane /break clean trick again.
tonight after I get off work I will hook up the wide ban and see is my o2s are are telling the truth . I have been chasing my tail a bit on this . I'm going to have to make a check off list so I don't back track. I have been trying to solve this for over a month so I'm starting to forget all my findings lol.

ill post what I find.
thanks for all the input I will solve this one way or another.

pdsq98gt

Where do you have the clean pcv hose on the passenger side valve cover to? It needs to be routed to the intake tube between the maf and the throttle body.

Project101

its routed to the top of the intake . its in the factory position . same as my Tahoe.

so today I hooked up a wide ban o2 it was a tail pipe style one .
I first measured my Tahoe a 15.0 AFR at idle and at 2500 rpm

wide ban on my rig while in open loop I was right a 15.0 (still was running rough)
LT fuel trims 4-6 % as soon as it goes closed loop long terms will creep all the way up to 20% at running temp AFR 14.7 .
I pinched the pcv and fuel trims went down to 4-6 % but miss fire still present

sprayed intake and anything going to intake with break clean no changes .

It seems like a leak, but even when fuel trims are low it still has the miss.

so then I checked power and grounds to o2s . they were good
then I checked power and grounds to coils they were good.

power and ground are good at the maf as well.

gsjimmy

Have you looked at the plugs yet? What color? Also, has this been tuned yet for your combo? Could have a lean condition going on (white porcelain on the plugs). Plugs should be tan.

Then see if there really is a vacuum leak somewhere.

Project101

yeah I haven't checked the plug sense I did the compression/leak down test.
ill look at them today. one would think with AFR close to 14.7 plug would be good.
ill pull them and take a look

I'm going to try the water trick for leaks this time, see if that makes a difference.
but it seem that even when I plug the pcv which brings long terms back down it still misses

and as far a tune my engine is all stock besides corvette c6 manifolds and cats.

after work today I'm going to get back at it.

Thanks

gsjimmy

Have to get mine to the tuner now, similar condition. I know its lean, so now we have to get things sorted out.

let us know on the plugs.

Jim

kingtal0n

iTrader: (1)

I made a little shield but it actually heated the shield over time, preventing the problem at first but eventually the shield just absorbed all the heat that had no where to go and misfired even worse. So I would drive the car for an hour until the shield got hot then swap it out for a cold one. It helped me realize I could run a small water pump powered by 12v to send a cooling tube along the coils. I am going to try some sort of liquid cooling system, since it isn't a critical feature (if the cooling pump fails for example, then I just go back to where I am now, the car drives fine when moving but gets too hot when stopped. nothing bad happens).

Project101

don't think its a heat soak problem. but ill look into it.

plugs are tan

ok so for todays fun. I tried to find a vacuum leak with water , with no joy...
next I varifyed the o2 grounds were individual to pcm(early models we case grounded.
next i unplugged both o2s and holy smokes it held 14.8 AFR but still was mis
next I tried unplugging maf still no joy missing oh and I replaced the cam sensor due to the fact I had a know good one from another engine...no joy still ..lol

ok so now I'm thinking the misses are causing the o2 to real lean hence the 20% long terms . valves...mybe I dunno I have some sea foam on the self let see what happens. no luck with sea foam ..lol swing and a miss

Project101

today I disabled each injector 1 by 1 to make sure the right injector was wired to the right cyclinder. with good old hp tunes injector disable feature ( don't use it for this function it shut down the wrong cylinders). ended up using the tech2 and injectors are where they belong.

tomorrow I'm going to unbolt the cats to see if its backing it up(cats had less then 10k when installed and looked like it) after that I'm going to Chase my tail a bit and check fuel pressure again

twomanyjeeps

I'd like to offer some things for consideration based off my nearly nonexistent tuners experience. So hopefully this helps more than hurts.
I haven't seen mentioned what vehicle the tune is made for.
I'm also curious what your air intake looks like.
My suspicion is that if the air intake, maf, o2s and tune are from different vehicles, then the computer might not know how much air it's getting. If it were me, I'd use the wideband in place of the upstream o2 and use the procedures mentioned on the hptuners help site to make sure the maf cal curve isn't out to lunch.
I've read one tuning case study where a completely stock vehicle's curve was off enough to leave something like 30 hp on the table. Didn't remember reading anything about it missing but just food for thought. Again, hope this helps.
Finally, I've got a YJ myself and would love to see pics of your setup, especially the manifold fitment. Good luck.

Project101

pm sent

fst100

iTrader: (5)

with your wideband, hook it up to the driver side then the passenger side and see if they're close to the same reading.

another is if you're able to get another pcm from a 5.3 04?

Project101

ok all I had time today for was to check for exhaust leaks,
so their are no audible exhaust leaks, then I put soapy water on the exhaust manifolds and collector flanges and it was pushing a little exhaust , not sure how small of an exhaust leak would cause fuel trims to go up.

tomorrow if I get time I will try wide ban in (CORRECTION EACH BANK ) if I don't find any leads
I'm taking on board. maf cal curve and ill start heading that way

btw the tune is stock only vats disabled . the intake is 3.5" airaid intake kit the kind you cut with a volant Donaldson style filter , here are to links to pics of intake below

https://cimg9.ibsrv.net/gimg/ls1tech...d6098124bd.jpg

https://cimg4.ibsrv.net/gimg/ls1tech...43878cfefb.jpg

fst100

iTrader: (5)

not per cylinder, each header lol

also from your pics maf is unplugged? and whats that thin vac line poking out the rear of the intake manifold? is this just a general pic prior to everything buttoned up?