jkwrangleru07

So I've been trying to chase down this problem with the jk. Its a 2007 3.8 auto I had the superchips flash paq running on 91 performance basically at all times until it started running bad. It is now in Stock tune. Heres the problem...started misfiring losing power and eventually it didnt have enough power to keep itself running. Originally I thought it was a fuel issue because it smelled extremely rich...I replaced plugs, wires, coil, iat sensor, b1s1 b2s1 o2 sensors and cam sensor. Crank sensor and cam sensor seem to be communicating according to the code reader. Still runs like crap barely starts and wont run above 3000 rpm. I was on the code reader and at idle its running -50 to -55 degrees retarded spark timing. Cats are running at about 3000 degrees normal it was running about 1500. I complete lost here please help! Thank you, mitch

Mr.T

That's an unusual amount of parts replaced. Did it ever produce fault codes (if yes, which ones)? Have any codes now? Did any of the parts replacements appear to make the problem worse (or better) afterward? Getting a bad replacement part isn't unheard of. Another thought is to try a different scanner/code-reader, what brand/model are you using?

jkwrangleru07

I had a similar problem with it a few weeks ago...replaced plugs and wires and it was fine. Now the problem came back just 100x worse. It gave me random/multiple cylinder misfire I believe thats p0300 and it was giving me system too lean codes AND system too rich code not sure of the code numbers on those...as of now it will idle just barely and CEL flashes but will only give me a random/multiple misfire code it has not given me any other codes other than that within the past week when she started acting up up again. Also i am not sure on the brand/model on the code reader, a buddies dad brought it home from the dealerahip he works at. I have only threatened to light my jk on fire a few times lol

JeepaRoo

do the 3.8's have any type of engine knock detection? its pretty normal if the PCM in a vehicle thinks the engine is knocking or pinging that it will richen the mixture a bit and retard the timing... i knpw GM was big for using knock sensors that would false fire all the time esp on older or modded engines.. just wondered if there;s anything like that on these that could be triggering the extreme retard and possibly rich mixture since the OP mentions strong fuel smell..

-CHristopher

Mr.T

The -50 timing is weird, makes me suspect the PCM has a failure or the scanner has a problem. But having it run fine immediately after replacing the plugs & wires a few weeks ago possibly points to fouled/incorrect plugs.

How did the old plugs look? Still have them -- take pics? Given this info, I'd be tempted to replace the plugs again (with the least expensive standard plug). Keep track of which hole they come out of.



edit: These engines have knock detection that retards timing, but this almost certainly has a reasonable limit.

jkwrangleru07

Checked again last night....timing at idle was -64 retarded still will not spit any codes...idling at about 400-500 rpm you can tell it just wants to shut down, it barely stays running. I'm having a guy look at it right now that says he knows these motors like the back of his hand. I should hear from him tonight and I will let you guys know whats going on if he figures it out. Otherwise 5.3 swap is definitely in the near future either way! I will pull a few plugs and check it out when I get her back either way. The only other thing I could think of is crank sensor or it needs a new computer if my flash paq wrecked it. Also the plugs that I took out were completely bad they were at about .080 gap

Mr.T

Best of luck -- looking forward to hearing how this turns out.

jkwrangleru07

well boys it all got figured it out. turns out my cats on bank 1 are bad, causing the computer to shut down all injectors on bank 1 and making the timing go way crazy. Basically it went into limp mode. I will be ordering magnaflows high flow y pipe system PN #49689 seems like the best way to go for me. i heard its a 13 hp gain from stock and the 3.8 needs all the horsepower you can throw at it. Thank you everyone for the input and i hope this can help others out in the future!

upalms

So I'm having the same issue, I replaced the cats, bank one downstream came out as a pile off soot. The deal is I replaced the cats, and still had same problem, replaced the EGR valve, same problem, any ideas??