My 4.6 runs like CRAP cold...

[95yj0645]

I built my 4.6 a few months ago for my 95 yj. Ran awesome for one month then all of a sudden it wants to run like a bag of a$$ at first start. itll buck and pop for about a minute then its like a switch gets flipped and it will run ok. It has an autozone flywheel, and ECM. Just this past month it will grind when tryin to start it like it has a bad spot on the flywheel. Has a new starter in it. I can answer any questions you guys wanna drill me with. Jeep forum guys cant seem to help me figure it out and I can always find the answer I need over there, so Im askin the stroker forum for help. Its getting frustrating. Also I used to live in Indiana and now I live in east Texas and my wrangler seems to have lost some power, could this be the altitude change?

[Cheromaniac]

Also I used to live in Indiana and now I live in east Texas and my wrangler seems to have lost some power, could this be the altitude change?

Possibly. How big was the altitude change? You lose ~3% of your HP for every 1000ft of elevation.
As for your engine running like crap when cold, check the resistance across the two wires going to the MAT sensor and the coolant temp. sensor. At 60*F it should be around 15k ohm.

[95yj0645]

I have heard that moving the manifold air temp sensor into the intake tube will advance my timing and give me another power boost? Well update I was leaving for work this morning and I didn't get but one block before it was like a switch got flipped and jeep started pinging and missing out like crazy. It wouldn't stop either it was continuous. By the time I got it limped back one block my entire exhaust system was cherry red (no converter to clog either). This leads me to believe that my timing got thrown way off or my fuel got leaned way out, maybe both?? I have ran MULTIPLE fuel pressure tests on my jeep during the times it runs bad Vs. the normal and my readings stay the same. So to me its pointing me toward a wiring short or an ECM issue. BTW when it pulled this stunt this morning no codes were thrown. Has a parts house ECM...

[Cheromaniac]

I have heard that moving the manifold air temp sensor into the intake tube will advance my timing and give me another power boost?

The power boost is small and the main benefit is that the engine won't feel as sluggish when it's been heat soaked for a long time in slow traffic.

[95yj0645]

Well that would be great. Because it does feel a little sluggish when it gets hot in traffic. What I really need to do though is figure out my running issue right now.