Limp mode 4.0

[Shturman]

My 4.0 feels like it is in limp mode, it’s a 4.0 manual swap and I did lifters in it and it starts and idles what seems okay but it’ll jump up and then shut off, but also driving it feels low on power, and will what seems like redline at 2.5k it just stops accelerating and sounds like it’s on redline but it’s only 2.5k, tach is fine and okay but I need some help, could it be not getting fuel correctly or?

 

[Dilligaf1]

Codes? IDK Crank Position Sensor or cam synchro maybe? More data is really needed before anyone could really diagnose anything. Running rich or lean? What was swapped engine, trans, both? Computer correct? Computer caps leaking?

I had a different vehicle that did something similar and it ended up being a cam position sensor. No codes, no power, completely give up at 3.5K. I've also seen VSS cause something similar, ecu was limiting throttle because it thought the vehicle wasn't moving, but I don't think your gen 4 ecu is that smart.

 

[Shturman]

No codes just transmission swapped, can’t really tell if it’s lean or rich but it sometimes will smell rich, right now it’s idling at 1k but will just randomly die, it might be the crank pos but the only thing I did for that was unplugging it

 

[Dilligaf1]

How long ago was the manual swap? Why did you replace the lifters? The issue happen right after the lifter change? I'm not familiar with how to change the lifters on a 4L, did you need to remove the intake?

Might want to pull some of the spark plugs you can get to, color will tell you if it's too rich or lean. 93 has a bank fire injection system, so at least get one on both sides.

 

[Shturman]

I didn’t do the manual swap that was the previous owner, I replaced the lifters becuase one of mine was clicky clacky, to get the lifters out you have to pull the heads off, they are still clacking after startup so it could be they need to bleed air out, I left them in a bath of oil for a day or two before I put them in.