Just bought a TJ for my son and I as a project and we have problems with it staying running and I can’t figure it out. It is a 1999 4.0 manual TJ. It starts and runs smooth for about 3 seconds and dies. If I feather the throttle it’ll stay running for another 10 seconds or so barely. It doesn’t have SKIM because we hauled to the dealer and they checked the VIN and security was never installed. We replaced the fuel pump and have a constant 45 psi at the fuel rail. Pulled all the injectors and cleaned them. Replaced the MAP, CKP, TPS, IAC sensors. New cap, spark plugs and wires. Good grounds, and 5 v at the various sensors were needed. Swapped out the auto shut down relay and no concerns there. As you can see, we’re frustrated.. lol Any ideas?
Starts and stalls
- Thread starter Ryanrice4785
- Start date
If it still dies with throttle applied that would rule out IAC or vacuum leaks.
Do you have a noid light? It would be handy to see injector pulse.
Do you have a noid light? It would be handy to see injector pulse.
no codes from my cheap hand held scanner. I’m getting a better one tomorrow to dig deeper. IAC has been cleaned and is new. Doesn’t run long enough to look for small leaks. But we did check over and make sure everything is attached. Ran a compression test today and all cylinders were between 140-145 psi.
Got the node light hooked up. At idle the lights go out when it dies. However if I “pump” the throttle the light will run intermediately for 10 seconds or so.
Sounds like you are either losing crank signal or the ECM drivers are going bad.
Does the Tach drop to zero before it dies? Sometimes that’s hard to tell, best method is to use a lab scope to see the sensor signal. Without a scanner or scope you might have to make an educated guess. I would try an OE crank sensor before condemning the ECM.
Bad ecm. Replaced with a reman and she runs good now. Thanks for the help!
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