94 4.0 stalls

[pettit5]

Hi,
I have a 94 GC Laredo with a 4.0 and auto trans. The thing runs great, but occasionally stalls. This has been a pain at times, but today it did it when I was pulling out into traffic. No check engine light and it starts right back up. One wierd thing is that even though the engine is idling the tach goes to the redline then the engine will die. I think it may be the Crank position sensor but I'm not sure.
Can anyone offer some input? Thanks

[CajunWon]

I'd first eliminate the IAC as the issue by disconnecting it while the engine is idling normally. This will not throw a code. I haven't had mine connected for years. Start here since it's easy to do.

But sounds more like a fuel delivery issue. If you have not replaced the original fuel pump, you are not tossing out good money even if this is not the cause. Don't get stranded in the middle of a long trip like I did at 150k miles. We all know they don't last forever. And replace the fuel filter at the same time regardless of its' age, since a failing pump will shoot debris into the filter. You can test the pump if you wish to see that it has the correct pressure while idling, then briefly remove the vacuum hose to see it peak-out. I don't recall the numbers off-hand, but something like 40# running and 90# with vacuum hose removed.

Consider pump replacement as a cost saving maintenance item. Cost me ~$750 on the road for something I could have done myself for $120 - $275 (new pump module/filter or new fuel pump assembly/filter)

[greasefingers]

Pull the codes first. You might get lucky and get a bad VSS vehicle sensor code or something.
Extracting Fault Codes:
Without ever starting the engine Turn the ignition switch ON, OFF, ON, OFF, ON and observe the CHECK ENGINE LIGHT. The CHECK ENGINE LIGHT should begin to flash a series of codes. The flashes will be separated by short and long pauses. The long pauses separate the "ones" and "tens" positions, and each code from the next. A code 55 will be displayed at the end of the test.

[ricking]

Hello everyone. I am new here on this board. I come from the Caddyinfo board. I have a 01 STS and have found these type of boards the best thing ever to trouble shoot our cars.

So. It's my wifes Jeep. It seems to be doing kinda the same thing mentioned in this post. It's a 1997 GC Larardo, V8. Warm or cold doesn't seem to make a difference. It will acellerate fine. No hesitation. Lots of pull. It's when you let up, the idle will drop to almost zero and then back up to about 650-700 where it should be. It will stall every once and a while when you do this. It will start back up most every time without trouble or extra cranking. At Hwy speed, the tach will drop from around 2000 to 1600 and then back to 2000 at will. It's at the shop now and the mechanic is kinda stumped. Fuel pump is good. No codes on the Tech I or II, which ever he uses. I suggested to him when I brought it in that it may be a crank sensor. Had this with my STS and new sensors fixed it. So he is going to try that.

Is there any thing else that any one can think of to help me out.


Rick

BTW, what is the IAC?

[02jeepGCL]

Idle Air Control.

It's a solenoid that opens a valve to let air bypass the closed throttle body while the engine idles.

[greasefingers]

Rick,

Scroll down in this link to thread #22 to learn more about the IAC:http://www.jeepforum.com/forum/showthread.php?t=150055&page=2

[ricking]

Thanks guys.