Stalling, Hard start SOHC 4.0

[offroadjosh]

ok my X had ALOT of trouble starting this morning (was -20F) and it was plugged in and the block heater is working... It took several hours, a battery charger and lots of playing with the throttle to get it to fire up. After i got it running and up to operating temp i came back outside and noticed that it was running funny... up and down in rpm(1100 down too less than 400 sometimes) so i rev'd it a bit and went to put it in gear... soon as i was in gear it died. it did it a few times and then stopped doing it but it almost dies when i do it now(sometimes it will still do it) it seems like its not running right at an idle either... i am getting fuel to the shraider valve.

any ideas???

New/cleaned

fuel filter-replaced
IAC-cleaned
throttle body-cleaned
air filter- replaced
new plugs and wires 6000miles ago
MAF-cleaned

1997 4.0 SOHC
145,000miles
auto tranny
temp again was -20F but was plugged in.


Josh

 

[williams.cory]

I WOULDNT mess with it. Vehicles do funny things when its really cold out. I came from Wyoming where it often gets to -40F without windchill and when its real cold like that and your vehicle is doing something weird I would touch it, because when it gets warmer something else will be messed up and hard to fix. But just my opinion.

But in this case since it took hours to try and start it, there has to be something wrong obviously. I know you cant just wait around waiting for it to start.

Could be fuel pump maybe not wanting to work in the cold? It will be kinda hard to test whats going on because it runs fine when warm, right?

 

[fixxxer]

Idle issues like yours could be caused by many things, especially when it's very cold out, vacuum leaks at a hose or intake gasket, IAC faulty or still dirty, MAF dirty or bad or electrical connections to any of those parts. Also the coolant temp sensor to the PCM (computer) could be bad or have a bad connection. Could also be a bit of water in the gas. Difficulty starting with the idle speed hunting like that, I would suspect the IAC or the wiring to it. Even though you have cleaned it, it might still be sticking a bit.

 

[offroadjosh]

it stalls when warmed up... (in gear)


Josh

 

[williams.cory]

Does it acclerate ok? Any bucking, popping under load? Maybe you need a new IAC, maybe cleaning didnt work. I'm not sure. maybe someone else will help out....

 

[fixxxer]

If the coolant temp sensor is bad or sending the incorrect signal to the PCM, the computer may think the engine isn't warmed up at all. The PCM uses the signal from the CTS (coolant temp sensor) and the IAT (Idle Air Temp) to adjust the IAC valve to the correct position.

 

[offroadjosh]

drives just fine, only when i let off the gas in gear and stop does it die.... sounds like an IAC... are they spendy?


Josh

 

[robertoa1a]

I would start with a diagnostic scan and measure some of the sensors with a meter. I'll bet that easier said than done as cold as it is. You ma need a warm place to work. I'll bet those wire harneses get brittle and you loose feeling in your hands. Never the less, the trouble shooting process stays the same. Check the throttle position sensor, idle control, intake air temprature, engine coolant temprature, and any other sensor.

 

[chapsdeva]

Sounds like what happened to mine a long time ago. I thought IAC as well so I cleaned it...didn't help. Changed plugs, wires, cleaned MAF...nothing. Finally took it to my mechanic and he replaced the IAC...problem solved. Cleaning the IAC does not always work. Unfortunately these are not cheap. Part typically runs between $90 and $120. Good luck!

 

[gijoecam]

Classic symptoms of the lower intake manifold gaskets needing to be replaced. The problem typically manifests itself as those exact symptoms you described, but at a much higher temperature. (40-50F and below). Your issue has likely been masked for some time by the use of the block heater. It took some extreme cold for it to do it... But that's where I'd put my money. Don't waste your money on an IAC valve for it... It won't fix the problem.

-Joe