Cold start stumble problem

[maddyn]

So I have a cold start issue with my truck that has been driving me crazy and I can't seem to figure it out. When I start the truck up first thing in the morning it starts fine, goes through the fast idle sequence fine, and then down to standard idle. It can sit at that point idling just fine for a few mins, but then when I put it in gear and go to take off it will stall, and will keep doing it unless I apply a little throttle before putting it into gear. BUT I drive 3 blocks down the road to the stoplight and it's fine and never does it again for the rest of the day. I've tried fast idling it for a min or 2, but that hasn't helped. I've gone through just about everything I thought it could be, replaced the fuel pressure reg, replaced the fuel filter, plugs and wires were changed about a year and a half ago, and I've checked connections on the MAF, throttle position and such. But it still has me stumped, any thoughts on what it might be?

1992 Ranger 4.0L Automatic


-Greg

 

[shadetree]

Check for a malfunctioning or dirty idle air control valve (IAC).shady

 

[super ranger 200k]

i almost have the same damn problem but, mine stalls right after the idle sequence. after refire it goes through the sequence again, gets right to the stall point, then catches and its all good.
my problem insues after i pull away. its like the engine bogs down more and more the harder i push gas the pedal down, but when the skinny pedal touches the carpet the engine revs like its supposed to. it'll do this for about 10 min. of driving in all gears, then never shows up again until it sits and cools off. i've had this truck for about 7 years and the problem showed up about 2 years ago and i can't get rid of it. i've tried everything from cleaning to replacing . PLEASE HELP!!!! i have a feeling that Greg's problem is associated with mine some how
how do u clean the IAC?

 

[dorman68]

Check for a malfunctioning or dirty idle air control valve (IAC).shady

I agree

 

[shadetree]

i almost have the same damn problem but, mine stalls right after the idle sequence. after refire it goes through the sequence again, gets right to the stall point, then catches and its all good.
my problem insues after i pull away. its like the engine bogs down more and more the harder i push gas the pedal down, but when the skinny pedal touches the carpet the engine revs like its supposed to. it'll do this for about 10 min. of driving in all gears, then never shows up again until it sits and cools off. i've had this truck for about 7 years and the problem showed up about 2 years ago and i can't get rid of it. i've tried everything from cleaning to replacing . PLEASE HELP!!!! i have a feeling that Greg's problem is associated with mine some how
how do u clean the IAC?

Your problem sounds like an engine coolant temperature sensor problem either with the sensor or it's circuit.

Remote possibility, TPS, MAF, vacuum leak. Very remote.shady

 

[super ranger 200k]

I Can Unplug The Maf And The Iac And Nothing Changes. No Sputter No Change In Idle Speed, Nothing. Its Like There Both Still Plugged In

 

[maddyn]

could be the coolant temp probe gone bad... I did pull the IAC off and clean it up, still the same problem. I'll see about picking up another temp probe and see if that helps.

Thanks

 

[maddyn]

well no luck on the temp probe, still doing the same thing. I'm wondering if it could be the throttle position sensor because if I just tap the throttle after restarting after a stall it will stumble and act like it's not getting enough fuel, or too much, you have to get it up past 1000rpm before it will stabilize. only other thing I'm thinking is something with the ignition, but I would think if it was the coil pack it would be having probs when its hot and not cold.