Has anyone experiensed this?

[Kidcapri50]

Upon cold start up, my 91 explorer will miss and carry on badly, almost not wanting to stay running. When I apply a couple pumps to the throttle the missing goes away and will run fine for about 10-15 mins at which a major power loss is felt when floored (not missing). It feels as the rpms go up and the speed does not follow suit. I thought it was a bad tranny, but if I shift into neutral and shut off motor, then restart, the truck is fine. It will have its power back for about another 15-20 mins. I think I might drive it off a cliff! But I'll have to shut it off then restart it to do it though.

 

[XLT]

The issue with it not wanting to stay running on cold start up sounds like you could have an iac issues. Trying cleaning it to see if that helps.

 

[Kidcapri50]

I did clean it, but would that give me missing / rough start up in morning? and like I said it feels like the tranny slips / not power after few minute of driving, but if i shut off and then start back up right away it runs fine for a while and goes right back to sluggish.

 

[manaen]

when is the last time you changed the fuel filter? and gave your truck a tuneup?

 

[little x]

Sounds like MAF or O2 sensors. When you first start the truck it runs off a set fuel map in the trucks memory. Once the truck warms up completely (after 10-15 min) it switches maps and begins adjusting fuel based on readings from the sensors. It sounds like one of your sensors is way off wack and causing the truck to barely run.

 

[jd4242]

Sounds like MAF or O2 sensors. When you first start the truck it runs off a set fuel map in the trucks memory. Once the truck warms up completely (after 10-15 min) it switches maps and begins adjusting fuel based on readings from the sensors. It sounds like one of your sensors is way off wack and causing the truck to barely run.

At what temp is the truck warm at? For the computer.

 

[92exp4x4]

The computer looks for O2 sensor temp rather than coolant temp for closed loop operation. Cars since about 1987 or 88 use three or four wire heated O2s. (HEGO sensors). Cold starting and open loop operation only last about 30 seconds or so. Once it is in closed loop it stays there until the system sees a problem, or you shut the motor down. For the most part if the CEL is on the computer runs in FMEM mode. A limp-home, open loop failsafe mode running pre-set parameters that Ford programed into it.

Coolant temp is used in timing the ignition and more so, controlling the mixture. A cold engine requires a more rich mixture than a hot one. This accomplishes the same function a choke plate has on a carburator.