Running Rough In The Morning

[hitman72]

So in the morning when I get in the truck and start it up it runs great (starts slower the colder it is, as to be expected). Then however, after less then 60 seconds of running I go to pull out of the driveway. In gear, little bit of throttle, I engage the clutch and pack out the 15 feet. Then when i push the clutch back in and let my foot off the throttle it dies. When I let it set and warm-up 5 min I have no problem (as is my normal protocol but can't always). Am guessing that it has something to do with the fuel system as if it starts to die and I catch it soon enough I can give it gas and save it.

 

Please excuse typos posted with my phone.

[Minuit]

Have you checked your fuel pressure? In the case of stalling and/or rough running, that's a good place to start. How old is the fuel filter? Bizarre that it runs fine after warming up for a bit.

[HOrnbrod]

I don't think it's a fuel problem. It sounds like a delayed transition from open to closed loop where it's switching back and forth until full warmup. Check the O2 sensor harness for obvious damage from exhaust heat, and verify it's connector is clean and tight. If all looks okay, then I'd replace the O2 sensor. It probably needs it anyhow, and there's really no reliable way to test it's operation except by replacement.

[Minuit]

:doh: Sounds about right to me.

[cruiser54]

Good idea on the O2 sensor. Have you ever cleaned your throttle body and IAC?

[hitman72]

So as of now all I have found is that where the exhaust pipe meets the manifold is very loose. I have yet to resolve this but could it be part of my problem? Also is there anyway to test the o2 sender or should I just replace it?

[cruiser54]

Replace it. They were due to be replaced about every 82,000 miles anyway.

[hitman72]

Hornbrod, sorry did not read that last sentence thanks.

[hitman72]

So there have been some new developments. I have yet to replace the o2 sensor, so i am hoping they are all related. Now if i start the truck and drive it about every other time i come to a stop it ideals high around 1200 rpm, the other half of the times i stop it ideals like normal. Also if i turn it off and start it again right away it runs up to 3000 rpm and holds that. When I turn it off and let it cool for a while it will run up to about 2000 rpm and then drop back down to normal. This morning when i started it it ran fine (let it warm up for a few minutes).

 

Does this sounds like it all has the same problem o2 sensor or is it a larger problem? 

 

Hope this week or weekend i can get the new o2 in.

[hitman72]

just trying to breath some life into this old thread. I am still experiencing the same high idle problems.

 

thanks

[cruiser54]

I think your TPS is taking a dump.

[87manche1]

I second that

[Eagle]

just trying to breath some life into this old thread. I am still experiencing the same high idle problems.

 

thanks

 

I've found that this is usually due to a dirty idle air sensor (IAS).

 

However -- if this is a Renix 4.0L, there's another possibility: The throttle cable from the gas peddle doesn't run directly to the throttle body. The cable runs to a bellcrank mounted down low on the driver's side frame rail, and from there it's a rigid connector. I have twice had that bellcrank pivot get either rusted up or gunked up, so that the return spring wasn't strong enough to pull the engine down to idle. Soaking the pivot with PB Blaster cured it.

 

Other times, when the high idle was due to the IAS (which is more common), running a few cans of fuel system cleaner through the tank cleared it up.