This morning on the way to work my truck kept surging at various times. RPMs go up, engine revs lurchs a tad and then comes back. Feels like goingdown the road in a 5 speed keeping your foot on the accelerator and bumping the clutch just enough to let it slip and then back again. First thought was tranny, TC slip lock unlock, but then I pulled over put it in park and it continued. IPR DC usally around 14.9-15.1 at Idle but would hold at 18.5-19 until I would rev it a bit and let it come down- several tries and it finally idled fine. Ran another 20 miles fine and then did it all over again.
Parked it for about two hours then left to a two other sites,drove another 50 miles and no problems.

The first time the engine was not fully warm Intake temp around 40 water temp 180's EGT's 450 or so. But the second time every thing was up. Just changed the oil two days ago-level at top of hatch.

Any ideas of what to check?

Thanks

 

Check the tin nut at the back of the IPR. I had one come loose on me and when taking off up hill the throttle would surge back and fourth bad. I would smoke out all the traffic behind me and not even be trying.

 

Thanks I'll take a look--It does produce alot of white smoke

 

15% is a hair high, 10-12 is more normal for idle. check what duck said.

if yo ucan get it do it more frequent you can try unplugging the icp sensor as it surges to see if she smooths out.

 

Would unplugging it just set the pcm to a default instead of live data? If it smooths out that would mean the sensors bad? I had a resistor in but when it acted up I pulled it and swapped for a lower(didn't have anything to put it back to stock)resistor. When I got home I checked all the connections and swapped stuff back and forth -Drove it awhile and it was fine but we will see in the morning. Well in like 5 hours when the alarm goes off.

 

What kinda oil did you use ? poor quality oil will have the same effect .If your icp and ipr check out ok try some engine oil defoamer sounds silly but it actually works $5 for a bottle
it may be worth trying.