Idle surge

I'm confused about your statement. You realize that once coolant temps reach normal operating temps, the T-stat should be fully open. It doesn't open and close. Unless I'm mistaken or not understanding what you are saying, you believe that a T-stat that does NOT fully CLOSE when cold...has an impact on the system's functions at normal operating temps?? The only time the T-stat should be closed is when cold. Once warm.. it's fully open.

I'm open to understanding what you are saying but please clarify your position on how a cold start motor with a partially closed T-stat has any impact on the ECU once the system warms up to normal operating temps and the T-stat is fully open?

This is not relevant to TJF's issue at this point because he has already replaced the T-stat and the problem still exists. But good for clearing up any misunderstandings for other readers with similar issues.

 

http://youtu.be/nGMDbosydFI

Here is the video from last night when it was cold and havent been started for a few hours. ALso notice the difference from the ultra auge tach and the stock tach. Big difference. Dont pay attention to the avg MPG. i was idleing the truck for a few hours trouble shooting and it brought it down from 19 avg mpg.

 

Watch the video I posted. This should answer your question.

 

I did some more test on the MAF today and the ohms are all all over the place. This would tell the ECM to increase/decrease fuel. The g/s on ultra gauge are also all over the place. Do you guys think the MAF could be causing it?

I will order a MAF tomorrow from rock auto. Couldnt hurt anyways to replace. Truck does have 165K on it.

 

Yes I know a T-stat stays open when engine is hot, however in my case my T-stat had a broken spring (should have clarified that the spring was broken ). I would assume that the T-stat in my old truck would flop around when driving around as well.

 

Still not fixed but as much as I hate to admit I will probably take it to the dealer and see what they say. But before I do that I was curious what other 3rz's are running for coolant temps. My ultra gauge is getting up to 172 and thats it. Most of the time its around 168. I have a brand new 180 degree tstat. So I guess the question I have is how accurate is the ultra gauge on coolant temp?

 

Man that is weird. Just thought id comment on everybody saying the white plugs are to lean. Yes, white plugs mean a lean condition, but most fuel injected cars nowadays will have white plugs because they run so lean. My 3.4 plugs are white with almost 15k on them

 

Im going to do some more test tomorrow. Fuel pressure, test the injectors resistance and try cleaning them.

If I disconnect the maf from the airbox and slightly cover it with my hand restricting the air it idles fine but goes rich and starts smoking out the tail pipe. That tells me that I am getting more fuel than needed. I think it is fuel related.

Thanks for everyone's help

 

I think i am on to something finally!

today it was 92 degrees and I actually got the temprature up to 190 acording to my ultra gauge. Surging is gone!! But if i let the truck cool it will surge again. I noticed according to the ultra gauge it surges at temps 180 and under. As soon as it gets over 180 the surging stops. My fan clutch is also coming on at 170-180.

I already replaced the thermostat(one with a jiggle valve) and repalced the temperture sensor on the back of the engine head.

Any ideas??

shouldnt these 2.7 first gen trucks run around 200 degrees?

 

What ever happened??? Sid u fix it? Im having the same prob

 

My 2004 2.7 is running way too cool these days. It's been down in the teens and single digits lately but last winter it still ran at 179 degrees or as low as 173 degrees on the interstate at 75 mph. This winter it's gotten down to 166 degrees at idle and rarely hits 179 degrees on the interstate. Idle doesn't surge at all but when it is below 180 degrees it idles slightly rough. I'm going to change the thermostat and if that doesn't fix it I'll change out both temp sensors and see what happens.

 

Hey TJF, did you ever find a solution to your problem? I have a very similar situation where my idle is just all over the place at different times. It's just very sporadic and inconsistent with the way it acts up. Thanks