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Idle surge

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Old 03-16-2014, 05:34 PM   #41
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Quote:
Originally Posted by seanboy View Post
Correct, however my old truck would idle fine at red lights. If the truck was idling for more then 5 minutes even after driving on the freeway, the erratic idle would start back up -not as bad, but it will present itself again.
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.
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Old 03-16-2014, 06:25 PM   #42
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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.
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Old 03-16-2014, 06:26 PM   #43
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Quote:
Originally Posted by crawl View Post
Before we continue trouble shooting this pita shit can you clarify something or double check it?

You said this..
which is really weird.
On cold startup, the motor is in "open" loop mode which you have said the idle is perfect. Then once it warms up, the idle surges you said. Once warm, you should be in "closed" loop, also the same while driving normal - under low load. So something is not kosher here?
Watch the video I posted. This should answer your question.
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Old 03-16-2014, 06:37 PM   #44
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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.
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Old 03-16-2014, 07:09 PM   #45
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Quote:
Originally Posted by crawl View Post
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.
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.
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Old 03-25-2014, 09:43 PM   #46
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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?
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Old 03-28-2014, 06:51 PM   #47
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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
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Old 03-29-2014, 08:31 AM   #48
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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
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Old 04-09-2014, 08:56 PM   #49
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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?
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