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another problem (very high idle)

1K views 3 replies 2 participants last post by  FoxMcCloud 
#1 ·
Alright i got a 2002 dakota with 4.7 manual transmission.
As I was leaving the city dump the truck start to idle really high. Had to keep turning off the truck just to move forward.
For what ever reason the engine wants to stay at 3500-4000 rpm until the engine get to temperate and tries to stall out, then recovers back to 4000 rpm. Then back and fouth stalling to high reving. On the side of the road I tried unplugging the IAC and TPS and the truck did the same thing. unplugged the battery for an hour for the ECU to reset same thing. Removed the air filter and plugged the air path with a piece of wood so I can hear any vacuum leaks, no leaks heard but did not even effect the engine rpms.
Got the truck towed home and one of the drivers knew for of a master dodge guy and asked him what was wrong and he had not ideas.
My guess is a fired my engine harness because i smell electrical burning. But I am going to start with voltages to my sensors and ohms readings on the sensors. I will start the engine again when it is completely cooled down. I have heard of GM's doing this but the ECU reset works everytime.
Any advise would be great.
 
#2 ·
I would bet you've got a crack in a vacuum line - a pretty major crack - and that the ECU is bringing enough fuel to keep the air fuel ratio in range.

My Malibu used to do the same thing when a vacuum grommet failed (turned gummy). Replaced the hose, and it idled back where it was supposed to.

Takeaway? Start walking ALL the vacuum lines, find the break, and fix it. Even the hidden stuff.

RwP
 
#3 ·
Well thanks for the advise. I replaced most of my vacuum lines about six moths ago because I was experiencing a higher idle. It only got up to 1500 rpm. I checked all the sensors and voltage and all passed, not surprised though I replace all my sensors within the last year. So when checking my sensors that needed the engine running, the engine start redlining so plugged the intake to calm down the engine and work until the engine started white smoking out of the Passenger side exhaust manifold. Turned off the engine and smoked out my house and the wife says it smells like burnt rubber. I have to wait until the engine cools down to check out with was smoking on that side. My guess is that I have a crack block or a blow head gasket. looks like I am buying a car today.
 
#4 ·
Just quick update. Checkout the engine after it cooled down and notice some things. First is the coolant, My Green Coolant has gone brown with looks like oil floating on the top. Both my coolant and engine oil has come down a bit. About a 1/2 quart oil and six full circles to two full circles on the coolant depth gauge. When checked about a month ago. Now I do not smell any sweetness in my oil, but I am not tasting it. (as suggested by my brother) I also saw this separation between my Block and Cylinder Head where most of the white smoke was coming from. Now i do not have a compression tool. I am going to borrow it from work tomorrow and see if there it a leak that way.
 

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