First the specs:
2001 Dodage Dakota Quad Cab 4x4
4.7l V8 w/ automatic tranny
just shy of 170K miles

On a warm day it runs just fine. But when it's cold out it doesn't idle very well until the motor gets up to operating temp. I can crank it up and drive off, but when I roll up to a stop light it wants to stall unless I give it a little extra gas as I come to a stop. If it dies it cranks for 5-7 cranks until it will fire up again.

It always takes 2-3 cranks to start (warm or cold), or if I turn the key to the on position to prime the pump then turn it back to off it will fire on the first crank every time so there is obviously a problem there, but my biggest concern is the stalling at stop lights.

It is throwing a code for a vacuum leak (can't remember exact code but will rescan and post back here). I have tried the old trick where you spray carb cleaner all around to see if it changes the idle speed but there are no apparent vac leaks that I can find with that method.

I really don't have the money to just throw parts at it so any help would be appreciated. I'm hoping it's a sensor or battery related issue, but worry that it might be something harder to get to like the torque converter staying locked up.

 

It might also be worth mentioning that I almost completely tore the engine down last year. Had the heads off and the cross hatching on the cylinder walls was great, threw a new head on one side due to a dropped valve seat and replaced gaskets all around including head gaskets, valve cover, intake manifold, exhaust manifold and throttle body gaskets. I replaced the spark plugs and wires as well (plus a bunch of other stuff that would probably not be related).

It's totally possible that I got one of the 8 intake manifold gaskets in there wrong and there could be a vac leak like the computer is suggesting. But could that cause a stalling issue?

 

I would say TPS needs replacing but throttle body may need cleaning especially the IAC usualy a vac leak would make it idle high. Good thing is the 4.7 throttle body is very easy to clean seafoam and some spray cleaner may clean it without removing it.


You could remove the IAC and see if its very dirty mucky clean it put back and see what happens.

 

Quote:

Originally Posted by 98DAKAZ

I would say TPS needs replacing but throttle body may need cleaning especially the IAC

Good call. I didn't even think about the IAC because I pulled the TB off about a year ago and seafoamed it a few times and cleaned it with a wire brush, but I never did take the IAC off and clean it individually. I'll give that a shot before dropping in a TPS.

Quote:

Originally Posted by 98DAKAZ

usualy a vac leak would make it idle high.

Exactly, and it's not giving me any symptoms of a vac leak. But the engine light it throwing the vac leak code. Could that be related to the TPS not reading like it should?

 

Wire brush wow dont do that just chemicals and a used towel.


Be careful cleaning the IAC no brush just carb/throttle body spray cleaner dont soak it and dont lose the O-ring give the hole it came out of a good spray or two.

 

OEM TPS cured all my idle problems. I agree, no wire brush... toothbrush yes, wire brush... no.

 

Well I cleaned the IAC and didn't see any difference so I replaced the TPS. That didn't seem to do the trick either. It is running slightly better at a cold idle, but I still stalled it twice in the last 3 days.

I did re scan those trouble codes though (which I should have done from the start). I'm getting the following 2 codes:

P0455 - Evap system large leak detected
P0442 - Evap emission control system leak detected

I had mentioned before that I thought they were vac leak codes, but I guess I was wrong. This is one of the systems that I'm really not very familiar with. I'm assuming it's probably a rubber hose somewhere with a crack or something along those lines. Where should I check first?

 

Figure out anything with this?

 

Check the fuel neck for rust, it can/does rust out and will cause a large leak. How's the gas cap?

 

Update:

New fuel pump assembly solved my issues. The evap leak codes were a separate unrelated issue. Had some dry rotted hoses under the hood, but the running issues were from the fuel pump. There is a built in pressure regulator that was going bad. You have to replace the whole pump along with that though.