4.0L overheating and running lean

[parkrangerjeremy]

i just started having my truck overheat. it doesnt sky rocket it just slowly starts going higher and higher while i am driving on the highway... when i let it sit there and idle it starts to slowly come down which doesnt make any sense at all. I checked to make sure the water pump is circulating water which it is and the thermostat is also opening and my radiator is clear. i pulled the spark plugs to check the compression and i have good compression the only weird thing is the are white and showing i am running lean.... i hae been also getting real bad gas mileage and it also smells like it is running rich which really confuses me...any ideas what could be going on??? thanks in advance

 

[parkrangerjeremy]

i have all new sensor in it besides a crank position sensor.... i was thinking maybe my crank position sensor could be taking a crap and advancing my timing to much and causing my cylinder pressure to go really high... any help is greatly appreciated.... does anyone know what the timing should be at about 2500RPM?

 

[AllanD]

The crank sensor tyically works or it doesn't

there is no middle ground.

a coil pack OTOH...

AD

 

[parkrangerjeremy]

so maybe the coil pack could be causing this whole thing.... it started getting bad gas mileage a few months ago now it is very bad and its leaning out and over heating

 

[parkrangerjeremy]

i checked timing at idle and got 36 degrees advanced for some reason and that doesnt seem right at all.... also was thinkin since the timing advance is controlled by the ICM that that could also be the problem... any suggestions?

 

[calypso93]

Looking from the cooling system end - if the coolant circulates too fast it may not be removing heat fast enough from the motor, and not staying in the radiator long enough to give it up. Conversely If the circulation is impaired, the coolant may not travel fast enough. Maybe a bad lower hose?

 

[parkrangerjeremy]

both the upper and lower hoses are new also

 

[UrbanRedneckKid]

A lean engine will typically run a lil hotter. It's like those lil nitro powered rc cars, you lean them suckers out and they fly which is great besides the motor and head being 200 degrees overtemp.

Check for vacuum leaks, especially the lower intake manifold to heads.

 

[parkrangerjeremy]

well replaced the ICM today and still doing the same thing and tried swapping PCM and no luck.... tomorrow going to try replacing the coil pack and the crank position sensor.... any body have any ideas please let me know all the help is greatly appreciated... will also check for some vacuum leaks

 

[dogboy]

Always try the free things first, and TEST parts, don't just replace them!
Just replacing things because you "think" it might be the cause, is not the way to diagnose a problem. As you can see you have dumped more money into the truck that you could have by only replacing what ever is wrong, because I highly doubt that all the things you have listed are bad. Since the problem still exists, all of those parts should have been good, and did not need to be replaced.

I would check for vacuum leaks. What about the O2 sensors, have they been disconnected or removed for any reason lately? I did a tranny swap a while ago and accidentally crossed the O2 sensor wires, and screwed up the fuel (I was getting horrible fuel mileage, yet other times it would be normal)

You say the timing was off causing the cylinder pressure to be higher. The timing has nothing to do wit compression... Compression is the same whether there is spark, no spark, late spark, it doesn't matter.

Coil packs, and PCMs/ computer don't go out very often at ALL. It is generally something else that leads you to believe the coil or computer is the problem.

I don't know how much help that will be of to you...

 

[parkrangerjeremy]

i understand what your saying i was just trying to eliminate possible cause with spare parts off my other truck...

 

[dogboy]

Ah, ok. I guess that ain't too bad then. I thought you were going out an buying all these parts new.

 

[parkrangerjeremy]

lool no not hardly i learned a while ago not to just buy new parts without knowing for sure they are bad...i lost bad on a job doing that and wont do that again...would the fuel pressure regulator cause this situation because it only seems to start overheating past 2000RPM... i can sit there all day idleing and it wont go above 190 degrees but when i drive it if i drive for a little above 2000RPM it starts going up, if i stay below that when i am driving it still stays normal

 

[plainsranger]

Fan clutch?

 

[parkrangerjeremy]

i got a flexlite black magic electric fan on it... i am going to take out the radiator and condensor and pressure was them to make sure they are clear of garbage