4.0 Running lean

[Glowin97x]

Hey Guys i haven't been here a while, now im back. Need some help
97 explorer w/ the 4.0

Ive got a CEL w/ a running lean code

Now i relplaced all the plugs and wires after getting a non spark in the 2 and 4 cylinders.

light came back

replaced the fuel filter

still running lean

im am thinking any of the following could be issues

leaking intake manifold gasket (i really hope not)

dirty IAC?

vaccum hose (i check them all but couldnt find any loose or cracked)

ANY SUGGESTIONS?!

 

[Runnin'OnEmpty]

Glowin, what was the code, was it lean on one bank or both? The problem is probably either a dirty MAF, or unfortunately a leaking intake gasket. My guess is that it's a leaky gasket; seems to be a very common problem......

 

[Glowin97x]

i believe it was running lean on both banks. I have heard about the commonality of the intake problem and unfortunatly i was unaware of it until after i am out of the warranty recall. Is there anyway to check it maybe like with some carb cleaner or something? I just want to be sure that this is actually the problem so i can stop throwing money at it. THANKS GUYS

 

[bandit_45]

I had the same problem for awhile but it turns out the intake started to leak antifreeze 2 weeks ago. First I tore it down to replace the intake gasket. Then for **** and giggles took the heads off to have the valves grounded and to my surprise the heads where crack between the intake and exhaust valves. I then took a closer look at the pistons and there where signs of alittle water in the every cylinder which would likely cause the lean code and why the exhaust sometimes was white. I just thought it was condensation the funny thing is it ran fine no problems. For about two years i drove it after I replaced the o2 sensors and cats and the only time the check engine light came on was when it was about 30 degrees and the code was lean bank 1 bank 2 I was told it was from the cold air intake but I think it was the heads along. Also check the tube from the egr valve that goes into the upper intake and spray some carb cleaner while its running I had one sucking air there, it also would cause it to run lean.

 

[Landho]

yesterday i performed the replacement of the lower intake manifold gasket on a '99 Explorer, 4.0L SOHC ... the codes were 0P300 (miss), 0P171 (lean), and 0P174 (lean) - and the issue only occured when cold idle.

To determine if the intake gasket was indeed the problem, i sprayed Carb Cleaner all around the lower intake and watched for white smoke out of the exhaust - and there was lots of white smoke.

There are tons of posts within these forums about how to repair this...

I'm a VERY novice DIY - and though I got stuck a few places (like getting the upper intake manifold off of the exhaust gas return, and I couldn't - to save my life get the PCV valve detached) It took a good five hours - but I did a lot of standing there (sipping a beer) and looking at things... also, included in that five hours, i replaced the IAC and IAC gasket (very easy), cleaned the MAF (easy), thoroughly cleaned the throttle housing and replaced plenum and gaskets (the valve was sticking it was so fouled), replaced the EGR control assembly (easy), new plugs and plug wires. While the manifolds are off - it is a great time to clean the inside of them, too.

Again, I'm a very novice engine repair guy and with the help of the Chilton's CD (from the internet), the Haynes manual (from AutoZone), and this forum - I was able to tackle the job with no problem. I was also able to find and repair the vacuum leak that occured after i put things back together.

My advice: Try spaying the intake with carb cleaner to see if you get white smoke... while the engine is cool (and problem is present). Get white smoke then you have leaking intake gasket.