98' Explorer Running Rough (air in gas tank)

[jimbo231]

My mom's 98 explorer has been running rough off and on for a while now. We noticed when we take off the gas cap air releases and it makes a hissing sound. We also noticed that the truck ran smoother when we released the built up air. What would cause air to build up in the gas tank?

 

[sport97]

Bad gas cap. They are supposed to breathe. Replace it. Creating a vacuum in the tank isn't good for the pump from what I've heard.

 

[Flash]

Isn't here a charcoal cannister for the gas tank vapours?

 

[jimbo231]

Thanks! I'll pick one up tomorrow.

 

[jimbo231]

I had an old 87' firebird that had a charcoal canister but do the 98' explorers?

 

[obie]

Yeah, it's located on a bracket just above the left rear shock. Don't be surprised if that bracket is junk with rust, they rot out real easily.

Do you have any Check Engine Lights throwing Evap System codes?

 

[FordOwnerGT]

My 1990 mustang gt has a pressure valve on the tank that relieves pressure.not sure if the explorers have it still trying to figure stuff out on my project 1994 explorer sport

 

[jimbo231]

The check engine is on but im not sure what's causing that. Do I still need a new gas cap or are you saying the evap canister might be causing the pressure build up?

 

[obie]

It could be a number of things related to the evap system, but it would help to get your codes checked and report them here. Autozone will do it for free. Usually, the check engine light means you should get it checked out...

Though, if it's something that you can't spot easily, like a broken evap line, broken gas cap or broken filler neck, you're probably going to need to take it to a shop so they can run smoke to see the leak.

 

[my98nnj]

It's not the gas cap. The EVAP system keeps pressure in the tank, what you hear, experience is normal.

Have the truck scanned and report back the error code. Advance auto does this for free.

 

[jimbo231]

Sorry for the delay but got the codes read. Came back with one code P0171 system too lean (bank 1). What would cause that code?

 

[jimbo231]

Brought it in and the scanner said a misfire on cylinder 1. ..they pulled the plug and it looked fine but before doing a compression test they decided to put a new plug in just in case. It ran fine until they put it in drive then it ran rough again. This time the misfire was jumping around to every cylinder. They ran out of time and were going to bring it back but any ldeas?

 

[sport97]

I have the same code for lean on bank 1 (mine could be bank 2, its been a while since it was checked) and a misfire on cylinder 3. I believe mine are 2 separate issues. The misfire is intermittent and I believe it to be the coil pack or possible clogged injector (new plugs and wires did nothing). I haven't actually fixed this issue yet.

My lean condition I suspect is either a faulty o2 sensor, or maybe bad intake gaskets (intake gaskets are a problem spot on the SOHC). Once again, I have bought the gaskets but have yet to fix the issue. Just tossing my thoughts out there for you to see.

Not sure what could cause the misfire to jump around, maybe a bad coil pack? My buddy had a camaro that would idle fine but under load it would misfire like crazy, coil pack fixed the issue.

 

[jremington59]

A lot of times, cleaning the MAF sensor and finding/fixing vacuum leaks fix the problem. If you're on a tight budget, start there, but that may not be the fix for certain. So, possible solutions include:

•Clean the MAF sensor. Consult your service manual for it's location if you need help. I find it's best to take it off and spray it with MAF sensor cleaner. Make sure you are careful not to damage the MAF sensor, and make sure it's dry before reinstalling

•Inspect all vacuum and PCV hoses, replace/repair as required

•Inspect all hoses and connections in the air intake system

•Inspect and/or test the intake manifold gaskets for leakage

•Check for a dirty fuel filter and proper fuel pressure

•Ideally you'll want to monitor short and long term fuel trims using an advanced scan tool

•If you have access, you may want to run a smoke test