03 explore won't start

[Cdub42]

Hello. I am having issues with 2003 explorer 4.0 v6. Once or twice a day, the engine won't start. It will turn over but won't run unless I fully depress the accelerator. Also, on my way to work most days it will stutter at a stop light after 7-10min of city driving. Then it drives fine. This all started happening after I replaced the drivers side valve cover. I replaced due to the tabs holding the PCV valve were no longer holding the valve in place. Tired of burnt oil smell. Anyway, I hooked up my OBDlink SX scan tool with obdwiz pro software and learned I am running rich. LTFT readings -13% bank 1 and -10% bank 2 @ 743rpm and -16% bank 1 and -14% bank 2 @2651rpm. Up to -17.9% [MENTION=234476]wo[/MENTION]T
I also found the evap leak test failed. Could this be causing the neg fuel trim readings? Any suggestions would be great. If more info is needed please ask. Thanks

 

[Cdub42]

I'd like to add that I do not have CEL.

Just checked fuel pressure 65psi. Haynes manual says 2003 should be 28-45psi. What would cause this?

 

[Cdub42]

I've got all day tomorrow to work on her. She needs brakes and front bearing assembly. I'm changing plugs and wires as well. If I could get any ideas on where to look for the possible cause of the failure to start and stutter at stop issues that would be great. I've got a buddy coming over to help out. Mainly to monitor the beer temp so we can enjoy a nice cold one after the work is done

 

[broncojunkie]

Surprised you're not getting a cel for it if it's running rich and running rough. I would be curious as to what the plugs look like when you pull them. Do you know how many miles are on them? I changed mine at around 100,000 and I'm pretty sure they were original. They are supposed to last a long time, but mine were toast. I'm really wondering if yours will show signs of running rich, though.

Dumb question, but when was the last time you changed the air filter and cleaned maf sensor?

 

[Cdub42]

Air filter changed and MAF cleaned last weekend. Will follow up tomorrow on the plugs.

 

[05XLimited]

Did you give your PCV valve a "shake test?"
A bad PCV can cause a rich condition. Yours may be sticking in the open position.

 

[Cdub42]

Replaced PCV when I installed the valve cover.

 

[Cdub42]

Plugs and wires done. Minimal signs of running rich on plugs 1-3. Plugs 4-6 were yellowish white with carbon deposits.

 

[Cdub42]

Cleaned the throttle body and took her for a good test drive with the scanner hooked up. Ltft never exceeded +/- 10%. I guess 98k miles is all factory plugs and wires can handle. Haha.

 

[Cdub42]

Well, she had troubles starting today. Cranked but didn't run until I held the accelerator down. So back to the drawing board. Going to put the scan tool back on later today. I know the evap leak test failed yesterday. Would that possibly be the cause? Maybe the purge valve dumping too much? Or the fuel pressure is too high? Any thoughts?

 

[Cdub42]

Hooked up the scan tool. Getting a lean fuel trim reading now. I can't win. Haha.

 

[Cdub42]

Still unable to solve this issue. Not sure where to start looking. I've thrown roughly $100 at it so far and am still right where I started. If anyone has had a similar experience or is willing to give an idea as to why she's acting up I would really appreciate it. Thanks.

 

[05XLimited]

Have you checked for any Vacuum leaks?

 

[Cdub42]

I sprayed some carb cleaner around the intake manifold. No changes in rpm. I disconnect the IAC and engine killed.

 

[05XLimited]

Check the 90 degree elbows for small cracks. Sometimes the carb cleaner trick doesn't work.

 

[Cdub42]

Will do. Thanks. I will report back after further inspection.

 

[broncojunkie]

Fwiw, I occasionally have a starting issue myself. It normally fires right up, but sometimes I let off the key before it starts up. When I do this, and have to try starting it again, the second time is very hard to start. I believe it might be a fuel pressure problem. If I researched how the fuel pump/regulator system worked, I have a feeling I would figure out what's going on. It hasn't really been that big of a problem, though, so I just ignore it. It is probably a fuel pump relay going bad or possibly something in the fuel system. I know I have a small evap leak around the filler neck I need to fix. I also have an oxygen sensor going bad, so I guess I should fix that junk first.

 

[Cdub42]

Inspected vac lines. No signs of damage or cracks. Put the scanner on at drove to work. Started fine. Ltft was within tolerance until it warmed up a bit. At around 150°f the Ltft were 25% both banks @ idle. And staying under 10% while driving. Bank 2 is usually about 2% higher than bank 1 while driving. The engine did not stutter yet today. Still no CEL.

 

[Cdub42]

Update: problem solved. Diagnosis, I'm a dumbass. Haha. Failed to tighten an intake bolt when putting it back together. Seemed to obvious to check and when I sprayed carb cleaner to check for leaks I somehow missed it. She's purring like a kitten now. Fuel trims are as close to 0 as I can expect for an 03. So have a laugh at my expense. I certainly am.