Well, the first really cold morning of this season and I go out to start the truck to go to work and I get an immediate backfire. Then the engine dies. I restart it and as long as I'm applying the accelerator the engines runs, as soon as I let off the gas at all it dies. I've noticed the past few weeks the engine had been running rough at idle on occasion, other times it was fine. In fact, it seemed like it would run OK at idle for around a minute and then suddenly start running rough. I'll wait to check things out this evening but I'm not sure I can drive it anywhere to get the codes read.

Any idea's?

 

I'd suspect maybe a MAF sensor, or maybe the IAC (Idle Air Control).
There are other possibilities as well. Vacuum leak. PCV circuit leak.
I think you'll have to get the code(s) read or just start digging and hope you get lucky.

 

I didn't check this morning, dark and way too cold. But could the hose coming off the PCV valve cause this? I ask because I tried to change the valve last week and the one they gave me was wrong. I had a dickens of a time getting the old one put back on and I don't think the hose was completely on the valve.

Again, I'll have to check this evening. I'm pretty sure I'll have to get towed to get somewhere (like autozone) that can read the code(s).

Thanks

 

Yes, I think so. Darned if I ain't havin' a brain fart right now, but I think the PCV is part of the DPFE system
Differential
Pressure
Feedback
Exhaust gas recirculation

Even if I'm wrong on that, I still think the PCV hose can cause what you describe.
Worth checking!

 

I'm actually cart7 but I've changed my user name.

I checked the codes

P0171 - System adaptive fuel to lean (Bank 1)
P0174 - system adaptive fuel to lean (Bank 2)

??? EGR valve? Timing Chain jumped?

This is looking like one for a mechanic unfortunately.

 

i just had the lean codes also. Check the rubber elbow at the front of the engine that connects the manifold to the tube that runs to back at the pvc valve. this elbow can crack at the inside and cause a vacuum leak. a vac leak will set the lean code. its hard to find the crack as you have to pull the elbow off. you will not see it when its in place. i wraped it with electrical tape untill i could get to the dealer to get the part $11.00.

i hope this helps, its a easy fix

gary

 

Nope. I went back out this evening and tried restarting. This is much worse than I initially thought. Once it turns over, barely, it coughing and backfiring before it dies. My initial assesment was under, it appears I've probably jumped a tooth or two on the timing chain. It looks like I'll be looking for a long block here in the very near future.

 

I don't know - sounds like there might still be a more simple cause.

On my previous truck (000 4.2) I had the MAC intake kit. One time one of the fittings came loose allowing the intake to pull in air that was not going through the proper channels. It had the MAF wacked out and it did about what you are describing.
Keep us posted.

 

This is just a shot in the dark, but my explorer just had the 171-174 codes. Could not find anything wrong. Took it on a 500 mile trip and it started exhibiting the same symptoms that you are talking about. Turned out to be a failing fuel pump. I realized how bad it had been running after I changed the fuel pump in a San Antonio Auto Zone parking lot at 9:00 on a Sat. evening.

 

The saga continues.

Came home Saturday, decided to start truck one more time. Uh-oh. It started right up!!! Everything seems fine. I decided, as a precaution, to change the egr valve and pcv valves.

Monday, going to work, I notice the dash lights dimmer than usual. As I'm going along they get dimmer and I notice the voltmeter reading low. I wound up shutting off all elect acc + lights and limping into work with the truck dying as I pulled into lot. Pulled 10 month old battery, it was already back up to 12 volts and I recharged it. I drove home without a problem. I pulled the 4 year old AC Delco alternator and replaced it. Truck starts fine now and runs. Apparently the battery had lost some charge due to a dead alternator and then the cold weather nearly killed what juice was left in it. I think.

except NOW it won't idle at all. Just literally dies at stop signs, etc. Won't slow idle. I checked to see if I pulled anything loose when I changed the alternator but I could find nothing. When I changed the pcv valve, I noticed that small elbow shaped rubber connector on one end of the pcv line, that's attached to the underside of the upper intake manifold had a small crack in the elbow joint. Not sure if that's enough to cause the thing to completely die at idle though.

Thoughts anyone before take this in to my local mechanic. 173,000 miles and I've never changed the fuel filter, I'm starting to think that may be the culprit.

 

Well, the fuel filter would be an easy fix. Supposed to be changed every 30k I think. You will need a special filter tool to get the filter seperated from the fuel line. It does sound like a delivery problem. Drop in a can of injector cleaner while your at it. Clean your throttle body too. Wynn's sells a good fuel system cleanout kit. But you won't find it in your local auto parts store. Would have to check with your favorite dealer or mechanic to get one. Or have a brother-in-law who happens to work for Wynn's.

 

Just as a follow-up I'll tell ya all what happened. After changing the EGR valve and PCV I still had the problem. Thing was, as the weather warmed the truck started running. I drove it into work and the alternator failed. Drove the truck back home and changed the alternator. Now the truck would start but wouldn't idle, it would just die or barely run till it died. Decided to take it in. I had the guy change the fuel filter, it needed it but that wasn't the problem. It turned out to be that small elbow shaped hose in the PCV line that attaches to the underside of the intake manifold had a small crack in it. He changed that and I'm back up and running again some 3 weeks later.

 

That is good to hear - that you got it all squared away.
I hate it took so long but at least it wasn't big $$ fix.
Thanks for the update!