Mercury nightmare.

[k122948]

1997 Merc Mountaineer 5.0. Runs great sometimes. Then sometimes, usually after it warms up it acts like it is running out of gas. Slows to 20 mph or so and won't speed up. Stop and the idle is fine. Turn it off for a minute and start it up and it will run fine for a mile or two and then acts up again. When its acting up and in neutral and you push on the gas it will rev to 3000rpm and then the rpms will start dropping. Replaced the fuel pump, filter and cleaned out the gas tank. Ran a fuel pressure test and it was at 30 psi. Took it to shop to read the codes and got 401 and 402. Replaced the EGR regulator and tested the Egr valve and checked all the vac hoses. Pulled the exhaust to check for a restriction and there wasn't any. Just noticed that if I drive like an old lady keeping the rpms down to 2000 to 2500 it seems to drive okay. If I try to pass or speed up any faster than that is when it starts. The only way to stop it is to let the engine sit until it has cooled down. Anyone have a suggestion where to go from here.

 

[BrooklynBay]

Welcome to this forum! I've moved your thread into the stock 95-01 section. Did you replace the DPFE sensor?

 

[k122948]

The parts house lists one for the car but I'll be darned if I can find it. Even the sticker under the hood doesn't show one. Read another post which said that certain 5.0's don't have one. The "tube" that is supposed to connect to the EGR is built internally in the intake.

 

[BrooklynBay]

Check WWW.RockAuto.Com.

 

[k122948]

I don't have a problem finding the dpfe part, it just doesn't exist as part of this car. I've seen it listed as being on the side of the valve cover and on the firewall but it isn't there. Even took the intake off to be sure I wasn't just missing something.

 

[Turdle]

I think your primary cats are clogged. There is no way you could have "dropped" them to check. What you did check were the redundant cats.


The primary cats are right under the transmission, and right off the passenger manifold. The upstream bank 1 o2 sensor will be in the primary cat on the passenger side. So, if it was dropped the engine would not have run good at all.

 

[Driveway2fast]

You may not have a DPFE sensor (Sonic EGR System). My 97 does not.

Check this link out:

http://www.explorerforum.com/forums/showthread.php?t=272428&page=1

 

[k122948]

Okay, I've completely removed the entire exaust and cannot find any restrictions. It's got to be some kind of sensor ??? I'm completely stumped on this one.

 

[cm8809]

I can't believe I'm going to be the first one to point this out, but there is definitely a problem with your fuel pressure. 30 PSI is very low, you should be closer to 100. That's why it's running ****ty. Weird because you said you just got a new pump - clean the lines and get new injectors?

 

[gavin]

I can't believe I'm going to be the first one to point this out, but there is definitely a problem with your fuel pressure. 30 PSI is very low, you should be closer to 100. That's why it's running ****ty. Weird because you said you just got a new pump - clean the lines and get new injectors?

fuel pressure should be closer to 100psi? serious? I don't think so...

specs call for 30-40.

 

[k122948]

Autozone repair info calls for 30 to 45 but this is for a 5.0 explorer. Haynes repair manual calls for 40 to 65. I rechecked it and it maintains 32

 

[gavin]

Autozone repair info calls for 30 to 45 but this is for a 5.0 explorer. Haynes repair manual calls for 40 to 65. I rechecked it and it maintains 32

hmm.. musta been lookin at something else then. I knew 100 was way too high though.

I can double check in my factory service manual when I get home from work.

but if that's the case, I would venture the fuel pressure regulator.

 

[cm8809]

Ok I said closer to 100, not 100 psi. 75 is ideal, 32 is much too low to run your motor well.

 

[gavin]

35-45 is for 4.0 or 2.9.
Looked in my Chilton's, and the only place it lists a fuel pressure spec is with a troubleshooting diagram, which shows an OBDI connector.

My factory service manual also does not list the fuel pressure specs, and tells me to purchase a serparate book (srsly!? 1,000+ pages specific to the 1997 Explorer and no fuel pressure specs?)

but then with some more searching, it appears it should be around 65PSI.

http://www.fordrangerforum.com/8-cy...anger-4-0-97-explorer-5-0-swap-keep-5spd.html

edit: according to 410Fortune, it should be around 35psi at idle.
http://www.explorerforum.com/forums/showthread.php?t=232922&highlight=fuel+pressure+5.0

and then according to this thread: http://www.explorerforum.com/forums//showthread.php?t=292490
30-40psi is spec for pre-99 model year vehicles, and 99+ model years are around 65psi

 

[1998Explodasport]

I would have to say 30psi is way too low but without looking at a manual I can't say for sure. Where did you get the fuel pump from? Please tell me you didn't use an Airtex unit from AZ. I would stop running the truck until you figure out the correct fuel pressure because if the truck is running lean it will kill your cats. If 30psi is the correct pressure then you may have a bad cat anyways.

 

[cm8809]

Okay. But you still don't have enough fuel pressure, that's why its doing the things you described. Don't waste too much time or money exhausting other paths first.

 

[gavin]

Okay. But you still don't have enough fuel pressure, that's why its doing the things you described. Don't waste too much time or money exhausting other paths first.

unless 30psi is still in spec.

then it obviously isn't a lack of fuel pressure.

shop manual spec is 30-45psi at idle. max stock pump output is 65psi.

http://www.explorerforum.com/forums/showthread.php?t=77962&highlight=fuel+pressure+5.0

 

[cm8809]

unless 30psi is still in spec.

then it obviously isn't a lack of fuel pressure.


http://www.explorerforum.com/forums/showthread.php?t=77962&highlight=fuel+pressure+5.0

It's not. It's barely half of an acceptable minimum if you want your truck to run properly.

 

[Joe Dirt]

This is my '97's fuel pressure test.




It starts hard when warm, but the pressures are all within spec. If the 30-45 is the acceptable spec, how is 30psi barely half of an acceptable minimum?
Is it on the low end? yes. Would that low end spec cause the truck to not run? I don't think so, but weird stuff happens...

Check this thread: CLICK ME

 

[cm8809]

Alright I'm not sure why everyone thinks I'm so uncertain but I think I've said it enough times to be clear. I'm going to stop chiming in. Good luck OP, be sure to let us know what you find as you trace the fact that your fuel pressure is way too low.