'94 XLT bogs....

[MidwestAl]

I have a high mileage '94 XLT that has developed a loss of power only after driving 100+ miles non-stop. It doesn't miss or overheat and the check engine light doesn't come on. It just seems to have very little power. After it sets for 30 minutes or so it's fine until you drive another 100 or so non-stop miles. Any suggestions?
Thanks!
Al

 

[88vert]

When is the last time you tuned it up?

 

[DeagleDave]

is it auto or manual tranny?

 

[ChuckyD]

Did u test for codes ?
I would test right after it does it.

 

[MidwestAl]

It's a 4WD AOD.....

new plugs and wires didn't make any difference and I've had the tranny serviced. The engine pings sometimes even with premium gas. Does it seem likely that the ECM is retarding the timing to compensate for the pinging? I know some vehicles have a knock sensor to do exactly that but I'm not sure about the Explorers. It makes sense in my head since it only happens on long trips and then clears when the vehicle sets for a while only to show up again further on down the road. Maybe fixing the pinging would fix this problem, too?
Al

 

[Alec]

Try cleaning your MAS, mass air flow sensor. Many threads and tips on this site on how to do it.

Does your temp gauge stay normal?

 

[DeagleDave]

yeah but i don't think the 94's had antiknock sensors.

do you burn oil? any funny smells in the exhaust?

 

[MidwestAl]

I don't have any oil consumption problems. It gets changed every 3K and never needs any between changes. No funny smells, overheating, or coolant loss. Everything seems normal except for this problem. I should have mentioned that at WOT, even when it feels like it has NO power when cruising; it will accelerate normally. Fuel mileage hasn't changed appreciably, either. Gets about 19 mpg on the highway. The power loss isn't what I consider a major problem, more of a minor aggravation, but something I'd like to take care of. I've really enjoyed this Explorer for many trouble free miles. So far, other than normal stuff like tune-ups, tires, brakes, batteries, belts, hoses, and tires; I've only replaced the thermostat, alternator, starter, and muffler.
Al

 

[DeagleDave]

you never specified mileage...you said "high" but how high are we talking?

if it's super high like over 200,000 miles you may be experiencing compression loss as the engine gets hot over the 100 mile trips. when you let it sit for the 30 minutes the engine cools and the metal retracts.

 

[Doug904]

Sounds like a fuel pump problem. The fuel pump can do weird things when its starting to go out. Everything from not starting after driving to poor performance while running, especailly at WOT. What I'd do to diagnosis this problem is have my fuel pressure checked. It sounds like you have enough to run but it deterotaes after driving. When you hook the guage up your pressure should be 28-32 psi @idle. When you hook the guage up to begin with just turn the switch to the on postition without cranking the engine, the fuel pressure should goto 38-40 psi. If its below either of these readings at these points then your pumps on its way out. With high milage its a common problem. You've gotten your life out of it if you have over 200K on it, replace it with a 155lph for a Mustang 5.0 and you'll be a happy camper.

Later Doug904.

 

[ChuckyD]

Now this is off topic but, Doug,what does your ranger run?

Looks like a Bad Ass Ranger!

 

[Jason_25]

Doug has very good advice there, but you may want to try re-torquing your intake manifold bolts as well. That will definitely cause a ping.

 

[MidwestAl]

First of all, I want to thank everyone for their suggestions. I've driven a lot of cars a lot of miles and this Explorer has been undoubtedly the most reliable I've ever owned. I've driven several others comparable miles, 250K plus; but spent a LOT more money on upkeep. I have a hard time convincing myself it's a temp-related problem since it only happens after a couple of hours on the road. It NEVER happens otherwise, even if the temp is in the high 90s. Seems it would actually be worse driving around town under those conditions. My thinking is that it's something cumulative causing either fuel delivery or timing problems. I think I'll clean the MAS and replace the fuel filter and fuel pump. Is the 5.0 Mustang pump a drop-in replacement and what should I ask my parts guy for?
Thanks!
Al

 

[Doug904]

I like the Mustang pump because it gives more fuel volume rather then pressure.. The FPR will regulate and return to tank what isn't needed. It is a direct swap for your explorer although you may have to trim the tube going down to the pump, nothing a hacksaw can't handle its very simple. Ask for a Mustang 155lph pump, there's no brand thats better then another that matters enough to mean a higher price. They main are all made by the same company Wal-Bro. DOn't go any higher then the 155 because the stock lines can't handle it. This will cause the pump to over heat and prematurly fail. I've replaced many a 255lph in a 5.0 mustang because of this.


As for my ride....

Thanks for the compliment. I've been really having computer troubles here latly but I'm right on track to having it resolved. I'm now using a custom wiring harness set-up and an Autologic chip for a V-6 96 Mustang proccesor. Its sounds more complicated then it is. My heads and intake are at the machine shop getting professionally ported and flowmatched so as soon as I get it all back together I'll let you know. As of now with stock heads and intake ports I've ran a 8.83 in the 1/8th at 84mph.

Later Doug904.

 

[Nate1]

Had a similar bogging down problem in my '99 x-sport and put brand new O2 sensors in and it ran like new. also same type of bogging was happening in a friends 93 blazer and it turned out to be fuel pump ... as stated before... but i doubt thats it in an explorer.

 

[Defender3]

For What it's Worth

I have a '94 XLT w/155,000 miles and had a loss of power after warming up (I drive the highway back and forth to work and had a distinct loss of power on the highway at high speeds). After some checking, we found the catalytic converter was clogged. In my case, there was also back pressure coming up through the EGR. I also had a knock in the engine at the same time despite using only high octane fuel (My '94 has a knock sensor). Too much of a coincidence, so I'm going to get that replaced as well as check the engine temp coolant sensor to ensure I'm not throwing to much heat into the converter and fusing the darn thing.

 

[Jason_25]

Re: For What it's Worth

Originally posted by Defender3
(My '94 has a knock sensor)

No, sorry it doesn't. The only explorer engine with a knock sensor is the 97+ SOHC 4.0L.

 

[irtySanchez]

Re: Re: For What it's Worth

Originally posted by Jason_25
No, sorry it doesn't. The only explorer engine with a knock sensor is the 97+ SOHC 4.0L.

Some people often mistake the camshaft sensor for a knock sensor on 1st gen Explorers.

And yes, some 1st gen Ex's DID have a camshaft sensor mounted on top of the"distributor" shaft behind the lower manifold. My Ex is in need of one, and that is the reason why my Ex bogs badly. Problem is, the are around $700.00 from the dealer. It comes with the sensor and the distributor shaft.

For some reason I think the sensor is only on use in Ex's with California emissions.

 

[Defender3]

I took a parts guys word for it that it had the knock sensor. I'll check more on what he meant as he also said that sensor controlled the knock by retarding the spark.

Thanks for the heads up!

 

[Jason_25]

I'm not aware of the OHV explorer being able to detect detonation at all. I'm sure the computer can do a math formula for detonation by taking sensor (IAT, MAF, 02's) readings to determine if there "might" be detonation, but it certainly wouldn't be exact like having a knock sensor would be. Many members with early explorers especially, complain of knocking and pinging under load. Normally, it comes down to a vacuum leak, such as the intake manifold gaskets being loose, or it could be the MAF sensor has gotten dirty and requires cleaning.