94 Explorer Stumble on acceleration and loss of power

[mawrazen]

Changing out my O2 sensors solved a similar problem on my 94 Ex. I had a stumble and a cel when hot and under a load. 2 new bosch O2 sensors later, no more problems. Total cost under $100. Good luck it took me 3 years to get all the bugs out my Ex.

 

[lonestar]

Was it intermittant? I'm not getting any CEL. Or any codes related to any sensors, other than Neutral Safety, which I don' understand since I have manual...

I know of atleast one vacuum leak at brake booster, plugged it with finger, idle improved slightly.

Intermittant issues tend to point me towards electrical. Next test will be fuel pressure, it was raining yesterday. Maybe faulty pump, relay or short, which is in alignment with Code 95 - fuel pump open circuit. I wouldn't have guessed fuel pump since I replaced it maybe 40-50K ago at 160K miles, and would think it would either work or not.

 

[Alan_V]

Was it intermittant? I'm not getting any CEL. Or any codes related to any sensors, other than Neutral Safety, which I don' understand since I have manual...

Do you know if the PCM has ever been replaced? Someone could have replaced it with one for equipped with an automatic.

 

[Joes4x4Ranger]

The simple fact that it still occurs in limp mode leads me to believe it's mechanical. A fuel pump on its last leg or a vacuum leak. Both upper and lower intake manifolds on these 1st generations are susceptible to leaking. The leak becomes much worse at warmer engine temperatures and can be very difficult to find with carb cleaner/ether.

The fuel pump could also be on its way out partially seizing when it warms up. If you have no codes other than the lean indication I would concentrate my effort on finding and fixing the vacuum leak and replace the fuel pump. Make a VERY thorough inspection of ALL wires running to the fuel pump as well.

 

[94Jo]

How did you get your codes read at autozone? I thought we had OBD1 and autozone only scans OBD2? Which autozone did you go to I would love to get it done.

 

[lonestar]

Never had the Neutral Safety code before, and I haven't changed PCM. Last time I scanned (few years ago) all I read was pass code, 11.

Intermittant vacuum leaks? Hopefully not, I did all intake gaskets when I updated with 93TM heads do to dissappearing antifreeze.

ahhh another Louvillian, whereabouts? Try the Autozone in Hillview out Preston Hwy. Some say they can only due OBD now, but sometimes you can get lucky when the one comepetent employee is working. I actually had a scan tool at one time, but I can't find it now. Those old EEC only scanners were pretty cheap.

 

[91exploreron37]

Same problem I'm having, a really bad constant stumble when I'm accelerating only, I mean its really bad and has no power and sometimes backfires a little. Some coworkers said the engine may have jumped time since I broke my axle and it violently cut the engine off. It ran fine before and a few minutes after the axle exploded and I towed it home and since then its been sitting for two days while I got it fixed and I went to take it for a test drive today and now have this problem. I'm hoping it's a minor fuel issue and not timing related.

 

[shucker1]

I had the same problem a few years back on a 98 5.0. Stumble on aceleration.

I have some rather high tech gear and ran a spark trace. I found bad ignition wires. They were breaking down inside the insulation. I changed the wires with a factory set and the problem went away.

 

[91exploreron37]

Was it a little stumble or a major stumble? because mine is really major, I've felt stumbles caused by bad plug wires but this is something totally different.

 

[shucker1]

Usually on light acelleration. As it got worse I noticed it come and go during idle at a stop light.

If I am correct the 98 series EEC-V (or any EEC-V for that matter) was a demand type ignition \ engine control. If you mashed the gas you got more spark. Therefore it did not show up really bad unitl the very end of the plug wire life.

 

[91exploreron37]

See my idle isnt really affected its more so when I give it gas and even more so when its under a load and it feels like the engine is literally running on two or three cylinders.

 

[94Jo]

I will try that autozone, I do it myself using a light but its hard to tell what the codes are. Im in the west end of louisville but can usually be seen in valley station and prp. The guys at the autozones near me just say they cant do it, hopefully the other one can help me out. Thanks

 

[lonestar]

Think I got it, FUEL PUMP. I had noticed fuel pump sounded sick, instead of a nice hum, it sounded like a squealling bearing. Bought a new pump and pressure guage to confirm my problem. Old pump showed approx 25-30 PSI but fell to 15-18PSI while running, new pump maintains 25-30 PSI while running, however it does not rise when vacuum line from regulator is removed, but it did climb to about 40 PSI with line attached once. I had changed my regulator also, it seems if regulator was bad it would have constant high pressure?

Manual states
30-40 line attached
40-50 line removed

It may be due to my high quality HARBOR FREIGHT guage set, not even sure if fittings fully depress schrader valves and fittings leak, going to take it back. OR maybe the cheapo NAPA pump, although it is rated to 65 PSI?

BUT I did have a smooth ride to work this morning.

 

[91exploreron37]

Cool glad to see you got it up and running again.

 

[8mmshooter]

try cleaning mas airflow sensor my 93 had same problem

 

[outlaw1977]

with me it was the converters

 

[MDewell]

Think I got it, FUEL PUMP. I had noticed fuel pump sounded sick, instead of a nice hum, it sounded like a squealling bearing. Bought a new pump and pressure guage to confirm my problem. Old pump showed approx 25-30 PSI but fell to 15-18PSI while running, new pump maintains 25-30 PSI while running, however it does not rise when vacuum line from regulator is removed, but it did climb to about 40 PSI with line attached once. I had changed my regulator also, it seems if regulator was bad it would have constant high pressure?

Manual states
30-40 line attached
40-50 line removed

It may be due to my high quality HARBOR FREIGHT guage set, not even sure if fittings fully depress schrader valves and fittings leak, going to take it back. OR maybe the cheapo NAPA pump, although it is rated to 65 PSI?

BUT I did have a smooth ride to work this morning.

Just curious...did it work? I think the fuel pump may be causing my problems as you describe..

 

[lonestar]

Yep... Runs fine. I a will drop in new airl filter and clean MAF, it's been awhile.

Now I have an mysterious alignment issue that popped up. Always something...

 

[djsk8r33]

make sure yu are running on all 6 cylinders. i recently solvd this problem of mine by changing ou t the spark plugs. the rear pass side one was all fouled pu from the wire leaning on the manifold and heating up. i moved the wire an replaces the plugs. problem solved.

 

[phantaztix]

Thanks for all the great Ideas guys. I was hoping someone else would take over my thread and get people to give up some good ideas. So now I know to check my fuel pump. My problem got slightly worse but never went away so far. Oh, and thanks for the carb cleaner trick. I will def use that one.