I have a 96 Ford Explorer sport 4.0 5 speed I have replaced 02 sensors EGR valve plugs and wires at idle it runs fine and revs up fine once I am going down the road it will accelerate fine up to 2500 rpm then it will begin to sputter no matter what gear and it seems to get worse the longer you drive it and if you come to a hill it will come close to stalling out if you stop and shut if off for a few minutes and then start it and go again it will do better for a few miles then do the same thing willing to replace the parts that are causing it if I only new what to replace Ik the maf sensor can make some funny stuff happen but normally I believe it affects the idle as well as the iac sensor it dose not seem to be a misfire but more of a lack of power had a local exhaust shop test the flow of the exhaust due to a past experience of clogged cat a few years back and they said it checks out haven't had the codes read since the EGR and 02 sensors were replaced anyone have any ideas ?

 

Tried to figure it out on a Tacoma a friend had. We replaced O2 sensors, checked injectors, replaced a cracked exhaust manifold, plugs, wires, etc. His would act up around 1500RPM. I had thought ( it was a distributor ignition ) that perhaps the gears had worn on the distributor, but the Ford is a DIS ignition, so that would realistically rule that out as well. We cleaned the MAF and his truck had no CAT and was a Manual transmission. I wish I had an answer, but hopefully it will help rule out some things. I had driven his truck for 10 years (Company vehicle from 89k to 350k ). The only thing that was happening to the truck when I got rid of it was the charging system was wonky...it charged and ran, but the lights would flutter. Perhaps it was the alternator causing feedback at a certain RPM back through the ignition system? Never got to check as he's gotten rid of it recently.

 

The IAC would only have an effect at idle so you can rule that out. The EGR, is stuck open or partially open, would also be more noticeable at low engine speed and idle, so I'd not spend any time currently focusing on that.

You mention that the plugs and wires were replaced. Was that in an attempt to fix this issue, or did that happen to be shortly before this issue started happening?

Did you check the air filter and replace the fuel filter as well? Have you measured the fuel pressure both at idle as well as KOEO?

The MAF can easily have an issue that is fine at idle but shows up at higher RPMs. The air flowing through the MAF will be higher at high engine speeds than at idle.

Similarly, the Throttle Position Sensor (TPS) can cause issues in certain throttle bands, but I'd expect that to be just a small band rather than from a certain point on up. It's easy enough to test though, especially if you have a scan tool with datastream mode. That will also make testing the MAF sensor functionality easier.

The camshaft position (CMP or CPS) sensor would be another sensor to consider.

-Rod

 

No codes at all?

Unfortunately it sounds like this is a problem best diagnosed with a good (expensive) scan tool that can read live data.

You can't rule out the MAF at this point, but I'd be checking out the fuel system as well. When was the fuel filter last replaced? That's probably the cheapest next step.

You could also try cleaning the MAF sensor. Only use a cleaner intended for MAF sensors, which you can get at any parts store. I kind of doubt just cleaning the sensor will fix your problem, but it's worth a shot.

Might have to bite the bullet and have a competent shop hook a professional scanner up before throwing parts at it.

 

We were told the TPS was a problem with the Tacoma, but tried to adjust it using an analog multimeter and didn't get much out of that. Perhaps a replacement would have been in order, but removing the TPS from the system by unplugging it didn't change how it behaved, so I was skeptical of that. We cleaned the MAF and I watched live data on my scan tool the best I could considering it didn't map out the data, just gives me changing values. Likely would need an oscilloscope function to see if it was ramping up voltage properly.