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1995 Ford Explorer Hesitating - Engine
Question: My 4.0L Explorer surges when the RPM's are higher than idle. It will do this if you try to hold the RPM at any steady RPM for example 1500 in park. When you are driving it is most noticable when excelerating. I scanned it and replaced the EGR position sensor which cleared the check engine light. There was a memmory code 157 so I replaced the MAF sensor. I have replaced the TPS, CKS, IAC. I installed a fuel pressure guage and it holds steady at 30 psi, when I remove the pressure regulator vacum hose the pressure goes to 40 psi.
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Technican: Have you checked for vacuum leaks. The intake gasket is common on the 4.0L.
Owner: I have checked for vacuum leaks. I have a steady 20 inch lbs of vacuum at idle and have sprayed throttle body cleaner all around the intake manifold with the engine running and it makes no difference in RPM.
Technican: Sorry for the delay.
Did you recheck the codes? Inspect the maf sensor connector/circuit. Do you have a scanner so you can monitor live sensor data?
I will check to see if any computer problems are known to cause your problem and post back later."
Owner: I have scanned again both KOEO & KOER and I get 111 each time.
Technican: Disconnect the egr valve and see if the problem remains.
Note- this will turn on the check engine light.
If there is no change there is most likely to still be a problem with the maf (especially if you bought a cheap brand) and secondly the PCM (computer). It would be best to have your truck hooked to a scanner at the ford dealer. Should cost 1/2- 1 hour labor at the prevailing labor rate in your area. If you choose this diagnosis make sure they offer an experienced driveability tech and not a rookie who will just check for trouble codes (you did that yourself). There is a big difference between the two.
Owner: I have plugged off the EGR valve and it did not make any difference. I was thinking maybe the Computer but what about the EDI module or coil pack. It does seem to almost cut out for a split second when it surges. I bought the MAF at Napa. When you talked about the intake manifold gasket is it the lower gasket that goes bad.
Technican: If it cuts out momentarily it could be anything that is shorting. Ohm the fuel injectors, see if they are the problem. If you don't have an ohm meter you could disconnect one injector at a time. Start engine and see if problem is gone.
The only way to test the module and coil for the concern you have is by using a scope (to view waveforms) or replace the parts. Only trick would be to ligtly tap the components with a stick to see if you can create a stumble. Here's How To Get Guaranteed Solutions In Minutes
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