93 explorer jerks under wot

[stx4.0]

I have a 93 explorer that recently started intermittenly jerking under wide open throttle and throwing a check engine light because of it,.I replaced the mass airflow sensor as the symptoms were exactly like two other 93/94 4.0 vehicles I have had in the past but it did nothing for it.I got a trouble code 186 from it which is fuel injector pulse width too high and I thought for sure the MAF sensor would cause a code like that but again replacement did nothing for it.It is at the point now where it almost wants to stop because the problem is so bad.As long as you ease into the throttle while you are driving it will do a little better.I had it at a shop and they said it either had a cracked head or bad head gasket but it does not lose coolant or get hot so I don't buy that right now.I did notice sometimes you have to crank it several times before it fires and then noticed sometimes when you turn the key to pre start the fuel pump does not buzz/pressure up but when it does that if you turn the key back and then back to pre start a second time then the pump always pressures up.I am wondering if I am having a fuel delivery problem or something as i get no trouble codes from sensors.Anyone got any idea what causes an issue like this?

 

[trashtruck]

might be a sticky or dirty relay.

 

[stx4.0]

You mean fuel pump relay?I did forget to mention if your sitting still you can hit the gas and it winds right up so I dont think its electrical.I am wondering if its the fuel pressure regulator.

 

[2stroke]

Test the fuel pressure

 

[jmdirk]

Service procedure for 186 is to check for air and vacuum leaks in around the air cleaner, air inlet duct, as well as between the MAF and IAC solenoid. Also checking all engine vacuum hoses for blockages and/or leaks. Next step is to check the fuel pressure which should be between 35-40 psi with KOEO or 30-45 with KOER

 

[Wolfie_85]

I don't think it's the head or head gasket. But check your oil, anyway.

I would do what jmdirk said, it covers all the things I can think of.

 

[Rhett]

bad FPR usually gives poor gas mileage, are you seeing that?

If all of the above isn't it -- I suggest inspecting the spark plug wires and coil. WOT behavior you describe is often either fuel cutting out or spark not firing up to snuff.

Also do you have the original injectors?

 

[stx4.0]

It has a new accel coil pack and new wires plus new plugs.I replaced the fuel pressure regulator as I think it is either fuel related or vacuum related.I may take the upper intake off and see if the gasket has been sucked thru in spots as I had one do that before and acted almost the same way.It got progressively worse over a 10 day period.At first it just missed a little when I would step on the gas as if to pass someone and it would throw the CEL but now you have to feather the throttle gently or it will fall on its face and you come to a hill you feel lucky you made it over.The code I got said injector pulse width high but another person said check vacuum leaks with that code which I did but I had already replaced the MAF sensor and everything was hooked back up correctly and sealed off.The injectors are the originals but I dont see those being the issue since one might go bad but not all of them within a period of a few days.The gas mileage was about normal but i have it parked now since it is running this poorly.The werid thing is I can go out and start it and it will start up fine/normal with no misses or shaking and it will wind up normal in neutral but when you put it under a load it starts messing up.

 

[Rhett]

Ok, then I'd test the fuel pressure as 2stroke and jmdirk suggested...

 

[Gadget X]

Sounds like what mine was doing right before I had to replace the pump! If you can, leave a pressure guage hooked up, and strap it to the mirror or something, so that you can see what the pressure is under different conditions, such as WOT. Good luck with it!

 

[stx4.0]

Thats what I am wondering is if its the pump giving warning its about to give up.

 

[acschilling]

Thats what I am wondering is if its the pump giving warning its about to give up.

Are/were you getting the detonation knock when it's under a load?

 

[stx4.0]

Not detonation,it feels like a miss but its not missing.If you floor it it cuts out and falls on its face like its going to completely die but it wont actually quit but whatever is doing it it causes a check engine light.That is why I thought it was the MAF sensor at first.

 

[Turdle]

So, what is the fuel pressure at idle and no vacuum line to the regulator?

 

[FR-425]

Does the CEL remain on or does it reset on it's own?

I ask because I suspect your EGR is stuck wide open.

Not usually a problem with the EGR valve itself, but with the valve that controls it.

Stuck up under here.