4.0 has a major miss

[96ranger96]

I've read through a lot of forums and have done some suggestions but now I'm at a total loss. First off the truck was running fine. It started running a bit warm ( not even 3/4 on the guage but warmer then usual) so I let the truck idle for a few min to see if it would get any higher. It never did but then all of a sudden the truck started shuttering and then died. Started right back up and that was that. Decided to change the thermostat and run a can of sea foam threw it. Ran fine for a a day then it died again. Then it got to the point where it would idle till it got hot then shutter then die. Would not restart hot. Once cooled it would start right up. Then I developed a miss. Changed iac, cam positioning sensor, plugs and wires are newer. After changing cmp it would start up cold or hot but miss was worse. It wouldnt stay running unless I gave it gas which it would smooth out. So progressively got worse so I was going to check out maf. Found out previous owner put it on backwards. Flipped it around and now its running worse! It starts up fine then goes into a lope like I have a cam in it. If I rev it sometimes with will sputter up then other times it struggles to stay running and dies. It lopes so bad the truck shakes back and forth and it will drop to 100rpm añd somehow sometimes still come back. I just don't know where else to go from here cause everything I've done has been making it worse. Please anyone with suggestions. It's a 96 ranger 4wd with the 4.0 in it. It has a multi misfire code, rev per min code, and bank 1 and 2 running lean. It has high flow cats on it but that's it.

 

[93 4x4]

Check the computer board should be up in the firewall in front of the driver side sometimes they get old and a diode leaks on the board and Messes it up it makes it throw all kinds of weird codes I had happened to my truck there about the same age. Look for black dots on the circuit board under the diodes

 

[RonD]

93 4x4, I think you mean capacitors leak on the board.

Warmed up miss fire could be coil pack, test it cold, then hot, with OHM meter.
Also double check plug wires, I mix up firing order all the time.

Did you reset computer after changing the MAF direction?
Computers "learn" sensor parameters during first 10 to 30 minutes of driving after being reset, if you just change or "reverse" a sensor without a reset engine will usually run worse for next 5 to 10 start ups, until it slowly relearns sensor's new parameters.
If you don't have a scanner to reset computer, just unhook the battery for 5 minutes, that will reset computer.
Just get into the habit of disconnecting battery's Ground cable when doing engine work, safer and it resets computer.

Cam position sensor usually can't cause a no start or a miss, it is for syncing fuel injectors with intake valves for better MPG, but if it doesn't match Crank position sensor's data computer ignores it and uses Batch fire instead of sequential injection.
CPS issue will also turn on CEL(check engine light)

Sensors rarely fail, not never, but it has been reported that 50% of mechanic replaced sensors were good, mistakenly replaced, and those are professional mechanics, I bet 90% of DIY sensors that are replaced were good.

IAC valve also can not cause a miss.

Spark plugs and wires can, and can also be effected by heat

Fuel pressure could be low, should be 30-40psi at the rail, failing fuel pump could cause that, but cold or hot wouldn't matter unless pump was cutting out after running for 10 minutes, fuel filter wouldn't but for $10 if you have never replaced it I would.
You can usually borrow or rent a fuel pressure tester from auto parts stores.
Test pressure at idle and at 2,500rpm for 1 minute.
Then shut off engine and watch pressure, it should be no lower than 25psi after 5 minutes of sitting.

 

[96ranger96]

Thanks for all the info. I will have to check everything out. The truck has a new fuel filter on it and the firing order is correct but I will double check. It used to only have trouble when it got warm but now it's all the time in all rpms. It's very discouraging and frustrating when it's just getting worse when I'm trying to fix it. I will get back to you guys with what I find later on. Hopefully I come up with something. Thanks again

 

[Angie]

hi 96,

here are 2 sites i use for trouble shooting.

hunt around in here to diagnose the prob. don't short cut procedures.

cheers

http://easyautodiagnostics.com/


http://www.aa1car.com/

 

[96ranger96]

Alright so I disconnected the battery and I figured why I waited if pull the plugs just to see. I pulled all 6 and 2 or 3 of them had these blister looking tips. So I researched it and that can be a sign of the engine lacking fuel. So I put a fresh set of plugs in it, hooked up battery and started it. No change. While the truck was trying to stay running I started thinking maybe it's getting enough fuel to run poorly but not enough to run correct. Grabbed a fuel pressure gauge and hooked it up. When I turned the key on it went to 10psi. Started it and it jumped to 20 but quickly fell to 15 and then bounced between 15 and 18 as the engine struggled. Took the fuel filter off and blew through it fine. So I guess it would have to be either fuel pump, the regulator, or fuel injectors right? Any thoughts would be great. I hope I'm heading in the right direction now.

 

[txgocartB3000]

My guess would be fuel pump.

Ray

 

[96ranger96]

It was the fuel pump. It was kicking on but then lost power the more it ran. Put a new pump on it and it's running good now. Thanks for all the advice.