Need Help!

[midtnranger]

I am having a issue with my 93 4.0, she started the other day idling rough, then missing and cutting when driving. Would run fine if you went to wide open throttle. CEL came on, codes 137 and 538. Anybody have any ideas? New plugs, wires and O2 sensors. I really baffled with this.

 

[Earl43P]

137 is Oxygen sensor not switching/system rich Left or Front HO2S - Fuel control

The other code 538 popped up because you didn't press the gas pedal during the test (ignore that one for now and repeat the test properly later).

WOT makes it run better may mean that a sensor is bad. WOT puts the computer back into open loop, by design. PCM ignores sensor inputs and runs off of pre-programmed values.

The easy things that need tested are the fuel pressure regulator http://www.fordfuelinjection.com/?p=41

However, that link does not really address the vacuum control aspect of the FPR. Once you have the gage hooked up and reading pressure, run the engine at idle, note the fuel pressure. Goose the gas to a pretty good rpm 3k or so. Note that the fuel pressure increases (as the manifold vacuum decreases) with engine rpm increase. You can also pull the vacuum line off of the FPR (engine running, plug the line with your finger) and see the same type of pressure increase plus it should run rougher (like yours already does). See if that removed vacuum line has gasoline in it (engine off) meaning FPR is leaking and bad.

the IAT (intake air temp sensor) http://www.fordfuelinjection.com/?p=29

the engine coolant temp sensor http://www.fordfuelinjection.com/?p=28

Don't confuse the two coolant temp sensors, you want to test the 2 wire one that feeds the PCM (not the one-wire sensor for the gage).


I would do the tests in the order that I listed them.

Very few things will make it run rich yet run OK at WOT. I'm betting that one of those three items is gonna test bad.

 

[midtnranger]

Thanks, I do not have a fuel pressure gauge, but once my ranger is 18 years old I decided to just go ahead and replace it all. I ordered the new fuel pressure regulator, coolant temp sensor, and IAT for it. I cleaned the MAF sensor. Check for vacuum leaks, did not find any. The ranger is running better after I installed new O2 sensors, I pulled the codes yesterday KOEO I got 111, KOER I got 116, and 137.

 

[midtnranger]

Alright can anybody help with this, I have changed the O2 sensors, the IAT sensor(waiting for my coolant tem sensor), and fuel filter. I have checked for vacuum leaks. The ranger will run alright at 1st, but after you turn off and restart, I get a cutting out or missing undr throttle. gives me code 137. This is driving me crazy. I have bosch platinum plugs, I am going to change these out. I have good fire from wires. Any help would be appreciated.

 

[hsfdfireman671]

I am having the same trouble did u ever find the problem?

 

[AaronC47]

My nephew had a Honda Civic and I put the Bosch Platinum plugs in the car,, it would NOT start with them in it. I would suggest putting old plugs back in and see what happens. if better, then use different plugs when putting new back in.