Computer problems

[PKH]

Hi, I have a 1994 ranger 4.0 5 speed 4x4, Have been having problems with the engine running poorly and missing then shutting off. Been though all the codes change almost everything it ran good for awhile and its back, now I get code 522 and code 159. Got a replacement maf still runs bad. Strange thing is if its running bad, turn the key off and it works good for a short time. Help would be great, out of ideas!!!

 

[adsm08]

Unplug the O2 sensors and see if it clears up.

 

[RonD]

Does it run better cold than warm?
The PCM(computer) doesn't use the O2 sensors until they heat up, approx. 650deg, so not usually until the ECT(engine coolant temp) sensor gets to 160-180deg, that's the two wire ECT not the 1 wire sender for the dash temp gauge.


Turning the key off then restarting causes the PCM to ignore the O2 sensors for a minute or two, there is a timer, this allows them to heat up again, above 650deg.

So it could just be a faulty sensor not the PCM at fault.

 

[adsm08]

Does it run better cold than warm?
The PCM(computer) doesn't use the O2 sensors until they heat up, approx. 650deg, so not usually until the ECT(engine coolant temp) sensor gets to 160-180deg, that's the two wire ECT not the 1 wire sender for the dash temp gauge.

That isn't as true by 1994. It will ignore the O2 sensors until they get to a certain temp, but with 3 and 4 wire sensors they kick in faster because two of those wires are for a heater.

 

[UrbanRedneckKid]

Pull an O2 sensor out, doesn't matter which one.

I'd be leaning on a plugged catalytic converter. Removing an O2 sensor will relieve the excess back pressure.

A plugged cat will set MAF and fuel trim codes. If it can't get the air out, it won't be letting the right amount in. Air flow is only measured on the intake side, thus that's all the ECU sees.

 

[PKH]

Computer Problems

Thanks I will try that.

 

[PKH]

Computer Problems

Hi thanks for your input, unhooked o2 sensors no change, took intake tube off and checked real good, it seems good, unplugged the maf and ran prettty good for about3 or 4 minutes and then shut off, restarted and heavy black smoke out of the exhaust and running real bad!! coding 159, 565, 556, 528, got me by the sneakers. Thanks for your help thus far!!

 

[RonD]

I would definitely check if exhaust is plugged up, collapsed CAT, as urbanredneckkid suggested.
It fits all the symptoms.

 

[Milton]

I do not think UrbanRedneckKid said to unhook/disconnect the O2 sensor. He said to pull/remove the O2 sensor. The theory being that removing the sensor will leave a hole for the exhaust to escape preventing pressure build up.

Good luck.

 

[PKH]

Computer Problems

Ok I unhooked the o2 sensors, I have side exhaust with no muffler just cat, If i jump on the gas it will clean stones from that spot, so I don,t think its plugged up, of course at this point who knows!! I did find one thing though, last month was having some what the same problem and changed the MAF with a rebuilt one, but at the same time I found my ignition switch was going bad, about that time everything started working?? This week I got a code for MAF and truck has been running bad, got another one, what are the chances this MAF is bad too the volltages arn,t right!!!!

 

[RonD]

Try here for the MAF

http://www.therangerstation.com/tech_library/CleanMAF.html

 

[adsm08]

Holy crap man, it might be faster and easier if you just bring it here.

 

[PKH]

Computer Problems

You know you are more than likely right, good truck, took alot to shut it down. Thanks for your help