87 ranger 2.9 5 speed miss when warm

[wolffpack08]

hi, im new here. I bought said truck last year and it had problems so i figured it would be a little project truck. Well im getting stumped at whats wrong with it. When you start it up it runs great, maybe a little weak on power but im not expecting much from the little 6 cylinder. Anyways my problem is after you drive it 5 miles or so it will run real rough unless you hold the throttle to the flour or cycle the key off and on. if you do that it will run good for another mile or so then you have to do the same and itll run good for another mile, over and over again. I know the fuel pump is good i had a gauge on it while driving during the problem. I cant remember the the pressures but a local mechanic said they were in line for the truck. also the fuel pressure regulator is not leaking. Im wondering if its maybe a bad computer or ignition module. Sorry if this is a common problem but nobody ive talked to has heard of it. Ive tried searching and searching the internet but either theres no answer in the forum or the problem is different. I dont want to throw alot of money at the truck since i only paid $150 for it. I just want to use it as a little gas saver for making my 6 mile drive to work. Im hoping that it gets better fuel mileage then my 05 f150 and it darn well better get better mileage then my 79 f150. I know people always say if you want fuel mileage buy a Geo but i like the fact that i have 4 wheel drive and a box to haul things. thanks for your time and for any opinions or suggestions on a fix.
Cory.

 

[RustedRanger]

The fuel pressure regulator can still be bad and not be leaking...mine was. Mine did something kinda like your problem (it's had many problems)....it was the coolant temp sender for the computer not the gauge.

 

[Earl43P]

Your symptoms are bad when it is operating in closed loop (reading all the sensors, especially the O2's). Turning the key off resets that and it runs good on its "canned values" or open loop until it goes back into closed loop.

In other words, you have an emissions system problem. O2 sensor on the Y-pipe would be my first guess for how badly it's running. Here's a good site to read up on all the sensors/functions: http://www.oldfuelinjection.com/

 

[wolffpack08]

how would you tell if the fpr is bad if the pressures are good? anyway to test the coolant temp sender or the O2 sensor? and thanks for your input.

 

[Earl43P]

Had you clicked on the link I posted, you wouldn't be asking those questions.


http://www.oldfuelinjection.com/?p=41
Do ^that teat plus goose the gas when the gage is hooked up. Pressure should change with a hard rev.

http://www.oldfuelinjection.com/?p=28 is the ECT testing.

http://www.oldfuelinjection.com/?p=31

 

[wolffpack08]

the engine coolant temp sender tests good. the o2 sensor test good also. i dont have a fuel pressure gauge here to test the fpr. sorry i didnt read into that site enough. also read codes with the KOEO test I got 31-31-13-13-1 looked into egr and i cannot find it unless its the unit on the passenger side of the throttle body thing, right next to the 2.9l thats stamped in to the top of throttle body. i could not find a tube going to the exhaust manifold or a vacuum line going to it.