92 3.0 rough idle when cold

[85_redranger]

ok guys i just bought a 92 ranger and when you first start it up for the day it studders pretty bad but after 30 seconds to a minute it idles normal anybody got any ideas?

 

[Rearanger]

How about during the day when you do a warm start, does it still stumble for 30 secs? Or maybe at the end of work when the engine's cold but ambient temp is good, does it also do it then?

 

[85_redranger]

it starts good when the motor is warm but after the motor cools it starts like what i described in the first post.

 

[Rearanger]

My first thought was that overnight moisture might have collected on the ignition wires and was causing misfire due to arcing, but only 30-60sec to correct does not indicate that. I also thought that maybe during long periods of shutdown the fuel drained back into the tank so that your fuel pressure was low for initial start-up, but again it should come back faster than 30-60 sec. I'd still do a fuel pressure test when engine cold after sitting overnight. But until you nail down spark or fuel it'll be hard to know where to look.

 

[Big Jim M]

Temp switch

it starts good when the motor is warm but after the motor cools it starts like what i described in the first post.

Them 3.0 engines have two temp sendors near the thermostat. One sends the temp to the gauge on the dash.. The other one is a switch that sends a signal to the computer telling it the engine is cold or warm.. Sounds like yours is telling the engine it is warm all the time..that is the fail-safe condition when they blow up.. So I'd replace that switch.. Most likely is your problem.
Big JIm

 

[Rearanger]

As you know the ECT varies resistance with temperature. The higher the temperature the lower the resistance. Correspondingly the higher the temperature the lower the voltage signal to the PCM. Higher temps will signal PCM to give leaner mixture. I'm doubting the fail-safe is a warm engine signal to the PCM, otherwise the problem would be hard-starting/stalling at cold start-up. I still think the 30-60sec problem window is too narrow to assume an ECT problem, they just don't react that fast and engine temp would have hardly moved.

You can test the ECT with an OHM meter and compare to specs or test voltage signal to see what voltage is being sent to PCM, but good ECT ground would also affect voltage, so you'd need to test that as well. As well if the reference voltage (5v) is low then the reading will be off. Some PCMs seem to have an internal "pull-down" resistor that reduces signal voltage further.

What may also be occuring is overnight leakage of an injector or two that creates a flooded condition in one or more cylinders. That flooded condition is something that will correct in 30-60 sec. A backyard DIY could pull all the plugs before letting the truck sit overnight so that any leakage would evaporate during the night. Install the plugs just before cold start and see if the rough idle is still there, if not then that's probably the problem. You could also get a used oil analysis which would show excess fuel in the oil if overnight leakage, assuming piston blow-by is minimal.

 

[jaxranger]

I had the exact thing happening to my 2002 Ranger. Same engine. I pulled the plugs and they were terrible. New ones gapped to .044". I think the ones that came out were originals since they were badly worn and the gap was over .100". Changed the plug wires as well as cleaned the idle air control valve. Now it runs like a new truck. Lots of get up and go and no more rough idle. Amazing what a little maintenance will do. I am curious about the gas milage now. Should be considerably better. Give this a try and you might be surprised.

 

[85_redranger]

thanks to all i'm going to start with the simple things first like the plugs the truck has all new wires and cap just installed a thrush turbo that i had layin around the house i'll get the plugs done as soon as i can and hopefully that'll be the problem if not though i guess i'll just have to try something else.

 

[volcomstone_1223]

let me know how this goes i have the same problem but i have replaced the plugs and the fuel filter and still no change

 

[basketranger]

my 93 3.0 started off pinging about 4-4 1/2 months ago. changed timing chain which had slop in it but not "worn out". even after changing chain and gears and setting timing still had pinging under hard acceleration. confered with you good folks here and started doing little tests and checks, cut to the chase changed coolant sensor (computer - not gage) had a little improvement changed IAC gskt and cleaned IAC, then did the sea foam thing a taqd better but still poor idle/drivability so found from another thread the procedure for checking IAC and found it to be bad, so I replaced unit. now hoping a puter reset will allow the RPM to come down from that hi idle even after running temp.

 

[85_redranger]

Truck has all new plugs and everything installed from a repair shop around here i bought the stuff to do an oil change i checked the oil yesterday and it was really really dark black so i'm going to change oil and filter today and can anyone tell me how to clean the IAC valve?

 

[ChargerOnDavins]

Had this problem with my 1992 3.0 ranger, and I cleaned out my IAC valve with lacquer thinner (filled it, let it drain, repeated for about 20 minutes) until I was done replacing my fuel filter (really easy).

When I put it all together it works fine.

Still runs a LITTLE rough (could be IAC or leaking injector) but the car runs/drives MUCH better. I'd say it fixed the problem 80-90%.

IAC valve is located near the throttle body. It's a small valve that has 2 bolts and 1 plug going in to it. Mine was covered by black plastic thing I had to remove too. Very easy.

 

[ragingbull2k2]

I'm having the EXACT same problem as the OP... still haven't found a solution and I'm running out of ideas... also, I pretty much have to feather the throttle if I'm in 3rd or 4th gear when all of a sudden it'll start pickup speed... it seems as though its starving for fuel... Has new plugs, wires, oil, oil filter, air filter, fuel filter, fuel pump, strainer, battery, coolant, cleaned IAC valve and MAF... it threw a CEL, but still trying to find someone who can lend me a scanner... the only thing I can think of are injectors? how do I test for those? thanks in advance!

Joey

p.s. been a long time lurker, just never signed up... also, the specs on my truck are on the left

 

[kimcrwbr1]

Allways erase the computer memory and then disconnect the battery for 1/2 hour to reset the computer when you clean or change a sensor so the computer can reset the values and drive it for 20 minutes to warm the engine up to operating temp before you check for codes while it is up to temp.

 

[ragingbull2k2]

Allways erase the computer memory and then disconnect the battery for 1/2 hour to reset the computer when you clean or change a sensor so the computer can reset the values and drive it for 20 minutes to warm the engine up to operating temp before you check for codes while it is up to temp.

Battery was disconnected for over an hour when I was replacing the fuel pump last night... went for a test drive, and there was no CEL... after 30 min or so, came home, turned off the truck, then turned it back on to a rough idle... shortly after, CEL... want to check the code, but having a hard time getting ahold of a scanner...

Joey