Warmed up engine hesitation/misfire

[jrquint]

I just got a '90 Ranger 2.9L 5-speed w/ 152,000 miles about 2 weeks ago. Truck was VERY well maintained by the previous owner and have had to deal with very few minor issues. One of the which is a hesitation/misfire that happens right when the engine reaches operating temp.

I have a very regular 7.5 mile commute in the morning and the problems are 100% consistant every day. I get to the last 2 miles and it happens without fail. I pulled the codes a few days ago with really no help(some possible old KOEO codes dealing with octane wich cleared and have not come back). On the first KOER test it posted a code 21 Coolant temp out of range, but the engine was fairly cool at the time so I didn't think much of it.

The coolant temp sender for the gauge was bad, so I replaced that. Since the ECT is in the same spot using basically the same type of sensor I figured maybe that was my issue (and the code 21 was legit). I did another KOER test with a warmer engine, and no code 21. I did a resistance test on the ECT. It seemed to be within specs, but when i tested it cold(35 degrees outside, car off for 5+ hours) the resistance corresponded to closer to 60 degrees. After my drive home(same 7.5 miles) the resistance read about 180 degrees, which seems a bit low but not out of whack.

The spark plugs look decent, someone put on new wires which look decent. haven't pulled the distributor. The engine basically has posted no codes. At least one O2 sensor was replaced in the last few years.

Last night, however I finally got a CEL. I didn't have my 'test wire' with so couldn't pull it right there. I pulled the codes this morning before going to work KOEO.

I got codes 21 and 24. Coolant temp out of range(maybe 'cuz the engine was cold? not sure if it was stored or new code.. was the first one retrieved) and

Air Charge temp out of range. No idea what that referes to however. I am inclined to pursue this one as it was the second code and more likely a stored code?

Any suggestions would be greatly appreciated. Was thinking MAP or ignition someplace, but not sure how to test (timing is good, dont see any spark arcing, etc) these sensors or ignition electronics

 

[IMenriched]

I just got a '90 Ranger 2.9L 5-speed w/ 152,000 miles about 2 weeks ago. Truck was VERY well maintained by the previous owner and have had to deal with very few minor issues. One of the which is a hesitation/misfire that happens right when the engine reaches operating temp.

I have a very regular 7.5 mile commute in the morning and the problems are 100% consistant every day. I get to the last 2 miles and it happens without fail. I pulled the codes a few days ago with really no help(some possible old KOEO codes dealing with octane wich cleared and have not come back). On the first KOER test it posted a code 21 Coolant temp out of range, but the engine was fairly cool at the time so I didn't think much of it.

The coolant temp sender for the gauge was bad, so I replaced that. Since the ECT is in the same spot using basically the same type of sensor I figured maybe that was my issue (and the code 21 was legit). I did another KOER test with a warmer engine, and no code 21. I did a resistance test on the ECT. It seemed to be within specs, but when i tested it cold(35 degrees outside, car off for 5+ hours) the resistance corresponded to closer to 60 degrees. After my drive home(same 7.5 miles) the resistance read about 180 degrees, which seems a bit low but not out of whack.

The spark plugs look decent, someone put on new wires which look decent. haven't pulled the distributor. The engine basically has posted no codes. At least one O2 sensor was replaced in the last few years.

Last night, however I finally got a CEL. I didn't have my 'test wire' with so couldn't pull it right there. I pulled the codes this morning before going to work KOEO.

I got codes 21 and 24. Coolant temp out of range(maybe 'cuz the engine was cold? not sure if it was stored or new code.. was the first one retrieved) and

Air Charge temp out of range. No idea what that referes to however. I am inclined to pursue this one as it was the second code and more likely a stored code?

Any suggestions would be greatly appreciated. Was thinking MAP or ignition someplace, but not sure how to test (timing is good, dont see any spark arcing, etc) these sensors or ignition electronics

there are 2 coolant sensors for this, just to be clear.
there is one for the gauge cluster and one for the ECM or main computer. they operate completely separate from each other.

the Air Charge Temp Sensor (ACTS) is on the passenger side of the upper intake, about mid stream.

either of these would be relatively easy to replace

 

[Hanster]

sounds something close to what mine would do. I replaced the MAP and 98% of my problems were gone. I would look into that, its really easy to replace. I'm not sure how to check it though.

http://www.fordfuelinjection.com/?p=27

that might help

 

[chazzone]

there are 2 coolant sensors for this, just to be clear.
there is one for the gauge cluster and one for the ECM or main computer. they operate completely separate from each other.

the Air Charge Temp Sensor (ACTS) is on the passenger side of the upper intake, about mid stream.

either of these would be relatively easy to replace

What he said.

This is a very simple fix, and I wouldn't put off doing it, since it'll cost you more in gas in a couple of weeks, than it'll cost for the sensors.

 

[jrquint]

ACT and ECT test fine, a little cool but within .2 kohms of each other.

 

[dawson111299]

A bit more info needed on the hesitation misfire. Is it bucking hard ? What does it do when you accelerate better or worse? Hows the idle after it reaches full temp compared to a cold idle? Do you ever drive it further than 7.5 miles to see if it gets continually worse.

 

[kimcrwbr1]

did you disconnect the battery for 1/2 hour then drive it till good and warm and is it getting to operating temp 195 degrees if you dont know how old the tstat is I would put in a good new one for general maintenance motorcraft preferred