My 93 is misfiring.

[decrelliott]

Hi everyone, new to this so please bare with me. I'm having a problem with my 93 explorer and need some help. It misfires after a 5 min. warm up. You can hear it start to misfire after idle drops down. EEc temp sensor has been replaced. Thanks

 

[BrooklynBay]

Welcome to this forum! I've moved your thread into the stock 91-94 section. Do you have a check engine light with codes?

 

[Roadrunner777]

Could you say that the idle speed is dropping too low? Can you describe the rpm readings on your tachometer during a typical start-up?

 

[mcelwajy]

Just had the same problem! Check your plugs and wires first...I had 3 cracked plugs...replaced and fixed.

Also, vacuum would be a good place to start....

 

[decrelliott]

I wold say the cold engine rpm about 1200 rpm drops back to about 800 and there is no check engine lights. It really skips and sputters under acceleration, but not when the engine is cold.

 

[Roadrunner777]

I think you are running too lean. You can do 2 things fast and economically that could address this. Clean the Mass Airflow Sensor, and the Idle Air Control. Both are pretty well documented in other threads.

 

[decrelliott]

Thanks for the responses to my problem,but still have it. I tried to pull some codes but seemed to be pretty erratic. The only thing I would say was made sense was I got 136 and 172 twice with koer. koeo was 111. I really hate to take this to a garage to fix something that I know I could if I just knew what it was. Easing into the throttle is ok but you stomp it, sputters pops back through the intake runs like junk, but not when cold. Any ideas?

 

[Roadrunner777]

Can you tell more about drivability? Is it missing at idle only, during acceleration, etc...

I would look at it from a systems view.

Ignition
You checked plugs and wires, all good, right?
Look at the running engine in the dark, the plugs, look for arcs.
This could be the coil pack. I have no way to diagnose except to swap it out.

Fuel/Air
Cleaned Mass Airflow sensor
Cleaned Idle control valve
Test throttle position sensor <- I added this one, just thought of it.
Fuel pressure and volume test
Reset computer to re-learn idle
vacuum readings nominal?

 

[backfrmcolorado]

For the above poster and original poster, to chek a coil pack is easy. Just make sure you have a good leather glove on so you dont spark yourself accidentaly. Just start the X up, open the hood and pull each wire one by one off the coil pack about an inch or less and see if you have a spark arcing from wire to coil pack, or if you dont like the sound of touching the wires try a timing light. Ground the ground wire of the light and conect the spark wire to a wire one by one to see if you have spark. Good luck and i hope this helps.

 

[Roadrunner777]

Yup, there is the arc test, forgot. There are fairly cheap gizmos you can up inline with the plug wire too. Be sure to do it when it is warmed up and consistent with the symptom.

 

[decrelliott]

when you first start up in the morning it runs fine for about 1/2 mile then as you step on the gas it misfires, pops back through the intake until you get up to speed then smooths out. almost feels like your in 4th gear and should be in first.

 

[Roadrunner777]

Backfiring into the intake...
When I see this, I think timing. In this context, that means crankshaft position sensor, computer, and coil.

If I had a fuel pressure gauge in hand, I would check fuel pressure. I can remotely see overpressure doing this, and it's a fast test.

 

[fishnhunt18]

Mine was having issues initially under load. I only had problems when accelerating, but that progressively worsened. I replaced the MAF, the IAC valve, throttle position sensor, cleaned the throttle body excessively, and replaced the stock airbox assembly and filter with a custom air intake and cone filter. This helped with horsepower some idle issues, but it wasn't until I changed the spark plugs and wires that it fixed my problem. It was probably the cheapest and I went there last. I must have had bad plugs and/or wires, because I had just replaced them and gapped them to specs.