misfiring after 30 seconds of driving

[jeff72496]

So I was driving and all of a sudden my car lost power and was misfiring. I didn't have a scanner on me but I pulled into an auto zone and they checked it for me and it said "random multiple misfire". So it started misfiring and then I pulled over and it idled rough. Then I shut it off, wait for about 30 seconds to start up and it's completely fine then drives fine for about 30 seconds and starts misfiring again. My plugs are fine and I already changed my wires last October so I doubt those are junk. Any ideas?

 

[bduran1220]

The power transistor I happend to me that way too

 

[jeff72496]

Power transistor? How do I fix that?

 

[bduran1220]

You can't you need to replace it

 

[jeff72496]

Yeah I know that . Is it something easy? I found out where it is in the engine bay. But not sure exactly what I replace. It looks like a plug

 

[gst-turbo]

Its like 3 or 2 bolts un plug the connection and put new one in

 

[jeff72496]

I must be looking at the wrong part then cause I don't see any bolts near it. Is it right next to the fuel rail?

 

[jeff72496]

I think this is it

 

[gst-turbo]

Thats it they are there look closer

 

[gst-turbo]

You can see the bolt from the picture

 

[me2151]

Use a scanner and check the voltage of your Upstream O2 sensor also. I had close to same issue and it was my O2 sensor constantly feeding a low voltage. Or just unplug the sensor and see if it still misfires after 30 seconds

 

[o0GuitarKid0o]

Check the harness that connects to the transistor unit because they come short from the factory and can wiggle loose.

I've even heard of the pins coming loose inside of the harness connector

Also while your at it check your injectors for cracked pintles , I got a code though for (injector malfunction)

Do you know if it's running on 2 cylinders?
You can check buy quickly pulling injector connectors and listening for a change in idle or no change

 

[bduran1220]

Trust me it's the PT I did a lot part swapping to only have the same random misfire AKA cel p0300

http://www.dsmtuners.com/threads/2g-p0300-cel.502086/#post-153579276

 

[OGDSM1989]

+2 on the Power transitor, my 2g acted the same way ... replaced this and that only to find out it was that damn transitor, I grabbed one from a donor car and off I went.

 

[jeff72496]

I posted before explaining what happened. Basically my car starts up fine. Let it warm up, then I'll drive it for 1/4 mile thwn the car will just feel like it's misfiring really bad. Then I'll pull over and it'll idle terrible. I'll shut it off and it turn it back on it'll be running perfectly fine. I changed the power transistor and it's doing the same thing. But while the car was misfiring I disconnected each injector 1 at a time. Nothing changed when I unplugged cylinder 4. But when I unplugged 1, 2, and 3 the car was about to shut off. So it's definitely something with cylinder 4. Something with igniton?

 

[delta448]

Pull the spark plug on that cylinder, make sure it's not carbon fouled and check it for spark.

If you have good spark, it's probably the injector or the injector resistor pack. You can check the resistor with a dmm.

 

[jeff72496]

Could it be a low compression possibility?

 

[pauleyman]

Low compression isn't intermittent. Likely a spark or fuel injector issue as suggested.

 

[jeff72496]

That's what I figured. My buddy insisted I get a compression test. But I had one done last October and it came up to be perfectly good

 

[bduran1220]

Change the power transistor I thought it was my injectors too then I swapped them out for my spares and still did the same thing.
Check your ecu

 

[jeff72496]

Already did that. Nothing changed

 

[442powerstroke]

Believe it or not i had same prob turns out it was a lifter that would lose psi when it got warm easy thing to do for you for start is by new plugs n swap injector over to other cyl its free then pick up a set of lifters u can change them out with out doing timing but its a pain

 

[Maxthepersonz]

I've also seen wiring in the harness go bad mid way to the ECU. Depends on how nice your harness is obviously but a wire could have been pinched and separated internally over time. Check all the plugs with a DMM and make sure they're all giving you the same reading.

 

[jeff72496]

Yeah I'm gonna test igniton coils today