Misfiring after warm

I have noticed my truck slowly starting to loose power in last few months. So I replaced the plugs and wires and cleaned the MAF sensor and replaced the air filter checked my coils with a multimeter and they all read the same on resistance. Now it runs great but after its warm and I shut it off and go to start it back up it runs rough acceleration is bad and idle is even bad. Engine code was a misfire cylinder 5.

So why would it run good than once shutting off and starting back up run terrible?

 

Wow,

You have definitely done your homework to try and get your Tacoma to run smooth. The only other thing I might of done in addition to what you have already done is clean out the Throttle Body and the Idle Air Control systems. It sounds like you have some kind of intermittent sporadic electronic problem. Does it consistently do the symptoms you just described? You could still have a bad coil.

Take it easy,
Paul

 

How hard is it to clean the throttle body and the idle air control system? Ya it's been real consistent the last few weeks. I start it up, drive to the store, runs like a top. So I go in the store come back out and it's still warm but been sitting and runs terrible. Wouldn't two cyclinders be miss firing if it was a coil?

 

Dear Tacoma4x4-7,

It is not that difficult to clean out the throttle body or the idle air control. It is just laborious and time consuming. There is probably a video on this site on how to do it.

Bad coils can be a strange animal. You are correct in your assumption that the problem should persist on two cylinders if it is a bad coil. The coil, however, could be electronically transmitting on just one side. The best thing to do to eliminate the coil is to switch coils, and see if the problem manifests itself on the new cylinder it is attached to.

Good Luck,
Paul

 

could be a leaking injector

 

Of all the items related to misfire (spark, fuel, compression), ignition components are more likely to be affected by temperature. Try swapping coils to see if the misfire moves to another cylinder.

What brand wires did you install? Toyota? Denso? NGK?

 

That fuel pressure

 

I'm going to try the coil swap forsure and clean the thottle body. I got NGK Iridium plugs and NGK wires I don't know if those are good or bad.

 

Thanks for all the Info

 

It's possible the NGK spark plugs aren't 100% compatible with OE. The OE plug (

$5 Denso 3194 Spark Plug

Denso 3194 / 16TR11) is somewhat unique with an extra-long electrode and two ground straps:

 

So I switched coils and the misfire is still on cyclinder 5. I'm guessing it's not a coil. I cleaned the throttle body and IAC and it seemed to idle higher when I first started it up in the morning and it seemed to have more power also it was running great. So I than drove to town and when I went to start it up again it did the same thing started missing and idled real rough. (I was real frustrated)

Think it could be a fuel issue? Injector?

 

Also this may sound dumb but could my master cyclinder be the cause? I have noticed a ticking noise by my master cylinder and didn't know if some vacuum lines could be causing a problem?

 

Check for exhaust leaks and make sure your EGR gaskets are intact. I had a similar ticking noise and it turned out to be a cracked exhaust manifold. It was making the truck run poorly after it warmed up and the crack was enlarged by it heating up.

 

^^ this.

 

Does it clear up and run fine after you drive it a bit?

 

You need to buy a scan tool so that you can monitor what is going on engine managment wise... decent ones cost less than $100 but you are going to have to do your research on this.
With a scan tool you can monitor opperation of the MAF sensor, the amount of fuel injection modifications(fuel trim), the various temp sensors etc.
It appears that you have isolated one issue to cyl #5. With a scan tool it would tell you if that bank has a questionable injector by how the fuel trims for bank 1 are being modified by the PCM.
Of course it has to be the injector on the difficult side to work on... but what the heck, when you have the throttle body and upper intake off you can clean these things easier.

 

I saw that the OP never posted a follow up, don't know if they solved the problem. I'm having the same problem, 1999 Prerunner I bought new in 99 for around $23K. It's been a good truck though I don't really like automatics. The problem is the same, it starts up and runs perfect but after it warms up, park it and start it about 20 minutes later, there is a steady cylinder miss. I went to Autozone, "My truck is misfiring". Diagnostic showed misfire on cylinder 5. I bought new plugs, no change. I bought a new coil for cylinder 5, no change. Found a vid about the problem associated with injectors so I bought 6 refurbished injectors. I put those in, ran terrible!, I barely made it around the block, truck died in the driveway, that was a close one. I took off the throttle body, cleaned that, no change. I thought I made a mistake somewhere but all hoses connected, nuts and bolts torqued down. "Refurbished injectors?" I thought, maybe some are bad. So I took the plenums off and put the old injectors back in after a clean, all but for number 5, I left a refurbished injector in there. Everything was as it was before I put the refurbished injectors in, no more refurbished injectors for me. I've experienced a mass air flow sensor fail, doesn't feel like that at all, I cleaned it anyway. Two more things I will try, a "brand new" injector for number five and a new spark plug wire. If that doesn't do it, I may take it to a professional mech, any other ideas?

 

you are on the right diagnostic path. If after the new injector is put in and she still misses then I would NOID light #5 injector connector. This verifies that there is current getting to and from the ECM. There is constant voltage applied to one side of the injector and the ECM provides the ground. The only thing I can think of after that is next time she is missing shut it off and pull #5 immediately and look for coolant, excess oil etc. If after all of this and she still misses it might be time for more experienced eyes. These are the things that make you want to shoot cars.

 

After what you said there, yeah, I think that's the answer, I'm just going to go shoot it over and over again haha. But really, yes what you said there makes me think the number 5 injector stops getting an electric impulse after it gets hot. But then I saw a vid of the ECM shutting off gas to an injector for different reasons, I've got my gun ready. I never heard of NOID lights, looked that up and saw a kit costs a lot less than I would have guessed, I might as well get a kit. If it's ever solved, I'll post it. It seems more Tacomas 15-20 years old are coming down with this problem whatever it is, among other things of course.

 

wiring gets old... at least you dont own a Dodge product. I have heard of 08 & up Challengers get scrapped because the harness's are crap and there are no replacements anywhere in the world. Too many CAN buss faults due to junk wires.