Cylinder 1 misfire

[556.sig]

Ok gentlemen (and ladies), I need your help.

99 V6. I'm getting a cylinder 1 misfire and associated code, but here is the tricky part. On a cold start, everything starts and runs normal. After driving around for even just a short period of time and turning off the car, I get the shudder and the misfire on restart - and eventually the code gets thrown. I get the flashing CEL and all and the shudder continues until I turn the truck off and let is sit for hours. As long as it cold starts, there is no misfire.

I've started with the simple things, replaced plugs and wires. I swapped the cyl. 1 coil pack with cyl. 3 to see if the coil pack was bad but that didn't change anything. Thinking it could be a ground issue I made sure all grounds were solid and well connected. My battery was old so I got a new one, that didn't change anything either.

Can't think of what the issue could be. It's not evap related (did a smoke test), or at least not that I can tell.

ANY IDEAS would help. Maybe a faulty fuel injector? I await your knowledge

 

[TheGhost]

This is an old post but I'll answer to the best of my knowledge since I didn't see any replies. Hope you get this.

Mine was getting a cylinder 5 misfire. Here's what I did.

1- plugs
2- wires
3- new coil pack
4- injector

Make sure to check compression on that cylinder.

 

[Ula'Tek]

Ok gentlemen (and ladies), I need your help.

99 V6. I'm getting a cylinder 1 misfire and associated code, but here is the tricky part. On a cold start, everything starts and runs normal. After driving around for even just a short period of time and turning off the car, I get the shudder and the misfire on restart - and eventually the code gets thrown. I get the flashing CEL and all and the shudder continues until I turn the truck off and let is sit for hours. As long as it cold starts, there is no misfire.

I've started with the simple things, replaced plugs and wires. I swapped the cyl. 1 coil pack with cyl. 3 to see if the coil pack was bad but that didn't change anything. Thinking it could be a ground issue I made sure all grounds were solid and well connected. My battery was old so I got a new one, that didn't change anything either.

Can't think of what the issue could be. It's not evap related (did a smoke test), or at least not that I can tell.

ANY IDEAS would help. Maybe a faulty fuel injector? I await your knowledge

I had the exact issues you're describing and it turned out to be a leaking injector.
While you're in there, it's never a bad idea to check plugs and wires.

 

[556.sig]

I had the exact issues you're describing and it turned out to be a leaking injector.
While you're in there, it's never a bad idea to check plugs and wires.

In your case, the leaking injector was due to bad o-rings or something else? I'm going to swap cyl. 1 and 3 injectors to see if it throws the P0303 code instead of P0301. Thanks for the replies.

 

[BrianSD_42]

How many miles and have you done a compression test?

Before you start messing with injectors or spending cash on parts swap it would be smart to do a proper compression test.

 

[Ula'Tek]

In your case, the leaking injector was due to bad o-rings or something else? I'm going to swap cyl. 1 and 3 injectors to see if it throws the P0303 code instead of P0301. Thanks for the replies.

Mine was the o-ring. That's also how I tracked the problem down, by swapping injectors around and following the code.
The o-rings area bit delicate so be careful installing, especially when they are older.

 

[556.sig]

How many miles and have you done a compression test?

Before you start messing with injectors or spending cash on parts swap it would be smart to do a proper compression test.

I'm above 200k now and I haven't done a compression test. You're right, I probably should do one. The only reason I haven't yet, is the way in which the problem occurs: Cold start no problem. Even if it is shut down immediately (while still cold) I get the problem on restart. I figured if it was compression it wouldn't manifest itself in that way.

On another note, I took a multimeter to my passenger side fuel injectors and the cyl. 1 injector (while I was experiencing the issue) would not generate a reading on the multimeter. The other injectors registered just fine.

 

[556.sig]

So, tested the injector with a multimeter while it WAS NOT under issue and it read at 15. Tested while under issue and can't get a reading on the injector at all. Would one believe this is the injector or something else causing the injector to malfunction at certain times?

 

[Konkordmusk]

So, tested the injector with a multimeter while it WAS NOT under issue and it read at 15. Tested while under issue and can't get a reading on the injector at all. Would one believe this is the injector or something else causing the injector to malfunction at certain times?

Swap the injector with one from another cylinder. If the problem follows the injector, it's the injector. If it stays in the problematic injector, it's a wiring problem.

 

[s20004runner]

also experiencing the same issue, but i have already done plugs and wires.

As a temporary fix, I put in the concentrated Techron injector cleaner and it helped a bit.

I need to do a compression test. After that I may switch out all six injectors as I do valve covers, just cause the injectors have over 200K miles on them and I don't feel like tearing apart again.

 

[99Runnr]

I bought my 98 Tacoma (same 3.4 engine) with 180k miles. The ad had it up for $2800, extended cab, 4x4, manual, ect. Too good to be true type deal. The truck threw a CEL on the test drive, and did this same thing. Misfire code when I scanned it. The seller didn't know shit about cars and kinda told me such and he hoped someone would just "deal with it".

I assumed the engine was shot, an left with the truck for $2500 cash, clean title. Did my research back then, same thing your doing. Bought a set of reconditioned injectors online for like $60 and the problem has been fixed for 40k miles now.

You can remove them and get a can of Chemtool and bench clean them with a 9v battery and aligator clips or just find some like I did. Prices may have changed, but they weren't expensive or difficult to do back then. Good luck, seems like injectors may be a fairly strong possibility though.

 

[gamefreakgc]

You are in the same area as I am, if it turns out to be dirty/clogged injectors I highly recommend this guy:

Fuel Injector Cleaning

He's local and you can drop them off at his place if he agrees to it. Knows his stuff and you come back with basically brand new injectors (new o-rings, pindle caps if applicable, flow rates, etc.). If it's an issue with the injector itself though and not just dirty, then that won't help at all though.

Have you cleaned your MAF just for kicks?

 

[jjuliefaye]

Just wondering if anyone else has ever had this issue.. Got a code for misfire cylinder 1... Put in a whole new coil pack, since 1 was looking bad. Still threw the code, put in new wires and spark plugs, same deal. Compression test on injectors and everything was fine. Still giving me the P0301 code and still driving and running funky. I have now put in a new coil pack, wires, spark plugs, and the injectors are testing fine after compression test. Then swapped injectors from 3 to 1 and viceversa, still threw a P0301 code. Not sure what else to do, I have read through multiple forums and everyone seems to say check the coils then injectors. It's a 99 3.4 with 248k automatic and rather stock, I just got it about a month ago and it started doing this a week into me owning it. (Sidenote: my 88 is easier to work on, lol)

 

[Danger Mouse]

did you do a compression test on the cylinder or just the injector? bad valve might leak enough fuel /air mix to stop it from firing correctly.
the original poster's sounds like an injector, and the one I had turned out to be the coil pack, but if you've already done those, and wires and plugs....
were the plugs oem toyota? i've heard of issues with aftermarket plugs with a single post instead of the double post toyota design, but that wouldn't make sense for only one cylinder misfiring. could have the exhaust tested for coolant, unusual but if the head gasket was starting to fail and leak coolant into that cylinder could cause issues.
could there be an issue with the signal going to the coil pack? I would think that would effect both cylinders since the coil pack also drives a plug on the other side, but I haven't looked at that system in depth.