Chasing my tail here. Misfire on 2/4/6 after t-belt replacement.

[StopHammertime]

Hey all. Recently replaced my t-belt, v-cover gaskets, cam seals, PCV valve, intake plenum gaskets (both mid and lower), etc. The basics while doing that job. Double and triple checked timing, it's spot on. The issue I'm having which I cannot track down is that the Runner starts up fine, runs and idles fine when cold, but after it reaches operating temp, I throw a CEL for misfire on 2/4/6, it idles like crap, and very low (about 600-700 rpm, very boggy), with a sulfuric smell (assuming my cat is getting hot from running lean or something). Any ideas?

'96 T4R SR5

I'm just stumped. I tried the carb cleaner trick to try and hunt down a vacuum leak, but came up empty handed. Thanks.

 

[TheDurk]

First, recheck plug wiring. 2/4/6 is a red flag.

 

[StopHammertime]

Thanks, but even with it running fine while it's cold? Seems to me it would run rough 100% of the time if the wiring was switched around.

 

[TheDurk]

Thanks, but even with it running fine while it's cold? Seems to me it would run rough 100% of the time if the wiring was switched around.

Good point, but a lifetime of wrenching teaches me not to ignore red flags.

What I would do then is hook a live scanner up and see if if it starts running badly right at the switch from open loop to closed loop or if it is just generally related to operating temp. That would change the way I would think about it.

 

[LittleCaesar]

As Durk said, try and get your hands on a code reader that shows live data.

I'd go back if nothing else produces a solution and recheck the marks lining up for the cams. I'd imagine it may be off a tooth and doesn't become FUBARed until hot/under load.

Keep us informed.

 

[StopHammertime]

Double checked the wiring, and it's all good. Regarding the t-belt, I double and triple checked it after letting it run for a combined total of maybe an hour now, so that's absolutely not the issue.

I have a scanner, but I don't recall if it does live data. I'll give that a look in the morning.

 

[PitbullRescuer]

I can honestly say I'm stumped. No chance it's 180* out, is there? I'd assume it would cause more issues than just what you're having if it was but figured I'd ask.

 

[StopHammertime]

I can honestly say I'm stumped. No chance it's 180* out, is there? I'd assume it would cause more issues than just what you're having if it was but figured I'd ask.

Nope. T-belt has marks to align everything up perfectly. Both cams are spot on, and crank matches.

 

[02SE]

I've seen more than a few misfires caused by spark plug wires that weren't firmly pushed down onto the spark plugs.

 

[PitbullRescuer]

Nope. T-belt has marks to align everything up perfectly. Both cams are spot on, and crank matches.

I know. And I doubt what I said is your problem. But it's possible to have the crank out 180* and still have the marks match up. ie. crank was spun with the belt off.

 

[StopHammertime]

I've seen more than a few misfires caused by spark plug wires that weren't firmly pushed down onto the spark plugs.

Not relevant - it would misfire from start-up, warm or cold wouldn't matter.

I know. And I doubt what I said is your problem. But it's possible to have the crank out 180* and still have the marks match up. ie. crank was spun with the belt off.

How is that possible when there is a mark to align the belt with the crank, and align the crank to TDC on the oil pump housing?

 

[02SE]

Not relevant - it would misfire from start-up, warm or cold wouldn't matter.

You would think so, but I have seen what you described happen..

 

[PitbullRescuer]

Belt off, crank and cams spin freely of each other, no interference. So the crank gets turned with the belt off, your TDC mark would line up on both the exhaust stroke and the compression stroke.

 

[StopHammertime]

Makes sense, but wouldn't it run like crap even from a cold start if that were the case?

 

[PitbullRescuer]

Makes sense, but wouldn't it run like crap even from a cold start if that were the case?

Probably, yes. But I don't really know what else to suggest so I think it's at least worth thinking about.

 

[StopHammertime]

I'll go buy a digital scope this weekend and pull the plug to check if TDC is correct. Thanks for the idea.

 

[Singtoe]

Check your grounds.

Run a compression test when engine is cold and then when it is hot.

While it is running, unplug spark plug wire and see if the symptoms appear when it is cold.

 

[LittleCaesar]

Did you change the crank seal as well? Members have had their problems with broken crank pulley teeth causing all sorts of trouble. I would think though that you would have a misfire code on both banks though if it was not good, not just the left.

And check the Diagnostic ground also.

 

[PitbullRescuer]

I'm a little drunk right now (rough week so far) but the more I think about it, it might actually run being 180* out. These use a waste spark system so each plug fires twice over the course of the 4 strokes. I'd think it would cause a mis on all 6 cylinders but since the coil pack side is okay and the non coil pack side is missing, I would venture to guess its a possibility.

Disclaimer: I may re-read this tomorrow and think differently but I'm going with it for now.