Misfire Mayhem! Help!

Alright, folks who know more about these yoters than me... here's hoping you can help. Stay tuned, this is a long one.

I've got a 99 SR5 with the 3.4L v6, for reference.

Last year, I had a misfire issue on cylinder 4. Replaced plugs and wires trying to nail it down, but neither worked - put in a new fuel injector, and that was it, she ran like a top.

This weekend, same thing happened. I was traveling and suddenly it was missing like wild - I stopped at the auto parts store and pulled the codes. A P0300, P0301, and P0302, which was the most prominent (the 302). I thought "wow, two injectors bad?" But given my previous experience, I replaced the fuel injector for cylinder 2. No improvement. Pulled the plugs, and the plug for cylinder 2 is fouled carbon pretty bad. I replace it with a new plug, wondering if it were bad enough to not fire, and still nothing. After running the engine a while longer, it starts throwing a 306 too. And eventually a 301 again (I'd cleared the codes from when I put in the new fuel injector)

The chance that 3 injectors went bad all at the same time isn't believable, so I don't want to throw money if it didn't work for the 2nd cylinder in the first place. I also tried swapping my 1 and 5 coil packs to see if I could get the 302 to move cylinders to number 4, but that also didn't do anything. Still a 302.

One added bit of information. On Saturday previous to this happening, I did a short stream crossing up in the mountains. Not extremely high water, but nearing the top of the wheels for a bit, most was mid-hub. After that crossing, I drove it for maybe 45 minutes around fire roads without issue. The next day I drove it for another hour and a half before the problem presented itself. No idea if this had an impact.

So, multiple misfires... if I manually bump the idle, it revs up and smooths out, but under load it bogs down. And at idle it chugs along and smells like it's just dumping pure gas out the back end.

That's my story... trying to get this rig back on the road. Any thoughts?

 

I just replaced the motor in my 02, fired it up and bam, multiple misfires.
I read about someone else who had a similar issue.
I had replaced the coil packs, spark plugs, MAF Sensor, so i knew that wasn't the issue.
Tested the compression, that was good.

I took the timing cover off and verified the belt was installed properly, which it was.

I think the other guy ended up tracing it back to a bad/dead wire on one of his injectors.

So I took the intake off, and carefully removed the junk plastic wire harness protector.
That is when i saw one of my coil pack wires had a cut in the insulation, and must have been shorting out on the motor.

Put some liquid electric tape on it and put it all back together, fired it up.
She runs real nice now.

Hopefully you get it figured out, it can get annoying real quick.

 

Thanks for the suggestion - I'm going to put a noid light on and make sure my injector circuit is firing as well, and swap plug wires just to make damn sure (although I hiiiiighly doubt that's the issue, but might as well rule everything out.

Next up, compression test.

I did talk to a Toyota tech who said that cracked valves in these guys at my mileage (240k) isn't an uncommon failure... ugh.

 

I would look at the air filter and housing first and as to the fuel injectors they are all the same age so it wouldn't be unbelievable that they would fail one by one after the first one.

 

About a month ago one of the guys here posted a "fix" for the "junk plastic wire harness protector". He removed it and used some rather heavy duty (I hate that term - "heavy duty") tape and wrapped it around the wiring harness. Can't recall how he secured it to the engine (maybe he didn't). You might go back to May 1 and look for the post.

BTW, the guy did a helluva job fixing his problem. Should also work for the "junk plastic wire harness protector" that goes under the front of the oil pan too.

 

I used hockey stick tape... it is wide, black and cloth wraped

https://www.amazon.com/hockey-stick-tape/s?k=hockey+stick+tape

I secured mine with electrical clamps

$10 LOKMAN 20 Pack 5/16" Stainless Steel Cable Clamp, Rubber Cushioned Insulated Clamp, Metal Clamp, Tube Holder for Tube, Pipe or Wire Cord Installation

https://www.amazon.com/Cable-Lokman...hvlocphy=&hvtargid=pla-4583657821922212&psc=1

 

Update for today... I pulled the plug out of 2 and turned the engine over, when grounded against the block i get spark.

I also performed a compression test on the 2/4/6 bank... with the engine cold, they all read right around 190, which is above the 178 spec, and the suspect cylinder (2) was dead on the same as the rest of them. I also did cylinder 5 on the 1,3,5 side just to verify, and that cold was also 190ish. I'll re-perform the test with a hot engine today just for additional verification.

I'm also going to put a noid light on the fuel injector and ensure I've got power there... although if I have a short in the wiring, it may stand to reason that the noid may light but it's still shorting consistently... I'll pull that plastic wiring harness apart and give things a look.

Aside from a noid light, are there any tests I can do on the injector wire with a multimeter that will yield more information?

Thanks guys. This is driving me crazy. Really don't want to have to take it in, but at this point I'm running out of ideas.

 

Uhhh, what's a "noid" light ("nerd" light comes to mind...) ?

 

I'm chasing something similar right now. Wanted to tell you to look at this note about the brown injectors. You said you replaced 2, not sure if they are new or used or what...but something to think about as our components get old.:
https://motorwestperformance.com/product/mp831-6pack-l1/

I got those from MotorWest maybe a year ago. Truck ran great. Latley, started getting cyl 1 misfire especially near idle. I started talking to Motorwest and they sent me a set of the Denso blue injectors, I'm hoping to install this week (these: https://motorwestperformance.com/product/upgrade-for-23250-62040/ ).

Also- as part of your troubleshooting have you checked fuel pressure at the fuel rail at all throttle positions (this would rule out bad fuel pump or bad fpr)? And have you replaced fuel filter with an OEM one lately?

 

Also- the ECU will throw codes for open/short injector wiring so don't spend too much time on the wiring. In response to the cracked wiring holder, get some TESA tape (

$7 Tesa Wire Loom Harness Tape Used By Mercedes BMW VW Audi

https://www.amazon.com/Tesa-Wire-Lo...ocphy=9032504&hvtargid=pla-309634072467&psc=1 ) and then use those padded 1-hole clamps as previously shown in this thread.

 

There lots of different type Tesa tape, you want the 51026 type, 300 degrees resistant,
GREAT STUFF

 

Thanks for all the feedback, guys. After a ton of head scratching I decided to replace plug wires (even though the plug wires were new a year ago)... and bingo. Maddening after pulling the intake off about 4 different times while i did the troubleshooting, but glad it's back up and running.

That TESA tape is awesome!