truck missing at high rpm help

[blue dog]

2000 5 speed 3.4 l 273,000 miles. always ran great until 2 days ago.
changed coil packs and wires
crank bolt tight
crank position sensor good
fuel pressure reads 45 psi
got a new fuel filter a month ago
Cat was restricted so replaced it.
maf changed

First truck started missing and backfiring at speed, after all above it misses under fast acceleration or high speed but no backfiring.

I do not think it is a injector because it idles fine and will run normal if not hammered on.

i am not a mechanic but have built off road rave trucks in the past and have the tools and ability to remove and change what ever is needed.

any help mucho gracias.

 

[02SE]

The first thing I would do, which I don't see as being done on your list, is install new spark plugs.

 

[LittleCaesar]

+1 on the plugs. It sounds like it is running rich.

In what condition would you rate those TRD headers?

 

[blue dog]

Tomorrow after work i plan to do the plugs and check the timing marks to see if everything is where it should be. Could it be possible that the belt skipped a tooth and is out ? Belt and h20 pump are not due for another 8,000 miles.

Trd headers have a tiny exhaust leak at the connector pipe, but has been that way for over a year. I would not recommend trd headers to anyone. I have had 2 pair crack.

Thanks for the input

 

[02SE]

There are quite a few possibilities as to what could cause a high rpm misfire, but I would start with the easy stuff first, which is replacing the spark plugs.

Let us know if that doesn't fix the problem.

 

[blue dog]

Plugs are all good.
could the timing belt have skipped a tooth ? if it stretched ? it is 80,000 miles old at this point.

 

[cordrayj1]

Seriously doubt the timing belt issue. Unless someone who has no idea what they are doing replaced it last time

 

[blue dog]

i am at a loss at this point. still backfiring randomly and missing when getting on the gas anything over driving like a grandma.
code reader shows misfire cylinder 3 and random misfire. throwing parts at it is not doing anything for at this point.
Guess i need to take it to a professional.
any other suggestions would be appreciated.

 

[blue dog]

swapped out the plugs today.
checked for vacume leaks
checked timing belt had not skipped a tooth.
ignitor ground checked
maf changed
checked injectors by unplugging them one by one.
checked tps
fuel pressure reg.

truck is still randomly missing, and only backfiring a little at high rpm.
driving in normal slow conditions, runs normal. sometimes original idle is rough but works threw it, then normal.

i do not know what else to look for . what am i missing. HELP.

 

[the great him]

try swapping the injector on 3 for another that isnt misfiring, and see if the problem fallows

 

[the great him]

the only other thing i could think of is a o2 sensor might be going bad. but i dont see that affecting the your truck in this manor

 

[LittleCaesar]

Find a code reader, or app for a smart phone that allows you to read live data. The kid may be on to something with the 02 sensor if they have never been changed.

How is the compression in that cylinder?

Coolant temp sensor original?

 

[blue dog]

How is the compression in that cylinder?

Coolant temp sensor original?

Did not check compression. Have never changed coolant temp sensor. o2 sensors are 7 months old.

 

[LittleCaesar]

What make/brand 02 sensor did you use?

 

[the great him]

what plugs and wires are you using? are you sure you got the wires routed correctly and seated properly? also an injector can work just fine and lower RPMs like idle and such but then under a load can crap out, so dont rule out the injector possibility. i have never heard of one of these motors jumping a tooth on the timing belt, if it was gonna do that it would have to strip off a whole section of teeth and then it would just die it would be so far off... im willing to bet your timing is right on. i have set a timing belt one or two teeth off before and ran the motor... it ran ok but it was noticeably down on power, but there was no missing or backfire so yeah i dont think its a timing issue.

 

[blue dog]

timing and belt are good. all parts replaced have been oem parts.
could it be something in the valve train ?

today trucks runs fine except at higher RPM. yesterday it was all over the map. sometimes idles rough at start up after sitting, other times does not.

Today backfired a few times, yesterday not one time, just missing.

code reader says cylinder 3 misfire and random misfire.

some electrical gremlin or random ground perhaps.

color me frustrated. I can not afford to throw parts at it.

anyone have a good reputable guy in the long beach or west side of los angeles area that knows his shit.

 

[LittleCaesar]

I would say it seems electrical in nature but could come from a bad vacuum line or a loose ground.

If it was a bad valve in cyl 3, the compression test would reveal such but I would imagine that it would show up all the time, not randomly. I still would perform a compression test if you have the time.

Good luck with a mechanic and keep us informed.

 

[blue dog]

Went over the truck high and low today looking for a bad ground or vac leak. found nothing.
Starting to get frustrated.

 

[kball]

2000 5 speed 3.4 l 273,000 miles. always ran great until 2 days ago.
changed coil packs and wires
crank bolt tight
crank position sensor good
fuel pressure reads 45 psi
got a new fuel filter a month ago
Cat was restricted so replaced it.
maf changed

First truck started missing and backfiring at speed, after all above it misses under fast acceleration or high speed but no backfiring.

I do not think it is a injector because it idles fine and will run normal if not hammered on.

i am not a mechanic but have built off road rave trucks in the past and have the tools and ability to remove and change what ever is needed.

any help mucho gracias.

So 2 days before this post everything was fine and then you replaced all this stuff to fix the new problem? ( Except for the fuel filter you said you replaced a month ago.)

Sounds like maybe you replaced the cat previously as well. What kind did you get? Maybe it's not providing enough back pressure and that's affecting the high rpm performance?

 

[LittleCaesar]

I remember a guy here outside of DC who was using the TRD headers and saying they were causing him nothing but trouble. That was back in 06, right before I got my 4runner so I cannot elaborate on the difficulties he was having with them.

Kevin may be beating around the correct bush so to speak.