Chasing this intermittent prob. on our 2000 3.4L...

Truck runs on what seems like 5 cylinders - rough idle & shakes all the way through the RPM range.

What I've done:

--installed new Denso plugs less than a year ago; pulled #3 plug & it still looks new.
--just installed new plug wires yesterday.
--listened to each pass. bank injector w/ stethoscope & all "tick' consistently;
--swapped coil over #3 cyl. to #1 to rule out a bad coil pack; reset ECM to clear trouble codes - same CEL comes back..

Funny thing is that each time I change something, truck runs smooth as silk until you shut her down. Start it back up & problem returns!

About to pull #3 coil pack connector to see if it runs any worse; if not, it would seem I have an intermittent short somewhere in the wiring harness that feeds that coil pack. Will report findings.

I'm not new to auto mechanics so this has me quite frustrated. Any other ideas, similar encounters?

Her4Runner

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2000 4Runner (Hers)
1992 Typhoon
1991 Syclone
1998 Camaro (DD)

Have you tried disonnecting the neg cable for a few mins so it can relearn its values?

Im having the EXACT same problem with my 97. It idles rough and shakes through the entire rpm range. Code keeps coming up with cylinder 2 missfire. Ive replaced the plugs, and the wires. The injectors are new. Im at a loss, just like you, because I'm not new to this stuff and I'm out of ideas. Ive had four mechanics tell me different things and none of them have solved the problem. Some of them worked for a few minutes, but after driving, the roughness returns as well as the check engine light.

Update me if you figure it out haha.

PS. Does your check engine light flash if you accelerate too hard? Mine does, and that CANT be good.

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'97 SR5 4WD
TRD Supercharger
Denso Iridium Plugs
318cc Injectors
URD PCU
TRD Intake

I've pulled the ECM fuse (which accomplishes the same thing - resetting the computer) after every change I've made.

Her4Runner

__________________
2000 4Runner (Hers)
1992 Typhoon
1991 Syclone
1998 Camaro (DD)

UPDATE:

--triple-checked all underhood electrical connections, incl. coil pack & fuel injector harnesses.
--triple-checked all vacuum hoses.
--swapped #3 plug w/ a known good one.
--cleaned MAF again, just to rule it out.

Start truck & it purs like a kitten. Drove around for ~10 miles, putting it through all its different paces. Ran perfect. Parked it & returned 15 minutes later to resstart it, & problem reappears. Shite! After sitting overnight though, GF drove it to work & it ran normal.

So, could a bad/stuck injector act like this? What about a break in a wiring harness somewhere? Due to the intermittent nature of this, & the fact that the DTC is so specific, I really don't think this can be a mechanical or "hard part" failure such as a bad cam lobe, valvetrain etc.

I'm at a loss...

Her4Runner

__________________
2000 4Runner (Hers)
1992 Typhoon
1991 Syclone
1998 Camaro (DD)

Since it

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2003 4x4 Sport 4runner V8, Scion HU w 4 upgraded speakers, Hella horns, MapLight Mod, de-badged 85 k + miles
1994 Jeep GC with 202,500 miles
1990 Corolla 168,000 miles
1994 Volvo 850 165,000 miles
2003 Camry 12,500 miles

The first time I took it to a mechanic he did a compression check, and it came back with good compression, so its not a burned vavle. I think Ill be taking it up to URD tomorrow since I have their fuel kit/injectors/plugs/computer etc. to have them look at it.

__________________
'97 SR5 4WD
TRD Supercharger
Denso Iridium Plugs
318cc Injectors
URD PCU
TRD Intake

Thought I'd update, for others' poss. info...

Problem turned out to be a BAD INJECTOR in cyl. #3. Couldn't pinpoint it until recently when symptoms became constant, having been very intermittent before. Confirmed power & pulsewidth at the injector plug connection. Put a stethoscope on that injector while running & no "tick" at all; all othes ticked consistent w/ each other.

Thought about replacing all 6 w/ a set of reman'd (cleaned & flowed) injectors off of eBay, but decided to just replace the bad 1 w/ a genuine Toyo part (~$155.) Mechanic said he'd do it for 1 flat-rate hour ($70.) Thought that was fair since they didn't charge me for either of the 2 "diagnostic" sessions, & I would've pd. them for at least 1 hour had I decided to do the job myself.

Hope this helps! Fhornerguy - did you ever figure out your problem?

Her4Runner

__________________
2000 4Runner (Hers)
1992 Typhoon
1991 Syclone
1998 Camaro (DD)