1996 Toyota 4Runner Rough Idling / VERY poor mileage

Tiny
JIMHARRISON
  • MEMBER
  • 1996 TOYOTA 4RUNNER
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 329,000 MILES
My wife's 4RN idles very roughly. Once driving, it smoothes out. Lots of power once moving, even to spinning tires, from a 10kph roll. It almost sounds as if it is missing. Appears to have more power when I manually shift the AT, or when the O/D is off or the ECT power switch is utilized. Cleaned AF (K&N lifetime), both 02's changed, twice, as the shop stated 02 sensors were coding. Check engine light remains ON. VERY poor mileage. As well, the engine is VERY loud, as if the exhaust / muffler have a hole in them, but a visual inspection does not confirm this. We also have the bee buzzing noise after shutdown, especially in the hot summer, as is apparently common with this V6 engine. Have had timing belt changed at normal mileage, as per OEM recom. Am thinking it could be plugged fuel filter, plugged cat, plugs / wires /dist. Cap or rotor, or dirty MAF / coolant sensor? Any suggestions? Thanks in advance.
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Friday, April 11th, 2008 AT 7:51 PM

2 Replies

Tiny
RASMATAZ
  • MEMBER
When was the last time this runner seen a major tune-up? The check engine light being On is telling you something that the computer has identified a problem within the engine management system, you need to pull the OBD2 code/s from it and give it to us to start the diagnosis.

For a start try checking the idle air control valve/throttle position sensor/MAF and EGR valve
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Saturday, April 12th, 2008 AT 6:24 AM
Tiny
JIMHARRISON
  • MEMBER
Thanks for the reply. The plugs (Bosch +2) are 1 yr. Old, 40,000kms ( 25,000 mi.). They were installed last year at a Toyota dealer, when the timing belt was changed & the pre & post-cat 02 sensors were changed & a major tune-up was done. Pulled them all today (after I bought a new set) & they all looked fine. Nice ash color on outside wires, nice white centre so took the new ones back. No difference left to right, so I presume the 3 coils & 3 spark plug wires are also ok, as they fire the opposing plugs. Disconnected the air inlet hose, talk about grunge inside the throttle body mouth. Took some Isopropyl alcohol on a rag & wiped most of it off, then used about 1/2 can of Wynn's air intake cleaner I had lying around. Checked the PCV valve as well & it appeared fairly clean & rattled when shook. Put everything back on & started it (cranked for a while at first & then started. Idled 2,000 rpms until it settled down. I noticed it almost immediately started sounding/ running smoother than it had, & my wife, who was outside raking the grass at the time, said the same thing. After a few minutes idling, (I also revved it a couple of times to 3,500 rpms. After it was warm, ) it settled down to 1,000 in Park & 750rpms. In drive with the brake on. Seems to start quicker than before as well (I started it a few times today while we were working outside) I haven't pulled the check engine light codes, as I do not have an OBD3 code reader & they are $250.00 here. It is a solid light, but every once in a while before it would blink 3 times & then stay on solid. Is there any way to use a check light to get the codes like on the old OBD1 systems? Toyota said the light was faulty because they had no code readings (but the same dealership also failed to notice the cracked relay rod on my 91 4Runner prior to the recall & I had a fan belt shred while I was pulling out of their parking lot after I treated it to a Toyota maintenance (glorified, oil change) service where they did not mention anything about a fan belt problem.

We have not changed the fuel filter, so it is quite likely the original one.

Tracked the loud exhaust noise upon start-up. The heat shield above the muffler is vibrating at start-up against the muffler, making a clanging sound.

So I guess I still have to check the following:
idle air control valve
throttle position sensor
MAF
EGR valve
Coolant temperature sensor
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Sunday, April 13th, 2008 AT 12:28 AM

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