Hello, friends... I'm hoping someone can help me solve a head scratcher. I'm trying to get my 90 ready for the 70 Series meetup in TN next week, and it's having a idle issue that I can't seem to solve. If I can't get it sorted, I'll have to skip the event and that's going to suck.
Details on the vehicle:
1996 Prado 90
1KZ-TE automatic
196k kms
Here's a summary:
Intermittently, but with increasing frequency the warmer the engine gets, idle speed will drop <600 rpm and it will not respond to throttle inputs. Occasionally idle will drop as low as 400 rpm, voltage drops will cause dash lights to flicker and there will be an audible miss. If I can get the truck moving with gravity, RPMs will pick up with vehicle speed and as soon as I get over ~2k rpm, boost comes up and the truck drives fine. If I constantly feed it throttle and never let it drop to idle, it's fine. Also occasionally, and I assume related, under load at low RPMs it will not respond to throttle inputs until it gets in boost (~10psi or so).
EGTs are fine- 300 F or so at idle, ~500 F around town and around 900 F under full load.
However, if I put it in Neutral or Park, idle jumps back up to ~900 and it responds to throttle inputs. Put it back in Drive or Reverse, idle drops under 600, it misses and nearly stalls, and I get the behavior above. This makes me think it's not a physical fueling issue... it would persist no matter what gear it was in if I had a bad lift pump or something. Also, I assume that a true fueling issue would be reflected in the EGTs.
What I've done:
-Rebuilt and re-tipped injectors
-Cleaned fuel lines
-Replaced fuel filter
-Replaced glow plugs
-Replaced timing belt
-Replace throttle position sensor
-Replaced leaking capacitor on ECU board
-lots of other things that I don't think are related
And the behavior is unchanged. Could it be fuel spill valve? Are there two different idle circuits for the auto 1KZ-TE, based on whether it's in gear or not? Any ideas?
Details on the vehicle:
1996 Prado 90
1KZ-TE automatic
196k kms
Here's a summary:
Intermittently, but with increasing frequency the warmer the engine gets, idle speed will drop <600 rpm and it will not respond to throttle inputs. Occasionally idle will drop as low as 400 rpm, voltage drops will cause dash lights to flicker and there will be an audible miss. If I can get the truck moving with gravity, RPMs will pick up with vehicle speed and as soon as I get over ~2k rpm, boost comes up and the truck drives fine. If I constantly feed it throttle and never let it drop to idle, it's fine. Also occasionally, and I assume related, under load at low RPMs it will not respond to throttle inputs until it gets in boost (~10psi or so).
EGTs are fine- 300 F or so at idle, ~500 F around town and around 900 F under full load.
However, if I put it in Neutral or Park, idle jumps back up to ~900 and it responds to throttle inputs. Put it back in Drive or Reverse, idle drops under 600, it misses and nearly stalls, and I get the behavior above. This makes me think it's not a physical fueling issue... it would persist no matter what gear it was in if I had a bad lift pump or something. Also, I assume that a true fueling issue would be reflected in the EGTs.
What I've done:
-Rebuilt and re-tipped injectors
-Cleaned fuel lines
-Replaced fuel filter
-Replaced glow plugs
-Replaced timing belt
-Replace throttle position sensor
-Replaced leaking capacitor on ECU board
-lots of other things that I don't think are related
And the behavior is unchanged. Could it be fuel spill valve? Are there two different idle circuits for the auto 1KZ-TE, based on whether it's in gear or not? Any ideas?