I posted this message in the new member area also. Sorry, new to this.


Here's the deal : I just bought a 99 Rodeo, 3.2 DOHC, 5-speed. Has codes P0121,0122,0123. All TPS codes. On cold start, it revs to 3000 rpm (at least), and sticks there until warmed up. Then it stumbles and stalls, like it has a vacuum leak. Codes are all related to TPS. Shows throttle position at 7% with throttle closed. Sweep is good with ohmmeter. Can't quite get a handle on what is wrong here. Any help appreciated. I have 15 years of mechanical exp.(not on Isuzu products, though). I would love to trade info or help anyone I can.

 

have you tried replacing the TPS?

 

The TPS was the first thing I tried. It was cheap at Auto Zone ($26). No change. Next, I started spraying carb cleaner around the intake. It appears that I have a pretty severe leak on the driver's side. When the idle finally drops, I can hear the whistle from 40 feet away. I'm considering replacing the IMG's. I'm just wondering why I get the high idle on cold start. Maybe the unmetered air sneaking in is confounding the TPS and the IAC valve. Any thoughts?


Thanks for your reply.


Drew

 

if you have a high idle on start, perhaps you have a problem with the electronic choke? i have a similar issue on an older dodeg truck, because of a bad choke unit.

 

Mullti-port fuel injection does not havea choke. Everything is PCM-controlled. On cold start, the vehicle runs in open loop (a default set of parameters), paying little attention to inputs. Once the coolant temp sensor reaches a certain temp, then the PCM goes into closed loop and fine tunes outputs. My problem has to be of an electronic nature.


I replaced my intake gaskets, and things have improved. I still have some very erratic idling problems, however.

 

mhmmm..i wish i could be of more help drew...

 

Subscribed to alldata online, followed TSB instructions.Replaced IMG, cleaned ground connections, reset PCM. All good now.

 

was that pricey for you, if i may?

 

My 99 Rodeo has a similar problem. It idles fast at 1500 rpm in the mornings even after a 35 mile commute but idles perfectly fine (750) in the afternoon. I have tried cleaning the EGR,IA valve,TB, and resetting the computer. I sprayed carb cleaner around my intake gasket but do not detect a leak and there is no check engine light on. anyone have any ideas? Thnaks, Cliff