Throttle Position sensor issue???

Joined
Oct 12, 2004
Messages
73
 
 
I think my 98 has a TPS problem- I have 110K on it and it just started acting up in the last week- No check engine light on at this point and no codes stored.

Here is what it's doing: at a steady state cruise, around 2000 rpm, the engine drops rpm without any change in pedal position- literally feels like you pulled your foot off of the gas. You can actually watch the tach needle drop when this occurs. When it happens, I stab the gas to WOT and it picks up and gets going again.

One thing to note is that the temp has dropped considerably here in Cincinnati recently

Anyone have a similar issue with no codes stored? Its pretty repeatable- Any help would be appreciated!
 
Joined
Apr 29, 2005
Messages
186
Location
Cumming, GA
Could be the throttle motor as well. There's actually a motor to open the throttle. It has several sensors that talk to each other that could be a problem. They usually throw codes I think, but possibly not always.
I'm an electrician and i know that severe temp changes can bring out problems with bad electrical connections. I wasn't particularly impressed with the quality of Toyota's electrical connectors on my LC. I'd wiggle all the ones around the throttle body and make sure they are tight. My TPS acted up after I cleaned the engine compartment. Could it be water intruision?
When my LC TPS acted up, I got the same symptoms. No throttle control, it just idled. But nothing I did would fix it. Only when I turned off the engine then back on would it get better. I didn't have any more problems with it after that time and I figured it was moisture in the connector and that the problem had solved itself. Good luck, as I got three different opinions from three different Toyota techs on what was wrong. One dealer wanted to replace the entire Throttle body! They really didn't know, but were more than willing to take my money to start changing parts out. I ended up doing nothing.
 
Joined
Apr 28, 2003
Messages
2,482
Location
Turquoise Trail, N NM
 
 
 
Is your TB clean, or is there sticky carbon buildup that might be making it stick? On the 80's and earlier Toyota trucks/LC's (non-electronic TB's, cable accelerator), you can simply pull off the airbox intake hose, spray carburetor cleaner in there, and use a wire brush to clean the gunk out. Then reconnect, start the engine (sounds terrible for half a minute until the carb cleaner burns off). Can you do anything like this on the 100?
 
Joined
Jun 6, 2003
Messages
2,604
Location
Cuyamaca, CA and Las Vegas, NV
Well it wouldn't be too hard to take off the TB assembly and clean any deposits you see.

Mine was fairly dirty when I pulled it for the starter replacement. I cleaned the inside and outside of the TB as best as I could.
 
Joined
Oct 12, 2004
Messages
73
 
 
Thanks!

Thanks guys- I did have the throttle body off earlier this year when I did the starter, so I'll check the connections (make sure I have them all reclipped properly, no wires pulled or bent/ retracted pins) I'll go ahead and clean the TB as well. It was pretty grimy, in hindsight, I should have cleaned it at that point

Im to the point that Im so tuned into this that I can repeat it at will. Always the same RPM, same RPM drop. I hope to have a buddy hook up his scan tool and check the real time data when the symptom occurs. If I can keep repeating the problem enough, we should be able to see something weird with the scan tool hooked up


Thanks again!
 
Joined
Oct 12, 2004
Messages
73
 
 
Sorry I never closed the loop on this one- turned out to be the accelerator pedal sensor NG. Replaced it and am good to go- I tried the TPS first with no sucess

Been running great since!
 

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