Torque converter lock up

N

Neil

Registered
Hello,
My 95's converter gradually stops locking in 3rd and OD. When it starts going it will unlock on small hills that I can usually make locked. While I usually have to give alot of throtle to get out of locked OD when it's going it just takes a little. Punching it and letting it shift back up to OD will get it to lock again. But eventually it will just stop locking at all. If I park it over night it still will not work in the morning. But if I disconnent the battery for five minutes it works just as it should. It's been doing this for months and the battery trick works every time! I suspect a sensor of some kind is just out of range.TPS maybe, but I get no trouble codes.
Thanks,
Neil
 
Thanks for the reply Driller. I agree that the soleniod is not opening but if it was just a bad solenoid disconnecting the bat. would not make it work again. I got the bat. idea from this site . Someone else had modified their car and the converter would not lock any more. They got it to work by clearing the keep alive memory. I'm thinking some PCM input is out of wack and it keeps adjusting shift strategy till it stops trying to lock the converter at all. But without trouble codes I don't Know were to start. TPS is not that hard to replace so I thought I'd start there. Has anyone else had troubles like mine?

Thanks
Neil
 
A failing TPS will usually throw a code and will mess with the shift program. I suppose it's possible it could be the culprit, but it doesn't fit the MO.

Since 'resetting' the PCM clears the condition, I agree it appears to be electrical. According to the manual, electrical concerns for this symptom include...

  • vehicle wiring harnesses
  • powertrain control module
  • TCC solenoid
  • TFT sensor
  • OSS
 
driller said:
A failing TPS will usually throw a code and will mess with the shift program. I suppose it's possible it could be the culprit, but it doesn't fit the MO.

Since 'resetting' the PCM clears the condition, I agree it appears to be electrical. According to the manual, electrical concerns for this symptom include...

  • vehicle wiring harnesses
  • powertrain control module
  • TCC solenoid
  • TFT sensor
  • OSS
Click to expand...

I've driven with the TPS unplugged (my mechanic's error) and got no codes. However, I noticed a HUGE decrease in performance. I assume the engine was running way lean in that instance.

A shorted TPS may result in a different set of symptoms...
 
I drive 43 miles to work each morning and never have lock up troubles. But on the way home it will somtimes act up. Higher outside temperatures? TFT sensor? It's times like this that a guy needs a parts car in his yard! Thank's for the ideas.
Neil
 
Well I replaced my TPS yesterday. So far it seems to shift better and has better torque converter locking but... Throttle response is much different now. When I rev the engine the RPMs don't come down quickly like they used to. Also when coasting at 25mph I don't slow down with no trottle. If I put it in neutral while coasting the RPMs go up to 1400. When I slow to a stop only then will the RPMs drop to 800 RPMs. Is this just part of the pcm relearn process or did I get a bad TPS. I took my time installing it and I believe I put everything back right. Also I get no trouble codes and passed the WOT test at the KOER test. Maybe time will tell.
Neil
 
Neil said:
Well I replaced my TPS yesterday. So far it seems to shift better and has better torque converter locking but... Throttle response is much different now. When I rev the engine the RPMs don't come down quickly like they used to. Also when coasting at 25mph I don't slow down with no trottle. If I put it in neutral while coasting the RPMs go up to 1400. When I slow to a stop only then will the RPMs drop to 800 RPMs. Is this just part of the pcm relearn process or did I get a bad TPS. I took my time installing it and I believe I put everything back right. Also I get no trouble codes and passed the WOT test at the KOER test. Maybe time will tell.
Neil
Click to expand...

My money's on the IAC. Sounds like it may need replacing.
 
I re-replaced my TPS and still have troubles. It starts with high idle and comes down to 800-900 RPMs normally. Is that controlled with the IAC or fuel delivery? If I stop on a hill and coast in neutral as soon as I get to 2 or 3 MPH the RPMs go up to 1400-1500. When I stop they go back to normal. I just want someone to say "classic IAC symptoms". Anyone?
Thanks
Neil
 
So I did some more trouble shooting today. With the IAC unpluged the RPMs don't go up when I'm rolling and I don't get high start up RPMs. I've got the right voltage at the connector (above 10.5) and the IAC ohms out at 11.0
Specs are 6.0-13.0 ohms. It doesn't test bad. It is opening but maybe to much? I guess I'll just have to replace it and hope thats my trouble.
Neil
 
Just remember the IAC is an actuator and responds to the PCM which commands a certain idle speed varying with sensor inputs. Among these would be the VSS, MAF, ECT, CKP and others.
 
I think I'll try a VSS. When I start coasting down a hill from a stop that is the only input that should be changing. It's also the cheapest one. I'll soon find out how hard it is to get at. I do think the IAC is just doing what it's told.
Thanks for the help
Neil
 
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