Throttle position Sensor ?
Thread Starter
4th Gear
Joined: Oct 2011
Posts: 4
Likes: 0
Throttle position Sensor ?
Hey guys, this is my first post on here.. well I have an 89 corvette.. The problem Im having is up and down Rpm's.. The RPM goes down to almost wanting to shut off.. I Had the Fuel injectors replaced. It ran good for a month before the RPM idling problem.
Well I believe the cause of this rpm idling problem is the throttle positon sensor. While the car is idling, I unplug the TPS and RPM problem goes away. It idles at 9-10 the whole time its unplugged.
As soon as I plug the TPS back in the problem begins to occur.. So I would like to have some input on any corvette owner that have had this problem before. The TPS is inexpensive and would like to change it out.. Is this an easy process? Would I have to remove the Throttle body? Or is it as just removing the two bolts and its done?
Im sure someone have posted TPS questions so forgive me. Im just looking for some feedback..
Thanks in advance..
Well I believe the cause of this rpm idling problem is the throttle positon sensor. While the car is idling, I unplug the TPS and RPM problem goes away. It idles at 9-10 the whole time its unplugged.
As soon as I plug the TPS back in the problem begins to occur.. So I would like to have some input on any corvette owner that have had this problem before. The TPS is inexpensive and would like to change it out.. Is this an easy process? Would I have to remove the Throttle body? Or is it as just removing the two bolts and its done?
Im sure someone have posted TPS questions so forgive me. Im just looking for some feedback..
Thanks in advance..
Safety Car
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From: Jacksonville FL
Heel & Toe
Joined: Sep 2011
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From: Indiana
Thread Starter
4th Gear
Joined: Oct 2011
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thanks brad.. I did some more research and found this link... https://www.corvetteforum.com/techti...D=55&TopicID=2
I will try this before I go and spend on a new TPS...
I will try this before I go and spend on a new TPS...
Team Owner
Joined: Dec 2000
Posts: 90,675
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From: SE NY
Cruise-In II Veteran
Insert pins into the back of the connector behind the Blk & Dk Blu wires. The Blk wire is common and Dk Blu is signal.
I recently adjusten my TPS for .63 Vdc with key On and engine Off; this gives a value of ~.74 Vdc at 900rpm idle.
To check your TPS, watch the DVM as you manually open the throttle slowly; the value should increase smoothly from the idle value to >4.5 Vdc at WOT.
If the TPS checks out Ok, look to the IAC as the problem area. The ECM may not try to adjust idle speed when it cannot see a TPS value??
I recently adjusten my TPS for .63 Vdc with key On and engine Off; this gives a value of ~.74 Vdc at 900rpm idle.
To check your TPS, watch the DVM as you manually open the throttle slowly; the value should increase smoothly from the idle value to >4.5 Vdc at WOT.
If the TPS checks out Ok, look to the IAC as the problem area. The ECM may not try to adjust idle speed when it cannot see a TPS value??
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Le Mans Master
Joined: Aug 2005
Posts: 7,392
Likes: 218
From: Merritt Island, FL
if the TPS is out of adjustment, it can affect the idle... but, since the ECM has the ability to self-correct to a degree (can recognize I think 0.3 to about 0.7 as being closed throttle), it's not all that likely unless the sensor is internally shorted or otherwise defective.
Team Owner
Joined: Dec 1999
Posts: 34,873
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From: Lacey WA RVN 68-69
NCM Sinkhole Donor
Check for vacuum leaks too. May not hurt to remove the IAC and clean the tip and clean the internal passages. Once you do this, make sure you follow Lar's procedure for re-setting everything.
Le Mans Master
Joined: Dec 2000
Posts: 7,839
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From: San Diego, Ca
I'd be more inclined to expect something else. When you disconnect the TPS, that sets a Code and it ignores input from the O2 which puts it on backup. If the idle only fluctuates once it's warmed up, then suspect that extra air is getting in from somewhere other than the MAF. Clamp off the air hoses to the headers to rule out a faulty check valve.
If the problem exists at any temperature, then it would help if you could scan it. Make sure it isn't getting a faulty a/c request which without the load of the compressor would cause a hunting idle. Also verify the Coolant Temp Signal. When cold, it should be close to ambient and then after you start it, rise to the thermostat; then drop a degree or two when it opens and then rise to the temperature for Main Fan Operation.
If the problem exists at any temperature, then it would help if you could scan it. Make sure it isn't getting a faulty a/c request which without the load of the compressor would cause a hunting idle. Also verify the Coolant Temp Signal. When cold, it should be close to ambient and then after you start it, rise to the thermostat; then drop a degree or two when it opens and then rise to the temperature for Main Fan Operation.