Code 24 update

[de3en16]

I've had a low idle problem for awhile so I went out and tried to set the base idle to 500 rpm. And ended up with code 24 at start up. I took the
tbi unit off cleaned and rebuilded it set the base idle again and drove it a little. And I still get code 24 on start and low idle plus high idle and no code. My haynes manual says code 24 is the vss but if no moving could be the tps but not how to check it or replace the tps. This is on a 90 Blazer with a tbi 350


How hard is it to replace the tps ?


Thanks

 

[y5mgisi]

TPS is very easy to replace.

 

[ktmoutfront]

TPS is on the passenger side. 3 wire connector, I think. 2 screws to remove and replace it.

 

[de3en16]

Cool I'll give a go in the morning and see how it goes. Thanks guys

 

[Fordum]

I have not seen the TPS on a TBI setup in a long time, and was not paying attention to it at the time.
But all those units are real easy to check.
All they are is a Potentiometer like a volume control on a radio. You will have three wires.
One on each end of the resistor, and the wiper in the middle.

You need to disconnect it, and hook a Analog ( needle type ) ohmmeter from one pin to the other.
If nothing happens when you turn it, then its either bad, or you are across the ends of the resistor.
Put on of the leads on the other connection and move it again.
Most likely the wiper is the center pin. Go from it to one or the other and move the little lever.

You should see a smooth change in the resistance from one end of the rotation to the other.
A digital meter will show the readings, but you won't see brief glitches like you will with a needle.

Rockauto shows them for a little as $24, it might be easier to just change it.
It looks something like this:

 

[ktmoutfront]

I just change them. Carry an extra when wheeling.

 

[de3en16]

Thanks for that info Fordum

 

[de3en16]

I just change them. Carry an extra when wheeling.

Never hurts to have a spare

 

[de3en16]

no code but still high idle

I replaced the tps and started my truck and it had a beautifull 750 rpm idle I shut it off and I was back to a 1500 rpm idle and code 24. I did some more research and found that the neutral safety switch can cause code 24. So since mine was broke I replaced it after I set the base idle and again right on 750 rpm drove around parked it and still 750 rpm. I shut it off and its right back to 1500 rpm idle but no code this time. I double checked for a vacuum leak and put in my spare IAC and no change. So could it be the coolant temp sensor? Or computer maybe?




Thanks

 

[y5mgisi]

Possible sticking egr valve.

 

[Russell]

You don't have a scanner hooked up while it is running, do you? That can cause high idle

 

[de3en16]

I make sure I pull out the paper clip before I start it

 

[y5mgisi]

Is your distributor tight?

 

[de3en16]

I make sure I pull out the paper clip before I start it