Can the VSS be faulty but still work ?

[135sohc]

Alot of the vehicles problems point towards the VSS putting out bad data and corrupting the system however the speedo works just fine :confused2:

Is it possible to be working faulty but the speed signal for the cluster still be 'good enough' to work ?

vss was replaced last year after the original one went dead completely.

[turbovanman²]

Do you have a cable running the speedo?

If the speedo works, and its the sensor only, then it can't be bad.

[135sohc]

All electronic here.

I just dont get it, sometimes when coming to a stop and pushing in the clutch the rpms will drop and bog and other times it will stay the same and hover around 2k and then slowly come down. IAC is all good and so is everything else. Has a mind of its own most of the time...

[turbovanman²]

Check grounds, TPS.

If the VSS was bad, the speedo would jump around too. Is it setting a code?

[Force Fed Mopar]

Are you sure the IAC is good? I have a newish one also and it sticks open sometimes and causes the engine to rev waay up on startup, then throws a map code.

Could also be the coolant temp sensor reading wrong. Is it a stock computer, or a custom cal?

[135sohc]

Two new IAC's and many used oem ones have been used, I dont think they could all be bad and fail the same way.

New CTS from mopar was defective and yesterday I put another used oem one in after testing it and it was within the resistance range for hot and cold.

2.2 EFI car, nothing other than stock.
No codes

[turbovanman²]

So its a TBI, hmmmmmmm, I would thoroughly check for vacuum leaks and check the ox sensor, if they are on the way out, they can cause this too.

[135sohc]

New denso unit installed a month ago.

As much as I hate to admit it I've taken the 'throw parts at it' method of troubleshooting because none of the usual things have made any real difference in it and its not popping fault codes left and right saying its messed up.

There is one possibility left I havnt looked at and it could have low compression on one or more cylinders ? Might explain the general roughness and just poopy idle this thing has.

[Force Fed Mopar]

So its a TBI, hmmmmmmm, I would thoroughly check for vacuum leaks and check the ox sensor, if they are on the way out, they can cause this too.

This, including the base gasket under the TB, also maybe try another HEP if you have one and check that the shutter wheel in the dizzy isn't loose, maybe causing odd timing advances. Make sure the line to the MAP sensor is clear also and that the MAP is reading right. IIRC it should read around 60kpa on a scanner. Baro should read 95-100kpa unless you're in the mountains or weather conditions are changing.

And, the EGR valve could be leaking also if it has one. The EGR causes a vacuum leak that is undetectable externally and doesn't throw a code either. Could also be the vacuum transducer that controls it. Take the EGR off and make sure it's clean, and you can check operation w/ a vacuum pump.