IAC causing shifting problems?

[Cardiogold]

I have owned my 2003 M/T Baja since March and it has been a nightmare ever since. Not the vehicle's fault.

 

Fast forward an engine rebuild, an idiot mechanic, 2nd blown engine, and an engine swap by another mechanic and I now have a Baja that runs great with the exception of a check engine light with a P0507 code. The idle is off and on a bit high so I plan to try to clean the IAC valve today to see if that helps.

 

That being said, I am starting to experience shifting issues. I saw on another post that I read at one point that on manual transmissions this can also be a faulty neutral switch. Is this a possibility if cleaning the valve doesn't help? Thanks in advance. I am no expert but I love to learn.

[montana tom]

The neutral switch on a manual transmission is for starting only.  About the iac valve, I just cleaned mine on a 2001 obw.  Was told to get a new gasket before opening , many times your original will be swollen. Mine was fine but be prepared for yours . After cleaning  ...my high idle issue was not changed ! I was disappointed as the replacement valve for a MT is spendy compared to an automatic . 2 days after cleaning i noticed that the too high idle seemed to be gone !!! Yes ! AND THEN... it suddenly started the opposite symptom... to low an idle , it even stalled twice, of course it was 11 below zero at the time and it did start right back up and idle. One day of that and now it seems to be perfect ! knock on wood ,cross fingers.... I used carb cleaner and alcohol with q tips to clean , soaking for a while would  no doubt help immensely. I suspect with q tips that i got about 90% clean and my after issues were caused by what I couldn't clean. 

[1 Lucky Texan]

describe your shifting problems. Any fluid changes done before this began? Our manual transmissions don't seem to like synthetic GL-5 for instance.

[Caboobaroo]

The neutral switch on a manual transmission is for starting only.

This is not correct at all. The clutch switch down on the pedal is for starting.

 

With that being said, the neutral switch needs to be replaced. The internal button portion of the switch is plastic and they wear out over time from riding on the steel shifter rail. Once worn, it can tell the ECU that the vehicle is in neutral, while you're doing 60mph at 2k rpm. This then confuses the ECU and throws the P1507 or P0507 Idle Air Control Fail-Safe depending on era of car. You can buy them aftermarket from any parts house but make sure they sell you the neutral switch and not the reverse switch. It's located in the side of the transmission closest to the driveline.