A little tick? Can you describe this mystery sound in more detail? You really didn't say anything about the noise at all. It could be just a loose exhaust manifold.
You should address the error codes, though.
12-mass air flow: If you are getting this error, your truck probably runs like crap around 2500 RPM because the ECU is going into Limp Mode. You can clean the MAF and make sure it is getting a good ground. If the heating element wire has burned out, you would need to replace it.
34-knock sensor: These are cheap. If you have the Z24i, it should be easy to get to (not so for the VG30 V6 engine).
* The idle switch, injector and injector circuit are built into the throttle body, so just replace that to knock out 3 error codes.
Where is the MAF sensor located on these older d21? I have a 1986 w/ same problem. It won't go over 35mph. And it goes into "limp mode" never had any problems before. This was out of nowhere, and now I've replaced the catalytic converter, fuel filter, air filter..
The MAF is on the throttle body right under the air cleaner.
These are all on the throttle body.
Thanks a bunch deerhurst, you have been very helpful! I'm gonna switch out the old MAF sensor and then restart my ECM if that doesn't work.
Me? Helpful? Got you fooled!! Haha!
I'm not sure what I did.
Be careful with the MAF. That little wire is very sensitive.