rpm limited to 2500revs

[RBAustralia]

Swapped out the PCV valve. Now its confirmed that it's not the cause.

Need to get codes cleared and re-scanned.

I might have mentioned that one of the first things I did was to disconnect the exhaust pipe fron the manifold, directly under the driver's feet. There was a clear 2 inch gap while reving it to its max. If there was a broken baffle, the exhaust gasses should have exited easily.
Didn't get any better. Was pretty loud.

[RBAustralia]

Had a thorough assessment with the mechanic just moments ago.

He reset the codes and then tried to find out exactly what the engine was doing.

He guessed the engine is backfiring.

When we had a look at the codes that had come up. We got "70 O2 SENSOR"

So I'll swap it out on the weekend but for now I'll try to just clean it up.

[Tgoode318]

I haven't heard of an o2 sensor causing that much trouble before but i think its a better guess then the pcv or knock, hopefully you are on the right track. As dave and i mentioned it does sound like a sensor problem because you said it behaves differently from cold/warm (closed loop/open loop). I Hope this fixes it because before long you will have a full on restoration going (not that that's a bad thing )
-TG

[Tgoode318]

Oh yah,  Rough idling, poor fuel economy, & misfires are typical symptoms for a failed o2 sensor so this is definitely part of your problem i would say, but i wouldn't be surprised if something else is bad as well.

[RBAustralia]

FIXED!!  FIXED!! FIXED!!

I'm so happy today because i replaced the cam and crank position sensors from a friends 1.6L engine that he swapped with a M42.

The cam postion sensor was easy to install... I replaced it first. But it didn't fix it.

I then replaced the crank position sensor. It wasn't easy because the 5mm bolt is positioned so inconveniently. See pic for my improv tool.
Furthermore, the cable for the smaller engine is slightly shorter and wouldn't reach the connector. I took the cable out of it's plastic cover/holder along the block and then manhandled it to reach the port. So it still didn't work. I thought it was connected  it wasn't.

Finally after connecting the crank sensor properly and trying again....I put my foot down to see the needle woosh past the dreaded 2400rpm for the first time in 10months. I can't stop smiling.... 

[Tgoode318]

Nice! Glad to hear you fixed it thank's for the update. I knew it was a sensor problem and CPS makes much more sense then what your mechanic was saying. If you had a check engine light you could have done a stomp test and quickly found the problem  . Oh well you did a nice tune up to her and i'm bet she runs great now.
Your problem of not having a check engine light bring's up a good point for me, in the future i was planing to buy an after market Gauge cluster but now im re-evaluating my decision because i will loose my check engine light!