FIXED: Idle was HIGH, now too low, popping and missing VIDEO, Solution was CHT Options

[ctc911ctc]

I could not get the idle down below 1800, I took the advice from the excellent suggestions within 914world-garage and replaced EVERY gasket in the vacuum chain, including fixed a leaky plenum. """But mine looked so good - it can't be leaky! """ It was VERY leaky!

When I rebuilt the plenum (both sides of the support columns were leaky) and put it all back together, the resulting idle was way too low. I now have the reverse problem!

If I open up the ARR (remove hose) the idle is still low. If I take off the air cleaner and loosen the idle screw (all the way) still around 800-900. hhhhmmmmm.....

Throttle works, car will rev.
When driving the car it runs ok, however it does not have the power it used to have.

Engine is popping/missing, though the audio is not optimum, check out the video:

https://youtu.be/p5uM67DXJnk

Looking for next steps, what would you do next?????? (IMG:style_emoticons/default/WTF.gif) (IMG:style_emoticons/default/WTF.gif) (IMG:style_emoticons/default/confused24.gif) (IMG:style_emoticons/default/confused24.gif)

Background; '74 2.0 all STOCK with 20K miles, I have rebuilt:

throttle sensor PCB
Throttle control - does not leak, very smooth control, set spec on the electrics.
MPS - tested and perfect
PCV - seems to work
Injectors - just back from Hurst injectors - all on spec
Distributor - clean and spiffy, advance works
plugs - new
AAR - tested and works
Computer Control Unit - I have 2, have swapped them and they both perform the same.
Flow Down - on spec
Dwell set
Timing set

Many thanks in advance

CTC911CTC

[914_teener]

So the CHT is just a thermister.

It is easy to check with a DVM and the corresponding temperature. The resistance values are on the B Anders site.

What invariably happens is that over time the ground connection gets oxidized or....the wire contact gets loose.

Without a good ground to the CHT the car will run like crap....or not run at all if there is no ground.

My quess is that the oxidation between the CHT and the head oxidized and when you broke it loose then put it back in you cleaned the ground connection up.

I think McMark was making one with a dedicated ground...I put it in my old car and never worried about it again. 914 Rubber might be making them now.

Test the old one anyway just to be sure.

[ctc911ctc]

In this thread there is a picture of me testing the thermistor Mr.! grin.. I was able to get the OHM meter to register metal-to-metal (base of the CHT thermistor) zero ohms. In the picture it is WIDE open! new one installed and working great,

Thanks for the help! car is running good, first time since 1984!

So the CHT is just a thermistor.

It is easy to check with a DVM and the corresponding temperature. The resistance values are on the B Anders site.

What invariably happens is that over time the ground connection gets oxidized or....the wire contact gets loose.

Without a good ground to the CHT the car will run like crap....or not run at all if there is no ground.

My quess is that the oxidation between the CHT and the head oxidized and when you broke it loose then put it back in you cleaned the ground connection up.

I think McMark was making one with a dedicated ground...I put it in my old car and never worried about it again. 914 Rubber might be making them now.

Test the old one anyway just to be sure.