1997 Cobra giving P0340 code

[97PacificGreen]

Swapped in fresh stock 1997 cobra engine in my cobra. Used code reader to find this code. The engine idles rough, sometimes dies out sometimes not. From other forums and haynes manual it says it could be the alternator, cam sensor or spark plugs. Replaced the cam sensor and tested the alternator and still have code. Looking for any further ideas on what to do to figure out the issue.

 

[mwolson]

Description:

The test fails when the PCM can no longer detect the signal from the Cam Position Sensor (CPS).

Possible Causes:

- CPS circuit open
- CPS circuit short to GND
- CPS circuit short to PWR
- SIG RTN open (VR sensor)
- CPS GND open (Hall effect sensor)
- CPS misinstalled (Hall effect sensor)
- Damaged CPS shielding
- Damaged CPS sensor
- Damaged PCM

Diagnostic Aides:

Harness routing, harness alterations, improper shielding, or electrical interference from other improperly functioning systems may have intermittent impact on the CPS signal.

 

[97PacificGreen]

Checked the routing and it was just like the old motor. Also cross referenced pictures and it looked correct. Some wires were hanging out of the shielding so I put them back in. Didn't have any electrical tape so idk if that would or wouldn't make a world of difference. Checked the code and it was gone. Fired her up and she idled great! But the response from gas peddle was still really sluggish. And code reader said it was still there. Also the check engine went away.

 

[mwolson]

Shielding is a metal sheath inside of the cable that carries the signal wire, not the plastic conduit that the cable runs in. The plastic conduit protects the cable from physical damage. The shielding protects the wire inside the cable from electromagnetic interference from other electrical signals running around the car. If the cables are not all beat up or melted, then they are probably ok.

I'd focus on making sure the connectors are all clean not oxidized, and properly seated.

 

[97PacificGreen]

Checked all my connections tonight and all seemed good. Also had my buddy take a look and he said they looked as good as any 14yr old car. So back to looking up forums and a lot of them keep saying the apt may be it and it's possible for the alt to to pass the autozone check. So I'm pulling the old one off the other motor. Just a link if you'd like to see where I found it.

http://www.moddedmustangs.com/forum...gine-light-still-off-but-backfiring-help.html

Btw thanks for all the help! Its truly appreciated

 

[mwolson]

Very interesting. I wonder what the failure mechanism is...

 

[97PacificGreen]

Im so very lost. I put the new alt in, spark plug wires coil packs and crank sensor (all of which I did separately to see which would fix my issue). No of which did fix my issue. I'm throwing in the towel cause I'm so very lost, taking it to the shop. Right after I try a DMM on the circuit to see if I should buy a new harness. By chance is there a way to test the PCM to see if it's the problem?

 

[mwolson]

The emissions manual says to try a known good PCM.

 

[97PacificGreen]

Okay, and do you think if I have the timing order wrong then it could cause this issue?

 

[mwolson]

I assume you mean firing order. I made a sketch of my plug wires so I would not screw mine up: http://www.classictiger.com/mustang/UnderTheHood/96CobraPlugWires.jpg

 

[tt54l32v]

spark plugs

 

[97PacificGreen]

Just keep you updated. I had a guy take a look at it and the guys are saying my pcv may be bad or clogged. I was wondering tho can the imrc kit w/o a tune cause the issue I'm having?

 

[mwolson]

I was wondering tho can the imrc kit w/o a tune cause the issue I'm having?

Not that I can imagine.