Engine Code 70?? KOEO

[5.0-5MT]

Hey guys, just pulled a code 70 with my innova code reader. The book that came with it is saying that mean ECM failure? but the car still runs fine. So I did a compression test and the results are as follows:

cylinder 5	110 psi
cylinder 6	110 psi
cylinder 7	100 psi
cylinder 8	110 psi

is this a big enough difference to warrant a concern? What should my next steps be? the plugs all look similar.

 

[AeroCoupe]

Why were you pulling codes i.e. was there a problem or problems that motivated you to pull codes? I would have zero concerns with the difference in the compression numbers but overall the numbers appear to be low. All the info on this I have seen is 130 psi and up. It will run just fine on 110 psi and you should always run an compression check with the motor up to operating temp. With the Code 70 my guess would be plug, plug wire, injector, or compression and you ruled out the last one.

 

[5.0-5MT]

The reason I pulled codes is because I took a video of my new exhaust to get a sound track and while I was watching the video, noticed smoke coming out of the tailpipe:

1991 Mustang

Shared using GoPro

gopro.com

Any other diagnostic tips? I got some other codes as well but I don't believe they relate to the issue. I can provide if it would help.

 

[AeroCoupe]

Provide all the codes, what you have deleted, modified, etc. Each thing you have done can have a direct effect or several of the things you have done can have an effect.

 

[5.0-5MT]

Ok I will provide a list later.

 

[5.0-5MT]

Powertrain related mods:
full 2.5" exhaust, off-road h-pipe, flow master super 44 mufflers, air pipe to exhaust pipes disconnected
egr intact but not working
MSD distributor
new tps (need to reset, just got code for TPS voltage out of range)
vacuum leak somewhere that I haven't diagnosed
new bigger radiator
that's all I can remember.

Codes (rescanned tonight and the code 70 is gone):
O
23
84

10

C
33

anything else you need to know?

 

[AeroCoupe]

23 - TP out of Self-Test range
33 - EGR valve opening not detected
84 - EGR Vacuum Regulator (EVR) circuit failure

10 - this is the spacer code that the computer puts out just before it starts to dump the rest of the stored codes. It will also identify #1 cylinder but that only happens when you run the cylinder balance test.

33 & 84 are due to the EGR and I would suggest that you plug the EGR in if it is still there so that these codes go away or just ignore them as they do not affect performance.

23 is the one you want to focus on so that you can get that code cleared and make sure there are not other codes hanging out behind it. These ECU's are for lack of better terminology dumb so when you attempt to fix a code then you need to reset the ECU and drive the car around and get it up to operating temperature and pull codes again even if the CEL does not illuminate. The CEL only illuminates on emissions related codes so codes can be present and the CEL will not illuminate.

 

[5.0-5MT]

I just tested the TPS and it is reading 0.98 volts. This is within the range, so I'm not sure what triggered the code. The EGR system is intact, I believe the EGR valve position sensor is bad. I will take it for a drive and scan the codes again.

 

[5.0-5MT]

I just dumped the codes using the paperclip method and here's what I got
KOEO
84

KOER
94
44
33

does this help?

 

[Noobz347]

I just tested the TPS and it is reading 0.98 volts.

This by itself is almost meaningless. Disconnect the TPS and connect an ohm meter so that you can read through the full sweep of the TPS. Look for resistance "spikes" as you rotate the TPS slowly from limit to limit.

 

[AeroCoupe]

44 - Thermactor air system inoperative (right side)

The rest of the codes are all EGR / emissions related and are most likely deleted so again either reinstall and connect or ignore.

Check the resistance through the full sweep of the TPS as said above.

 

[5.0-5MT]

Ok. for testing the resistance, do I unplug the TPS and then test the resistance through the same wires that I tested the voltage of?

 

[AeroCoupe]

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