Banksysvette

Hello, lookin for some help.
I have an '85 l98 and am getting spark knock and a code 43, however after i get the service light the knock goes away even at WOT.
I have replaced both the knock sensor and the harness. I even get the code 43 after i unplug the sensor?
Does anyone have any ideas about this issue that could maybe help me,

Thanks,

MrWillys

Here's a flow chart for diagnosis.

http://www.chevythunder.com/maf_esc_module_code_43.htm

Banksysvette

Thank you MrWillys : i will give it a go when i get home tonight.
I don't ever get the code until the car is under load or at WOT and then there is knock present and the service engine light lights up.
After that the knock disappears even at WOT.
I can stomp on it 15-20 times with the service engine light on and
there is no knock apparent again until i either clear the code or turn the car off and start again.
Puzzled.

antfarmer2

How old is the o2?

Banksysvette

I'm not sure how old the o2 sensor is but it looks farely new to me.
Is there a way to check if the sensor is operating with a meter?
Could the o2 sensor wire and the knock sensor wire be mixed up?
I did troubleshooting on the esc module yesterday and its okay.
Any ideas why the o2 would be giving me spark knock and a code 43?

Thank you

antfarmer2

I don't see how they could mix up the wires. But the o2s control the fuel that can make it knock and set off the sensor. My 94 o2s never put a code out but did have a knock code. I replace all and runs great now.

Benny42

Its highly unlikely the O2 sensor. Don't go down a side track while you
are chasing an ESC issue. When the check engine light is on, the ECM
pulls the timing way back. This is why it won't knock after the code sets.
Check your base timing and start suspecting the ECM. Good luck

Banksysvette

I found out the problem, finally closure on this issue.

The problem was that the wire going to the knock sensor connector was the wrong one.
I read an article in Superchevy about a classic mistake that guys do with tpi engines. They swap out the green wire which is for the fan relay for the blue wire which is for the knock sensor that comes from the esc module.This guy before me had used the green relay fan wire to hook up the knock sensor and left the blue one disconnected. He ran another wire from the fan relay sensor to the fan relay and that's how the fan was working and not the knock sensor.
I just want to thank everyone for their advice and to know i appreciate it.

Cheers!

WVZR-1

Interesting for sure! Good you posted back. Many don't!!!

You actually "assumed" it was correct on your replacement also I guess. You mentioned KS and harness (pigtail/connector) replacement.
"Assume nothing" I guess still works.

"Benny42" was right on - one situation at a time and diagnostics of that situation only.

An O2 seems like WAG certainly for a single wire early -

antfarmer2

Good job and easy fix!!!!!