I keep getting an intermitent check engine light, the last day or so I have kept a close eye on it and it doesn't seem to make a difference in driving conditions. I just checked the codes and it gave me 43-which is esc has been retarded for too long. The way I interpert it would be possibly a bad knock sensor or a bad spark plug/wire or the esc itself. It is an OBD 1 system so I don't think much else really has anything to do with the timing. I just wanted to make sure I was heading in the right direction with this before I started swaping parts.

1993 Gmc Jimmy 4x4
4.3 vortec spider injection

 

If you have a timing light, hook it up and as you are watching the timing mark tap (with a metal bar or small hammer) near the knock sensor and see if the timing changes. I've found that's a fairly good test for knock sensors.

 

Check your drivers side Knock sensor. That connector has a habit of getting old and cracking then the wire falls out. Also, if you "played" with the plug wires lately it could have been knocked loose.

You also have one on the back of the passenger cylinder head (a bear to get to). I've had a problem with that one in the past tracking down distributor issues.

 

The plugs on the knock sensors looked good and were both connected. I put a timing light on it and at an idle the timing is fluxuating. It moves up and down probably about 4-5 degrees. I tried unplugging the knock sensors to see if that was make it fluxuate but it didn't make a difference. Then I though mabey it was a loose timing chain so I took the distributor cap off and turned the crank but there is hardly any play in the chain. I did try tapping on the block next to the knock sensor but If it did make a difference I couldn't tell with as much as the timing was jumping around. Also when you rev it up and hold it the timing smooths out and pretty much stays in one spot. Now I am completely lost so any help would be apreciated.