Knock codes were setting, then I got caught up preparing for a trip and let the oil run low, causing the timing chain guides to wear, thenceforth there was guide noise. I had previously used Restore and that buildup on the valves wrecked the valve seals. My mpg went up to
29 as the computer tried to compensate for oil from the head going out the exhaust. Naturally there was a ping code. It had a new catalytic converter and all else seemed fine. I was going to have the head changed but was advised by the mechanic to go with a used engine. He said he could get one with only had 60,000 miles. Then after he had the car a month he said he couldn't get that engine but got another, a 90,000 mile engine that was suppose to be good and said it was 2 years newer than mine. I accepted. That engine turns out to be from an earlier year (the valve cover breather hose is at 90=B0 from the '95 and a '91 I think it was at the junk yard was identical to that which he put in). My loss. The ping code sets along with the EGR solenoid valve code (3-4 and 10-5). I got under the car tonight and finally physically looked at the knock sensor. I can't say when it happened but although the Haynes manual says it gets a white wire and is grounded, the harness has both a white and what looks to be a brown wire But the brown wire is cut. Not just cut but cut right to the quick on the plug making a splice impossible. This engine gets a stable 26 mpg so I don't think a great deal of carbon is going out the exhaust. I use cheap gas. I swapped the EGR valve from the earlier engine as it hadn't been setting any codes but the EGR code still sets.I see online that the analog filtering used in pre-2000 Altima's isn't very good and will set a ping code from other noise -- valve train or I suppose timing chain. The codes set if I run the car for some distance, turn it off, wait not overly long (not cooled down), then start and accelerate normally.
So, I have three questions:
a) Is the brown wire to the knock sensor critical?
b) Will an ECM from a 2000 or later Altima drop right in? I understand that from 2000 on the knock sensor is digitally converted and goes through a complex calculation to differentiate knock from other noise. Since the fuel isn't leaned down to a degree that can produce 29 mpg I'm hoping it isn't ping. My present ECM has a minor problem. The rheostat that used as a simple debounce circuit has lost its stops and one must feel carefully for the rheostat start and stop when checking or resetting codes. If a 2000 ECM would fit in I'd give a go.
c) If I obtain a knock sensor from a junker along with its harness, splice some length to the wires, and remount the knock sensor distant from the timing chain and power steering pump, say near the distributor, will I see any improvement?
Thanks for your interest and advice.
Bill