QuestionHey Bill, could you help me. I recently purchased a beutiful 1993 Sedan Deville with everything and gold package to boot. The 4.9 is a pretty fair engine and it has 140K Hiway miles on it,but Wiped down and garaged after every trip.
But now, after a few thousand miles, I got a service engine lite on at all times. Also, it really pings under load and a sliight knock (Real Quiet) runs very slightly rough. Got an EGR code only, could that be it.
What should I look for. If i go to rev it the engine backs off like a govener?
Please help me. It runs so good that I can't believe that a dead cylinder is possible, thinking that would cause the quiet knock.
Please help me. I cannot afford to spend much or anything really right now as I have just battled a Brain Tumor.
Please tell me what I can check for. My son just scaned it today at school and it appeared that his auto tech class did have a Snap-On Scanner so I do trtust the code. 42 or 46 something like that. Was EGR code anyway.
Thanks, I look forward to your reply
Larry Oyler SR.
Retired Transmission Rebuilder
PS. Clim Cntrl gives cool action but no Heat?
AnswerHi Larry, Yes the EGR valve could cause the ping. If you push up on the valve with the engine running and if doesn't run rougher or die then the passage is plugged. If it runs rougher then look for reasons why the valve won't open such as hole in diaphram or solinoid not allowing vacuum to the valve...Timeing might be too far advanced, it should be 10BTDC, or maybe you need to be useing premium and instead are useing 87 in which case the timming can be backed down to 6 BTCD and the ping might be eliminated. Check the vacuum door is letting outside air into the aircleaner housing after the engine has warmed up...The knock you hear if it seems to be lower in the engine is from the main bearings. Caddy has had problems with bearings in this type engine since 1982 when it first came out and you can eithor live with the noise which seems like it shouldn't be a problem by your discription or you can replace the main bearings with the updatted numbers per the service bulletin and the noise will be gone. As for the temp. 2 areas to look at are the programmer motor and the inside temp. sensor. Remove the glovebox and command the door to 60 and watch it for skips and then to 90 and watch it. On older cars the gears inside strip out and then the motor gets confused about where it needs to be. If you are unsure of some tests I'm sure your son could ask at school or you could repost with your questions. Hope that helps. Bill
