I have a 1987 Caddilac Coupe Deville. The engine is a Goodwrench remanufatured 4100 it has about 16k on it. Regardless of what fuel or octane boosters i use. She still preignites under light acceleration. I've replaced the entire EGR system. I've set the base timing advanced and now back to factory 10btc. I've had a diagnostics computer hooks up and the only thing that was out of specs was the cell was dead. I understand that this is a 9 volt battery in a box under the dash. Is this true? Would it help to find it and replace it. It's like the space shuttle under the noise covers. Advice?
2006-08-19 08:19:29 · 5 answers · asked by Digital Angst 1 in Cars & Transportation ➔ Maintenance & Repairs
Tryed Top end cleaner from the Caddy Dealership. Tryed the (Base timing computer off) advanced as much as 4btc degrees and differant trials Timing helps very little but noticable. Yes, it's more pronouned when at operating temp and taking off at red lights. By the way I get 29 mpg hwy. Mid or premuim gas makes no differance in the preignition.
2006-08-19 08:39:14 · update #1
Power braking also produces the preignition. I'm running out of idea's. This is only a 1 and a half year old Goodwrench rebuild.
2006-08-19 13:03:00 · update #2
Sounds like you are running lean. What is your O2 sensor reading? Check your fuel delivery, pressure, filter, etc.
2006-08-19 16:32:34 · answer #1 · answered by B H 3 · 0⤊ 0⤋
U replaced the Entire EGR system! - butt - Did U check 2 C if it's working under a load ?? I would start @ TDC & C what happens & up it 2 Degrees untill it started pinging again then retard 2 degrees.IF U are getting FULL advance @ startup u will also get pinging,like if IT had a Vaccum advance the was stuck all the way or the plate was frozen to full advance.IF IT even had a vaccum advance ? U will never know untill U put a degree wheel on the Crankshaft & C where your #1 piston & valves are !
2006-08-19 11:06:16 · answer #2 · answered by Anonymous · 0⤊ 0⤋
are you sure your not hearing piston slap or broken piston skirt try disconecting spark plugs one at a time and see you can make a difference in engine ping! Most ping happens at high throttle high load. Thicker oil perhaps? Piston noise is more noticiable under the car if you can find a lift. also check the flex plate to torque converter for rusty looking bolts or cracks
2006-08-19 08:30:49 · answer #3 · answered by John Paul 7 · 0⤊ 0⤋
well why dont you stop paying attention to factory specs and adjust the timing to get rid of the light pre-ignition. your harmonic balancer could be off a little and giving you a false reading. also check the spark plug gap. as for the 9 volt, i dont ever remember replacing them but good luck finding it.
does it pre-ignite from the moment it starts up or only after it gets to operating temp ???
2006-08-19 08:28:44 · answer #4 · answered by Christian 7 · 0⤊ 0⤋
You might get yourself some spray carburetor cleaner and spray it around on the intake while the old girl is running to see if you have a vacuum leak. The idle WILL change if a vac *** leak sucks the cleaner in, and thus you will know if and where you have a leak.
2006-08-19 08:31:12 · answer #5 · answered by Gary Gearfreak 3 · 0⤊ 0⤋