| Re: Spark Knock is back.... and I figured out why... And it's BACK AGAIN!!!! |
Subject: Re: Spark Knock is back.... and I figured out why... And it's BACK AGAIN!!!! by bogus on 2011/10/26 16:30:00 Current status and specifications of issue: I thought it would be a good idea to sit down and update the problem and summarize the specs of my car. Specs: 1992 LT1/MN6, 180k miles Engine - internally stock and original Ignition - LTCC; uses a brain box to intercept Opti commands and fire one of 8 GM (Denso made) coil8 from an LS1. System was installed Oct 2003 and has shown to be very reliable. Only issues have been related to the harness (bad insulation on solder joints or belt explosion tearing up harness). This system has never shown failure. DynaSpark Opti, without cap/rotor. New last year due to warrantee claim. Prior unit failed; tone disc was bent and rubbed the optical sensor until damaged. H16 resulted, similar driviblity issues. Sensors: All stock or stock replacements. Knocks new May 2011, O2, new Bosch, this week. All others of varying age. I have a new PCV, need to install. Vacuum lines: All present and snug. Have small clamps to install. Air Filter: K&N, does need a cleaning. Plugs: New NGK Platinum Wires: Taylor universal, I made them to fit. 2 years old Exhaust: Newer (60k) exhaust manifolds with copper gaskets, all torqued, new bolts (no studs) holding cats to collectors, Corsa cat back. Cats were used, from a CF'r, bought about 4 years ago with 15k miles on them. NO EXHAUST LEAKS UPSTREAM OF O2 SENSORS! First time in several years, actually... sounds nice when it's running well. Very quiet. Fuel Pump - newish, about 3 years Fuel filter - New in May 2011 Fuel Injectors - New (18 months) from FIC, Bosch III injectors. All ohmed between 17.3 and 18.2 Tested spark, all coils seem to be firing ok. Swapped ECM's, no change. Same stock chip. EGR replaced 9 years ago. Will test. With all the recent repairs, nothing has fixed it. Depressing doesn't even come close.. Symptoms: Spark knock, back fire, sluggishness, constant miss, generally poor drivablity. This problem has been coming and going since May. Initially, I thought it was bad gas, and treated accordingly, and it went away. I added a couple of cans of SeaFoam and that seemed to fix it... I will say that the engine has felt soft on power, but running smoothly. It came back, and that time, about 3 weeks ago, it has been getting progessively worse and worse. Fuel pressure appears ok; 40 PSI at idle, jumps up 2 or 3, drops to 38... It seems low, nut not insanely so. I hope this reboot will help us come to terms with this and fix it. I have an email into LTCC guy, Bob, and hopefully he will see something we have missed. Only funny sounds are from the dual mass flywheel jerking around when the engine runs like crap. Immediate plans: Chase LTCC harness. Confirm it's ok. Inspect all grounds underhood and on engine block. New fuel pump, strainer and filter. Clean air filter. Test EGR valve. Random Commentary: Back in the mid-80s, my brother had a then new Thunderbird. 3.8l V6, very nice car. It either ran fab or ran shit. And there was no warning. The dealer could not trace it and it was very random. I suggested then that it was either a ground or vacuum problem... but it was under warrantee and I never touched it (good choice, why ruin warrantee and lose complaint rights?). I am going with that approach, too. EGR has been discussed... Honda had issue when the EGR injection ports in the intake would clog. These ports, about 3mm, would carbon and block up. This would cause an at cruise stumble and on OBDII cars, a code. The fix was to pull and tank the manifold to clear the ports. My problem has transcended this. |
