cylinder missfire info 99 suburban

Recently I had gotten a cyl #5 missfire and a random missfire.I checked cap and rotor,drive gear backlash and took the ignition module and heat sink off.I cleaned the back of the module and heat sink.I then put a new layer of die electric silicone on each component.I then got to drive on the same hill that brought on the missfires.No codes this time.There may be two other factors that may affect the results.I just refueled with Shell gas and it wasn't raining.I don't know if these would affect the results,but I will monitor the misfire situation.I just want to let other members know what I have tried since I do find many members with missfire problems.
Chuck's

Misfire can be caused by many things.
Always scan for what cylinders are missing and how many times.
Fuel pressure and camshaft retard setting can cause misfire.
Also do not forget basics .
Like plugs and plug wires and coil.

I have a story of cylinder misfire on my own '99 Sub. When the car was brand the check engine light would come on whenever I was on a long incline and I pulled the trans out of overdrive. As soon as the revs reached close to 4000 the check engine light would come on (not towing). If the rpm's were not decreased the light would flash on & off signaling big problems. The engine never missed a beat. The car seemed to run fine with no noticeable problems, but the code would be thrown for No 7 cylinder misfire. The dealer checked everything and could find nothing wrong. Under the described conditions the check engine light would invariably come on, with the car running fine.I wanted the problem resolved before the warranty expired so I took the car back to the dealer every time the light came on. Umpteen trips back to the dealer over a long period of time saw the following repairs attempted: plugs,wires,cap & rotor,cpk sensor,cmp sensor. The computer ground wire to the block was removed and super cleaned, and reinstalled with dielectric grease.They finally out of desperation pulled the heads to ascertain possible carbon build up on No 7 valves (this was at 40,000 miles and a complete valve job and head surfacing was done (at no expense to me). And guess what? Every time I hit a grade at 3500 to 4000 rpm the check engine still came on! And now with 130,000 miles it continues to do so.I reset the light for smog checks, but have long since given up on what causes the "light" to come on. Car runs great,so who cares about the "light."

I have a story of cylinder misfire on my own '99 Sub. When the car was brand the check engine light would come on whenever I was on a long incline and I pulled the trans out of overdrive. As soon as the revs reached close to 4000 the check engine light would come on (not towing). If the rpm's were not decreased the light would flash on & off signaling big problems. The engine never missed a beat. The car seemed to run fine with no noticeable problems, but the code would be thrown for No 7 cylinder misfire. The dealer checked everything and could find nothing wrong. Under the described conditions the check engine light would invariably come on, with the car running fine.I wanted the problem resolved before the warranty expired so I took the car back to the dealer every time the light came on. Umpteen trips back to the dealer over a long period of time saw the following repairs attempted: plugs,wires,cap & rotor,cpk sensor,cmp sensor. The computer ground wire to the block was removed and super cleaned, and reinstalled with dielectric grease.They finally out of desperation pulled the heads to ascertain possible carbon build up on No 7 valves (this was at 40,000 miles and a complete valve job and head surfacing was done (at no expense to me). And guess what? Every time I hit a grade at 3500 to 4000 rpm the check engine still came on! And now with 130,000 miles it continues to do so.I reset the light for smog checks, but have long since given up on what causes the "light" to come on. Car runs great,so who cares about the "light."

Was a coplete fuel pressure check ever done?
Was the camshaft retard seting ever checked?
Do you have any print out or specs on fuel pressure and cmshaft retard settings?
How many misfires on no 7 cylinder? andother cylinders?
Can you feel a misfire on load?

When the car had about 5000 miles on it we took our first trip through the mountains in it and noticed the check engine light.At that time they did a fuel pressure check, and although it was within specs (64 psi I believe), the dealer insisted in changing the fuel filter (at my expense). I don't know what the cam retard readings were, how many misfires, or any other of the actual data, but the cmp sensor and ckp sensor were replaced along the way. The car never gave any sign of missing a beat, and no smell of unburned fuel when the MIL was on or blinking. or any actual indication of a problem. The dealer was happy that they were able to replicate the problem of the MIL coming on when test driving the car, but never noted any actual driveability problems either. A TSB on this problem advised to R&R a computer ground cable on the rt/side head. This procedure did in fact make the MIL less sensitive to come on, but did not entirely rectify the problem.The service advisor felt it was some kind of quirk in the diagnostic system, and that the car was actually fine. If it weren't for regular emissions testing,I would have put some black tape over the MIL a long time ago.

the pcm on these are very sensitive to the p0300 dtc / random miss fire.

with this code only, this may be triggered by going up a grade with poor / rough road conditions at the higher 3,ooorpm .

with the rear wheels slipping then grabing the shocking effect travels into the engine where the cam moves in an irregular way. the system is calibrated so closely that this throws the p0300 code.

vehicle operates with no problems of pinging/power loss/ misses/ idle issues etc....

this does occur more often in tow mode, going up grades with poor road surface.