Ive had a remanufactured engine installed in my 95 blazer,(4.3 ltr cpi type W with flat top distributer cap) The guy at the engine shop told me that the computer has been reset and that it is normal for upto the first few thousand kilometers for the check engine light to flash while the computer relearns all of its perimeters, Its been 2500 kms now and its still doing it, I know that a flashing check light signals a misfire, The engine seems to be running smooth, I have a scanner and its not showing any stored faults, I know a misfire indicates lack of fuel or spark in a older engine, My question is, What sensors determine a misfire, Where should I start looking and if anyone could speculate on a probable cause and/or soultion...Thanks

PS the engine shop is 2 hours away from my house and its a big deal to drive all the way there for something I might be able to fix myself, the bottom end and heads are new with my old intake installed,

 

Heres what Ive done so far,

!) fuel pressure test,,, started out at 60 and after 15 minits it was 58

2) did a compresion test and found 4 and 6 were 150 the rest were 160 , this engine has 3500 kms on it,,,should I be concerned with the 4 and 6 cylinders?

3) the plug in #4 was carboned and the rest were normal, they are champion plugs, Ive bought ac delco plugs but havent put them in yet, if that doesnt take care of it I will try a new plug wire on #4,


any help would be much apreciated...Thanks

 

have you tried disconnecting the neg terminal at the battery and let it sit for about 10 minutes or so? and def get those champion plugs out of there... if you trybattery idea, drive it around at normal speed for at least an hour or 2, see if the light comes on again... if your near an auto store that checks the eng lights go there and have them check it while the light is on dont shut the truck off..hope this helps ya sum..

 

And don't forget to take into account that the code system on a 95 is a hybrid, that not all scanners will read the stored codes.

 

What would cause one plug out of 6 to be black carbon fouled? Ive tried different plugs and wires, Im thinking this is the reason for the random misfire...

I noticed the heat sheild was tight to the spark plug wire boot...could this cause loss of spark somehow?

 

what # plug is fouled? Cheap quality wires could cause misfire!! what kind are you using?if you can swing the pricing of the AC Delco wires def get them,I know i paid alot for mine but i didnt care, i only use name brand stuff..put the proper AC plugs in it gap them at 60 as far as the heat shield goes , make sure you have the correct wire with the correct boot on the right plug, some are straight boot some are angled. mine are close to the heat shield also but def not rubbing against them. of course #3 plug is a biatch!!! if you dont have the plug in properly esp seated all the way you`ll lose spark and fire incorrectly,If you livednear me i`d come by and help but i think you live in a diff state than me..get back to us and keep us updated...

 

every plug except #4 was a nice tan color, #4 was carboned dry, there is 3500 km on a rebuilt motor, Ive had 3 different plugs in #4 and 2 different wires, The wires are ngk 7mm, the wire on #4 is now ac delco, I bought 6 ac delco plugs and relaced the champions the engine shop used, I will check the distributer cap today, The ac delco plugs are the same plugs that the manufacturer calls for, I gaped them at .45 as the sticker on the fan shroud says to,

The engine seems to run well except for the flashing check engine light, it doesn't flash all the time, with one plug being fouled I feel like I have something physical to chase now..Im just trying to figure out how only one could be bad...

I adjusted the heat sheild so that it doesn't touch the boot of the wire and the light still flashes



***UPDATE***

I changed the dist cap and rotor, the old cap (that is 2 months old) showed the same marks on the inside on #4 as all of the others, I always keep my old parts so Im testing with older stuff but when the old stuff was on the engine there was no problem,

anyways the misfire still presists, Im led to beleive that my problem is not electrical but is fuel injector related,

The intake is clean...So they must have removed the spider and injecters when they installed the new engine, Im running injector cleaner in the gas right now..

If an injector is bad could it be bad while the fuel presure doesnt indicate any leak down?

 

i may be reading that wrong but it looks like your mixing brands of wires?? I wouldnt do that ,NGK is for foreign cars normally, is there smell of gas or anything on that #4 plug? like you alos said def check the dist cap again, also at night In a dark area start the truck let it warm up a little bit, fine mist from a spray bottle ( water) around the spark plug wires and look for sparks anywhere, that will also give you that msifire sign.. Still try and get that CEL light checked..

 

Im not mixing brands of wires..I just used a ac delco wire to replace the #4 wire temporarily to see if the wire was at fault for the misfire and the black plug, The plug is black and dry and does not smell of fuel, If I pull the wire off #4 and run the engine it runs alot rougher,

If the poppet on #4 was stuck or leaking could that end up causing the misfire? are the poppets pressurized with fuel constantly? If so is it conceivable that if one were stuck open that it would be causing the #4 plug to foul? if one poppet were leaking would that show me a significant leak down when testing? Or could it be that the poppet is stuck closed when the misfire is occurring and there is no fuel passing trough and the plug is fouling due to the unburnt gases being supplied by the egr system? If the poppet was sticking closed that may explain why Im not seeing a leak down? Am I making any sense?

Is a cmfi engine capable of storing codes to each specific cylinder of will it just tell you when the o2 sensors detect unburnt fuel? Or the knock sensors are reporting the misfire light due to no fuel other than unburnt egr gases being supplied to #4 cylinder?If I drive 5 miles on a brand new plug in #4 cylinder it fouls black and dry, Its not a solid check engine light thats storing a code, It flashes then goes away then flashes again, I always thought that unless the light stays on solid there wont be a code stored.


If I have 2 different plug wires and 3 different plugs and 2 different caps all producing the same results, wouldn't it be fairly safe to assume that the one plug out of 6 is being fouled by a rich fuel condition, And knowing that the 5 other plugs are working fine,,, The fouled plug could be the result of a stuck poppet?

would running fuel injector cleaner through the fuel help a bad poppet or would that only help the central fuel injector?

Im waiting for the engine to cool down , Then I will put the new cap and rotor back on and reinstall the ngk wire, when its dark out I will try spraying the cap and wires and post the results, I have an actron scanner that works with a 95, but it isnt showing me any stroed codes, I had always thought that on a 95 there is no monitoring of the fuel system , So Im thinking I would be wasting my money taking it in to the dealership for a scan,