Ive had this problem for a while now, The engine is a fresh rebuild, the check engine light flashes, Ive had it scanned and it returned the following , p0304,p0326,p1441 Heres a list of what Ive done so far

1) compression test, all cylinders at 160 except 2 and 4 that were 150

2) distributer was new with the engine rebuild, tried a different cap, rotor, plug. and wire

3) replaced the fuel spider/regulator/injector tested and holds presure ok ..no leaks

4) ran a different coil for about a month


Every other plug except #4 is light brown in color, #4 is dry black carbon fouled

Im at a complete loss as to what could possibly be the cause of this

 

Somebody definitely knows better than me but could the valves on that cylinder be out of adjustment?

 

Im going to bump this...Im all out of ideas

 

I put a new fuel filter in, The old one was fairly restricted...One thing I noticed was that the fuel pressure fluctuates with rpm, At idle its at about 52psi and when I rev it up it goes to about 62, when I turn the engine off the pressure holds at about 60, The filter made the check light not flash as much but what I dont understand is how could this only affect one cylinder, It was the same with 2 different injection spyders...

 

GM does not publish any "engine running" fuel pressure specs, there are far too many variables involved. Fuel pressure is tested with the engine cold and off, and the fuel pump running. Pressure holding at 60psi indicates leakdown is acceptable. What is the KOEO fuel pressure?

Just to clarify, this is a CMFI system and not the CSFI system, correct? If it's a CSFI system, the following does not apply:

The intake runner for #4 cylinder has a drain hole that runs to the back of the intake valve. The drain is there so if the fuel pressure regulator leaks, it won't fill the intake with fuel. There is also a drain hole in the #3 intake runner that serves the same purpose if the pressure line to the injector leaks. It's possible that you have a fuel leak in the return line in the plenum. Leaks in that line will not show up with a leakdown test.

 

Yes its a CMFI system,,,Thanks for the info..I didnt know that #4 and #3 had drain holes to the intake valves...Knowing that the regulator is holding pressure and is closer to #4, If there were a leak in the return line wouldn't it be more likely to show up in the #3 cylinder? (#3 plug is golden brown) And is there any way to test for a return line leak?

The new fuel filter has improved the misfire by about 50%,

Also ..What is KOEO fuel pressure?

When I replaced the fuel spyder there was no sign of washing on the drivers side..The passenger side was actually ok too,,,there was oil in the upper plenum tho..But the oil was there before the new engine was done...

Does the EGR valve feed into just one cylinder or does it feed into all?

 

Can you tell us which of these pictures best matches your #4 plug? Have you verified good spark to that plug?

 

#3 picture best describes my plug..carbon fouled..Its dry and not wet or glazed in any way, I have tried 2 different plugs and 2 different wires and 2 different distributer caps, Ive verified that the cap fits evenly and flat on the distributer,,, I have verified that there is nothing steel touching the spark plug wire boot at the plug, If I unplug the wire all together and run the engine it runs very noticeably worse ..I havent had any kind of tester on the wire to measure the output..But it seems like its working ok,,,The wires plugs rotor, cap, and distributer are all brand new...

This may be nothing but one other thing I noticed was that the part number on the cam pos sensor is a different number that the one that rockauto would send me if I were to order a new one...

when Im driving the blazer there is no obvious indication that there is any misfire, It seems to run smooth,The check engine light flashes.. Before I replaced the fuel filter it would sometimes shake as if there was a problem with the torque converter when I stepped on it from a stand still but its not doing that anymore

 

The fuel pressure regulator is on the passenger side, if it leaks, it will leak into cylinder #4. Both the pressure line to the injector and the return line from the regulator are on the driver side and will leak into cylinder #3.

KOEO= Key On Engine Off

The EGR valve feeds into all cylinders.

Did you check fuel pressure and leakdown? That test will tell if an injector is leaking, (stuck open & not sealing).

 

Thanks again for the reply...

The FPR is only one week old and holds 60lbs for 30 minits----KOEO

when I installed it I also checked for leaks at the nut kit when I had the upper plenum off with pump running and it looked good..

Im sure there is no leaks...Ive tested it many times now..

The FPR and injector/ poppets are all one unit on a 95 so the whole thing is brand new..

The engine block and heads are freshly rebuilt...5k miles on it, It has flashed the check engine light from day 1