Misfiring Woes

Misfiring Woes

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1998 Blazer 131000 miles, 4.3 l, 6 cyl, 4X4

Two days ago at a speed of 60 mph my Blazer's motor began to misfire and the "Check Engine Soon" Light came on and then began to blink on and off. I pulled over and took my scan-tool (a reader...Accutron, $80 model) and a
P0300 error wich told me that a random series of misfires was logged. I cleared the code, drove on (40 miles from home) and the light came back on immediately and the engine was misfiring.

Reading the code again I now had a SPECIFIC cylider misfire (P0305) which told me the # 5 cylinder was at fault. After several code readings the last two days, the error code has ALWAYS been P0305. The P0300 never logged again.

I am haven a dickens of a time with this problem and I cannot seem to solve it. So far I have changed the #5 wire and spark plug with new parts and I still get the misfire.

I used an ignition spark tester by connecting it to the # 5 plug wire and starting the engine. It appeared the spark was normal and strong although it may be my aging eyes, but the blue spark sometimes had an "arc" shape instead of going straight across from node to node. Again, I'm not sure if this is an issue.

I checked the ignition coil primary with my handy Sears digital multimeter and read 1.5 ohms that quickly decreased to settle to .6 ohms across the primary as if I had some type of capacitive element involved. (Haynes service manual says .5 ohms is maximum but again I am not sure about the accuracy). The secondary resistance meaured 6 k ohms (Haynes service manual says 5 k ohms to 25000 k ohms is acceptable).

The distibutor cap and rotor were changed out (by me) 5 months ago but I removed the cap and rotor this morning and found no hot arcing spots. I did find that the six nodes to be coated with a white, chalky substance which I cleaned up with a pencil eraser. I re-assembled the rotor and cap, wired it up but it still misfires with the PCM returning a # 5 cylinder misfire.

So, I am at a loss and the ol' back is broke trying to reach plugs that are (impossible??) most difficult to get to. So far I have replaced the number 1 plug and the # 5 plug, and their corresponding plug wires and also the # 3 PLUG WIRE. I cannot remove the # 3 plug as there is a steering shaft in the way it seems. I have not even attempted to get to the 2, 4, and 6 cylinders (plugs and wires) as they appear to be even more inaccessable than the three on the left side of the motor.

Could the scanner be sending me a lousy error code by perhaps having another cylinder misfiring and the PCM is (for unknown reasons) defaulting to the # 5 cylinder error code (P0305) ?

Is there something else I am missing here and should be checking ?

The Haynes manual leaves alot to be desired some times. It appears as though I have a High Energy type coil and a CSEI (???) disributor system.

Missed two days of work already and any help would be very much appreciated.

Thanks,

Paul in Massachusetts

How Do You R&r The Ignition Cylinder On A 95 Blazer

Paul T,

First of all, I agree with you about the Haynes manuals. I've used them for years, and they're great because they are cheap, and they cover most things. But, yesterday I broke down and paid $25 for a subscription for an online manual at www.alldatadiy.com (http://www.alldatadiy.com). It's incredible, uses all factory GM tables, charts, and diagrams, and has probably 3-4,000 pages if you were to print it all out. It has flow charts for every PXXXX code there is, and I highly recommend it. I only have the subcription for my '95, which has a different engine so I can't apply most of that info to your problem.

To replace the #3 spark plug, the best way can be found in this thread:http://www.automotiveforums.com/vbulletin/showthread.php?t=503231. I did this myself just last week, and it took less than 20 minutes.

If replacing the plug doesn't fix it, it sounds to me like you have a fuel problem. Your CSFI system has six individual injectors, as opposed to my '95s one big injector. I'd check your fuel pressure, and if that's fine take a good hard look at that injector and the rest of your fuel system.

Good luck!

How Do You R&r The Ignition Cylinder On A 95 Blazer

To reduce confusion, please post your question in a new thread. To start a new thread, click on the link below, then click on "New Thread"

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Thanks

Sounds like you have a stuck injector. I've had #5 injector problems on my 98 blazer too. I would first try some "SEA FOAM" injector cleaner. I think a GM dealer has this same stuff for more $$$ available and they call it "TOP END CLEANER"......or something like that. Put this stuff in when you fill your gas tank and run it till your gas tank needs refilling. You should notice the truck run a little bit better after a few 100 miles. If it doesn't then you probably have a totally plugged injector and you will more than likely need to change out the #5 injector. Also.....don't worry about running the engine with a plugged injector......I've put a lot of miles on mine and it doesn't hurt the motor. Right now I have 192000 miles on mine and it purrs like brand new.

FYI....next time you change your plugs, try taking the front wheel off and reach in under the wheel well. It saves on the back a little.

Many Thanks to TOM B and RLITH and everyone. The link to RILTH was absolutely amazing advice. I may have given up on getting the Number 3 Plug out but the pictures along with the advice regarding the disconnection of the intermediate steering shaft from the steering box for access was right on the money and nothing short of pure brilliance!

So then, did the "tune-up" get rid of the misfire? Unfortunately the answer is no. But because at the very least I have 6 new plugs/wires, the misfire no longer stalls me and I could get to work.

Right now I still have two error codes. The P0300 (Random Misfire) and the specific P0305 (Number 5 Cylinder Misfire).

Have poured in to the fuel SEA FOAM and have driven the Blazer 120 miles without success. My biggest obstacle is being totally down and missing work which of course isn't good.

I don't know if I have the talent to pull-off an injector replacement in a short period of time. I know the injector is about $90-100.

Any idea on labor or how labor intensive this kind of a job is?

Thanks again to all. I know that at some point I will get to the bottom of it. Soon I hope.

Paul T

Paul, What Brand of spark plug are you running in it, and what is the gap on it? Also what brand of Distributor cap and rotor? also are all the wires new?
These are funny trucks, They like ONLY AC DELCO Parts

I wouldn't worry about missing work with a stuck injector. Heck drive it like you stole it with the Sea Foam in there......meaning hammer on the throttle every once in a while.:grinyes: What you are trying to do is build up different pressures in the line so the injector cleaner has a better chance of making it to the stuck poppet valves. I did this about 2 years ago with mine and had success with a stuck valve, but my biggest mistake was I didn't put any more injector cleaner in there and about 6 months later it stuck again. The 2nd time the injector cleaner didn't work and I ended up replacing the injector.

I replaced the injector myself and it took about a whole day to do. If you decide to change the injector yourself I would recommend getting a Chilton repair manual to help you through it. :2cents: