Thank you Greg!
I’ll give her a go once the weather breaks (truck is in driveway) and I’ll post how it all works out.
Stay well,
Mike
1998 GMC K1500 +HELP+ It all started with a P0300 code…
Hello and thank you in advance for your insight into my challenge. I’m going to write a lengthy and chronological post in hopes of providing the best insight as to what I did or didn’t do or check.
Disclaimer: I’m obviously not a mechanic but I’m trying to do as much work on my truck, as I live out in the country and getting into town, for me, is more of a hassle than me just doing the most I can. Plus it’s fun learning and working with your hands! I will often google/youtube fixes and they usually work 99% of the time. I apologize in advance if I’m not using the proper auto mechanic terminology but I will do my best.
Last year I replaced my spark plugs (NGK’s) and distributor cap with no issues.
This winter has been slightly colder than normal, it dipping into the - temps at night. I’m not sure if this would cause some of my issues. And it obviously snows where I live and drive where “salt” is used.
Part I
Recently my truck gave me a P0300 code (random misfire). My understanding, I went down the laundry list of potential issues as they could be many, as several YouTube videos indicated. I disconnected my negative battery cable and got to work. I replaced both oxygen sensors (up stream) and I cleaned my EGR valve and reinstalled it with a new gasket seal. I also cleaned my Mass Air Flow sensor and reinstalled. I connected all associated electric cables. I went ahead and reconnected the battery cable and the truck ran fine for a bit but that pesky engine light came with with he same fault code.
Part II
I went ahead and continued on the list of potential issues. I installed new AC Delco spark plugs (I’m under the impression the OEM plugs work better than other plugs) I also made sure the proper air gap (.060) was achieved. I reinstalled the spark plugs wires and a new fuel filter, making sure I installed in the correct direction (arrow facing engine). I also installed a new ignition coil. I also added dialectic grease where appropriate. I started up the truck and I still had a fault code indicating my Mass Air Flow sensor cable was not reinstalled. I made the quick fix and re-connected it. I cleared the fault code and started up the truck fine after that initial priming of fuel through the new fuel filter.
I drove it home from a friends house about 1/2 a mile with no issues. I didn’t drive my truck for a couple of days. I then attempt to start my truck but no luck. The engine would crank but no start. It sounded like my battery was getting weaker and weaker. It’s a two year old battery which seemed odd. I decided to replace the battery after several attempt starts. After the install of a new battery, still no luck.
I made sure all my electric connections were properly installed, to include my ignition coil and wire leading to distributor cap. Still a no go.
Part III (spark/fuel/air)
I removed two (independently) spark plug wires and tested them both for a spark, which occurred. I also listened for the fuel pump to engage (both by drivers door and by gas fill). It “sounds” as if it’s working. I also checked the fuse box in the engine bay to make sure my 20 amp fuse (ECB-*) related to fuel was good, which is was. I also had someone turn on truck for me (position key 2) and I listened to fuel pump relay (boxey looking fuse) which made a sound kinda like a click.
Whew! So that’s what I’ve done thus far.
I recently watched a youtube video where the mechanic determined a ground cable (undercarriage of engine area) was corroded and broke off. I believe it was attached to frame of truck. After fixing that, the truck started right up. Crazy! Something so simple. Not to mention a horrible place to install it, unprotected and exposed to the elements.
Anyways, if you have some suggestions or know exactly where these ground wires are located, much appreciated and Happy New Year!
Mike
Disclaimer: I’m obviously not a mechanic but I’m trying to do as much work on my truck, as I live out in the country and getting into town, for me, is more of a hassle than me just doing the most I can. Plus it’s fun learning and working with your hands! I will often google/youtube fixes and they usually work 99% of the time. I apologize in advance if I’m not using the proper auto mechanic terminology but I will do my best.
Last year I replaced my spark plugs (NGK’s) and distributor cap with no issues.
This winter has been slightly colder than normal, it dipping into the - temps at night. I’m not sure if this would cause some of my issues. And it obviously snows where I live and drive where “salt” is used.
Part I
Recently my truck gave me a P0300 code (random misfire). My understanding, I went down the laundry list of potential issues as they could be many, as several YouTube videos indicated. I disconnected my negative battery cable and got to work. I replaced both oxygen sensors (up stream) and I cleaned my EGR valve and reinstalled it with a new gasket seal. I also cleaned my Mass Air Flow sensor and reinstalled. I connected all associated electric cables. I went ahead and reconnected the battery cable and the truck ran fine for a bit but that pesky engine light came with with he same fault code.
Part II
I went ahead and continued on the list of potential issues. I installed new AC Delco spark plugs (I’m under the impression the OEM plugs work better than other plugs) I also made sure the proper air gap (.060) was achieved. I reinstalled the spark plugs wires and a new fuel filter, making sure I installed in the correct direction (arrow facing engine). I also installed a new ignition coil. I also added dialectic grease where appropriate. I started up the truck and I still had a fault code indicating my Mass Air Flow sensor cable was not reinstalled. I made the quick fix and re-connected it. I cleared the fault code and started up the truck fine after that initial priming of fuel through the new fuel filter.
I drove it home from a friends house about 1/2 a mile with no issues. I didn’t drive my truck for a couple of days. I then attempt to start my truck but no luck. The engine would crank but no start. It sounded like my battery was getting weaker and weaker. It’s a two year old battery which seemed odd. I decided to replace the battery after several attempt starts. After the install of a new battery, still no luck.
I made sure all my electric connections were properly installed, to include my ignition coil and wire leading to distributor cap. Still a no go.
Part III (spark/fuel/air)
I removed two (independently) spark plug wires and tested them both for a spark, which occurred. I also listened for the fuel pump to engage (both by drivers door and by gas fill). It “sounds” as if it’s working. I also checked the fuse box in the engine bay to make sure my 20 amp fuse (ECB-*) related to fuel was good, which is was. I also had someone turn on truck for me (position key 2) and I listened to fuel pump relay (boxey looking fuse) which made a sound kinda like a click.
Whew! So that’s what I’ve done thus far.
I recently watched a youtube video where the mechanic determined a ground cable (undercarriage of engine area) was corroded and broke off. I believe it was attached to frame of truck. After fixing that, the truck started right up. Crazy! Something so simple. Not to mention a horrible place to install it, unprotected and exposed to the elements.
Anyways, if you have some suggestions or know exactly where these ground wires are located, much appreciated and Happy New Year!
Mike
1 - 5 of 6 Posts
I’ll give her a go once the weather breaks (truck is in driveway) and I’ll post how it all works out.
Stay well,
Mike
Hi Greg,Great detail, Mike.
The fuel tank ground is located on top of the frame rail at the filler neck. It‘s a 13mm screw on top of the frame that is a little hard to see. You locate it more by feel. The fill tube rests on it.
Other grounds:
Fender next to battery
Frame rail above the starter back to the firewall and forward to the back of passenger side head. Intake manifold should have at least three. Main negative, thermostat housing and at least one other spot on the intake.
So I checked all the ground wires and they all appear in tact. I went ahead and swapped out my fuel filter again just to make sure it wasn’t a bad new fuel filter. I even checked the fuel pump when the line was disconnected from the fuel filter and it was moving fuel through the line.
At this point, I’ll just get my truck towed to a reputable mechanic shop and have them figure it out. I think at this point it’s above my mechanical abilities.
I’ll post what the final fix is once the work is done.
Thanks again for responding,
Mike
++UPDATE++Hi Greg,
So I checked all the ground wires and they all appear in tact. I went ahead and swapped out my fuel filter again just to make sure it wasn’t a bad new fuel filter. I even checked the fuel pump when the line was disconnected from the fuel filter and it was moving fuel through the line.
At this point, I’ll just get my truck towed to a reputable mechanic shop and have them figure it out. I think at this point it’s above my mechanical abilities.
I’ll post what the final fix is once the work is done.
Thanks again for responding,
Mike
So I took my truck to a great mechanic shop in my area. The advisor and I spoke for quite some time. He was genuinely interested in what I had done and asked if I could email him the list of things I did so he could pass it on to the technician. Thankful for their honesty and desire to do good work.
Turns out I developed a lot of moisture in my distributer cap and rotor causing the misfires. It was very odd being I replaced it this past summer making sure I properly re-installed it. Once they replaced it with OEM D&R, it ran just fine. He also noticed that my truck was running on the cooler side (thermostat). He hypothesized that perhaps it running colder and me not driving the truck for several days caused enough moisture to create oxidation. So I also asked him to change my thermostat to make my truck run a bit warmer (190/200 degrees, if my memory serves me). I explained to him I used to live a hotter climate and perhaps my previous mechanic made the modification.
So I was thankful is was something relatively minor but it also taught me I should have talent the time to check that myself. Regardless it was a win win because I now have a solid mechanic who I can trust to do the work I can’t when needed.
Cheers!
Mike
Final update!
Apparently I was having issues on the upper part of my engine block. Two separate mechanic shops suggested I get a new engine in the event that if they fixed the upper part of the engine, the lower part could also crap out on me. The idea being instead of taking a risk at investing that money at potentially half the of problem, I would be better served to just replace the whole engine. Fortunately I was able to locate a brand new GM engine with a 100K / 3 year warranty.
It was pretty pricey but it beats a car payment on a new vehicle or buying another used truck. It’s been said, it’s better to deal with the devil you know.
Thanks again all for the help.
Stay well,
Mike
Apparently I was having issues on the upper part of my engine block. Two separate mechanic shops suggested I get a new engine in the event that if they fixed the upper part of the engine, the lower part could also crap out on me. The idea being instead of taking a risk at investing that money at potentially half the of problem, I would be better served to just replace the whole engine. Fortunately I was able to locate a brand new GM engine with a 100K / 3 year warranty.
It was pretty pricey but it beats a car payment on a new vehicle or buying another used truck. It’s been said, it’s better to deal with the devil you know.
Thanks again all for the help.
Stay well,
Mike
1 - 5 of 6 Posts
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