Mooseman
Moderator
It will give p0300 until it can figure out which cylinder is actually misfiring.
No crank, no start,tried everything
- Thread starter knuckled1
- Start date
Yes, I did clean throttle body. I changed coil boots/springs and gaskets when I did the plugs, so I wonder if maybe a coil boot/spring isnt making good connection. Will check could first. Then I'll repair the broken wire correctly (solder). Can switching a coils position effect the firing order?
I also think I'm having transmission problems now too. It's in neutral/tow mode, so I don't know if its stil supposed to move by putting in gear and driving, or do you have to re-engage the transmission/transfer case first? I also noticed when I shift from anywhere to Park it makes a whining sound, like something spinning, then a grinding sound like it's being stopped from spinning. Is this normal? Or really bad?
Why does my truck roll backwards if I'm in gear, on a hill, like stopping at stop sign on a hill, when I let off the gas I notice it rolls backwards. What causes that?
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Tiggerr
Member
If your TC is in neutral the trans is disengaged basically from the wheels
Put it back in 2hi and see what you get...
Put it back in 2hi and see what you get...
Yes, that was it. No problems there anymore, except the rolling backwards while in gear issue. When on a hill and I stop, it rolls backward if I don't put my foot on the brake. Transmission or rear end isn't holding like it should. Tomorrow I will tackle the coils, solder repair and reset PCM. Thx again. Until next time!
Mooseman
Moderator
No. In fact, that's how we diagnose a defective coil. Switch it with another cylinder and check codes if the misfire follows the coil.
What about if you just give it a bit of gas? It's kinda normal for it to roll back a bit depending on how steep the hill is. If you give it some gas, that should either hold it or make it move forward. As long as the transfer case is not in neutral, it should work.
How long would it take for it to figure out which cylinder is actually misfiring? I fixed the wire with the western union and solder, and I pulled each coil off to check for clean contacts on the coils, that the springs touch the plug and coil, i made sure they were seated correctly, checked all the wiring, hooked battery back up, and it popped yhe same P0300 code.
Is it possible cleaning the throttle body could have damaged the internal electronics, and would that cause a misfire? How about the fuel line repair I spoke of, with the brass bars connecting the hose/line and high pressure clamps. Could the change of inside diameter, albeit minimal, cause a restriction in flow or pressure change, after the test port? Could that cause a misfire by not pushing correct amount of fuel?
Not sure what else to do, but take a spare coil and change each one out and see if possibly one is bad. What else could cause a random misfire? Should I let truck run for a period of time to see if it will figure out a specific cylinder?
Someone also said to do another PCM relearn after checking coils and fixing wire. Does security light have to be on to do a relearn? Do I have to disconnect PCM again and set of security/BARS and start over? Or will a relearn take while security light is out? List again. So close I can't stand it. Been without truck for 5 weeks now.
Did some reading last night and it leads me to believe that the fuel line repair is suspect, or ypossibly the throttle body's position sensor, or idle control could have been damaged during cleaning? Apparently the sealed part of t/b can be damaged if cleaner gets inside and the components no longer function correctly.
I also read that the A/C Delco 41-103's come pre-gapped, I never gapped or checked the gap because I don't know what it calls for.
Can the camshaft position sensor, or variable valve timing sensor, cause a random misfire, setting off a P0300 ?
Buying a spark plug tester and compression tester roday, and will also test fuel pressure with my new fuel pressure test kit.
I also read that the A/C Delco 41-103's come pre-gapped, I never gapped or checked the gap because I don't know what it calls for.
Can the camshaft position sensor, or variable valve timing sensor, cause a random misfire, setting off a P0300 ?
Buying a spark plug tester and compression tester roday, and will also test fuel pressure with my new fuel pressure test kit.
Mooseman
Moderator
Saw the pic of your repair and it looks fine. Did you check the fuel pressure at the port near the fuel filter while it's running?
I doubt it. This "drive by wire" system has checks to be sure it is working properly. If the throttle doesn't match what is being commanded by the gas pedal sensor, it will go into Reduced Engine Power (REP) and throw codes specific to that system. The only thing that could happen outside of that is that the throttle body is dirty and it idles rough. It might throw a code for idle speed for that.
That is correct. Trying to gap them will damage them.
No. Codes specific to those would happen.
Not sure if there is a spark tester that can work with coil over plugs. Misfire is possible if compression is low.
One thing you should get is a Bluetooth ELM327 OBD interface and get the Android app Torque. It can give you live data, including misfire counts, as well as error codes. Way better than a simple code reader. I have this one and works well.
https://www.amazon.com/dp/B019SURWYO/?tag=gmtnation-20
Wooluf1952
Member
I also read that the A/C Delco 41-103's come pre-gapped, I never gapped or checked the gap because I don't know what it calls for.
Agreed. However, plugs should be visually checked for the iridium pieces. Also, I had an intermittent miss on my '03 Envoy. I checked every thing. Finally I found that when one of the plugs was inspected upside down (with the electrode up) it looked fine. But, when turned over (the position when installed) the ceramic part inside the plug was loose and would slide down covering the spark area. The engine seemed to run fine, but occasionally it would set a P0300. New plug, miss never returned.
Agreed. However, plugs should be visually checked for the iridium pieces. Also, I had an intermittent miss on my '03 Envoy. I checked every thing. Finally I found that when one of the plugs was inspected upside down (with the electrode up) it looked fine. But, when turned over (the position when installed) the ceramic part inside the plug was loose and would slide down covering the spark area. The engine seemed to run fine, but occasionally it would set a P0300. New plug, miss never returned.
I mentioned it early on in the threads, I did remove and clean the throttle body. I did it without spraying cleaner directly on, or inside of it. A post I seen on YouTube discussed damaging the throttle body by cleaning it, so I sprayed clean rags with cleaner and gently, and carefully cleaned and polished that thing front and back until it looked new. I have a spare throttle body now, think I'll clean that one too.
WTF!!! Ok, so i I did a fuel pressure test today, on the new fuel pump, came up with 56 psi, and 55 psi on my second test. So no issues with the fuel pump.
I'm still concerned with the fuel line repair, although it's working, I wonder if the fuel pressure can be checked at the fuel rail, just to verify there is no restriction?
I pulled all the coils last night and checked that they were all seated correctly, and the connections were all secure and all hooked up. No change. Tonight went over the ignition system and changed one spark plug, and one coil, with known good pnes, then switched it out and tried it in the next position, trying to locate a bad coil or bad plug. No change. While doing each plug/coil swap, I also did compression check. 1-3 (150 psi), 4 (155), 5 (140), 6 (130).
I also tightened any intake bolts I could reach. During this fiasco, I found that all 4 throttle body bolts were loose, I never tightened them all the way apparently. Again, no change. I also used dielectric grease on the coil gaskets, and the coil boots. No change.
I took it for test drive after clearing the code with my bluetooth scanner,
and drove around to see how bad misfire/skip was. Ran like crap, check engine light came on then went off with no change, when I parked it, the code hasn't come back yet but still ran like crap. Im sure code will be back today.
I'm at a loss here. Not sure if I should try to change throttle body and fuel line, or if there unrelated? I also cleaned air temp sensor. I have not touched O2 sensors, but if dirty could that cause a misfire? All new coils? Swap out PCM and then try security relearn procedure?
Any body got any idea's???
I'm still concerned with the fuel line repair, although it's working, I wonder if the fuel pressure can be checked at the fuel rail, just to verify there is no restriction?
I pulled all the coils last night and checked that they were all seated correctly, and the connections were all secure and all hooked up. No change. Tonight went over the ignition system and changed one spark plug, and one coil, with known good pnes, then switched it out and tried it in the next position, trying to locate a bad coil or bad plug. No change. While doing each plug/coil swap, I also did compression check. 1-3 (150 psi), 4 (155), 5 (140), 6 (130).
I also tightened any intake bolts I could reach. During this fiasco, I found that all 4 throttle body bolts were loose, I never tightened them all the way apparently. Again, no change. I also used dielectric grease on the coil gaskets, and the coil boots. No change.
I took it for test drive after clearing the code with my bluetooth scanner,
and drove around to see how bad misfire/skip was. Ran like crap, check engine light came on then went off with no change, when I parked it, the code hasn't come back yet but still ran like crap. Im sure code will be back today.
I'm at a loss here. Not sure if I should try to change throttle body and fuel line, or if there unrelated? I also cleaned air temp sensor. I have not touched O2 sensors, but if dirty could that cause a misfire? All new coils? Swap out PCM and then try security relearn procedure?
Any body got any idea's???
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go into the torque data and check which cylinders are not "happy" and go from there. Try spraying around areas to see if you have a vacuum leak somewhere.
P0302 all the sudden today. Changed coil again. Gone. Runs great. Think it may need to recalibrate to run better yet. All the new parts I think made a difference, but I still have some tinkering to do.
Thank you for your time and assistance, and to everyone else that helped, thank you too!
Thank you for your time and assistance, and to everyone else that helped, thank you too!
Mooseman
Moderator
Like I said, just needed to wait a bit for the actual cylinder code to manifest itself. At least it's fixed now 
Not sure if it's appropriate to add this here, or if it should be new topic.
Since getting the TB running, and it runs great I might add, I've noticed it shifts different. It only seems to be from take off (first), where it sort of winds out before it shifts into second. It's like it takes longer to shift. I noticed I can almost control the shift by letting off the gas, and then resume pressing the gas. I haven't tried out passing gear yet, so I don't know if it does then too. I tried once but couldn't really tell, it's hard to do in the city, I'll have to go out on the highway and test it. I already purchased a transmission filter/gasket, and plan to do a flush as soon as I get the fluid. MAY03LT has a good video for this, I wanted to add it here, for easy reference, and for others to access directly from this thread.
What would cause this change, it didn't shift like this before the new fuel pump, and the tune up.
Will the flush/filter,gasket change remedy the shift delay, and is there a specific brand of fluid recommend? I already have the gear oil and will do a drain and fill on the rear differential. I think I will do the front differential when I replace the universals.
Has anyone else experienced similar shift issues, or a delay in shifts?
Since getting the TB running, and it runs great I might add, I've noticed it shifts different. It only seems to be from take off (first), where it sort of winds out before it shifts into second. It's like it takes longer to shift. I noticed I can almost control the shift by letting off the gas, and then resume pressing the gas. I haven't tried out passing gear yet, so I don't know if it does then too. I tried once but couldn't really tell, it's hard to do in the city, I'll have to go out on the highway and test it. I already purchased a transmission filter/gasket, and plan to do a flush as soon as I get the fluid. MAY03LT has a good video for this, I wanted to add it here, for easy reference, and for others to access directly from this thread.
What would cause this change, it didn't shift like this before the new fuel pump, and the tune up.
Will the flush/filter,gasket change remedy the shift delay, and is there a specific brand of fluid recommend? I already have the gear oil and will do a drain and fill on the rear differential. I think I will do the front differential when I replace the universals.
Has anyone else experienced similar shift issues, or a delay in shifts?
Mooseman
Moderator