Cant figure out P0300 and loose steering feel

[JWUAV]

I have a 2004 tahoe with 176k miles on her. I have a random issue that causes her to stumble while driving. It happens randomly while driving and at idle. I've tried to pinpoint a speed that it happens around, hot or cold temp, load on motor and no luck. It will happen for about 4-5 seconds and the CEL flashes on my drive and then everything goes back to normal. It feels like you are driving into a strong wind and you can hear the miss in the exhaust. Bellow is what I have done so far:

New fuel filter
Ran 3 tanks of fuel through with injector cleaner (thought maybe a dirty injector or line)
Fuel pump pressure is at 53psi with key on and without engine running
Fuel pump pressure is at 46psi with engine running
Cleaned MAF
Cleaned Air Filter
Fuel regulator is not leaking fuel on the vacuum line side
Cleaned Intake

I am hoping that it is not the fuel pump but that is my next stop once I get some money set aside for one. Any one have any thoughts on something I missed or can point me in a better direction? It seemed to get better after cleaning MAF and Air Filter, it didn't stumble as long, maybe only 1-2 seconds and no flashing CEL.

My other problem is a loose steering feeling. She has a 6" rough country lift on 33x12.50x20 Kumho MTs. Again, Bellow is what has been replaced:

Gearbox with a red head unit
Idler arm
Idler arm bracket
Pitman arm
Driver and Passenger Upper and Lower ball joints
Driver and Passenger Inner and outer tie rods
Driver and Passenger upper and lower control arm bushings
Driver and Passenger hubs
Driver and Passenger sway bar links
Driver and Passenger wheel hubs
Driver and Passenger shocks
Driver and Passenger rear upper and lower control arms with bushings
Driver and Passenger rear sway bar links
Driver and Passenger Rear shocks
Driver and Passenger Rear springs
Alignment checked
Wheel balance checked (road force)
Hub centric rings for wheels
Intermediate steering shaft

When I did the lift I did everything I could think of but the loose feeling is still there. I do not have an EVO sensor on it, again any help on something I overlooked or a direction to look in would be appreciated!

 

[swathdiver]

John, it's hard to say, are there any other codes stored in memory? Could be plug, plug wire, coil pack, catalytic converter, etc. A good scan tool will sure save a lot of guessing and throwing parts at this truck. Do you have access to a Tech2?

 

[JWUAV]

I dont have access to a Tech2, It does have new plugs, wires and coils with about 25k on them. I replaced them when I did new knock sensors...My rear bank was rusted bad. It also got new 02 sensors about 1k ago due to short on bank 1 sensor 1. With how random it is and how quickly it comes and goes I may just have to wait unitl something actually goes out.

 

[M1Gunner]

Your crank sensor may be going out

 

[Chubbs]

If the CEL is flashing, you need to get serious. Waiting for something to completely fail is going to cost you more & more as the catalytic converters and oxygen sensors get roasted with raw fuel. It may have already come to that. If it was my truck I would just replace the intake gaskets and fuel injector O-rings, test all of the FI for spray pattern while they are out. Cheapest attempt @ repair without spec diagnosis & it's all prevent maint in the event a repair is not successful.

Take out each SP and wire. If 1 of them is faulty it will be evident. It's a good exercise to inspect the electrodes too, see what kind of shape they are in & if any specific cylinders are taking more punishment than others.

 

[JWUAV]

CEL is no longer flashing. I re cleaned the MAF and throttle body and the duration is much shorter now, maybe 1-2 seconds. I can now accelerate when it is happening and it does not stumble anymore. I would think if plugs or wires were at fault I would have a code to that cylinder not a the random misfire one correct? Ill pull them today and look and report back.

 

[JWUAV]

If the CEL is flashing, you need to get serious. Waiting for something to completely fail is going to cost you more & more as the catalytic converters and oxygen sensors get roasted with raw fuel. It may have already come to that. If it was my truck I would just replace the intake gaskets and fuel injector O-rings, test all of the FI for spray pattern while they are out. Cheapest attempt @ repair without spec diagnosis & it's all prevent maint in the event a repair is not successful.

Take out each SP and wire. If 1 of them is faulty it will be evident. It's a good exercise to inspect the electrodes too, see what kind of shape they are in & if any specific cylinders are taking more punishment than others.

Pulled the plugs out and with wires attached they are getting spark, none of the electrodes look damaged, slight grey in color and dull. I will pull the injectors and test, I can make a manual pulse to clean and check the pattern...any issue with doing this or do I need to have a shop check them out.

 

[Tonyrodz]

I'm having the exact same problem, but it's in my 05 express with the 4.8. Sub'd for progress. I also had my intake gaskets, plugs and wires replaced too with no results.

 

[Chubbs]

Bench test with a battery and can of gasoline is more than OK. I have a spare connector for the FI that I snatched from a junkyard or something; works great with a couple of alligator clips, piece of tubing and go to town

 

[JWUAV]

Bench test with a battery and can of gasoline is more than OK. I have a spare connector for the FI that I snatched from a junkyard or something; works great with a couple of alligator clips, piece of tubing and go to town

Noticed today in the drive thru that I have a ticking noise happening now. I listened with a mechanics stethoscope and I can't pin point the sound but it is in time with the injectors and sounds exactly the same when I place the stethoscope on the injector plugs. I plan on testing and cleaning the injectors tomorrow or next weekend, I know you can hear injector tick and I can with the hood up but when the hood is closed I can only hear this tick on the drivers side, my first thought was lifter but the noise is only evident on the fuel rail and injectors, no noise on exhaust manifold either. Hopefully this is the fix i need.

 

[swathdiver]

Being that the problem lessened with you cleaning the MAF again would have me taking a hard look at it. Once you tally up all the parts thrown at this, compare that to a Tech2 and consider what your time was worth too.

 

[muncie21]

My 99 tahoe would occasionally throw a death wobble while driving. I replaced most of the front suspension in an attempt to fix it. Once I replaced the center link, all was good.

 

[JWUAV]

Got P0303 today, hopefully the computer was able to find the misfire and this isn't a bi-product of the original issue. I will be switching out the plug, wire and coil today to see if the problem moves cylinders or stays. If it stays this would lead me to believe injector or internal problem....Am I on the right track here? I sprayed brake cleaner around the intake gaskets today with her running and didn't notice any change that would make me believe I had a leak there. Checked the few vacuum lines I saw and again nothing. I will report tomorrow for the fix! (I hope).

PS, where would I get a tech 2 and about how much are they?

 

[JWUAV]

Swapped the plug, wire, coil AND injector to another cylinder and were back to random misfire. I think Im just gonna drop it off at a shop and see what they say.

 

[sonic_the_hedgeh]

I have a 2004 tahoe with 176k miles on her. I have a random issue that causes her to stumble while driving. It happens randomly while driving and at idle. I've tried to pinpoint a speed that it happens around, hot or cold temp, load on motor and no luck. It will happen for about 4-5 seconds and the CEL flashes on my drive and then everything goes back to normal. It feels like you are driving into a strong wind and you can hear the miss in the exhaust. Bellow is what I have done so far:

New fuel filter
Ran 3 tanks of fuel through with injector cleaner (thought maybe a dirty injector or line)
Fuel pump pressure is at 53psi with key on and without engine running
Fuel pump pressure is at 46psi with engine running
Cleaned MAF
Cleaned Air Filter
Fuel regulator is not leaking fuel on the vacuum line side
Cleaned Intake

I am hoping that it is not the fuel pump but that is my next stop once I get some money set aside for one. Any one have any thoughts on something I missed or can point me in a better direction? It seemed to get better after cleaning MAF and Air Filter, it didn't stumble as long, maybe only 1-2 seconds and no flashing CEL.

My other problem is a loose steering feeling. She has a 6" rough country lift on 33x12.50x20 Kumho MTs. Again, Bellow is what has been replaced:

Gearbox with a red head unit
Idler arm
Idler arm bracket
Pitman arm
Driver and Passenger Upper and Lower ball joints
Driver and Passenger Inner and outer tie rods
Driver and Passenger upper and lower control arm bushings
Driver and Passenger hubs
Driver and Passenger sway bar links
Driver and Passenger wheel hubs
Driver and Passenger shocks
Driver and Passenger rear upper and lower control arms with bushings
Driver and Passenger rear sway bar links
Driver and Passenger Rear shocks
Driver and Passenger Rear springs
Alignment checked
Wheel balance checked (road force)
Hub centric rings for wheels
Intermediate steering shaft

When I did the lift I did everything I could think of but the loose feeling is still there. I do not have an EVO sensor on it, again any help on something I overlooked or a direction to look in would be appreciated!

I did have a similar problem with my 2004 Yukon Denali XL. I had error codes showing lean on both banks. So I ran Royal Purple Injector cleaner through and the error codes are gone now.

I did some research before choosing an injector cleaner and royal purple was said to be very good..

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[JWUAV]

Finally heard back from the shop (family friend that didn't charge so it took forever) and my coils are bad. 5 of the 8...Luckily they are under warranty and I will be getting new ones to put on tahoe, any reason that many of the new coils would have gone bad? Im driving now on some spare units that he had at his shop and its running great.

 

[Tonyrodz]

That's awesome that you were able to figure it out.

 

[sonic_the_hedgeh]

Finally heard back from the shop (family friend that didn't charge so it took forever) and my coils are bad. 5 of the 8...Luckily they are under warranty and I will be getting new ones to put on tahoe, any reason that many of the new coils would have gone bad? Im driving now on some spare units that he had at his shop and its running great.

I don't know about regular yukon's but my 2004 GMC Yukon Denali I was going to change the fuel filter and found out it has a filter within the tank itself. Yes I am still not sure of the cause of mine. Although strange after using royal purple the CEL doesn't come on steady like it used to.

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