HELP!

[DaveL]

I have gone back to posts made in 2009 and have not seen anything like I'm looking for....

I have a 2000 Tahoe Limited with 250,000 miles on her..She runs pretty good..Been pampered most of her life..never been driven hard by me..Done some towing but nothing really major...

The old girl started missing under a load and threw a P302 code...So I changed plugs,wires,cap and rotor...they needed it bad..I know all of the above have over 150,000 miles on them...I don't know how the rotor and cap were even throwing fire...BAD SHAPE

Now she runs great under a load and has all kind of power...But...she will sometimes have a slight miss at idle and it shows a P304 code now..

I've back tracked all my wires..rechecked gap..cleared the code..and it comes back..and I still have an intermittent miss at idle..it's so slight most people don't feel it but throws the P304...and it's time for tags and it wont pass inspection with the code...Any ideas?

 

[Slammed]

Googled it found this which sounds right.
P0304 code means that the computer has detected that one of the engine's cylinders is not firing properly. In this case it's cylinder #4. Concentrate your efforts on this cylinder.

Symptoms may include:
the engine may be harder to start
the engine may stumble / stumble, and/or hesitate
other symptoms may also be present

Causes
A code P0304 may mean that one or more of the following has happened:

Faulty spark plug or wire
Faulty coil (pack)
Faulty oxygen sensor(s)
Faulty fuel injector
Burned exhaust valve
Faulty catalytic converter(s)
Running out of fuel
Poor compression
Defective computer

Possible Solutions:
If there are no symptoms, the simplest thing to do is to reset the code and see if it comes back.

If there are symptoms such as the engine is stumbling or hesitating, check all wiring and connectors that lead to the cylinders (i.e. spark plugs). Depending on how long the ignition components have been in the car, it may be a good idea to replace them as part of your regular maintenance schedule. I would suggest spark plugs, spark plug wires. Otherwise, check the coils (a.k.a. coil packs). In some cases, the catalytic converter has gone bad. If you smell rotten eggs in the exhaust, your cat converter needs to be replaced. I've also heard in other cases the problems were faulty fuel injectors.

 

[DaveL]

Thanks for your reply Slammed...

Like I said earlier..I have back tracked every thing as far as the new tune up goes..all is good there..

I dont feel as there is a problem with compression or a burnt valve..she runs to good for that..Like I said, she runs great now. All kinds of power...And when the miss is happening she idles so smooth it's silly...The miss comes and goes and I can't see a pattern length to it..it drove for 2 days with no code popping up then it appears..I cleared it with my little cheapo code reader and it came back on within 15 mins...

I've put a bottle of Seafoam in the tank..about 10 gallons of fuel in it so it will be a pretty strong mix..

I think my next step will be to check the fuel pressure to make sure it holds stable...

Any other ideas will be appreciated! Again, thanks for your reply.
And any one else that would like to reply please feel free to chime in..maybe some one else has seen this happen before?

 

[lesterl]

P0304 is cylinder 4 missfire.

Swap plug wires from #4 and #3 (switch wires from side to side) you can always get a bad wire.

What brand of Cap/Rotor/Plugs/Wires did you use? House brand or some others are junk... OEM is good for wires and plugs and cap/ rotor.

 

[twicepipes]

I have had problems with brand new aftermarket caps in the past. GM is the
way to go.

 

[DaveL]

Thanks for the input LesterL and Twicepipe...

I picked up a fuel injector pump tester yesterday..I will try swapping the wires before I check the pressure at the test valve..

I do know that I will have to do something as far as the injectors go because it acts like the pressure drops off over night..I have to turn the key and let the pump run once and then turn the key again to get a good start..if I don't it acts like there is no fuel in the system and just turns over a long time before it starts...

I don't know if I will get time to do the pressure test today but I will swap wires and see what happens today for sure...

Everything I have ever had to change out on her has been OEM/GM/AC DELCO

Again, Thanks for the input!

Oh yeah...I turned the service light off yesterday and drove about 60 miles up and down the interstate giving the injectors a workout and the light hasn't come back on yet...

 

[lesterl]

With your difficulty starting you may have a fuel pump getting weak on ya, battery getting weak, or something of the like.

Do you know if you have the CSFI or MPFI upgrade injectors? To check if you dont know, pull intake tube off Throttle Body, open throttle plate and look down in. If you see small black tubes then you have CSFI, if you see medium white with 2 wires then you have the MPFI upgrade.

I would be running a fuel injector cleaner also on a regular basis as you dont want the poppets to plug up and the MPFI injectors either.....

 

[DaveL]

You may have something there LesterL...My battery has been playing hell this winter..

We've had a colder than usual winter here in Chattanooga..I've woke up to a dead battery a few times...If the truck sat for 3 days it would be dead..as long as it's driven daily it starts...

I've ran 1 1/2 bottles of Seafoam in the gas..not on a full tank so the mix would be strong..I got the truck through emissions Friday with the service light being out..it hasn't come on since last Thursday so it may have been a dirty injector..

I need to go by Autozone and let them check the battery..it's about that time. I bought their best battery a few years back and it started acting like this about 18mo in and they swapped it out for a new one...then another 18mo goes by and the same thing..except I had to purchase a new one(in the truck now) and it's about 18mo in on this one...

I believe I will run another can of Seafoam through the tank and maybe through the top side to clean any deposits on the valves and see where I'm at then...

Oh..I replaced the fuel pump about 3-4 years ago

 

[lesterl]

News?

 

[DaveL]

Went by Autozone..the guy checked the battery and said it's fine..told me to go home and put the it on a 2 amp trickle charge and it would be fine...

I bit my tongue because I didn't have time to argue the fact that if it needed to be trickled every so often the battery is shot...smh.

This happens to these Autozone batteries every 18mo...this is the third one I've had installed...you buy one then in 18mo it dose this sh!#...they give you another, then 18mo and it dose the same thing...

 

[lesterl]

Nice....