Suburban miss fires after going up a hill?

[Jeff V]

I have been tring to solve the misfire issue for almost two years. This past week $300 more, with the same result. Don't spend another dollar sell it trade it but don't put another dime into the thing. Too many people have the same problem and after reading all these posts nobody has found the smoking gun. I am told there is a problem with the design of the heads and they must be REPLACED with NEW ones. But no guarantee. My advice sell it!!

[Fireplug]

It cant be sticking valves.
Everyone in here has said the problem started after having a intake manifold gasket done right??
So why would it not do this problem before the gasket was done??? only after.
I have 104564 miles on mine (5.7) and it has never had a gasket done and has no miss at all.
I just dont buy the sticking valve Job
My money in on a sticking egr valve. If you take a running engine at idle and open the egr valve what happens the engine misses and or stalls now add a heavy load and bingo you have a very bad miss that was not there before the gasket was done.
Fireplug

[LastOne]

MIne did it before I had to replace the gasket, about 20K miles before. I replaced my cam sensor and it did not help much. I have not found a scanner to check the cam retard but I have moved the dist around a bit. I too think it sucks. A truck having this kind of common problem. I am leaning toward a Tundra if I ever buy something new. GM, Ford, and Dodge don't seem to care after they have your money. Lots of Honda and Toyota cars for sale in my local paper with near 200K on them and there is still a buyer for them.

[rksand]

My 94 has done this often and usually I find a bad wire or plug. Get out at night and see if you have any arching going on. I bet you find a light show.

[bg862]

I too saw a light show under the hood and replaced all plugs (AC/Delco) and wires (Bosch). The light show has tamed considerably, but still see a constant flashing around one particular spark plug. I don't know the numbering system, but it is on the left (driver side) second back from the radiator. I swapped plugs and the problem stays at the same cylinder. Don't know why. Anyone?

[Fireplug]

That would be cylinder number 3
1,8,4,3,6,5,7,2, is the fireing order.
Driver side has cylinder 1,3,5,7,Pass side 2,4,6,8,
The wire that is still sparking please check that the rubber boot is all the way down on the plug.
There should be NO sparking at all . If there is that means there is a voltage leak in the wire.
I have seen new wires leak so try switching wires and see if the sparking goes with the same wire.
You can use a spray bottle with water in it and spray a mist on it to see where the wire is bad.
Fireplug

[bg862]

Yes, #3 is the one.
I will try swapping wires. The boot is all the way on the plug. Thanks for the tips!

[Houston54]

I had the severe miss-firing probem on my 99 Sub. The mechanic was unable to get a fix on the problem but suggested I replace the plugs, cap and rotor. This was done using all delco parts (platinum plugs) and I have not had the problem since. I think if it does return then I will replace the EGR valve as it is not expensive and easy to get to. I did not replace the plug wires yet but will if the problem returns.

The mechanic checked all the related sensors and found all to be in working condition. I think the problem is a result of one thing going wrong that is causing a cascade effect.

[LastOne]

Another forum, Ten Mag Chevy truck had a thread running, person with the problem like described here reports a cracked valve seat..... Some Beach!!!!!

[jb128]

Told by dealer its the injectors, which they say they now have a service bulletin that reccomends replacing them for about $850 verus cleaning them for about $250.

Has anyone replaced the injectors? Did it fix it? I may just clean them and trade it in - my 2002 is paid off now anyway!

[Jeremy-WI]

I replaced injectors in my 96 K1500 but not because of misfire, I had a couple leakers and needed a new fuel pressure regulator. Cost me $270 for parts delivered to the door, took two hours to replace.

After I paid to have my intake manifold gaskets replaced I had a misfire at light load cruise- 60 mph with foot barely on throttle- and I'd just feel it misfire a little. Hooked my auto xray scanner up to it and checked the cam retard- it was -11 degrees and its supposed to be 0 degrees +/- 2 degrees. Once I got it to 0 degrees the misfiring was gone. I wonder if you would get misfiring under load(or heavy acceleration) with the cam retard too positive

[back2life]

Originally Posted by Fireplug

That would be cylinder number 3
1,8,4,3,6,5,7,2, is the fireing order.
Driver side has cylinder 1,3,5,7,Pass side 2,4,6,8,
The wire that is still sparking please check that the rubber boot is all the way down on the plug.
There should be NO sparking at all . If there is that means there is a voltage leak in the wire.
I have seen new wires leak so try switching wires and see if the sparking goes with the same wire.
You can use a spray bottle with water in it and spray a mist on it to see where the wire is bad.
Fireplug

DESCRIBE EXACTLY HOW YOU USE THE SPRAYMIST TO FIND BAD WIRES! I HAVE THAT SAME PROBLEM WITH THE LIGHT SHOW UNDER THE BOOTS!

[Fireplug]

With the engine running spray a mist of water on all ign parts , wires , plugs , coils and look for any sparks. If there are any sparks the there is a problem. Lets say the ign wire boot has sparks comming from it . The wire is bad or the spark plug is cracked. To pin point the correct 1 switch the sparking wire with a nonsparking wire and see if the light show goes with the wire or stays at the cylinder if it stays at the cylinder then you have a cracked spark plug. also mad sure that the ign wires are all the way down on the plug and snap or click tight.

[yardion143]

Originally Posted by 99subhelp

I have a 99 chevy sub with the 5.7 and I had the seal replaced under the intake manifold and now it miss fires when I climb a hill and get to peak it will missfire badly. It will never do it when your climbing the hill or on flat ground but only when the engine has been enganged on the hill and then comes off of a little. It only happens at speeds over 50 MPH. I have replaced the plugs, wires, cap & rotor, and the fuel filter. The dealer wants to replace all these parts again and charge me 500 for it. I need some Ideas. I took it to another mechanic and he sees it misfire with the scope while driving but can't pinpoint it.

Thanks

Tony

Hi,
check your timing...maybe distributor was loose enough to be turned by mechanic torquing down the manifold.

[frootl00p3]

Originally Posted by Fireplug

It cant be sticking valves.
Everyone in here has said the problem started after having a intake manifold gasket done right??
So why would it not do this problem before the gasket was done??? only after.
I have 104564 miles on mine (5.7) and it has never had a gasket done and has no miss at all.
I just dont buy the sticking valve Job
My money in on a sticking egr valve. If you take a running engine at idle and open the egr valve what happens the engine misses and or stalls now add a heavy load and bingo you have a very bad miss that was not there before the gasket was done.
Fireplug

Um, mine does it and I have not had the gasket job done. My suburban has 90K miles on it. Haven't put any money into it yet. Love my truck wouldn't sell it, just want to fix it. think there might be something to the fuel system cleaning idea. Had a 77 chevy, put bad gas into it one time, it ran like crap for months. I went through 30 plus fuel filters, and it always misfired until it eventually stalled, at which time (rain, hail, snow or never sun) I had to replace that darn fuel filter on the side of the road.
Jodi