96 GMC Suburban runs rough

[Pastor Dave]

I have had the injectors cleaned at the shop 2 X, replaced the fuel filter, cap and rotor, wires, plugs and still no success. The codes change constantly the only one that stays consistent is the fuel injector on cyl. #5. Several of the plugs get such a white deposit built up on them that the entire plug end is covered - no spark. This occurs over short periods of time. No one has answers except pay me money to clean the injectors!

Other symptoms - the idol is inconsistent, when stopping the vehicle tries to lurch forward, when starting or setting the idol will periodically jump from 1000 to 1500 the vehicle smells like unburnt fuel. When you step on the gas there is no hesitation it has plenty of power - holding it back seems to be more of the problem.

It has 135,000 miles, 4X4, 350 vortec

any help would be greatly appreciated

[GMMerlin]

Originally Posted by Pastor Dave

I have had the injectors cleaned at the shop 2 X, replaced the fuel filter, cap and rotor, wires, plugs and still no success. The codes change constantly the only one that stays consistent is the fuel injector on cyl. #5. Several of the plugs get such a white deposit built up on them that the entire plug end is covered - no spark. This occurs over short periods of time. No one has answers except pay me money to clean the injectors!

Other symptoms - the idol is inconsistent, when stopping the vehicle tries to lurch forward, when starting or setting the idol will periodically jump from 1000 to 1500 the vehicle smells like unburnt fuel. When you step on the gas there is no hesitation it has plenty of power - holding it back seems to be more of the problem.

It has 135,000 miles, 4X4, 350 vortec

any help would be greatly appreciated

Do you know the code numbers?
The deposit on the plug may be oil or coolant residue(I can't tell you for sure without physically seeing them)
From what you are describing, I am not convinced you have an injector issue...also on that model truck, there is only one way to truely clean the injectors and that is with high pressure nitrogen.

[Pastor Dave]

I don't recall the codes, but will read them tomorrow and let you know. The plugs are covered with almost pure white hard deposits.
It does burn about 1 to 2 qts of oil per tank of gas. I have only added coolent one time since flushing the cooling system 1 1/2 years ago.
thanks for the help!

[GMMerlin]

Originally Posted by Pastor Dave

I don't recall the codes, but will read them tomorrow and let you know. The plugs are covered with almost pure white hard deposits.
It does burn about 1 to 2 qts of oil per tank of gas. I have only added coolent one time since flushing the cooling system 1 1/2 years ago.
thanks for the help!

Well there is your problem...oil consumption. 1 to 2 quarts per tank is too much.
What could cause this? Could be a couple things
1. PCV valve stuck open
2. Valve stem seals or guides worn
3. Internal leak of the intake gasket
4. Rings

[Pastor Dave]

Thank you. I will change the PCV valve and read up on the other three.
Are there any way for me to diagnose the last three mentioned? If not how would a shop diagnose them? I would like to be somewhat knowledgable so I can hopefully avoid throwing money away.

[Pastor Dave]

Days late this is what I found out.
The PCV Valve is ok. However, when the engine is running there is a great deal of suction when the pcv valve is removed or the oil cap. So mch so that the engine dies when they are removed. I am not sure if that is normal or not, but I was surprised at the amount of the suction.

Trouble codes PO305, PO430, and PO507 came up. No pending or Freeze codes.
The 305 and 430 have been there in the past.
The 507 is a new one.
I guess my real question is "do I need a new engine or should I spend money trying to fix this one?" It seems like I would be farther ahead to invest in the new engine unless this is a simple fix. What is your more educated opinion?

Thank you and happy new year. 05 - where did the time go?

[handymandp]

Sounds like rings to me. Try doing a compression test this will answer alot of questions. All cylinders should be running about the same pressure.