Expert: Skip Bollinger - 5/1/2007

Question
QUESTION: my problem is that when i hit the gas, my truck does not get up to speed as quick as it used to, and sometimes when im sittin at a red light, it will sputter a little bit almost stalling out. also when i hit the gas, there is a bad rattling noise that sounds like theres something loose on the engine but ive checked pretty much the whole engine and could not find anything loose, it kind of sounds like theres marbles in the engine, pretty loud. do you know what this might be, or maybe you know any known problems with that kind of truck?
ANSWER: Brandon,
  I'm a Parts Professional, NOT a tech but I have some ideas you might look at. The "marbles" sound to me sounds like "pinging". This can be caused by ignition timing too far advanced but I don't think the timing is adjustable on your engine. You might to have to ask someone smarter than I on that aspect. Compression ratio being too high for the gas we get today could be another problem. Now... the compression ratio was not that high from the factory but depending on how the truck has been driven, it could have a lot of carbon built up on top of the piston and combustion chamber to raise the compression ratio. You might try waiting until the tank is about empty and put in $5.00 worth of Premium and see if the noise goes away. IF it does, you just need to get a cleaner and get the combustion chamber area cleaned up.
  Brandon, I have some other ideas but there is a severe thunderstorm watch here and I'm going to shut things down and unplug the computer. Please send a follow up to this as I have some other ideas but want to hurry before the computer becomes a toaster.
Skip

---------- FOLLOW-UP ----------

QUESTION: hey skip, its brandon again. i got your email and i did try putting premium in it. the noise is not as loud as it was before with regular gas but you can still hear it rattling a little bit. i was also interseted in hearing about your other thoughts on what that might be. also, what kind of cleaner do you mean and how do i use it?

Answer
Brandon,
  Higher static compression ratios require a better fuel (more octane) or the fuel will not burn evenly, cause an erratic flame propagation across the top of the piston and cause the piston to slap against the cylinder wall causing the noise you are hearing.
  There are many products you can purchase but I'd just use plain old water. If you have ever torn down an engine that had a blown head gasket, sucking water into the combustion chamber, the top of the piston, the combustion chamber and valves are as clean as my wife's dentures!!
  What I'd do is remove the air cleaner to expose the air intake on top of the intake manifold. Have someone start the truck and hold the gas pedal to maintain about a 1,500 R.P.M.. VERY SLOWLY, pour a cup of water down the air intake. It should take you about 15 minutes to put that much water down the intake. What you are doing is "steam cleaning" the combustion chambers and piston tops. If you pour it too fast, you can hydraulically lock a cylinder. This could break a piston or, if too severe, split a cylinder wall so just do it slowly!!!  
  Now, when you clean something, the "dirt" (carbon) has to go somewhere. As it comes loose, you may hear noises from the piston crushing chunks of carbon between the top of the piston and cylinder head. I have never seen this hurt an engine but it may bother you. OPTION 2:
  As above, remove everything so you can get to the air intake. Instead of water, take a 1/2 cup of transmission fluid. It is a very high detergent lubricant. Again, have someone start the truck and rev the engine to 1,500 and hold it there. Pour a 1/2 cup of transmission fluid down the air intake VERY SLOWLY. When you get to 2oz. to go, just pour it down quickly and have them shut off the engine (if the trans fluid doesn't kill the engine). Let is sit over night to soak the carbon. This will soften the carbon and make it easier to expel from the combustion chamber. The next day, start it, put it in low and drive it up to about 30 mph and back off the gas, do it about 10 more times. It will smoke like crazy. If you choose not to drive it, read on.. PROBLEMS:
 Now, all this crap has to go somewhere. IF you remember High School Chemistry, an object will not burn twice. Carbon in a cylinder is a product of burnt fuel but mostly oil. It won't burn again and the chunks have to go somewhere... catalytic converter... It can clog up a converter. IF you have the time, the tools and slack noise restriction laws, I'd take the exhaust loose before the converter so any crap that comes out doesn't get into the converter. That sucker will be loud but not for that long. Just for grins, I'd soak a large piece of cardboard in water and put under the exhaust just to see what comes out. Soak it so it doesn't catch on fire.. Keep a hose close just in case. IN CLOSING:
  Water is going to produce steam. Transmission fluid is going to produce a LOT of white smoke. Expect it and don't worry about it. Once you have done either of the above, I'd change the oil and put in new spark plugs. We are working on a vehicle that is over 20 years old so anything we put in the cylinders, some will probably end up in the oil pan. Also change the spark plugs because as carbon comes out of the combustion area, it can imbed itself in the plugs causing irreversible fouling.
  ALL of this speculation is contingent that the "noise" was reduced by running Premium fuel. That leads me to believe excessive compression ratio caused by carbon in the combustion area. Brandon, I hope I'm not leading you down a dead end. From what you have said, this is what I believe is the problem. Please don't be upset with me if it isn't. I'm a Parts Professional, NOT a Tech, Okay? Let me know what happens..
Skip