Poor throttle response Denali after long trip

[scottg918514]

I have seen carbon build up in the exhaust... I assume you already tried putting it in low gear and standing on the throttle to blow out the carbon...

I drive like a Grandpa, (I actually average 18.5 as indicated by the dash) in my LTZ (wish I had the Denali Engine). Every few weeks or so I have to really get on the gas, to clean out the carbon. If I do not it starts eating into my power and my MPGs

John

Hmmm, can't hurt. Do you have to put in gear, or just rev engine high in park?

 

[okfoz]

Hmmm, can't hurt. Do you have to put in gear, or just rev engine high in park?

Just revving the engine never seemed to do it for me. I had to take it on the road and just "get on it" Make sure the engine really revs high. IE, get on the expressway, and just punch it. Also it never seemed to work as well at higher speeds, I can usually get it cleaned out by the time I hit 60 mph...

You should be able to hold the trans down into a lower gear, One of two things will happen. 1) it will shift up regardless of what gear it is in. or 2) the Rev Limiter will kick in.

When I do it, I just step on the gas in Drive from a stop or really slow to get the carbon out. It might tick off the guy behind you, and make sure the coppers are not around, they might find it a bit odd... Usually don't have to go over 5500 RPM

Of course it could be one of many things that could be plugged, even dirty injectors. or plugged Catalytic convertor, BUT it is worth a shot regardless.

John

 

[Lancaster]

I can almost guarantee you need to clean your throttle body. The carbon gums up the inside of the throttle body. The plate gets hung up until enough input is received to overcome the resistance from the carbon - then whoosh - off you go.

Don't waste time with the snake oil. Get some throttle body cleaner (very important - not carb or brake cleaner) disconnect battery so the auto reset is not at a high rev. as it was previously compensating for the reduction of air flow by opening slightly. Remove it and make it look like new. I like using a toothbrush and a clean lint free rag.

---------- Post added at 09:47 PM ---------- Previous post was at 09:41 PM ----------

While you are in there - remove and clean the MAF too. Again only use MAF cleaner. Other cleaners will kill it and cost you $60 to replace. That and a new air cleaner, assuming your plugs and wires are the correct ones and are in good shape, you should be good for 20mpg+ on the highway. That is what I get even in the mountains of northeast pa.

---------- Post added at 09:57 PM ---------- Previous post was at 09:47 PM ----------

Just re-read and noticed you use a k&n. I used one for 225k on a car- certainly paid for itself in air filters but I also constantly had sensor issues. I think the oil really impacts sensitive sensors. Take it easy on the those tiny MAF wires.

 

[ezdaar]

Berry mans b-12 will remove any nasty crap on that TB with ease. Just remove it from engine and hose down the back side of it.

 

[scottg918514]

Update: went back to stock air filter and cleaned MAF again. Problem still there, but better. Going to clean throttle body (which I think I did less than a year ago).

I'm having similar issues with my daughter's Ford Fiesta, which I put in a K&N drop in air filter 2 yrs ago. Had codes (MAF), stalls sometimes (manual transmission), rough start. A few months back, I clear codes and replaced MAF. Still stalling sometimes and rough start. Last night I cleaned TB and MAF and duct work, cleared pending P0068 code, but didn't go back to stock air filter (not at store, ordered one online). Today it started fine and no stalls.

K&N swears their oiled filters can't foul MAFs or cause TB issues, but I'm definitely leaning towards them as the culprit for my MAF issues in 2 vehicles.

 

[Lancaster]

Hate to say it too because they seem like a great company. I did the same as you for years, spending hundreds on diagnostics and new sensors. I went back to the plain paper filters and have never had a problem. I have nothing against them personaly. I thought I would save money as I drive 30-40k per year and keep my cars for 2-300k. My experience is the stock filter is better.

 

[okfoz]

K&N seems to be a crap shoot. I have had good experiences and bad experiences. Some cars it seems to actually slow them down (does not make sense) I know from talking to people with the old LS1 engines that it made no difference at all to actually slowing them down. Which seems counter intuitive to think that better air flow would be detrimental.

The only thing I could come up with is the paper air filter creates a particular turbulence in the Cold air intake, as the air crosses the MAF (which is more or less a meter that the faster air flows across a wire or screen the voltage changes because it is cooled) If you got rid of this turbulence then it would not wash across the screen in a uniform way or in the way that the car/truck was used to reading so you get false readings.

Just a thought

 

[scottg918514]

cleaned TB and a noticeable improvement in throttle response. That seems to have been the culprit.