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Discussion Starter · #1 ·
Wife's 03 Envoy 6 cyl doesn't accelerate well, won't shift into higher gear until about 45 mph, 5500 rpm. Lower gas mileage as well. Went to check plugs and coudnt lift off the coil caps--long bolts came off easily but caps wouldn't pull off. 2 qstns: 1. Am I right to check plugs for these symptoms, and 2. tips on getting coil cover off?

Thanks
 

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2003 chevy trailblazer_ls
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Please fill you the user CP so we know what you have. Have you cleaned the throttle body? Is the cooling fan sounding a lot louder? If this sort of happened all at once I doubt it is the plugs. You ever use tectron gas treatment or use top tier fuel? Is the check engine light on?
 

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Discussion Starter · #3 ·
Robert, have not used any additives at all ever, no other noticeable symptoms or noises. Have not cleaned the throttle body. Only use 87 octane.

Any suggestions would be greatly appreciated, and thanks.
 

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Yes sir, clean the throttle body and put a can of tectron in the tank. You can use seafoam if you would rather, 1/2 down down the intake and 1/2 in the tank.
 

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2004 chevy trailblazer_lt
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Just a shot in the dark, but could something be plugging the exhaust? Sounds strange that all of a sudden (like one day it was fine, and then the next it was like this?) this happened, so I would check the exhaust. Maybe a clogged catalytic converter? I'm not sure how you check the exhaust, but that's what I'd try and do. I'm guessing you don't have a code reader, but it'd sure be nice to see what codes it's set off. And if you do decide to run the additive, it's Chevron Techron, and you can get it at pretty much any autoparts store, maybe even Walmart. If you go to the parts store, see if they can pull your codes real quick and maybe let us know which ones they are.
 

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2004 gmc
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Most of the really disastrous items to cause those symptoms should also light up the Check Engine Soon light. The coil packs pull straight up off the plugs, but they can be sticky. Put it's probably not plugs because one or two intermittent plugs would cause stumbling that you would have mentioned, and also set off the CEL light and set codes.

How many miles, and does it have any other history of service issues in its past? Fluids changed at the recommended intervals? Air filter checked, and not by the untrustworthy Jiffy Lube idiots?

We're trying to get a case history of the vehicle so we (like Dr. Gregory House and his team) run an informed diagnosis. Sticky throttle bodies often cause erratic idle RPMs and stalling, but may give symptoms on acceleration. A collapsed or clogged air filter would harm driveability and mileage as you're reporting.

Have you consulted a local mechanic or dealer or is trailvoy your first stop?
 

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2003 gmc envoy_slt
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This may or may not help but I had the same problem a couple years ago.

When I first bought the car, i was putting in 89 and 91 octane all the time, when the gas prices went up I started putting 87 octane. I had the same feeling after a year or so- sluggish, slow acceleration, gas consumption- (i was getting 12 mpg hiway and less than 10 for city. No CEL, no warning, nothing.

I first changed the spark plugs - still same problem
Cleaned my Throttle body - helped but was still sluggish
Changed my Fuel Filter - helped with mpg but still sluggish

I had a feeling it was the catalytic converter, so I decided to bring it to Firestone (bad idea after all). They said it was the converter, had it changed and the problem was solved.

I was still putting in 87 octane. After 2 years, it happened again. Again it is the catalytic converter. I have determined that putting 87 octane is the problem. Where I am, there are no top tier gas that I know of. Mobil, Sunoco, Citgo, very few Shell, and BJ gas are the only ones near me.

Hope this helps...:undecided
 

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2005 chevy trailblazer_lt
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I had a similar problem in 2006 with my '05 TB. Got more and more sluggish every week. Finally, I took it in to a shop and they told me that there was build-up in the fuel injector. They said that with that engine (4.6) the holes in the fuel injector are particularly small and can get clogged easilly. I figured I needed major work, but they charged me $30 (if I recall right) to clean it out, and it's been fine ever since.
 

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Does the Chevron Techron work well at cleaning injectors? i have typicaly used prestone in previous vehicles with decent results. I just bout my TB and i want to make sure its running efficently.
 

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Does the Chevron Techron work well at cleaning injectors? i have typicaly used prestone in previous vehicles with decent results. I just bout my TB and i want to make sure its running efficently.
chevron techron is a very good product.
so good- that GM also resells it at the dealership (they sell it in a GM bottle).
But the techron also cleans sulfur buildup in the fuel system.
 

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With the odd shifting pattern, as well as no-power, it sure sounds like a clogged cat. The I6 really likes to breath, plug either the intake or exhaust and they don't run well. If I'm right, you'll eventually get a CEL for low catalytic efficiency detected. - Problem is the truck will barely run by the time that happens.
 

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Just curious, but does your engine reach operating temperature efficiently? I'm thinking something with the cooling system as well...

And I have had good results with techron as well, bad I've had better results with a whole can of seafoam in a full tank of gas. It's cheaper than techron and also works much better IMHO.
 

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Hi, I have Trailblazer 2004, lately I noticed when starting the engine it will crank but not start from first time, some times from 2nd or 3rd try. I took it to a shop to check the battery as it has a life of almost 2 years; he checked and said it is weak, so I replaced it. When engine start it was ok. But next morning problem came back again. So I took it to the dealer, they said it is fuel pump, it gives low pressure. So I decided to change the pump and filter. After the replacement Problem solved.

I used to add 95 octane fuel, after the replacement of the fuel pump and filter I filled the half tank with 98 octane and added GM fuel treatment solution to the tank to clean the engine from inside. After I used all that fuel I refueled again with 95 octane full tank. I notice a fuel consumption. My full tank before was making about 370 KM but now it came down to 250 KM per full tank. I took the car to the shop they checked the engine for any fault code but every thing was ok.

:weird:What went wrong here please advise, thanks.
 

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Honestly...I would just stick with 87 Octane Regular. There's no point in going to a higher grade unless you're tuned for it. Eventually the PCM will calibrate on its own to use less fuel.
 

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Honestly...I would just stick with 87 Octane Regular. There's no point in going to a higher grade unless you're tuned for it. Eventually the PCM will calibrate on its own to use less fuel.
:iagree:

This may or may not help but I had the same problem a couple years ago.

When I first bought the car, i was putting in 89 and 91 octane all the time, when the gas prices went up I started putting 87 octane. I had the same feeling after a year or so- sluggish, slow acceleration, gas consumption- (i was getting 12 mpg hiway and less than 10 for city. No CEL, no warning, nothing.

I first changed the spark plugs - still same problem
Cleaned my Throttle body - helped but was still sluggish
Changed my Fuel Filter - helped with mpg but still sluggish

I had a feeling it was the catalytic converter, so I decided to bring it to Firestone (bad idea after all). They said it was the converter, had it changed and the problem was solved.

I was still putting in 87 octane. After 2 years, it happened again. Again it is the catalytic converter. I have determined that putting 87 octane is the problem. Where I am, there are no top tier gas that I know of. Mobil, Sunoco, Citgo, very few Shell, and BJ gas are the only ones near me.

Hope this helps...:undecided
How did you arrive at this conclusion? These engines were designed to run on 87 octane. A converter going bad in a relatively short period of time is either a bad converter or indicative of a mechanical problem.

I have tried premium octane fuels and EVERY time I have noticed decreased power and lower MPG.
 

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my truck was doing the same thing...
I cleaned the Throttle Body and it was like I had a new vehicle...
It seriously made that much of a difference
 

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In the country I am working in (UAE)they have 90, 95 and 98 octane and I have been using 95 for 3 years. is there any tuning process or calibration I need to do to restore fuel economy back.
 

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chevron techron is a very good product.
so good- that GM also resells it at the dealership (they sell it in a GM bottle).
But the techron also cleans sulfur buildup in the fuel system.
:iagree: Chevron Techron is AWESOME. I use it in my TB every 3,000 miles (thats what the bottle reccomends also). Techron Offers Much Better Results than other fuel additives:
Capabilities Techron Concentrate Plus: Leading Competitor
Cleans carburetors Yes: Yes
Cleans fuel injectors Yes: Yes
Cleans intake valves and ports Yes: Yes
Cleans combustion chambers Yes: No
Restores lost power and performance Yes: Yes
Lowers emissions Yes: Yes
Relieves cold startup problems Yes: No
Reduces deposit-related engine knocking and pinging Yes: No
Cleans sulfur deposits from gas gauge sensors Yes: No
Protects against fuel system sulfur deposits Yes: No
Protects gas gauge sensors from malfunctioning Yes: No
Contains PEA chemistry Yes: No

Any other additives including seafoam especially can really cause problems with the engines parts. I heard of just after one treatment with seafoam it caused parts to fail. (search around trailvoy.com you can find a couple of instances).

Pick up two bottles of the techron 12 gallon additive. Add them BOTH =24 gallons. because most TB's have 21.7 gallon tank and some have 25 gallon tanks. Put those BOTH in around 1/4 tank or so put the chevron Techron in FIRST (very important). Then Just punch the gas a few times on the highway to get the full effect of the techron.
:eek:fftopic: BTW My TB is running great. I get around 22-24MPG on the highway with passengers in it. I love my SUV TB.
 

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This may or may not help but I had the same problem a couple years ago.

When I first bought the car, i was putting in 89 and 91 octane all the time, when the gas prices went up I started putting 87 octane. I had the same feeling after a year or so- sluggish, slow acceleration, gas consumption- (i was getting 12 mpg hiway and less than 10 for city. No CEL, no warning, nothing.

I first changed the spark plugs - still same problem
Cleaned my Throttle body - helped but was still sluggish
Changed my Fuel Filter - helped with mpg but still sluggish

I had a feeling it was the catalytic converter, so I decided to bring it to Firestone (bad idea after all). They said it was the converter, had it changed and the problem was solved.

I was still putting in 87 octane. After 2 years, it happened again. Again it is the catalytic converter. I have determined that putting 87 octane is the problem. Where I am, there are no top tier gas that I know of. Mobil, Sunoco, Citgo, very few Shell, and BJ gas are the only ones near me.

Hope this helps...:undecided

Aftermarket catalytic converters are known to fail within a few years because they have much less precious metal in them than the factory cats. It happened on my brothers 2000 Silverado 4.8l. Got a new one put in for inspection and it went bad and threw a code, not even 2 yrs later.
 
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