I'm trying to determine what's causing a very apparent miss during moderate acceleration. It does not occur under light or heavy acceleration. I routinely use fuel injection cleaner to keep things from glogging up, and I have replaced the spark plugs. Any thoughts as to what it might be?
I'm just about at 98,000 miles, and regularly maintain things.

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Bob N

what plugs did u use??

did u replace the wires?

also make sure your rear wires are at least an inch away from the O2 wire...

where is crestwood in relation to palatine, barrington or lake zurich?

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-Juan

No bonnie!
93 s10 ex cab: 2.8: t5: exhaust: tbi mods. 5.3, 76mm, and a D.r cam on a stand

Was it missing before you changed the plugs?

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2006 Chevy Monte Carlo SS

Also, what brand FI Cleaner do you use? Only a few actually do any good.

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Bye Bye:

RIP sandrock

It sounds like it could be a vacuum leak. Look at the tee under the supercharger snout as a place to start.

I used Autolite APP606 plugs, and yes, it was doing it before I changed the plugs. I've been using Gumout Regane fuel injection cleaner.
I think I'll take a look at the tee under the supercharger. I replaced the black plastic elbow last year when it had a crack in it, and I know the tee may have a crack in it too.
Thanks for the reminder Mark.
Gonzo, Crestwood is located about 13100 South and 4800 West. A long way from Palatine, Barrington and Lake Zurich.

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Bob N

OK, I found the vacuum leak, it was the tee under the supercharger. I found a tee in my garage that I made work, so I saved the $38.00 bucks the dealer wanted.
Now I'm having trouble when the car is first started cold in the morning. Starts fine, but after a few seconds the rpm's swing wildly and the engine wants to die. Starts right up but continues to want to die. After several minutes, it smooths out and seems ok. But If I put it in neutral and raise the rpm's up to 3000-4000 it starts to shake and run bad. I'm wondering if it could be a choke issue or maybe a fuel issue? This all started after I put in new plugs,(autolite APP606, capped to .060) and wires. Any thoughts?

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Bob N

bob,

what wires did you use? did you check that they aren't touching the O2 wires? i had the exact same issue. pull your plugs and post them for us. numbering them to each cylinder.

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-Juan

No bonnie!
93 s10 ex cab: 2.8: t5: exhaust: tbi mods. 5.3, 76mm, and a D.r cam on a stand

There's no choke, as it's fuel injected. Remove the fuel line from the Fuel Pressure Regulator. Is there fuel in there? Also check the schrader valve on the Fuel rail. Mine was loose, and leaking gas a little bit, and caused some weird issues.

Also, when was the last time the Throttle Body was cleaned? Might want to remove that along with all the sensors and give them a good cleaning.

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Bye Bye:

RIP sandrock

Thanks for all the advice. I'll be checking things out tonight.
I pulled all the plugs last night, and all looked just fine. Still have not been able to get the boot off number 6, so it's still the original plug and wire. I did reroute the OE wires I bought and will see what happens this morning.
I'll update later.
Thanks again to all!

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Bob N

I think we have a winner. I'd be willing to bet that it's that #6 plug and wire that are causing the problem. Similar thing happened to harofreak00 on his last Park Avenue. Replaced 5 of the 6 plugs and it ran like crap, replaced the 6th and it ran perfectly.

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Bye Bye:

RIP sandrock

bob, things like that you need to mention first and foremost

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-Juan

No bonnie!
93 s10 ex cab: 2.8: t5: exhaust: tbi mods. 5.3, 76mm, and a D.r cam on a stand

O.K. guys, here's the latest.
Finally got #6 plug wire off!!! Had to remove the engine lift bracket and viola, lots more room to work. Pulled the wire out of the boot and then got a pair of vise grips on the boot and pulled like hell. Out it finally popped! Engine seems to be running good, but I'm still having missing/hestitation/shuddering, under moderate acceleration in 3rd and 4th gear.
Put in some more fuel injection cleaner, and I'll see what happens. I bought some throttle body cleaner and after reading the instructions it said not to use it on supercharged engines? Took the hose off the throttle body and everything appeared to be clean. Don't know what to try next?
Thanks for all the advice.
Bob N.

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Bob N

Bob: Remove the Throttle Body and clean it off the car. Pay attention to the IAT passages, they carbon up really bad.

I don't think Injector Cleaner is going to do much. When was the last time your Fuel Filter was replaced? Did you check the Fuel Pressure Regulator?

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Bye Bye:

RIP sandrock

Could this be a transmission problem instead of an engine problem? It could be a torque converter issue. Light acceleration won't get the TCC to unlock in 3rd and 4th. Moderate will. If it's having problems unlocking, that may be the bucking/missing. Is there a lot of shuddering when the TCC engages once you're up to speed?

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2012 Chevrolet Cruze Eco - Current car

1999 Buick LeSabre Custom - Former car

Learn from the mistakes of others, that way when you mess up you can do so in new and interesting ways.

Bob:

How to Change Fuel Filter

Almost identical, except for the location of the Schrader valve. The Valve is dead center on the fuel rail. The Fuel pressure regulator is just to the left of that, and has a vacuum line running to it. Remove that line and see if it smells like gasoline. If it does, it's bad, and needs to be replaced.

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Bye Bye:

RIP sandrock

To: 00Beast,
Nice write-up, I'll take care of it tomorrow. Really appreciate your help.

I'm starting to think the transmission could be the problem thanks to LeSabre in Buffalo's thoughts. It's certainly not getting better, and only seems to be an issue under light to moderate acceleration. If I jump on it, everything seems fine.

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Bob N

A bad EGR valve once caused me to have a hesitation/shudder in both low speed (take-off in 1st) and lockup with low-moderate load. It disappeared with throttle, and everything was fine under boost.

And that was with a fresh transmission.

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Jerry /// Past: 95 SSEi (June 2010 COTM) -- 04 GXP (July 2011 COTM)
91 Honda Civic Wagon DX 2WD (fuelly) -- 208,000km -- 92hp -- Autocross Warrior
09 Lexus LS460 AWD -- 94,000km -- Daily Driver
09 White Hot G8 GT -- 155,000km (fuelly) -- LS3 Cam -- GM LS3 CNC Ported Heads -- Kooks 1 3/4" Long Tube Headers -- Solo Catback Midsection -- Hooker Maxflow Mufflers -- Pat G Tune -- Rotofab Intake -- Tein S-Tech Springs -- GXP FE3 Dampers -- BMR Subframe Cradle Inserts -- BMR Subframe Connectors -- Forgestar F14 Gold 18x9 +40 -- Michelin Pilot Super Sport 245/45/18 -- Maverick Man Carbon Fiber Spoiler

Definitely couldn't hurt to remove it and clean it well with carb cleaner.

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Bye Bye:

RIP sandrock

There's nothing to lose in that case, but it didn't help me. I replaced with a junkyard unit and keep several spares in the garage.

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Jerry /// Past: 95 SSEi (June 2010 COTM) -- 04 GXP (July 2011 COTM)
91 Honda Civic Wagon DX 2WD (fuelly) -- 208,000km -- 92hp -- Autocross Warrior
09 Lexus LS460 AWD -- 94,000km -- Daily Driver
09 White Hot G8 GT -- 155,000km (fuelly) -- LS3 Cam -- GM LS3 CNC Ported Heads -- Kooks 1 3/4" Long Tube Headers -- Solo Catback Midsection -- Hooker Maxflow Mufflers -- Pat G Tune -- Rotofab Intake -- Tein S-Tech Springs -- GXP FE3 Dampers -- BMR Subframe Cradle Inserts -- BMR Subframe Connectors -- Forgestar F14 Gold 18x9 +40 -- Michelin Pilot Super Sport 245/45/18 -- Maverick Man Carbon Fiber Spoiler