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What would cause loss of top end power?


bigfoo

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Any ideas?? I seem to have less power now at 4500-6500 rpm than I did before.. No codes are set. Low end power seems about the same 2000-4000 rpm seems good......

My initial suspicion is the fuel ratio / mix, etc.. but since that's not possible to change on this car , what do we do? :)

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Fuel filter ??

Fuel pressure (Regulator or pump) ??

Poor fuel (Low grade - timing retarded) ??

2008 STS V8
2016 Colorado Z71
1970 Corvette LT-1 Coupe

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hey, that's not very nice... j/k retarded timing would result in lotsa bottom end loss. fuel filter and reg and maybe pump? what about exhaust restrictions?

maybe you just caught it on a bad moment... a/c on, alt. on, going around a corner (p/s pump) with your parking brake stuck on! :o

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Hmm.. I've been thinking about it.. but there's so much on this car that could go wrong :) That's the only downfall to having such an electronicized car hehe..

I can't tell if it's getting enough fuel or even what the timing is. I have CORSA exhaust system so I doubt that's being restricted, and a high flow converter. I guess I'll do the fuel filter and spark plug wires (they probaly need it, i see what looks like a buncha micro fireflies at night if i spray the wires hehe). injectors after that.. Guess I could throw on a new FPR for the heck of it as long as it's not too expensive....... fuel pump is the last thing since i'm sure it costs and is a b*tch to replace. I think maybe the P/s pump is sucking power or the AC..

Try this......... leave tranny in 2nd gear, go up to 3000 rpm and turn on the AC, it will put a serious hit on the engine like it's suckin 50 HP away :) I can even FEEL it it jerks the car when i turn it off.. Must be a BIG A/C :)

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FPR is easy to check man. Don't throw parts at it. Just pull the vacuum hose and (pardon the expression) see if the nipple leaks. If it does, replace it. If not, it's good.

If you have a fuel pressure guage with a long enough hose, tape it to the windshield. Then take it for a ride and see what the fuel pressure does when you duplicate the problem.

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I wonder how much a fuel pressure gauge costs and where to hook it up :)

The filter is fine.. the CAT is not even a year old so I doubt it's clogged :) What about coils/wires , fuel filter, an accessory going bad ( i have a high whine coming from something over there at high rpms ).

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I wonder how much a fuel pressure gauge costs and where to hook it up :)

The filter is fine.. the CAT is not even a year old so I doubt it's clogged :) What about coils/wires , fuel filter, an accessory going bad ( i have a high whine coming from something over there at high rpms ).

The spark plug NUDGE is back.... Did this loss of power occur before or after the aftermarket plugs?

In addition, you commented on your AC Compressor having a big HP impact and note a possible 50HP loss. Was it you on another thread who commented that when the compressor cycles on that you get a chirp? Did you mention that you thought you might have too much oil in it? Its possible that your compressor has a problem, as I have not heard or seen NS compressors chirping. Too much oil would bind up the compressor and make it harder to turn thereby causing the chirp and HP loss... I would look into that compressor, Mike

Early on sailors navigated by the stars at night and the North star became the symbol for finding ones way home. Once you know where the Northstar is you can point your ship in the right direction to get home. So the star became a symbol for finding ones way home or more symbolically even finding ones path in life.

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I wonder how much a fuel pressure gauge costs and where to hook it up :)

The filter is fine.. the CAT is not even a year old so I doubt it's clogged :)    What about coils/wires , fuel filter,  an accessory going bad ( i have a high whine coming from something over there at high rpms ).

The spark plug NUDGE is back.... Did this loss of power occur before or after the aftermarket plugs?

In addition, you commented on your AC Compressor having a big HP impact and note a possible 50HP loss. Was it you on another thread who commented that when the compressor cycles on that you get a chirp? Did you mention that you thought you might have too much oil in it? Its possible that your compressor has a problem, as I have not heard or seen NS compressors chirping. Too much oil would bind up the compressor and make it harder to turn thereby causing the chirp and HP loss... I would look into that compressor, Mike

By the way, I do not 'feel' my compressor cycling on or off in my car at all, check around but I dont think its common. These engines have too much torque for you to be feeling it. That you feel your compressor could be related to the loss of power you are talking about, but I would take a look at the compressor due to the chirp. Mike

Early on sailors navigated by the stars at night and the North star became the symbol for finding ones way home. Once you know where the Northstar is you can point your ship in the right direction to get home. So the star became a symbol for finding ones way home or more symbolically even finding ones path in life.

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I wonder how much a fuel pressure gauge costs and where to hook it up :)

The filter is fine.. the CAT is not even a year old so I doubt it's clogged :) What about coils/wires , fuel filter, an accessory going bad ( i have a high whine coming from something over there at high rpms ).

Hook up the fuel pressure guage to the shreader vavle on the front fuel rail (looks just like a tire valve).

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I didn't service the A/C unit myself so i really don't know what is wrong with it. THe dealer did the last service i think a year ago or so.. This has nothing to do witih the spark plugs.. As I stated before the plugs are something I replaced to try and fix the problem. In fact i think they increased low end a little bit but high end is still not (at least in my opinion) where it should be. I want to get one of those gtech pro comp things so i can actually test modifications when I make it such as plugs/wires/coils, etc.. That would definitely tell me if there's a problem. I mean it's nothing major. I can't even tell unless i'm WOTing it big time. I'm just all about tweaking the most performance I can get out of anything, period. even my computers :>

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I'm running 93.. Maybe an injector is clogged or something.. I haven't put sea foam in the gas for quite a long time.. Ill try that out next tank and see.. sometimes that clears stuff up right away. The only other difference that the car has is that I had a K&N filter and now I don't (temporarily) and I'm using mobile 1 instead of amsoil (the last oil change the shop was out of amsoil.. ugh) I don't think the K&N could possibly make THAT much difference but I can't tell without something to monitor it.

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