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Discussion Starter #1
I took it down to have a baseline dyno run done. I walk into the land of rice! A turbo Nisson was in the waiting room. Pretty nice layout actually. They strapped the car down which i got to watch in the waiting room in comfort then they came and got me. It reminded me of a dentists office. They did 3 pulls, all were real close to each other. I listed the single one for clarity. Its an automatic so he had a little trouble with the low rpm part of the run. 169hp @ 4,000 RPM and 241.9 torque is fair enough for a stock 5.0 HO with factory fuel injection.

What concerns me is that after 4,000 rpm it has a high speed miss. I wish i had the exhaust checked but i didn't. The engine is basically stock with 124,000. It only shows up at higher RPM. any thoughts? or any thoughts on how to narrow it down? The 3 things that comes to my mind is weak/damaged ignition, bad injector, bad valve spring. I doubt it is detonation being a stock engine. Whatever it is, it is intermittent and not very obvious from the drivers seat.

http://www.alltel.net/~motorhead/dyno.jpg
 

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Was there any smoke coming out of the tail pipes at the higher rpms? For cars that never get reved that high, they often need to "clear their lungs", and it can easily disrupt 3 runs.

If you're thinking ignition miss, start with the wires, and the distributor. What dist are you running? Quality cap? I had a buddy with a '85 LX. He had a miss that you only see on the scope, and the only way he was able to get rid of it, was by installing a MSD. We never did figure out what individual component was the culprit, but we changed out just about everything, including the ignition module.
 

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Discussion Starter #3
since i have owned the car the gas has frequently visited the floor of the car. But when i first got it there was some carbon to be blown out.
 
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124K miles I would start to thing everything is getting loose. You might pull the distributor & take it to a professional & see how bad the bushings are, after that, a valve spring check would be in order.
 

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Discussion Starter #6
now that i know to look for it i can. It sounds like a missed cylinder.
 
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I had a high end miss that I just could not track down. Plugs, wires, confirmed TDC, timed, reset the intake, chased and chased. Ended up that I had the secondaries and primaries too far apart and it was leaning out at the high end....just about pulled my hair out for that one.
 

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The curve also seems to be low between idle and about 3k as well as the 4K+ miss.

You can buy an injector cleaning kit from Summit/Jegs that comes with a can of solvent and the valve/hose.

Did you check your plugs?

You didn't tune her up before spending all that money on the dyno??
 

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Discussion Starter #9
the guy had problems with the low rpm, something about being an automatic.

The plugs, cap, rotor and air cleaner are new, everything else you have as much of a clue as i do. I was just looking for a "before" number. Last friday i got a 1/4 mile before time. I still need to take my mustang up to the track and dyno.

I've planned on dropping my supercharger on the stock engine to do some testing but i really don't want to do that with that miss. I'll see how it feels after the mass air.
 

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170 RWHP - I'm almost there, with more torque than you, too. My dream is to be able to beat out a 5.0 Mustang, even if it IS stock and an automatic.

I've had my car on the dynamometer 3 times and it's an AT, never had my tuner say anything about there being a problem...
 
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