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Help! l28 not as "peppy" since move


g3nesis

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After rebuilding my l28e and having the car moved to Vegas it isn't as "peppy" as it once was. After 3500pm it almost just flat lines in power it seems, random bursts of power then flat line then repeat, it also has a problem breaking 5k rpm. Not that I'm going around racing all over the place, but it just doesn't as alive as it use to be. Could this be due to the 2,000+ feet in elevation difference and that my AFM needs to be tuned for proper air/fuel mixture? How do I do this? Should I just try to find an AFM out here that has been on a car that was built for the elevation here?

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I'm experiencing the same thing, at sea level. The 2k elevation should not affect power much at all; the AFM is probably fine. Below 3k, the engine is really strong and torquey. But yeah, from 3-5k you can tell there is power there, but it just feels like it's being strangled.

 

I'm assuming it's a fuel delivery issue...

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Yeah I'm starting to think that it could be that, but im literally in the same spot as you. It feels strong, but its not what it should be. I'm starting to think it could be fuel delivery as well but injectors are firing just fine, fuel pressure seems to be good. Just don't know what it could be and its starting to irk me!

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What have you checked? We can't help you if you don't help us. How are your plugs? Any timing advance? Filters changed? Vacume leaks?

 

If you think it's fuel get a guage on it and see if there is any change in pressure as you rev it. It could be the pump or a clogged filter/ pickup. It might even be spark related, an old rotor or cap could do the same thing.

 

Hope you can figure it out!

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New plugs and wires, spark is strong. Injectors are good and fire corretly, timing is set 10 degrees advanced. Hoses are good, no known vacuume leak anywhere. It reves freely to 6.5k its just once in gear it hesitates.

Edited by g3nesis
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I had an E12-80 ignition module go bad on my 1980 280ZX once. It ran fine below 4100, and above it, it would cut out on cylinders, bog down and run like crap until its self imposed redline of around 4500. Also, check the distributor for wobble, as the bushings may have gone out and the rotor my be contacting the inside of the cap at high(ish) rpm.

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I had an E12-80 ignition module go bad on my 1980 280ZX once. It ran fine below 4100, and above it, it would cut out on cylinders, bog down and run like crap until its self imposed redline of around 4500. Also, check the distributor for wobble, as the bushings may have gone out and the rotor my be contacting the inside of the cap at high(ish) rpm.

 

Is there any way I can really check to see if the ignition module is going bad? Distributor seems pretty solid and no movement but I can check it out again. Trying to get my list ready for the weekend of things to check!

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Check the ignition module and make sure its bolted/ clamped down. Mine was loose and giving me hell. I work at an auto parts store here in vegas, my z is always out front, come by and say hello.

 

Which one are you at? Im pretty basic when it comes to figuring this out. My fuel pressure is at about 32-34lb. #6 cylinder wasn't firing, replaced plug and wire and that solved that but it still has problems breaking 4k and power still doesn't feel quite right.

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  • 2 weeks later...

I just realized I hadn't changed the fuel filter since adding an inline filter and swapping the tank. Der. I put in a new one today and it definitely has more power and less of a bog than before... Still not 100%, but maybe I can fix that with the rest of the tune up I need to do.

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Something that is usually over looked when diagnosing a lack of fuel condition is the little screen inside the inlet of the fuel pump. Over time this screen will get clogged with rust particles from the tank. Remove the screen, clean it out and replace.

 

Joe

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Something that is usually over looked when diagnosing a lack of fuel condition is the little screen inside the inlet of the fuel pump. Over time this screen will get clogged with rust particles from the tank. Remove the screen, clean it out and replace.

 

Joe

 

Will have to take a look at that, fuel filter has not been replaced. If it was clogged though wouldn't I notice a problem with me fuel pressure? Guess I didn't mention it in this post, but it holds at 32-34 PSI, probably slightly higher the one I bought was leaking.

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My understanding is that if the filter isn't completely clogged, it will only not flow properly when it's under load. The load at idle is really small, same with at cruise or partial throttle or lower rpm's. When the rpm's are higher and the load is increased, the flow isn't enough to supply the full throttle enrichment and the higher rpm's. Give it a shot; I paid $16.

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Well fixed one thing. Looks like the sensor that plugs in to the head had a bad connection, it now revs to whatever I throw at it. It still isn't 100%, still times when it will suddenly "open up" and power is all there. Going to check fuel filter this weekend, still running nasty rich as well.

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So got it finally running to what it should be. After replacing my fuel filter, new fuel pump, several sets of spark splug and a new set of plugs it actually turned out to be my timing being way off. Damn the simple things and over looking!

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