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low rpms spit and sputtering help?


joshb530
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ok so over the weekend i did plugs, wires, fuel filter and oil change on my new 88 conquest, also set initial timing to 10btdc.

 

it had a stutter at part throttle just before it would start building boost that i could power through usually and it would go away.

after the tune up it has got worse and will pop through the intake, other wise it runs very smooth.

i have sprayed some carb cleaner around the intake and vac lines and havent found a vacuum leak yet, also since i got it a couple weeks ago it wont make above 7psi and falls of to 2-3psi by 4500rpm.

 

i have a new 02 on the way and will put together a boost leak tool this weekend any other thoughts on what i should check?

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Mine was doing a similar drop in boost (10, down to 7-8)until I replaced my fuel pressure regulator. Your knock control is probably sensing knock and reducing boost, so I'd check the fuel delivery system for sure and maybe a clogged cat or cats if you have them
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ya i have been thinking clogged cats also, ill start looking at the fuel system also, i have a 3" downpipe coming that i can weld in a second 02 bung so i can get my lm-1 on it.

i have to smog it this week so i may just bring it in as is and cross my fingers and grab main cat and gut the primary if i have to, ill be putting in a 3" catless exh once it passes and putting the stock in the rafters till next time.

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So the previous owner told me he replaced all the vacuum lines so I decided to check them out and what a mess lol, I am pretty sure they just guessed on the routing, so I ripped it all out yesterday and replaced it all, runs much better now, not 100% yet but much much better.

It's still only makes 7psi and drops fast.

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If you don't have a moderate boost plumbing leak then a cat could be clogged. But smog is what counts first. You won't be going anywhere if it fails.

ya it will be going in in the next couple days, it is running pretty good, idles smooth no miss and i am in a basic area so just idle and 2500rpm test, no load test so i am crossing my fingers lol.

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