pop up through carb when revved up

fast68 · Last edited by fast68 on Fri Aug 29, 2008 5:43 pm; edited 2 times in total

got an all original 1984 oldsmobile 307ci with the common electronic feedback Q jet on it still, all stock original unmodified in any way

it starts right up and runs fine and all sitting and idling and such

but if you rev it up normally(not excessively) it will sometimes cough or hiccup through the carb and it kinda bucks in gear under acceleration wont get its power to accelerate properly

cant figure out whats going on with it ?

i checked timing with a mechanics vacuum guage and it needs more advanced because the needle is sitting on theline inbtween greed normal and red late timing,

but if you advance it any more then it wont crank start up right- it will then have that too-much-advanced timing starter crank lag problem that happens when the distributor is advanced too much initially

any ideas whats going on here ?

seems it is not advancing or something when rpm increases

it is ECM controlled advance., not vacuum advance

maybe the ignition module is not workign right ?

try another one real quick and see ?

the carb may be dumping a little extra fuel than it should in which seems to be a common issues with these E4M series Q jets when they get old and worn

i have an edlebrock 1405 i can try if i have to i guess

its actually an 84 riviera with 116k original miles that i picked up

all stock original correct unmolested even down to all the trim, bought from old farmer from his barn where it sat since 2000(plates expired in 2000)

drives great, like a caddy, and plushy comfy nice

thanks for ideas
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randy the vehicle-aholic in lincoln il
85 Elky SS restored mostly stock LG4 .030 over 2004r 2.73 axle black and maroon
MANY vehicles and parts at all times..

pops86 · Posted: Fri Aug 29, 2008 12:47 pm Post subject:

Is the service "engine soon light" on? If it is, read the code and begin there, after a thorough inspection of vacuum hoses, connections, etc.
If there is no SES light on, then have you checked to see if the accelerator pump is squirting two strong streams of fuel in the primary venturi? If not replace the acc pump.
Check the fuel pump output.
Check the fuel level in the carb, with the engine running, and not running after the engine has set for a couple of hours.
Did you check the fuel filter in the fuel inlet of the carb to see if it is clean?
The timing, in my opinion, is probably not the problem. Unless you dissconnected the 4 wire distributor connector the timing will not necessarily change by just turning the distributor.
Try dissconnecting your egr valve, pull the rubber connector off and plug it
Hope this helps.
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bigjames4xl · Posted: Fri Aug 29, 2008 1:33 pm Post subject:

I'm bettin it's the timing chain/gear may have jumped a cog, could also be a lobe going flat on the cam.
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Hansmanbo · Posted: Fri Aug 29, 2008 4:56 pm Post subject:

You say it sat since 2000, so maybe the carb is gummed up. Also, pull dist. cap to see if counter weights are siezed. A drop of oil may be all you need.
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fast68 · Posted: Fri Aug 29, 2008 5:32 pm Post subject:

its 80 and newer

its EST/ESC system so it has no mechanical advance

it is computer advance

the vacuum needle does jump at the same interval and not irregularly

hopefully not a bad lobe or valve hmm

dunno how i could figure out that it is unless i pull the rocker covers and check with it running i guess that all are moving good

the accelerator pump is doing fine, two good squirts from it

it rves up fine no bog down or anything

but in gear it doesnt speed up worth a crap, under load in geat that is

20mph or so is it before it jerks bucks not being able to go anymore

and hiccups up the carb once now and then trying ot make it go and speed up some more

hmm

the carb is probably gummed somewhat

may have to try fuel system cleaner for a while on that one

thanks more!
_________________
randy the vehicle-aholic in lincoln il
85 Elky SS restored mostly stock LG4 .030 over 2004r 2.73 axle black and maroon
MANY vehicles and parts at all times..

CANTED · Posted: Fri Aug 29, 2008 8:15 pm Post subject: hiccups

Sounds to me like you are getting a lean condition. If the accel pump is OK, there may be a problem with the primary main circuit. I would advise having the carb rebuilt and being sure there is no problem with fuel delivery.
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Jim
70 ElCamino 461 solid M20 331eaton
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dougs85 · Posted: Fri Aug 29, 2008 10:58 pm Post subject:

Replace the fuel filter.

Doug
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85 El Camino 305, TH350, K&N, dual exhausts
87 El Camino 305, 2004R, K&N, dual exhausts
1964-1/2 Mustang conv, 260 V8, dual exhausts
2002 Jaguar XJ8, 2000 Harley Road King
Lakewood, CO

Robby85 · Posted: Fri Aug 29, 2008 11:47 pm Post subject:

In your first post you say, " it starts right up and runs fine and all sitting and idling and such". I assume you mean when the car is parked and the transmission is in park? Then you said, "but if you rev it up normally(not excessively) it will sometimes cough or hiccup through the carb" Is it still in park or is it in gear when this happens?

Let us know.
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77 HD Sportster
79 Corvette L82
85 El Camino SS LG4
93 Camaro Z28 LT1
05 Dodge Caravan daily driver - yeah baby!