Just bought an 85 GMC Jimmy full size blazer with a 305 motor
carburated. Had blown mufflers, replaced them with 24" glass packs.
Replaced cap, rotor, coil, wires and plugs. Here is what it WAS
doing.........Hesitation/Bog on initial ecceleration from stop.
Misfire when you let off the gas from exaust while goin down the road
at steady speed. It would flood itself out if i let it warm up in
driveway. If I took off with cold engine, no bog but much louder and
frequent miss fire. Once warm, little to no miss fire. Ecceleration
was ok and otherwise it ran pretty good. Everyone told me to junk the
quadrajet that was on it and get an edlebrock, so i did. Today i
fired it up and guess what, the miss fire is MUCH worse. The
hesitation/bog when warm is completely gone, BUT, the missfire is
louder and more frequent. Mostly when I just let off the gas I get a
good pop out the exaust. Any advice as an easy quick fix or something
simple to check for would be great. I am gonna check the plugs again
and maybe get a hotter plug cuz the ones i got are cheap and the old
ones were black. The more I read on these early 80's 305's the the
worse it looks for my pocket book. Mostly cam trouble from what I am
reading. If someone could also tell me how to get rid off all these
vaccum lines and sensers without creating an elusive vaccum leak that
would be great too. Thanks, Vince
Is it a manual transmission? Kind of sounds like you might be letting off
the gas and driving the engine, they tend to not like that.
Fix up the vacuum tubes, they do a world of good for my asthma and your
performance. If you can't read your vacuum diagram I'll take a picture of
the one on my '85 K5 305CUI.
What kind of cap/rotor/coil/wires/plugs did you use? Crappy shit gives you
Use AC Delco whenever possible, and if not available get something from
NAPA. Auto Zone is the next choice, and remember that Pep Boys carries 7
different flavors of beef jerky.
What kind of carb did you waste your money on for this 305? You need
something in the 450-500CFM range. Anything more and you'll have drivability
issues. Sounds to me like your Rochester needed a little bit of love,
especially the accelerator pump. But not much more...
What kind of mileage have you been getting?
Make sure your EGR is present and functional.
Its an automatic tranny. As for the cap/rotor/coil/plugs/wires ac
delco on most and generic wires i think. The carb is 600cfm. Would
not clear the EGR soooo.....I took it off and plugged it. After
installation there were 2 vacuum lines in front of carb with no place
to go and 1 in back so i plugged em. Dont know how to rebuild carbs
and cheapest quote was about the same as a new edlebrock. Most
friends think its sticking valves so if thats true how do you fix it?
Since half the vacuum lines are plugged how do I take em all off and
just use advance of dist? Dont really need high performance, just
wanna get rid of the back fire.
on an edelbrock carb. the drivers side vacuum port is used for the vac.
advance, the pcv valve can be hooked to the center bigger port on the carb,
other than that just start yanking on the hoses, thats what i did, i also
went to a local auto parts store to pick up vacuum port plugs, or just use
some of your left over vac. hoses that you yank off and put a screw with
some silicone in the other end, works like a charm....
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One is in the wrong place take them all out and put them back in right!
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firstname.lastname@example.org (Web Master) wrote in message
When I bought the truck i replaced the plugs and all as I mentioned in
the first post. Is it possible to have foulded a plug in the two
weeks I drove it until I got the new carb? If someone has got this
same year engine it would be a great help if some one could email me
some photos of their engine after pulling all the vacuum lines. I
originally had the vacuum advance on the passenger side of the carb
and I changed it over to drivers side. Seemed to help drivability a
little but still back fires. The only thing is I dont have it going
directly to the carb, it still is joined up with other lines that go
to sensors and crap cause I havent began the process of taking off all
vacuum lines. Going to try new hotter plugs tommorrow. Currenty us
AC Delco, any recomendations for plugs would be great. One last
question, someone told me that to loosen up sticking valves try adding
tranny fluid straight into the carb while running just until it starts
bogging then let idle till smoke is gone, is that true? If it is, do
I aim for the side if inside of carb and miss jets or just poor away?
Also if it is loose or sticking valves is there an adjustment I could
make with just the valve covers off? Somethin about tightening till
slight ping then back off certain amount???
Always label what you are taking off to put back where it belongs.
The tranny fluid thing?
Get carb cleaner from any parts store!
Tranny fluid will leave residue and mess shit up!
No better! go to jiffy lube and tell them you want the injector cleaner
system. The ennema for your car or truck! 40 bucks but worth it!
Cleans everything from the carb through the tail pipe!
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