Problem with '77 won't idle
Thread Starter
Intermediate
Joined: Jul 2004
Posts: 34
Likes: 0
From: Naperville IL
Problem with '77 won't idle
Hi All,
I drove the car this morning over an hour and it was running good. It's a stock 77 350 (L48) w/ quadrajet. I went to take it out this evening and it dies the minute I take my foot off the gas. I turned up the idle screw so it will run and noticed it's not a smooth idle - it goes up and down in rpms. I have always had a problem of dropping in oil pressure down to about 25 from 40 when in gear.
Checked the plugs ok, replaced fuel filter. Compression isn't bad, all cylinders range around 140 with a couple at 135. Does need valve job - blows smoke when started after sitting. I tried to check timing but my timimg light doesn't work. The carb prob needs a rebuild. Not sure where to go from here?
Does this sound like vacuum leak - timing issue other?
Thanks in advance,
Tom
I drove the car this morning over an hour and it was running good. It's a stock 77 350 (L48) w/ quadrajet. I went to take it out this evening and it dies the minute I take my foot off the gas. I turned up the idle screw so it will run and noticed it's not a smooth idle - it goes up and down in rpms. I have always had a problem of dropping in oil pressure down to about 25 from 40 when in gear.
Checked the plugs ok, replaced fuel filter. Compression isn't bad, all cylinders range around 140 with a couple at 135. Does need valve job - blows smoke when started after sitting. I tried to check timing but my timimg light doesn't work. The carb prob needs a rebuild. Not sure where to go from here?
Does this sound like vacuum leak - timing issue other?
Thanks in advance,
Tom
Le Mans Master
Joined: Dec 2007
Posts: 6,422
Likes: 591
From: McHenry Illinois
1. Could be a vacum leak, with the engine idling and warmed up, pull off the air cleaner. Use a small rag in your hand and try to choke off the air going into the carb, the choke plate should be open. If the idle speed increases and smooths out before the eigine dies out then the engine is lean, indicating a vacuum leak.
2. Could have gas dripping into thte carb, with the engine running, look into the carb and see if there is fuel dripping in there, could be a stuck needle seat valve or the float is saturated and sunk.
2. Could have gas dripping into thte carb, with the engine running, look into the carb and see if there is fuel dripping in there, could be a stuck needle seat valve or the float is saturated and sunk.
Le Mans Master
Joined: Dec 2007
Posts: 6,422
Likes: 591
From: McHenry Illinois
Yep,
Here's one thing to try before you rebuild it. With the air cleaner off and the engine running, rev it up pretty high and choke it down with the rag but don't make it die all the way. If there is a piece of crap stuck in the needle seat vavle for the float, in rare cases this will pull enough gas out of the float bowl that the debris will dislodge. It's a long shot, but I have seen it work a few times.
this can be done with the choke flap too.
Don't let the rag get sucked into the engine.
Here's one thing to try before you rebuild it. With the air cleaner off and the engine running, rev it up pretty high and choke it down with the rag but don't make it die all the way. If there is a piece of crap stuck in the needle seat vavle for the float, in rare cases this will pull enough gas out of the float bowl that the debris will dislodge. It's a long shot, but I have seen it work a few times.
this can be done with the choke flap too.
Don't let the rag get sucked into the engine.
Instructor
Joined: Mar 2008
Posts: 173
Likes: 1
From: New york New york
If all the above does'nt help check all vac. linesyou said it happened in the eve. maybe a headlight vac.leak, try shutting off the lights allowing them to close. next check the intake manifold gasket . Mine blew two years ago and the rpm's were bouncing .
Good Luck
JRL
Good Luck
JRL
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