440-3 Idles horrible when warm

[The_Handier_Man1]

From: BonneauBago  (Original Message)
Sent: 10/27/2003 8:26 PM

Hello everyone, it's been awhile since I've posted, been super busy with to many projects! LOL  I've been having a problem with the Bago that I can't nail down:  It starts and runs great (well a very slight rough idle), after I drive for an hour or so, if I have to stop (red light, stop sign, etc.), it wants to shut off, and if it doesn't shut off it idles very rough, spits and coughs . . .  If I stop long enough for the engine to cool then its fine until I go another hour or so then the same problem.  Its a 79 440-3 with a Holley 750cfm carb (rebuilt less than a year ago).  Any suggestions?? Thanks in advance.

BonneauBago
Bonneau, SC



From: Sea Hag
Sent: 10/28/2003 8:46 AM

Check you vacume system for bad or diconeected hoses , and EGR valve if so equipted , check the choke also for a start ------ Sea Hag



From: denison
Sent: 10/28/2003 6:21 PM

I agree with Sea Hag - and a vacuum gauge connected to the manifold should show about 16 to 19 inches of whatever when it is idling. Another thing to check would be the timing - and wiggle the rotor to make sure it is springing back from the advanced position it gets to in highway driving. If its still doing it, it could be a piece of crud in the idle air-bleed system, that percolates air into the fuel stream for better idling. This might show up if you are in a position to fiddle with the idle mixture adjustments when the engine is fully warm Oh, make sure the carburetor base gasket hasn't shrunk-in and allowed a vacuum leak, and that the secondaries are really closing as much as they should. Mine is starting to do the same thing this fall. Its a 413 with a Holley, rebuilt about 8 or 9 years ago. denison 



From: daved27c
Sent: 10/28/2003 9:52 PM

Another possibility is that the winnie could be vapor locking. This is caused when the fuel gets too hot and actually begins to boil. Does your winnie have the oringinal exhaust, or headers? If it has headers than the gas line may be too close to the heat. This is not causing your rough cold idle, and I agree that it could be a vacuum related.   



From: BonneauBago
Sent: 10/29/2003 7:37 AM

Thanks guys, I will be looking at all of the vacumm lines today now that the rain has subsided!  I do have headers, but I'm pretty sure the fuel line is clear of them, but will double check.  If it is vapor lock, wouldn't it affect it more than just when idling?  Thanks again.

Mark
Bonneau, SC



From: Sea Hag
Sent: 10/29/2003 1:49 PM

I' not sure about vapor lock effecting more than just idle but it is a possibility . the reason i tend twarwd vacume is that there is a colant activated vacume switch up twards the front of the engine on top by the temp sending unit , it has two vacume  hoses going to it . it opens when the engine water temp is at operating temperature and closes when cooler . it controlls the EGR valve , so it is olny open at operating temp. - also vacume hoses also expand when warm thus expanding any cracks .  I had a 86  S-10   2.8 all of the vacume and emisshoin system was controlled by several of these colant activated switches some mutible port . it was quite challanging  - I also found after market switches didn't always do the same thing , I went back to OEM AC switches on it . ----Sea Hag



From: haloscorned
Sent: 10/31/2003 11:34 PM

I know this might sound strange... but I was told that mine was due to the
brakes? Something with the vaccum booster or something like that. I also
have the 440 engine, but I'm not sure what the carb is. I just now jumped
into restoring mine. I know that my suggestion might sound somewhat silly,
but it was something that my mechanic told me. He said that when I pressed
the brakes, the vaccum was robbing the engine of horsepower... I don't know
if that helps. Let me know.

~Alex 73' Brave D20



From: denison
Sent: 11/4/2003 7:15 AM

haloscorned: Its true that putting the brakes on will have a momentary effect on the engine vacuum, but only for a second. If the vacuum is unsatisfactory after that then you have a leak in the booster or boosters somewhere.
denison



From: BonneauBago
Sent: 11/6/2003 11:14 PM

Finally got around to replacing my vaccum hoses, I didn't find any that were leaking though.  So I replaced them all and believe the leak may have been coming through the cruise control, not sure though.  My vaccum guage reads around 18 at idle??  I haven't ran it long enough to see if the stalling has gone away after it gets good and warm, maybe this weekend.  Thanks to you all for the help!!

Mark
BonneauBago
Bonneau, SC