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Rough hi idle

Started by Bob, August 30, 2007, 09:21:48 AM

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Bob

August 30, 2007, 09:21:48 AM
Drove my charger to work today. Starting is fine, cruising is fine but after a while when I would stop at a light it idled rough. This has happened the last few times out. Sounds like a vacume leak to me. Timing and ignition system is fine. Thoughts?
400 4bbl auto.

Bob

firefighter3931

#1
August 30, 2007, 09:47:31 AM
Quote from: Bob on August 30, 2007, 09:21:48 AM
Drove my charger to work today. Starting is fine, cruising is fine but after a while when I would stop at a light it idled rough. This has happened the last few times out. Sounds like a vacume leak to me. Timing and ignition system is fine. Thoughts?
400 4bbl auto.

Bob


Could be vacuum related or maybe bad fuel. Has the rough idle condition started since the last fillup ?  :scratchchin:



Ron
68 Charger R/T "Black Pig" Street/Strip bruiser, 70 Charger R/T 440-6bbl Cruiser. Firecore ignition  authorized dealer ; contact me with your needs

Bob

#2
August 30, 2007, 09:51:07 AM
ACTUALLY ABOUT 6 TO 8  MONTHS AGO.
JUST FILLED IT UP AGAIN THIS MORNING WITH MID GRADE TO SEE IF THAT WOULD HELP.

firefighter3931

#3
August 30, 2007, 10:13:34 AM
Quote from: Bob on August 30, 2007, 09:51:07 AM
ACTUALLY ABOUT 6 TO 8  MONTHS AGO.
JUST FILLED IT UP AGAIN THIS MORNING WITH MID GRADE TO SEE IF THAT WOULD HELP.


Bob, check the vacuum lines and carb base gasket. Make sure the carb is tight (snug) to the intake manifold.


Ron
68 Charger R/T "Black Pig" Street/Strip bruiser, 70 Charger R/T 440-6bbl Cruiser. Firecore ignition  authorized dealer ; contact me with your needs

Bob

#4
August 30, 2007, 01:05:13 PM
Would you recommend spraying anything around the engine to find a leak? Something combustable?
I tightened the base and replaced all the hoses. The problem was still there after changing all hoses.

aifilaw

#5
August 30, 2007, 06:39:34 PM
possible that a heat issue has cropped up as well, depends on how bad the idle gets, easy way to test is to run it until it provides you with the problem, and then retard the timing a bit, see if that clears it up. If not then put it back and adjust the idle fuel circuit and see if that cures it, if not you've shown its neither of those problems (assuming your adjustments work on the carb) in all of 1 minute. Then go hunting vacuum leaks.
'72 B5 Metallic Blue Hardtop
426" Wedge - Hydraulic Roller Stealth heads

Bob

#6
August 30, 2007, 08:27:16 PM
Will do.
Thanks
bob

Musicman

#7
August 30, 2007, 08:45:29 PM
Maybe a float out of ajustment or a needle sticking... do you smell gas? Probably a vacuum issue, but you never know.

71ChallengeHer

#8
August 30, 2007, 09:26:54 PM
Maybe it needs the carbon blown out. :drive: :drive: I can help you out with that. :smilielol: :smilielol:

Musicman

#9
August 30, 2007, 09:41:31 PM
 :iamwithstupid:   What are friends for... :ohhthesarcasm:  :smilielol:

firefighter3931

#10
August 30, 2007, 11:08:34 PM
Bob, how warm is the engine when the idle quality begins to tank ? What kind of carb ?


Ron
68 Charger R/T "Black Pig" Street/Strip bruiser, 70 Charger R/T 440-6bbl Cruiser. Firecore ignition  authorized dealer ; contact me with your needs

Bob

#11
August 31, 2007, 05:49:04 AM
Quote from: firefighter3931 on August 30, 2007, 11:08:34 PM
Bob, how warm is the engine when the idle quality begins to tank ? What kind of carb ?


Ron

Operating tempature. I would say 180 by the gauge. Start up, initial take off and cruise for awhile is fine. After completely warmed up is when it starts.

Bob

Bob

#12
August 31, 2007, 05:49:34 AM
Quote from: Musicman on August 30, 2007, 08:45:29 PM
Maybe a float out of ajustment or a needle sticking... do you smell gas? Probably a vacuum issue, but you never know.

No hint of a gas smell at all.

Bob

#13
August 31, 2007, 05:50:56 AM
Quote from: 71ChallengeHer on August 30, 2007, 09:26:54 PM
Maybe it needs the carbon blown out. :drive: :drive: I can help you out with that. :smilielol: :smilielol:

I thought about that but am to darn scared of a ticket and busting something I can't afford to fix.
The thought has crossed my mind though. Wanna run em? I'll even be a gentleman and give you 2 car lengths. Matchbox cars that is. :nana:

firefighter3931

#14
August 31, 2007, 08:23:36 PM
Quote from: Bob on August 31, 2007, 05:49:04 AM
Quote from: firefighter3931 on August 30, 2007, 11:08:34 PM
Bob, how warm is the engine when the idle quality begins to tank ? What kind of carb ?


Ron

Operating tempature. I would say 180 by the gauge. Start up, initial take off and cruise for awhile is fine. After completely warmed up is when it starts.

Bob


Bob, you didn't answer the carb question...what type of carb ?  :scope:

If it's a thermoquad ; they are know for their warpage issues. I would pull the carb and make sure it isn't warped....check the baseplate. You can also use an unlit propane torch around the base of the carb to search for vac leaks....engine speed will increase if there is a leak and the LPG is drawn into the engine.


Ron
68 Charger R/T "Black Pig" Street/Strip bruiser, 70 Charger R/T 440-6bbl Cruiser. Firecore ignition  authorized dealer ; contact me with your needs

Musicman

#15
August 31, 2007, 08:39:22 PM
 :iagree: A couple of quick shots of carburetor cleaner aimed at the base of the carburetor works well for finding vacuum leaks too. If that doesn't work, play around with the idle air/fuel mixing screws and see if that changes anything... If nothing else, I would at least heat up the engine and reset the idle air/fuel mixing screws anyway, just to make sure, they could be out of adjustment.

deputycrawford

#16
August 31, 2007, 08:40:13 PM
I was just going to suggest what Firefighter did. Use an unlite propane torch. Turn the gas on and run it around everything you think could leak. If the engine revs, you found it.
If it ain't wide open; it ain't running.        Rule number one in motocross racing: Pin it; row the gear box; and wait until you hit something.     At work my motto is: If you need me, call someone else.

Bob

#17
September 01, 2007, 05:54:04 PM
It'a still the original TQ. It has been rebuilt once. If the propane torch does nothing I will remove and straight edge the base to see if there is any warpage. The base is where the warpage would be right?

Thanks all.
Bob

firefighter3931

#18
September 01, 2007, 06:00:47 PM
Bob, sometimes the baseplate will be warped....other times the plastic main body will warp.  :P

Let us know what you find.



Ron
68 Charger R/T "Black Pig" Street/Strip bruiser, 70 Charger R/T 440-6bbl Cruiser. Firecore ignition  authorized dealer ; contact me with your needs

Bob

#19
September 02, 2007, 03:55:08 PM
Sure, Thanks firefighter.

Bob

Bob

#20
September 03, 2007, 03:50:31 PM
Ok, double checked the hoses and used my propane torch everywhere. Nothing. No rise in the engine at all. The base plate on a straight edge was fine. I'm thinking it's just a worn out carb. I guess by now you know I have a charging problem. One time your on top running without any problem and bam, they hit you all at once.

firefighter3931

#21
September 03, 2007, 06:22:27 PM
Bob, it's possible that the carb has an internal vacuum leak. Try swapping on a known good carburator and see what happens.



Ron
68 Charger R/T "Black Pig" Street/Strip bruiser, 70 Charger R/T 440-6bbl Cruiser. Firecore ignition  authorized dealer ; contact me with your needs

Steve P.

#22
September 03, 2007, 08:29:58 PM
I agree with the above. I just want to add one thing that many people blow right on by..

Many times I hear people say that they thought they had a vacuum leak and just went ahead and changed all the vacuum lines. Well new lines are normally better than old, but just replacing a line doesn't mean that what the line runs to ISN'T the problem.
I always suggest looking for the obvious first. (Cracked or missing vac. hose, etc). Then I like to pinch off lines that run to the dash, brake booster, choke, distributor and anything else. Many people forget all about what that vacuum line is even there for...
Steve P.
Holiday, Florida

aifilaw

#23
September 03, 2007, 10:49:48 PM
Quote from: Steve P. on September 03, 2007, 08:29:58 PM
I agree with the above. I just want to add one thing that many people blow right on by..

Many times I hear people say that they thought they had a vacuum leak and just went ahead and changed all the vacuum lines. Well new lines are normally better than old, but just replacing a line doesn't mean that what the line runs to ISN'T the problem.
I always suggest looking for the obvious first. (Cracked or missing vac. hose, etc). Then I like to pinch off lines that run to the dash, brake booster, choke, distributor and anything else. Many people forget all about what that vacuum line is even there for...
:iagree:
'72 B5 Metallic Blue Hardtop
426" Wedge - Hydraulic Roller Stealth heads

Bob

#24
September 04, 2007, 07:55:44 PM
OK, went through the hoses again and plugged each one separately. Nothing changed. So I guess I'm back at carb. It amazes me how much you learn on a single string.

Bob
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