Non-Steady Idle While in Gear and Brakes Applied

Michael Dimock

Michael Dimock

IH Parts America Sales Assoc.
Okay, I have a 72 travelette w/ a 304 and 727 auto. The 304 has a rebuilt carb, new distributor internals, new vacuum line, and all the extra vacuum ports capped. It idles great in park, and has great acceleration and on road manners, but when I get to a stop light and stop with the brake on in d 2 1 or r the engine will idle, then lug down sporadically. It doesn't matter how hard the brakes are applied. It won't do this idling and rolling, only when stopped.:rolleyes5: sometimes upon takeoff it will die and come very close to that when stopped. There is no constant lugging, sometimes its good for 10 secs and other times it lugs down right away. But it will always come back up to idle then lug, repeat.... Is this a linkage problem? With the linkage bouncing around and causing the trans to want to engage more (when engine lugs)? This is just the last issue that I'm fighting to get it to be a perfect dd drivetrain wise. :idea:
 
Did this drivability issue begin after you and pop left here with the trailer last week?? It had a perfect idle characteristic when we finished diddlin' with the carb and stuff at that point.

I know that rig doesn't have power brakes, so it's not a vacuum-related issue as related to a potential leaking vacuum booster. At least I don't "think" it does, but I've become confused with all the vehicle comings and goings between you and the roth klan!

And the transmission shift control/linkage won't cause any issue like this.

Rig a vacuum gauge on it and let's see some numbers and describe needle movement when the stumble occurs. Needle "action" is real important when the problem occurs, that can mean several things...including a valve/rocker trying to "semi-stick" due to poorly-lubing rocker assembly. We know there is potential for that based upon the condition ya found the valve train in!

Also...put the dwell meter on it (28*>32*) or verify that the breaker points are still set at 0.017" gap.

Remove/plug the vacuum feed to the distributor and see what happens also.

Pop the air cleaner back off and make certain the choke is being held open by the internal pulloff when the choke is fully open.

Rig your fuel pressure gauge on it and watch pressure when it starts acting up. The fuel pump would be just as crappy as the carb was originally due to the previous situation with that truck. On that carb you are watching for a nominal 5psi at any engine rpm,witha fuel delivery rate of one pint of liquid within a twenty second crankover of the engine into a glass jar for observation.

It's a remote possibility that a failing torque converter can be creating this, but that would be extremely rare and is not a normal failure mode of a 727 torque converter.
 
No, it's been like this since when I got it. I unplugged the vacuum line going to the "#9 tomato can" and capped it, along with the 3 ports on the vacuum switch. I have a vacuum gauge that I just recently acquired. The torque converter appeared to be brand new, as there was no oil on it and it was a very bright and spotless blue. Will check the gap of the points again this weekend. Will hook up the engine analyzer to see if the dwell is correct first. Will probably need another person to operate the brakes while I check the vacuum, etc.
 
Tell me one more time...power brakes on this rig or not???

I thought I had some underhood pics of this ride, but I can't find 'em in the roth vehicle folder I keep on the desktop! Guess I need to move all those jpegs to your folder now.
 
Idle quality diminished slightly yesterday..... It was stumbling a lot when I applied the brakes at some points.:icon_exclaim: can a closing point gap cause these problems?
 
michaeldimock said:
idle quality diminished slightly yesterday..... It was stumbling a lot when I applied the brakes at some points.:icon_exclaim: can a closing point gap cause these problems?
Click to expand...

Of course! Not only does the dwell change...so does the base timing!

Were you asleep leaned up beside wes at the last training session??? Ya need more private lessons???

Review that handout ya handed out to everyone! Or did ya not take it home???
 
Well, did some parking lot tunin' and discovered when I popped the distributor cap that my point gap was way wide! Set it at .018 before, but must of not had the points on the highest part of the distributor lobe or it wandered. :idea: anyway, it still stumbles a little bit every once in a while, but I don't have to worry about it dying at every stoplight! The new muffler is breaking in, and I'm getting a better exhaust note now. But, I think I have a new exhaust leak on the passenger side now....:rolleyes5:
 
When you just re-set the breaker point gap...not only did you get the "dwell" back within range, you have now changed the base ignition timing from what it was before you re-set the point gap!!!

So now ya need to verify ignition timing...again! Do the power timing thing, all it takes is a 1/2" wrench on the distributor hold down.
 
Did some more parking lot tuning, as when I got to the lbcc parking lot and shut the truck down, that sucker backfired so f$%^ loud that a couple people in the parking lot thought someone was firing a gun......:rolleyes5: luckily it didn't blow a hole in my newly installed muffler.:idea: ended up advancing the distributor a little more than before, and man does it run good now!:icon_up: I can feel the hydrocarbons being burnt more efficiently and it has a little bit more pep off the line. The great thing is, I have no problems sitting at a stop light anymore. She just idles along beautifully!:yesnod: just when you think you got it right, you find out it is always best to check again, just to make sure.:icon_twisted:
 
You must log in or register to reply here.
Back
Top