Help with rough idle ... vacuum leak.

[bakerhillpins]

All

So my Charger bliss is great but my run time is short. 

It has been running well with a little hesitation when starting from stop but not too bad. Decent idle as far as I know anyhow.  On the way home from a soccer game the other day idle got rough and hesitation from stop got real bad. Seemed like a sudden change. Higher RPMs seem fine. So been sifting through tons of posts on rough idle and it seems that I should start with a vacuum shake down. I will be picking up a vacuum gauge tomorrow but started with simple visual inspections and unhooking lines and plugging with finger to see if there is any difference.

Poking around I found a broken nipple on one of the ports. This is the port that is attached to the #8 cylinder. Right now there are 3 lines tapped off of that port, the head lights, the brake booster, and one line that goes through the firewall between the ballast resistor and the voltage regulator. The small one going through the fire wall is the one that is broken off. Well it is now. It was cracked when I found it. What does that line go to and can I block it off for the time being?

Second, In the many threads I sifted through I noticed that there was some notes about the vacuum tap off the #8 cylinder being a bad idea. What should be connected to that port, if any, and should I think about moving them?
http://www.dodgecharger.com/forum/index.php/topic,30347.msg332002.html#msg332002

[Troy]

Vacuum going into the car is probably for the heater controls (since you ruled out the headlights).

Troy

[b5blue]

Also re torque the intake manifold. 

[Just 6T9 CHGR]

Yes that is the vacuum signal line for the HVAC controls inside the car (blend doors etc)

You can leave it unplugged for now

Im assuming you are referring to the vacuum tree on the rear of the intake?  That is the factory location for it....

[bakerhillpins]

Yes that is the vacuum signal line for the HVAC controls inside the car (blend doors etc)

You can leave it unplugged for now

Im assuming you are referring to the vacuum tree on the rear of the intake?  That is the factory location for it....

I kinda figured that was what that line was for. That explains why the heater blew hot, then cold, then hot, then back to cold. 

Yes, the tree on the back of the intake on the drivers side. I see it in your engine pics on the registry site. Do all 3 items tap into it though? Can't tell from the pics. Will need to order a new nipple if so since one of them is now busted off. 

I took off the air cleaner and if I cup my hands over the intake butterflies and slowly squeeze them together the engine RPM increases which I believe is also a sign of a vacuum leak. I tried to plug the manifold tree but that didn't seem to change it's behavior.  I need to disconnect all three lines and tape it up to do a proper test though.

I am thinking of just changing the intake manifold and carb to intake gaskets just for good measure. Anyone think this is warranted.

I had the compression checked when in the shop last week for new tires and they all came back in the 170-180 range.

[Just 6T9 CHGR]

I leg of the fitting actuallly broke off?  i thought the hose itself just broke off

Yes with an A/C & power brake equipped car 3 hoses are tapped into it.

I would fix the tree issue first then check further for leaks

[bakerhillpins]

I leg of the fitting actuallly broke off?  i thought the hose itself just broke off

Yes with an A/C & power brake equipped car 3 hoses are tapped into it.

I would fix the tree issue first then check further for leaks

Yep, the little metal arm of the tee was broken. When I put my hand back there to check the hose connection it was ovbiously cracked as it flexed with very little effort. It basically fell right off when I tried to pull the hose off to get a better look.

[lokalik]

question for you guys about this post. if you put your hand on top of the carb and the engine dies does that mean there is no vac leak? also what is a good method for checking/testing for a vac leak, ie starting fluid?

[bakerhillpins]

question for you guys about this post. if you put your hand on top of the carb and the engine dies does that mean there is no vac leak? also what is a good method for checking/testing for a vac leak, ie starting fluid?

Sounds like your asking about smothering the intake, It's my understanding that the point isn't to completely close off the intake, but to restrict it more than the butterflies would. It should also be done slowly.

If you type "vacuum leak" or "rough idle" into the search box you will have plenty of reference material to go on. 

In those posts there are several suggestions on how to look for leaks. Starting fluid is one, so was an unlit propane torch, sprayed water and a few others.

[bakerhillpins]

Anyone have a part # for that triple tee or know where to get one? I am assuming it's a Chrysler specific part since nothing came up when I picked up some new vacuum hose to feed the brake booster.

I need to get some manuals. Have to put that on the old xmas list. 

[Just 6T9 CHGR]

Anyone have a part # for that triple tee or know where to get one? I am assuming it's a Chrysler specific part since nothing came up when I picked up some new vacuum hose to feed the brake booster.

I need to get some manuals. Have to put that on the old xmas list. 

Used only...nothing repro.  Sometimes pop up on ebay but looking now couldnt find any...

[bakerhillpins]

Yipee.. 3 weeks in and I am already in need of a part that is unobtainium. 

I tried to heat it up with a torch and possibly remove the broken segment and then install a new one but no go. At least my little torch wasn't hot enough anyhow. For the time being I found a small screw and have torqued it down in to seal it up. Seems to work great. I get a lot of vacuum on the 3/8 nipple going to the brake booster. But alas still a crappy idle.    And to top it all off I got held up leaving the office (tried to get out half hr early, ended up late) so I didn't get a chance to get the vacuum gauge after work. 

I can slowly push down on the throttle and the engine RPM doesn't seem to change. Then all of a sudden it jumps up to 2.5k and seems fine. Then I can back it down to about 1.5k and then it drops to crap again.

Here is a pic of the tee. You can see it's been cracked for some time as the upper half is dirty and the lower is a clean new break.

[maxwellwedge]

Until you put a vacuum guage on it everyone is chasing their tails.

Could be anything - including distributor.

The Tee?  Go to a wrecking yard - that was a semi common vacuum tee. Even a 4 tree will work (cap off the 4th nipple) until you find the proper one.

[stripedelete]

Yipee.. 3 weeks in and I am already in need of a part that is unobtainium. 

I tried to heat it up with a torch and possibly remove the broken segment and then install a new one but no go. At least my little torch wasn't hot enough anyhow. For the time being I found a small screw and have torqued it down in to seal it up. Seems to work great. I get a lot of vacuum on the 3/8 nipple going to the brake booster. But alas still a crappy idle.    And to top it all off I got held up leaving the office (tried to get out half hr early, ended up late) so I didn't get a chance to get the vacuum gauge after work. 

I can slowly push down on the throttle and the engine RPM doesn't seem to change. Then all of a sudden it jumps up to 2.5k and seems fine. Then I can back it down to about 1.5k and then it drops to crap again.

Here is a pic of the tee. You can see it's been cracked for some time as the upper half is dirty and the lower is a clean new break.

Is that a 440, 2nd-gen-only, part?

[bakerhillpins]

Until you put a vacuum guage on it everyone is chasing their tails.

Could be anything - including distributor.

The Tee?  Go to a wrecking yard - that was a semi common vacuum tee. Even a 4 tree will work (cap off the 4th nipple) until you find the proper one.

Yea, that's why I am so jacked that I didn't get the chance to get the gauge after work. I will probably run out early in the AM tomorrow for it.  Ill have to start looking around for a yard that has some older cars in it.

Is that a 440, 2nd-gen-only, part?

From maxwell's post it sounds like no, but from Chris' earlier post it is a tee that is for an AC car.

[bakerhillpins]

So I have a big old vacuum leak somewhere. Gauge reads about 12 in hg at idle. While the engine is running I can hear a sucking sound but it seems to me it's the air rushing into the open 2 bbls. Tried the propane torch trick but it didn't make any difference in the idle. I am no carb expert by any stretch of the imagination but some of the linkages on this thing seem wrong. Look like they are bent at weird angles. Anyone have a manual for the Carter AVS scanned in that might be useful, or where to get one?

Time to go back out an futz with it.

Just ordered up a new manifold gasket that may be in tomorrow. For the whopping $3.99 Ill just get it regardless. Hope it is in when I go pick up the wife on her return from a business trip.

[Dans 68]

This may help.

Dan

[bakerhillpins]

Thanks Dan!  

So I am just going to ramble a bit here and see what happens.

I pulled each and every vacuum connection on the carb and plugged it with no change in reading. Checked for loose bolts and found none. I ran a propane torch around the manifold and didn't get any idle change. I have ordered a new carb to manifold gasket and can change that if needed. Found the following site that talks about vacuum readings:

http://www.secondchancegarage.com/public/186.cfm

I have done a bunch of searches and read a lot which is probably clouding my ability to think rationally.    I read that if the engine has been hopped up will have a lower vacuum set point. Plus they talk about the needle having a flicker or shake to it because of the valve overlap. The vacuum gauge exhibits this shake and a steady lower than normal reading. (Suggest that 15 in is normal) The car had a compression test for which the cylinders came back in the 170-180 range. I read that stock is in the 150s.. So seems reasonable to assume that something has been done to it. When it is accelerated the vacuum drops momentarily to near zero and then jumps up into the low 20s and stays there with a steady foot. When the throttle is released it jumps up into the high 20s low 30s and then drops to normal. So all that looks and behaves as expected.

One thing I did note, not sure if it means anything though..
I was manipulating the throttle with my finger (the air cleaner off was) and as I slowly raised the throttle the RPMs were doggin and not really going anywhere. It almost sounds like an old tractor. Then at the same point (did this multiple times) I could hear a click come from inside the carb and all of sudden the RPMs would jump up to 2.5k and smooth out.

It just occurred to me that I might be describing this wrong. It idles, but there is a rhythmic shake to the engine and with the shake it seems to decrease the RPM just slightly and pick back up. Application of throttle stumbles badly until a certain point of throttle is hit and then it picks up. But then you are at 2.5k and the car wants to lurch forward. Which makes parking in the garage an experience.

The plugs/wires/distributor/coil/air filter are all new.

[bakerhillpins]

Does someone know the initial setting for the dual idle mixture adjustment screws on the bottom of the carb? The results I get in searches seem to suggest 2 1/2 or 1. Either that or it's the difference between the single and dual models. The carter carb I have has 2 adjusting screws on the bottom front of the carb as in the pic above and no center adjust. (looks to be blocked off) I figured I would see where mine are set at and I stopped turning at 4 turns in (clockwise). I still had not hit bottom. I can tell the screw is going in as when I back it out to the previous setting you can see the cleaned threads.  This seems COMPLETELY wrong. Most of the stuff I have read in searches has final adjustment within 1 turn of initial setting.

Also checked the vacuum on the vacuum advance to the distributor and it's zero at idle and goes up to 10 at 2k. I thought that one should always get vacuum from the manifold points at idle?

[b5blue]

I would go all the way in till they snugged up and back out 1 1/2 turns to see what happens. Check the #6 item on the blowup chart, the "step-up rods", they effect metering also. My FBO set-up dizzy takes vacuum for advance from the manifold not a ported source from the carb. (I run a six pack) The ported feed was an emissions improving attempt that made everything more complex.     

[Back N Black]

Does someone know the initial setting for the dual idle mixture adjustment screws on the bottom of the carb? The results I get in searches seem to suggest 2 1/2 or 1. Either that or it's the difference between the single and dual models. The carter carb I have has 2 adjusting screws on the bottom front of the carb as in the pic above and no center adjust. (looks to be blocked off) I figured I would see where mine are set at and I stopped turning at 4 turns in (clockwise). I still had not hit bottom. I can tell the screw is going in as when I back it out to the previous setting you can see the cleaned threads.  This seems COMPLETELY wrong. Most of the stuff I have read in searches has final adjustment within 1 turn of initial setting.

Also checked the vacuum on the vacuum advance to the distributor and it's zero at idle and goes up to 10 at 2k. I thought that one should always get vacuum from the manifold points at idle?

Vacuum advance suppose to be zero at idle because it is hooked up to ported vacuum not manifold vacuum. Ported vacuum occurs when the throttle plates open and manifold vaccum is max at idle and drops off when you accelerate.

[b5blue]

No not for mine. It responded quite well to having full vacuum, but it's set up for that. The quality of idle got much stronger, you can feel it when put in drive or reverse, RPM's are less effected by the drag from the tranny being engaged. 

[NHCharger]

Bryan, call Gary at Winkel Auto in Milford. I guarantee he'll have a half dozen of those vacuum trees. He might have some advice for you as well. He's wrenched on Mopars his entire life.

[bakerhillpins]

I would go all the way in till they snugged up and back out 1 1/2 turns to see what happens.

So the drivers side was 5.5 out and the passengers side was 6.5 out. Turned them both out to 1.5 and it started but it was REALLY rough. Fiddled with it a bit and going in it died and wouldn't start. Going out progressively got better and a bit smoother. Took it out to 2.75 and that was the last change that made an improvement so I left them there.  Took it to Karate class with my daughter and there didn't seem to be the hesitation at the stop signs that I recall. Need to stick the vac gauge back on tomorrow and check it again. Probably take it down to the shop to and see if I can borrow a tach and set the idle. So Ill run it here for a the rest of the year unless it acts up again. Maybe just change the gasket for grins as it was only 4 bucks.

This winter when I store it I will pull the carb and clean/rebuild it. Then in the spring Ill get all the stuff I need to check the timing and start from the ground up.

I am theorizing that the previous owner had hopped up the engine and had an aftermarket carb on there, took it off and put an older stock carb that they had laying around on and got it running to sell. Which might explain the lower vac reading.