Still shaking at idle

[Anonymous]

I've posted a few times in the last year or so trying to find ideas as too how to get rid of the shake/vibration at idle in gear on my older 200 with C4. I visited this week with a local machine shop owner who just happened to have read a letter to one of the mustang magazines describing this same problem a few days before I called him. The magazine response was that they had heard of this problem several times and it always came down to carburetor idle circuit problems with the autolite 1100. They continued to say that sometimes several re-built carbs had to be tried until it went away. Anybody reading this ever had this experience?? I have had this same problem with 2 engines, 2 carbs, 3 distributors.... I am currently running a YF carb and Duraspark ignition. The YF is cheaply adapted by filing the hole in the original spacer into a conical shape. The machinist looked at the torn-down first engine this started with and didn't see anything valve wise etc that he thought would cause the shaking. I am not holding out much hope that a proper adapter for the YF would make much difference but might try it. Any ideas or comments would be appreciated.

By the way...Thanks to this forum the car runs way better off idle than it has in years.

 

[Anonymous]

I'll have to give you my completely unprofessional expereince on this subject after dealing with timing, vacuum, and other issues on my car.

I am going to assume that your idle speed is smooth in Neutral or Park, and it's only when you're on the brake in "D" or "R" that the vibration is really bad.

The basic reason that there seems to be so much vibration is because, when setting the idle to stock specs, the engine just isn't pulling enough vaccum. Introducing more timing, richening the fuel mixture, etc, just help improve the vacuum which improves the idle. Obviously having too rich or lean of an idle circuit will affect this as well, but let's assume your idle circuit is OK.

I don't know what you have your "in gear" idle speed set to, but I would be willing to bet that if you checked your vacumm you're pulling less than 10hg in 'D'. In my car, with a new rebuilt head and decent cylinder compression readings, I was pulling about 7hg at 650rpm.

Again, I fiddled with timing advance, plugging of vacuum ports, Duraspark conversion, different heat ranges of plugs and gapping, etc. and nothing really changed.

Assuming that you have already checked your system and can confirm with certanty that you have no vaccum leaks, the easiest, quickest, most headache free way to fix the vibration is to simply increase the idle speed. On my car, I found that just 100 more RPM, to 750 in D, and the car is very smooth with little vibration, and my vaccum was reading over 10hg. This keeps me at 950 RPM in Park, and I have no gridning or clunking problems when going into gear.

Also, I would recommend a new harmonic balancer. I though mine was fine, but replaced it with a rebuild from the Damper Doctor. For $50 I was really happy with the quality, and I also benefitted from a slightly smoother idle.

Last point - check loose bolts. I know this sounds wierd, but noise can be transmitted to the driver as vibration. I had a varietly of loose bolts holding the fender on, and I also had a loose alternator bracket bolt that was causing a pretty loud rattle. I know that my alternator wasn't shaking the whole car, but locking down that loud sound definitley increased the perception of smoother idle.

Good luck and I'd like to know how it works!

 

[Anonymous]

I have played around with idle speeds etc many times but just tried it again and....

750 in drive = 1275 in park
750 in drive = 12 in vac
650 in drive = 1175 in park
650 in drive = 14 in vac
if drop the idle even more vac continues to rise ???

I have my vac gauge in the "pcv" port in the stock carb spacer.

What I'd really like to find out is if anyone has had this problem and corrected it via carburetion like the magazine letter answers claims ??

 

[Anonymous]

So you're pulling 14hg of vac at 650 and you're still having a rough idle?

Does is smooth out in Park or is it always bad? Understanding what conditions it smooths out will help diagnose the problem.

What does the vac. needle look like? Is it steady at 14hg or does it sway or jitter? If it slowly sways a few deg. that's the sign of a vacuum leak. If it's steady but the needle is jittering that's valves.

Describe rough? I was thinking about your problem on the way home and there are different types of rough idle. Could be a broken or cracked motor mount vibrating the car. Or something else in the drivetrain.

Certainly the carb is a component. Those 1100 carbs are notoriously troublesome and I've certinaly seen improvement in idle with better tuned carbs. But you're saying you've had the same problem with different carbs, yes?

Have you played with the idle mixture screw at all? What happens to the idle quality as you adjust the mixture in and out? I can't say that I can explain how vac increases as idle speed decreases, but perhaps you have a lean condition that is richening as you're sucking less air.

What about timing? What advance are you running at 650?

 

[Anonymous]

Just checking - but have you replaced your motor and transmission mounts?

I had a very bad idle in drive and reverse until I replaced these.

 

[Anonymous]

I think I've eliminated valves in that the vac gauge is fairly steady and I have the first engine that this occured with torn down and they look OK per the machinist that looked at them.

I am not sure where the timing is per the rpm vs vac checks I did last night. But I did lossen up the distributor and rotated it around a little to see if it made much difference. From the point it was at, it seemed to run worse rotating either direction.

Yes I have had different carbs. It started with an 1100 which I could hardly keep tuned well enough to use the car. It would flood out regularly and/or stall a lot not to mention lots of hesitation problems etc. I tried various combinations of parts from 2 - 1100s, I got it working OK for a while and then it went bad again. I then switched over to a YF I bought off E-bay and rebuilt. This has been considerably better after solving a flooding problem with the rebuilt needle/seat.

The vibration is fairly harsh. Enough to rattle anything even near loose. Early on in this problem I believe it destroyed my tranny mount. I replaced it. I have tried 2 different sets of motor mounts. I really think I have elimnated anything to do with mounts, exhausts or other "hard" contact.

I have consulted with a local transmission guy who says it doesn't act like any imbalance he's experienced. Similarly the machinist I consulted says the same.

The vibration is very "even". It does increase with engine RPM. And, best I could try to determine, it is very much near or at the engine RPM frequency. I think it is still there in park/neutral but much harder to detect. IT goes away as soon as the carb is "off idle".

With the first engine I tried all sorts of things... running with out the belt on, Running withouth the vibration damper, running with no exhaust. disconneted various mounts and supported with a floor jack. All ran the same. I've tried different grade fuels with or without a valve seal protectant additive fed out of a gas can. different grade oils, and as I have said before 2 different engines and transmissions and 3 different torque converters.

May latest thoughts are that I can't absolutely be sure I don't have some very slight vac leak with the way I have "jury-rigged" the YF carb. I think I'll proceed to make a decent adapter. If that doesn't help I think I'm headed toward getting a later model head.

 

[MustangSix]

14" is low for a stock cam. You should be up at least 16-18" at idle.

This may be a worn out distributor. If there is a fair amount of play in the shaft, you'll get results like the ones you're getting.

Shaky idle can also be a result of inconsistent cylinder pressure. You might need to do a compression check and a leakdown test to see if you have one or two that aren't doing their fair share of the work at idle.

One other long shot. You say it happens in gear. Only in gear? Is it ok in neutral? I have seen one case where a bad torque converter with a busted vane caused a helluva hard to find vibration. Usually something like that causes a transmission failure, but in this case it kept on running.

 

[Anonymous]

I had the same problem with my Mustang as you are experiencing with your 200.

I went through everything. I mean EVERYTHING! I eventually narrowed my problem down to the fuel mixture which was do to a not so decent carburator. Eventually after swapping out several Autolites and Carters I got one to run fairly nice.

Just my two cents worth but these motors can be very frustrating. I would be interested to know what the block and head codes are of those who have had this same trouble. I say this because it seems like no matter how experienced some of us are at working on these engines, some motors just seem to be more difficult to work on. Could there be some connection? Manufacturing defects?

Just some thoughts.

-Chris

 

[Anonymous]

if it was his distributor being loose or worn, he would have tell tale signs in the spark plus, wouldn't he? that happened to my bro-in-law. It took the mechanic a long time to figure it out. His plus were all over the place in deposits and melting etc...

my non-technical relaying of this story....

 

[addo]

Didn't the early motors have heavy metal counterbalance plugs in the crank? What if one came out?

 

[Anonymous]

Couple more points - if you don't have a light and can't confirm your timing settings - you need to start there. Timing can have such a huge effect on idle, that to just "lossen up the distributor and rotated it around a little" is a very bad idea. You don't know what types of problems that could be causing.

To fix this you need to eliminate each problem one at a time. FIRST confirm that your timing and dwell are set properly. You should be at 7-12 deg just to be safe. Not sure offhand the proper dwell (probably 28-32deg)

After that I would disconnet all external lines from your carb and plug them - vac advance, PCV, and if you have an auto trans remove the line off the manifold to the trans.

You can check for vacuum leaks by spraying carb cleaner around the base of the carb, mainfold, etc. If your RPM increases then you know where your leak is.

After confirming that you have no leaks, then you want to play with your mixture screw. This will determine if you have a a problem with your dile circuit. Turn the screw all the way in and the car should die. Back out 1 1/2 turns then re-start the car. You should turn the screw in or out in 1/2 turn at a time until you achieve best idle, then turn IN 1/4 turn and you're set.

After all that, I would have to say that I don't think your problem is carb related. The reason is that after about 1000 rpms, you're probably not on the idle circuit alone - at least on my car at 1000 - 1100 my throttle plate is open slightly. If you had an idle circuit problem that would stop farily quickly - again by 1000 - 1500 RPMS your idle should be silky smooth.

This type of problem sounds ignition related - like some sort of miss. That woud be the case where the vibration harmonizes with RPM. In those cases it really takes freeway speeds to hide a slight miss.

I would think there is something wrong with your points/cap/rotor/plugs/wires/coil or you have a serious timing problem. Make sure that, with your timing mark at '0' TDC, your pistion is at the top of the compression stroke, and your rotor is pointing to the #1 plug on your dizzy.

Good luck! I know how frustrating these things can be!

 

[Anonymous]

It did something new today. For the first time in literaly years it ran acceptable at idle in gear especially cold. It got a little worse after warming up. This has always been the opposite -worse cold- better warm, All it it did was sit overnight. I am really thinking I have some sort vac leak thing going on. We're experiencing our wettest weather in a very long time which just rolled in last evening. Maybe the thick gasket I have under the carb swelled or something????? Anyway I going to check the timing settings etc and then proceed to build a better adapter.

mustangsix: Best vac I've ever seen is about 16 in neutral. and it drops to about 14 in gear. I'm going to check those numbers in the morning too. Being on the low side of the spectrum might have to do with being at 7000 ft. Same cfm of lower density air than sea level kinda thing ????

 

[Anonymous]

Two things I have found on my 200 this weekend in tearing things apart.

I too had this same vibration, not as bad as yours, but most noticeable in idle at curb. What I found today has me wondering?

My torque converter looks pretty toasted, there is a small crack in it.
Also the cam in this car is worn really bad. Going from memory I read in the Ford Six Handbook I think, that cam wear can cause vibrations and such in these sixes too....

Those two things alone explain a lot about what was wrong with my car.
I am replacing them both anyway, so it will be a few months before I can tell you if that fixes the problem???

By the way.... this engine config was...
C8 200 block
C9 "M" 250 Head
C4 Auto
Carter YF carb and DurasparkII

Had a vibration at idle for two years.

 

[Anonymous]

Got the new adapter for the carb in today but haven't had much chance to run it. First impression is that it runs as good as it did the one day it seemed better last week. Next month I will have had the car 30 years. I can remember when I first got it I had trouble keeping the spare tire and jack from rattleing at idle (it's a wagon). I'm really beginning to buy in to the belief that it is primarily a carb condition vs design problem. At this point I can "cheat" the idle up a little and it becomes bearable which is a significant improvement. I am disapointed to hear that Jimbo65 is having this problem with a C9 head. I thought a head upgrade was in my future with the thinking that the bigger log etc would make this go away for good. I wonder if any of the 2 bbl or 2V owners have had this problem: Jimbo, I have had damage to a torque converted too. The Pump bushing and TC hub wore bad enough to cause the pump to whine. I have some thought that these could have been victims of the fairly severe shaking.


The 2 configs I have had the problem with are:

C3 head on C5JE (4-main) Block, 1100 carb, stock ignition, C4

C5 head on C5DE (7-main) Block, 1100 carb, stock ignition, C4
Carb/ign then swapped on this config to YF and Duraspark

 

[Anonymous]

That's really very curious, because that is exactly what happened to my converter, it was making a bad sound cause it was worn like that.

I can only hope the T-5 and 200 will not have this problem. Once that is in I am sure the problem will go away. Not to mention the new engine will run much different than the old one....

I am curious what your findings are and will watch for updates.

As for the C9 head I am pretty sure the head has nothing to do with this vibration, mine always seemed more internal to the engine and bellhousing.

I am even wondering if the wear inside the TC and bushing was not the source of the vibration itself, since it seemed to get worse as of late. If this thing was getting worse it would vibrate more, and it would do it worse in idle. Then once the car is up to speed the vibration doesn't really stop it just gets so minimal you can barely feel it.

I noticed a subtle surge like sound in the engine at speed, it was not really a surge because the car didn't gain or lose speed. What it felt like was a vibration that pulsed like a surge would, but you could feel it more than you could hear it. Kind of Whump Whump. It's hard to describe.
But I am thinking that was the off balance TC.


Seems likely to me, these two are related.
But I am only guessing here, since I know only so much about these things.
Do you know what condition your current TC is in?
Can you rule that out completely?

 

[Anonymous]

I'd like to think I could rule out the TC. When I first went after this vibration I swapped the one I had for a rebuilt. The rebuilt is the one that I experienced the bushing/hub wear with. Then I swapped engines but kept the same C4 and TC. Then I swapped the TC for one from the donor car I got the 2nd engine from. Then I swapped the C4 for the one from the same donor car. All this time the vibration stayed essentially the same. It wasn't until this latest carburetor experimentation that I had any improvement.

 

[Anonymous]

hi

for your problem i would check your engine mounts and replace them my mustang had the same problem you have, i replaced them and it did the trick. Some motor mounts just get old and break.:wrench: :checks:

 

[Anonymous]

Hi Falc64,

As you have probably gathered by now this problem is not unusual. I suffered with it for many months after purchasing my 66 Mustang. As a matter of fact Corellian Corvette, 66200I6 and I shared a lot of research and "trial and error" over this problem. While there is always more than one way to skin the cat, I think it safe to say it is a carb idle circuit / idle timing issue. I say this based on the fact that all of the other possibilities have been covered, i.e, vacuum leaks, timing chain, valves, mounts, TC's, etc. While C Corvette didn't mention it, I know he went with the Holley 5200, as did 66200I6 and I. I also know that all three of us spent much time with the dizzy issue (idle and advance curves). By the way, everyone with this problem has an automatic, the ruff idle is in gear at a stop (brake on), and usually clears up as soon as you add even the smallest amount of throttle.

The fix for me was; 1) Holley 5200, 2) Pertronix ignition in a dual advance dizzy with the vac advance capped, 16* initial and 36* all-in (this car, with stock cam, likes a lot of initial); 3) in gear "brake on" idle of 700rpm (15 -16 inches of vac).

I subsequently added the header and the 1.6:1 adjustable rockers and am very happy with the result.

For the record my 200 is a C6 block and a C9 head with the 1.5" carb mount bore, i.e., not an "M" head.

Hope you feel less alone - Steve

 

[LEROY POLL]

HELLO FALC64

....YOU BEING AT 7000 FT HIGH....THEN 14LB VAC. IS VERY GOOD AND 16.. IS EXCELENT.

....THE TIMING LIGHT IS THE FIRST THING YOU NEED TO GET. BY CHECKING THE ADVANCE YOU WILL UNDERSTAND WHAT IS HAPPENING. YOU SAID THAT THE ADV. WENT UP AS YOUR RPM WENT DOWN AT IDLE. WHERE DO YOU HAVE YOUR VACUUM ADVANCE LINE HOOKED TO? MANIFOLD VACUUM...OR VENTURI? HAVE YOU CHANGED YOUR DIAPHAM LINES? THEY COULD BE LOOSE OR BACKWARDS

....ALSO CHECK WITH FORD, THEY DO HAVE SPECIAL CHANGES FOR CAR THAT ARE RUN AT 6000 FT AND HIGHER. YOU JUST COULD BE RUNNING TOO RICH FOR THAT ELEVATION. ( I BELIEVE SMALLER JETS)

.... THIS IS SO INTERESTING THAT IT'S SOME THING I WOULD LIKE TO SEE. NEXT TIME I GO THUR I'LL GIVE YOU A CALL.

KEEP THE FAITH WE WILL FIND THE PROBLEM........ IN TIME.

LIVE IN GRACE

LEROY POLL

 

[Anonymous]

Timing.... I was running with a direct manifold connection when I first put in the duraspark (single advance). I switched over to one of the ports on the YF carb. The YF I have has 2 ports both have 0 vac at idle and "pop up" to what appears to be full vac as soon as your off idle. I haven't spent much time on this. I do have a light... It isn't a dial-back so best guestimate is I'm currently running 20° plus at idle (sounds best). I do need to work on this... Can anyone tell me what the 2- ports are inteneded for :

Jets.... When I was running the 1100 carb I did try different jets. The last I had was what my 64 shop manual said I should for my altitude. I had so many problems with that carb I can't tell you what worked best. Anybody have jetting info for the YF v.s. altitude :