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1966 289 Mustang Vibration

6K views 31 replies 17 participants last post by  babodzenta 
#1 ·
I purchased my second classic mustang a few months ago. It’s a 1966 2 barrel 289 with a C4 automatic. It drove great during the test drive but it had issues on the highway home it kept cutting on and off at highway speeds I had to get it towed home. Anyways since then I have been trying to get the car to start running the way it should. However it has a bad vibration in idle, the hood shakes badly and so do the rest of the car. I have changed spark plugs and the wire, new carburetor, new gas take and fuel pump, new thermostat, temp sensor, water pump, new throttle linkage, new vacuum line, new distributor cap and rotor, new harmonic balancer. I have tested compression and the lowest was 115 And the highest was 120. I have set the timing to 6 degrees and it still has the vibration issue. I have probably done more but that’s all I can think of at this point. Any ideas or a list of things I can check... I love these cars but I’m at a loss on this one.
 
#2 ·
Sounds frustrating! Have you checked it with a vacuum gauge? That might give you some more information. I would recommend more base timing (seems like 12* BTDC is the magic number for most). I wonder if your distributor could be the culprit? if the mechanical or vac advance were not working right, the result could be poor timing, although it doesn’t necessarily explain the idle situation. I’m sure my cars (C codes) would idle rough at 6* BTDC. In fact, with my manual trans car on manifold vac. advance, I am at about 20* BTDC at idle, and it just purrs. My other initial thoughts are timing chain stretched past the limit changing your valve timing, and just a straight vacuum leak. I’d love to know what you find out. You’ve eliminated a lot of possibilities so far, so shouldn’t be much more left!
 
#3 ·
Sounds like your just missing something in doing a thorough tune-up. Points or electronic ignition? More timing maybe, set things watching vacuum gauge readings, spray some carb cleaner around the base plate and intake checking for leaks...rechecking the new carb settings...Plug gaps...it could be several things that are not set right vs one thing...with good, even compression you should be able to get the thing running like a swiss watch. No weird ticking noises right? Enough voltage to the coil? There's a lot of things to dial in. Heck, watch a bunch of utube videos on how to tune up a small block ford....keep at it !!
 
#4 ·
If you have verified you are using the correct firing order (1-5-4-2-6-3-7-8) and cylinder numbering (from front to back..passenger side 1-2-3-4 and driver's side 5-6-7-8), counter-clockwise distributor rotation, and that you have #7 and #8 plug wire separated as far as possible, not touching and only crossing each other at a 90* angle (to prevent inductive crossfire) then I'd be suspecting a timing chain that has jumped a tooth or two on the cam sprocket, especially if it's a bit hard to start.

You can check for timing chain slack by watching the distributor rotor while you rotate (by hand) the engine back and forth. Start by rotating it CCW (from standing in front) until the rotor moves a bit. Then rotate it back CW and note how far the balancer travels before the rotor starts to move. It shouldn't be all that far....
 
#5 ·
I’ve actually already done the timing chain check and I don’t believe there is any play in the timing chain. The rotor turns perfectly as I turn the harmonic balancer I’ve done it both directions and the rotor always moves smoothly along with it.
As far as vacuum there is only three lines right? The manifold vacuum to the power breaks and the transmission and then the line from the vacuum advance to the carburetor. Now I have noticed than all of the pictures I’ve looked up show that the vacuum advance should only have one outlet. Mine has two, I have plugged one of them. Should I try a correct one. The only issue I have with working on these cars is all of the aftermarket and mismatched parts that have been switched out over the years....
Should I switch to a pertronix ignition system. I have one it’s just not installed yet. A mechanically inclined family friend wants me to hold off. I have sent the points and all of the lobes on the distributor shaft look good. I haven’t replaced the condenser but if I switch to pertronix I won’t need to so I’ve been putting it off.
I’m not sure what was meant by the 7 and 8 spark plugs being 90 degree apart? I would like to check that if you can show me how or what you mean.
The firing order when I got the car was wrong. Two plugs were backwards on the cap. I thought for sure that was the problem but it’s not. I know the order is correct now I’ve checked it about 100 times.
I’ll get a vacuum gauge and I’ll see what I get as a reading.
 
#7 ·
Now I have noticed than all of the pictures I’ve looked up show that the vacuum advance should only have one outlet. Mine has two, I have plugged one of them. Should I try a correct one. The only issue I have with working on these cars is all of the aftermarket and mismatched parts that have been switched out over the years....
Should I switch to a pertronix ignition system. I have one it’s just not installed yet.
Sounds like you have a vacuum advance meant for a later model engine. I would get the correct vacuum advance. I would also bump timing up to 10-12. You can try running the vacuum advance on the ported vacuum or manifold vacuum. I am running mine on manifold vacuum. Pertronix is a great ignition. I have the pertronix iii and it was super easy to install. That being said it should only make a mild improvement on your idle. If you can't mAke it idle with points there is something deeper wrong. When talking about #7 and #8 plug wires you can get some cross firing between them because they are next to each other on the cap and at the cylinder head. Try separating the two wires so that they don't touch.
 
#6 ·
Sounds like bad timing or a bad vacuum leak...

:eek:)

Tony K.
 
#8 ·
Be sure there is no vacuum leak at the small hose that connects the steel line for the trans to the modulator valve on the trans. Ask me how I know...

Is it possible someone installed a camshaft for a later 302 or 351 Windsor with the 351 firing order of 1-3-7-2-6-5-4-8 ? The crank is esentially same but this changes when the intake vs the exhaust are open and it fires.

Set the static timing and start with all vacuum lines plugged on the engine, then attach them AND a vacuum gauge, dial in your idle speed and carb mixture screws (if they make no difference your throttle is open too far) to achieve max vacuum at idle from 500-ish to 700-ish rpm depending on cam profile, then re-curve the distributor to get no more than 36 degrees total timing advance around 2500 rpm.

Drive. Rinse. Repeat.
 
#10 ·
Ok just as an update I bought a new distributor and I set the initial timing to 12 degrees. The car still vibrated too much in idle so I bought a vacuum gauge/tester. I noticed there was a fitting on the intake manifold that had two nipples and one port for the transmission vacuum line. one of the two nipples was poorly plugged so I connected my vacuum tester. The vacuum gauge read 15/16 in idle I had read on a few other threads that the vacuum in idle should be around 20. So I determined that it much be a vacuum issue or at least the vacuum was part of my issue. I bought new rubber vacuum lines, a new pcv, and a new transmission vacuum modulator. I installed everything and to my surprise the vacuum still read 16 at idle. With the vacuum gauge still connected I adjusted the fast idle screw until the vacuum gauge read 20. I'm not sure what RMP the engine is running at during idle and I have now way of checking as I don't have a tach. To me it sounds like it is idling high however the vibration has completely stopped and the PCV now makes clicking sounds so I believe its working properly. Is there any way to check the RPM without a tach? I'm positive I've heard that you can check it with a multimeter? is this true? Anyways I've noticed that I get shocked when touching the spark plug wires on the top of the distributor. I'm sure this not normal and I don't know what else to do about it. The 7 and 8 spark plug wires are routed in such a way that they never cross and that they always stay at least 2 inches apart. Thanks for all the help and all of the ideas!
 
#11 ·
To me it sounds like it is idling high however the vibration has completely stopped and the PCV now makes clicking sounds so I believe its working properly. Is there any way to check the RPM without a tach? I'm positive I've heard that you can check it with a multimeter? is this true? Anyways I've noticed that I get shocked when touching the spark plug wires on the top of the distributor. I'm sure this not normal and I don't know what else to do about it. The 7 and 8 spark plug wires are routed in such a way that they never cross and that they always stay at least 2 inches apart. Thanks for all the help and all of the ideas!
The PCV clicking does not mean it's working. Actually just the opposite. Its probably the wrong valve for the engine. If your plug wires are shocking you they are probably bad and cracking. Did you replace the plugs and wires with the distributor? Bad wire can cause and idle issue.
 
#13 ·
Anyways I've noticed that I get shocked when touching the spark plug wires on the top of the distributor. I'm sure this not normal and I don't know what else to do about it. The 7 and 8 spark plug wires are routed in such a way that they never cross and that they always stay at least 2 inches apart. Thanks for all the help and all of the ideas!
Put a new set of plug wires on, buy yourself a tach, tach dwell meter or a timing light with a tach. Hard to set a proper tune on a car without the necessary tools.

https://shop.advanceautoparts.com/p...ltimeter-and-engine-analyzer-cp7677/9020009-P
 
#14 ·
The PCV valve I defiantly correct for the car I believe the clicking sound is because the vacuum hose was slightly to long therefore not allowing the PCV to sit properly. Like I said in my first post the spark plugs and wires were changed about a month ago right after I bought the car however they could have been defective out of box? I'm not sure. I can put a new set on but I'm not sure that that would fix the problem. As far a video of the car running I can post on later and I will buy a cheap tach to test the rpm.

Something I forgot to mention yesterday...While timing the car I plug the vacuum line running to carb. Usually I never noticed a difference neither sound or a difference in the amount of vibration. However after increasing the idle RPM when I adjusted timing I noted a major difference in sound when the vacuum line was unplugged from the vac advance.
 
#15 ·
This is happening because you are running the engine fast enough to be off the idle circuit. Vacuum advance is being applied to your timing because the throttle blades are slightly open. This also suggests that you are connected to ported vacuum. When you are idling properly with ported vacuum advance, there *should* be no impact from it on your base timing. The trouble is that if your vacuum advance unit is poorly adjusted or mismatched to your carb/engine, the spring tension may be light enough to actually advance your base timing artificially or with just a slight amount of vacuum leaking past the throttle blades, this can make you think you are setting your base timing properly, when you actually may not be. That's why it's a good idea to disconnect the vacuum hose from the advance unit when setting base timing just to be safe. Did you adjust your idle mixture screws with the vacuum gauge connected? This could feasibly get you to run well at the proper RPMs and generate more vacuum. With a stock engine, 15 is too low. At least 18 would reflect a normal-ish amount of idle vacuum. I would also confirm at this point that your TDC marking on your balancer is accurate. It's possible the balancer outer ring has shifted. A TDC indicator that fits in your spark plug hole is what you need to check that.
 
#16 ·
Attached is a video of the car running. I can try adjusting the idle mixture screws with the gauge connected. I just need to buy a tach to verify what RPM the car is running at. Also the harmonic balancer is new so I'm not sure how the outer ring could shift. I'm also not sure what your calling the outer ring I believe the balancer is all one molded part.

 
#17 ·
I couldn't get that video to play, but I'll try again later. The balancer is probably not damaged if new, but it's worth confirming that the marks are where they are supposed to be. Aftermarket stuff never fails to amaze me with how irregular it can be. The balancers are two parts, though. The outer ring that has the timing marks is bonded to the central core by a bead of rubber material. That part tends to dry rot in the old ones and can allow the ring to shift with the timing marks indicating the wrong position of the crankshaft. They can also completely fail and fall apart. A new one should be good there, but that TDC tool is a good thing to have around.
 
#19 ·
Just from the sounds of things the ignition timing sounds very "late". I'd reconnect your vacuum gauge and advance the timing until attaining maximum vacuum, then retarding until the vacuum just starts to drop plus 2* and then road test. If you get a "ping" on acceleration under load, retard in 2* increments until gone.
 
#20 · (Edited)
I haven’t messed with anything on the car since I took the video that I posted the other day. The day before I recorded the video I had a meeting 30 min away from the house and I decided to take the mustang. I was able to drive it all the way there and back with no problems. However today I went to start it up and to my surprise it wouldn’t start. I got it running for about 3 min but it was really rough and it vibrated a lot. I feel like it was misfiring really bad but I’m not sure. When giving it gas it got worse. I don’t understand what could cause the car to run great one day and terrible the next. Anyways I have put about 700-800 into mechanical components at this point and I’m tired of buying tools and parts not knowing if the old ones are even bad. I will try to get a video of it running later. I haven’t changed the coil but I really don’t want to buy anything unless I’m sure that’s the problem now. Any ideas. I’m sure the car wasn’t running perfectly the other day but at least it started right up and ran somewhat smooth. I might change the spark plug wires later due to the shocking issue however the wires are only a month old.
 
#21 · (Edited)
I had the same issue, it turned out to be 2 MSD plug wires arcing out on the headers.
It just started out of the blue.
Replaced the wires with a new set and now she is purring like a kitten.

Best way to check is have a look in the engine bay at night with the engine running.
 
#22 ·
Keep at it, don't throw any more parts at it yet..Have you set your idle mixture screws yet? It will run rough if not adjusted correctly.. Small 1/4 turns to idle mixture screws, don't have idle too high, what you do to one side you do to other, have vacc gauge connected, keep adjusting to achieve max vacuum.
Also, double check that you locked dizzy back down..

Sent from my SM-G950F using Tapatalk
 
#24 ·
I should probably just teak a break from the car for a day or two and then jump back in. I don't notice a difference when I adjust the fuel mixture screws. I adjusted them half a turn each today with the vacuum gauge on and the gauge reading didn't change. However I will lower the RPM and get a tach and I will see where that gets me. Today I showed a friend how the car was running and again I got shocked when touching the distributor cap. The spark plug wires that are on the car are:

https://www.oreillyauto.com/detail/...1966/ford/mustang?q=Spark+Plug+Wire+Set&pos=0
Any thoughts on the wires should I get 8mm wires I don't want to buy anything else but if I have to then I will.

Also I live in Austintown Ohio if anyone can come take a look at the car that would be great any advice would go a long ways.
 
#25 ·
Babodzenta-
I know what you're going through. I had some idle issues going on and I installed a Pertronix. I took it off, went back to points and still had no satisfaction. I went BACK to the Pertronix and...well I'm not going to say how great it is because I wouldn't want to jinx it, so let's just say I'm driving happily now.

But I know how frustrating it can be.

One piece of advice: if you plan to own your 'stang for years, you might want to buy an "engine analyzer." With a vacuum gauge, you can check quite a few things. I don't know enough to recommend a new one. Here's the one I use that I got from my dad years ago.

Hang in there. Be methodic and patient. It ain't easy!
 
#26 ·
You may be idling fast enough to bypass the idle circuit on the carb, so turning the idle air screws wouldn't have any effect. Get a tach so that you know what your idle speed is. If you don't want to mount a tach inside the car you can hook one up temporarily under the hood. Set your idle to about 750 for an auto trans or 650-700 for a manual, then turn you idle air screws to find max vacuum.

You can also set your timing with the vacuum gauge by advancing timing to max vacuum and then backing the timing off until you lose 1-2" of vacuum. A healthy 289 should pull around 20" of vacuum at idle.

I would reduce idle, set idle air screws, adjust timing, and then readjust idle air screws.
 
#27 ·
@babodzenta I can't remember if you installed the pertronix or not. But if you did, you have to make sure you bypass the pink resistor wire. It only allows 9v to the coil when you need 12. Also did you get the correct coil for the pertonix? I really feel you on how frustrating it can be chasing an issue. Keep working it. You will figure it out.
 
#28 ·
I’ve done a lot more work to the mustang since the last time I added to this post. I was hoping to tell all of you that the problem is solved...but it’s not.

Current List of everything Replaced:
Vacuum Lines
PCV
Transmission Modulator Valve
Carb
Fuel filter
Fuel line from pump
Fuel Tank
Fuel Pump
Spark Plugs
Spark Plug Wires
Distributor
Harmonic Balancer
Water Pump
Thermostat
Neutral Safety Switch
Engine Wiring harness
Timing Chain
Intake manifold gasket
Valve Cover gaskets
I’m sure I’m missing something

I’ve tested a coil it is not the problem. After installing the timing chain I drove the car a few times in two separate days no issues but now it won’t even start I have spark air and fuel. The starter is working it’s turning over just fine. I ran a wire directly from the positive terminal to the positive connection on the coil and tried starting it to see if the ignition was bad but it still won’t start. This is starting to become a nightmare...
 
#29 ·
Morning

A couple of months back I had a very similar issue and it took a lot of parts, time and great info from the forum and we did resolve the issue. It ended up being the small ground wire in the distributor, a simple fix. This hobby is not for the weak and you have proven your willingness to succeed. Keep in there. Good luck.
 
#30 ·
You should not be getting shocked when touching the distributor. I would focus on that. Maybe a loose wire, cracked cap, something like that. Do you have the spark plug wires going to the correct cylinders? Maybe you have one mixed up.
 
#31 ·
Speaking about the ground wire in the distributor. About a month ago one one of the few chances the wanted to run I got about 15 min from the house before the car died. And it took about 20 minutes before I realized that was the issue.

However that can’t be the case because I bought a new distributor and the wire is definitely connected.

I just can’t figure out why it won’t start.

Is there a way to test if the ignition is bad? Or intermittent....
 
#32 ·
1966 289 Mustang Running Rough

I got the mustang running the other day. After cleaning and setting the points multiple times. I issues I had weren’t: slipping points( gap kept changing), and it would arc to the base of the distributor instead of in between the points.

After playing with the distributor the car now starts every time but still runs rough. I have been told to try a new coil even tho my spark is blue for the most part sometimes yellow.

A friend of mine’s father told me that that the pink resistor wire might be faulty because the coil was getting hot after only two minutes. His theory was that the coil was always getting 12 volts instead of 6.

After doing research I believe that the coil should get 12 volts while cranking and then 8 volts in the run position. Is this correct?

I tested mine and I received 10.4 volts during cranking and 6.18 volts while in the run position. What could cause this?
 
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