alright, my car has developed a high speed miss and I think its the distributor but I want to get a second opinion before I go out and blow 60 more dollars on a motor I don't want to keep much longer , pretty much what it's doing is it will miss fire and hesitate a lot anywhere from 3000 rpm and up, especially if I am just barely on the gas and excelerating slowly or cruising, but if I stomp on it it pulls fine. I've replaced all the tune up stuff ( plugs, points, wires, cap, rotor, fuel filter) and it still does it. I've also checked the timing 10 times and it is set right on (6 degrees), I also tried different gas and octane booster but it didn't make any difference. Also it will do it about twice as bad with the vacuum advance hooked up so I've been having to drive with it disconnected. thanks in advance everyone, Chris. Also has anyone installed the pertronix kit on a 2.0, if so should I try and get one of those or would that even help if my distributor is shot?
What are the chances that your timing belt jumped a tooth?
Jake
That was one of the first things I checked, any other ideas?
Do you have the ability to check timing dwell while the engine is running?
Jake
I have a dwell meter and I checked it yesterday and it seems ok right around 40, but I don't think I ran it all the way up to 3000 when I was doing it so I will check that when I get home, what is it supposed to be at and if the distributor is bad will the dwell fluctuate or what? Any ideas on why it gets worse with the vacuum advance connected? The only thing that makes me think it might be the distributor is it is just about the only thing I haven't replaced lately and a couple people I spoke to ( although they where C@#%y guys) said it sounded like the distributor. Also I don't think this has anything to do with it but it runs like crap when it's cold, but I think that's because my choke is disconnected.
To be honest I would have to look at my valve cover tonight. I don't remember the exact number for the dwell but it is at idle. If you have an automatic you need to disconnect the vacuum advance and put the car in drive with the emergency brake on when setting the timing and the warm idle. Make sure it is warmed up when you do it. Usually the bearings will go bad in the distrubutor housing before anything else. When look thorugh the timing light you will see the timing mark jumping around. Also check the ground wire under the cap for the points to the housing. If its bad it could cause this.
Jake
When I had checked the timing it was with the advance disconnected and the idle turned down ( I think I had it at about 600) and it was warmed up. one thing I did notice though when I was setting the timing was that the light didn't seem steady, it seemed every few times it would flash their would be a pause. You don't think it would be a fuel problem do you, because I allways thought that if it was something to do with the timing or distributor it wouldn't be fine when I punch it. I guess I am just thinking to much about it or something ( stupid boring work)
If I remember correctly its suppose to be a 750 rpm. But if the car is not in drive warmed up at that RPM then you are at the wrong place anyways. Sounds like maybe your timing gun is having a connection problem. Or the spark to your number one is going goofy.
Jake
If you actually are getting an inconsistant spark, (this may or may not be the case, if evidenced only by the non-steady flashing from your timing light, which ITSELF may be defective), it would seem that trying to isolate where the inconsistency of spark is originating should be the first thing to determine.
First thing that I would try is to borrow someone else's timing light to double check the inconsistant spark situation.
If the second timing light gives similar results, then you need to determine precisely where the electrical miss is coming from.
You said that when you "...stomp on it, it pulls fine." Also that "it runs like crap when cold" That, coupled with a possible electrical spark miss you may be picking up, indicates to me that you may have a situation where you are getting too much spark advance. So much advance in fact, that the timing is overadvanced.
I'd suspect that either the initial timing is off first, or that either the vacuum advance or centrifugal advance are allowing too much advance for some reason. You mentioned that you've already checked for a possible timing error stemming from the timing belt, i.e., that the campulley to crank pulley relationship is incorrect. It might be worth rechecking, if only to see that your tensioner isn't so tired that it is allowing the crank pulley to pull a lot of belt (by compressing the tensioner) before the cam pulley moves.
From your description of the symptoms, an overadvancing timing situation may also be happening from too much ACTIVE distributor spark advance (i.e. centrifugal or vacuum advance) rather than from the crank to cam relationship being inorrect, or from too much initial advance.
My reasoning is as follows:
When an engine is run at very small throttle openings, especially when it is significantly above idle speed, with no load on the engine, the vacuum advance is designed to be near to it's maximum set adjustment. BUT, when you floor the accelerator pedal on many older engines, you instantly drop the distributor's vacuum advance to zero vacuum advance(or close to zero, anyway), and are then for a time are running the engine on centrifucal advance ONLY, until the engine gains enough power that you back off on the throttle, at which point the vacuum advance rapidly climbs.
For example, let's say that your initial timing is set at 6 degrees BTDC, with no vacuum advance and at idle speed.
The centrifugal advance on a four cylinder engine will probably be something in the neighborhood of 10-20 or so additional degrees. Let's choose 20 degrees, just for the heck of it. That would make a total of 26 degrees BTDC so far.
Now comes the vacuum advance.
Let's say that it too has a maximum advance of 10-20 degrees. Let's choose 20 degrees.
So you add this second 10-20 degrees to the 26 degrees BDTC that the centrifugal advance had already given you and what happens? Now you potentially have a total spark advance of as much as 46 degrees BTDC, when the engine is at a high vacuum state.
You also said that when you run on centrifugal advance ONLY, it still does it, but not as bad as when the vacuum advance is hooked up.
That says to me that:
1. your initial timing is off quite a bit (maybe you are looking at the timing marks themeselves incorrectly?) or
2. that the cam to crank timing is off; or
3. that the problem actually has nothing to do with the timing or the distributor, (that you timing light is somehow defective and is indicating an electrical miss that is actually not happening), and it is really a carburetor/incorrect-amount-of-fuel-suppllied-during-certain situations-problem. If so, that would also explain why changing the gas and adding octane booster had no effect.
In. re. carburetors:
It's quite possible for some of a carburetors' circuits to function properly, while others do not. foe example, the idle circuit seems to be working here, and also the power circuit, but at an intermediate power requirement situation, (like when the accelerator PUMP is supposed to be just starting to work, or when the secondary's throttle plate is barely opening) there may be a problem.... (This might just be a linkage out of position or an accelerator pump problem, or may be a partially plugged up carburetor.)
BTW, you mentioned a high speed engine miss. This type of miss would be there at high engine speeds, which would of necessity require a larger throttle opening, but if the engine is NOT under load (like when the car is not moving) on many engines, this high engine speed can be achieved without using the secondaries much , IF AT ALL, so IF your engine really has a high speed miss, try to determine if the miss is there when the engine is under load and not under load.
When the car is at the curb, you can look down the venturis to see if the primary and secondary are open, while reving the engine to the point that the miss shows up. Then, if the secondary is closed, manually crack it open a bit to see if the miss goes away. Perhaps the screw for setting the "rest" position for the secondary throttle plate has vibrated and the secondary plate stop needs to moved slightly in the direction of a more open position. Or the plate may resist moving from it's stop for some reason. Eliminating this as a potential problem may help eliminate a "lag" when trying to slowly accelerate.
I've narrowed it down to be an ignition problem now, when I got off work today I borrowed a friends light and double checked the timing and it was doing the same deal, so then I tried to narrow it down some more and retarted the timing to the point where it would barely idle ( I think it was about 10 or so degrees atdc, I am not positive though because the marks stop at three. anyway I took it for a quick drive and presto the problem was gone ( upper rpm anyway, it ran like crap at anything under 2000), so I guess it's getting way to much centrifugal advance, those springs in there where out in time I am guessing, anyway thanks a bunch everbody I guess I am off to find a distributor.
you can get new springs and weights from NAPA. Its called a curve kit or an advance kit. I just bought a set for the race car last week, $6.79 i think.
Here's a no cost alternative to new advance springs for the distributor.
If you're careful, you can probably either snip off a coil or 2 at a time from one or both springs and reform the ends, (which will make the springs stiffer), or just bend the retaining tabs for the advance springs slightly outwards to put more pressure on them. (It's possible that one or both of the springs may have broken, which would be givving you full centrifugal advance at much too low of a distributor rpm.)
Also, on many distributors, each spring is unique, so if you do any changes to the springs, be careful to only take one off at a time so that you know which goes where. Mis-matching the springs and weights can dramatically change the centrifugal advance curve from what it is supposed to be, and can make street driving more difficult (if the advance happens too soon), and/or waste gas (if the advance happens too late).
I'm not certain on this particular distributor, but concerning vacuum advance units in general:
there is also frequently a spring and some spacer washers inside of the vacuum unit. They are there to calibrate the amount of total advance and WHEN it comes in. You could slow down WHEN the vacuum advance takes place and limit the total there by making the tension greater and or limiting the total travel available there also.
To see which is the bigger problem, run the engine with the vacuum advance detatched, and then very slowly accelerate while watching the timing marks, to see the total advance coming from the centrifugal advance, and WHEN it starts and at what rpm it reaches maximum. You will also then have something to compare against after making any distributor parts adjustments/changes.
Since you most likely do not have a custom timing tape on the dampener or the pulley that has the refernce timing mark, you will probably have to make some scratches, use tape or make paint marks on the crank mounted part that lines up with the timing "comb" to have an accurate idea of how much the 2 separate advance mechanisms are advancing the timing.
Happy wrenchin'.
well I am pretty sure it's the centrifugal advance because I tried 2 different vacuum advance assemblies and both of them did the same thing. Anyway, last night I pulled the distributor apart to look at the springs and they seemed a little loose, well to me anyway, plus the cam lobe for the points seems a little worn so I think I'd feel better just getting a new one, I'd end up messing the curve up completely if I tried cutting the springs. Thanks again everybody, Chris.