How do you know where to set the timing?
ammcf1
09-20-2007, 08:32 AM
1994 3-cyl Metro - automatic. I was toying with the timing in an attempt to increase fuel economy a bit - lowering it from where it originally was set. It ran fine for about a week, until I drove it to a higher altitude than normal (3000 ft. higher - up to 10,000 ft.) and when I tried to start it after parking for a day, it did start but spit and sputtered and then died. It would not restart. I readjusted the timing (placed it all the way toward the firewall) and it started right up and has been driving OK since.
I suspect though, that I have it set too high... how do you know where the "right" setting is for this car?
Thanks,
I suspect though, that I have it set too high... how do you know where the "right" setting is for this car?
Thanks,
Mikey_K
09-20-2007, 05:16 PM
I can only give you a partial answer on this one, but oddly enough, I was going to make my first post in the forum asking pretty much the same question you did -- what are the basic ground rules for setting timing?
If you're driving a vehicle that's pretty close to stock condition -- not too many changes to the original set of parts it came with, when it left the assembly floor -- you might be able to advance or retard the timing a little bit, but it's normally not something that needs to be messed with too much. 90% of the time, you can leave it at the original setting and forget about it.
HOWEVER -- if, like me, someone's replaced parts on the vehicle so that it's *not* exactly in an OEM state of tune, you might need to do some messing around with the timing. In my case, my '92 1.0 3-cyl has about 150K on it, and the catalytic converter plugged up. When I got the converter replaced, I told the guy at the muffler shop to go ahead and put in a straight section of exhaust, and not replace that small, resonator muffler in the middle of the vehicle. Believe it or not, with less "back pressure", I'm getting the poorest fuel economy I've ever had with the car. Even on long trips, with straight freeway driving. In this case, I have enough knowledge 'volumetric efficiency' to know that having changed the passageways through which the engine is pumping air, it's very, very possible that the spark timing needs to be re-set, to compensate for the gas flow change. (I remember being told that it's like 'tuning a pipe organ'.)
Only I'm not sure in which direction to start making adjustments.
The first thing I was going to do was use something metal and sharp-edged to make a mark by the distributor, so that I can always set it back to the original setting. Then I was going to play with it, like you've been doing, maybe advance the timing a little bit.
But, to save time, I thought I'd log in here and see if anyone else has gone through the same thing, and has any specific recommendations, or history of experimentation of their own.
The fact that you're driving around at assorted, various and sundry differing altitudes is kind of a similar set of circumstances. Sorry I don't have a more specific answer for your driving conditions, but I'm floating around in a more or less similar boat.
The only thing I was going to tell you was that before you make too many other changes, it might be a good idea to look under your car, as well, to see if you still have a resonator muffler. Open the hood and check out your air filter. Make sure you don't have anything goofy going on with the emissions system, no blinking red lights next to the passenger 'seat belt' display, or anything like that. Unscrew a couple of your spark plugs and see how sooty -- or how baked-clean -- they look. Then go ahead and mess with the timing. (It's usually one of the last items on the list, in any troubleshooting flow-chart.)
Good luck.
If you're driving a vehicle that's pretty close to stock condition -- not too many changes to the original set of parts it came with, when it left the assembly floor -- you might be able to advance or retard the timing a little bit, but it's normally not something that needs to be messed with too much. 90% of the time, you can leave it at the original setting and forget about it.
HOWEVER -- if, like me, someone's replaced parts on the vehicle so that it's *not* exactly in an OEM state of tune, you might need to do some messing around with the timing. In my case, my '92 1.0 3-cyl has about 150K on it, and the catalytic converter plugged up. When I got the converter replaced, I told the guy at the muffler shop to go ahead and put in a straight section of exhaust, and not replace that small, resonator muffler in the middle of the vehicle. Believe it or not, with less "back pressure", I'm getting the poorest fuel economy I've ever had with the car. Even on long trips, with straight freeway driving. In this case, I have enough knowledge 'volumetric efficiency' to know that having changed the passageways through which the engine is pumping air, it's very, very possible that the spark timing needs to be re-set, to compensate for the gas flow change. (I remember being told that it's like 'tuning a pipe organ'.)
Only I'm not sure in which direction to start making adjustments.
The first thing I was going to do was use something metal and sharp-edged to make a mark by the distributor, so that I can always set it back to the original setting. Then I was going to play with it, like you've been doing, maybe advance the timing a little bit.
But, to save time, I thought I'd log in here and see if anyone else has gone through the same thing, and has any specific recommendations, or history of experimentation of their own.
The fact that you're driving around at assorted, various and sundry differing altitudes is kind of a similar set of circumstances. Sorry I don't have a more specific answer for your driving conditions, but I'm floating around in a more or less similar boat.
The only thing I was going to tell you was that before you make too many other changes, it might be a good idea to look under your car, as well, to see if you still have a resonator muffler. Open the hood and check out your air filter. Make sure you don't have anything goofy going on with the emissions system, no blinking red lights next to the passenger 'seat belt' display, or anything like that. Unscrew a couple of your spark plugs and see how sooty -- or how baked-clean -- they look. Then go ahead and mess with the timing. (It's usually one of the last items on the list, in any troubleshooting flow-chart.)
Good luck.
91Caprice9c1
09-21-2007, 01:51 AM
Factory setting is 5°BTDC with the electrical connector under the hood jumpered. The jumper (paper clip, piece of wire) in said connector is important, because it keeps the ECM from adjusting the timing at idle - it allows you to set "base" timing. Anyhow - my fleet seems to run best somewhere between 7 and 9°BTDC depending on the car, and a lot of guys seem to be pretty comfortable in this range. The factory setting really does leave some 'spirit' on the table for the anemic metro.
see: http://www.automotiveforums.com/vbulletin/showthread.php?t=722808&highlight=timing
Your car will tell you if you're going too advanced via 'pinging.' You need to understand what pinging sounds like, because its presence means trouble and you need to not let it continue lest you engine destroys itself. You also need to not go too far retarded (there is no benefit to retarding the timing beyond the factory 5° anyway) because it will burn your exhaust valves. With this in mind, do some experimenting, and some searching on the forum.
-MechanicMatt
see: http://www.automotiveforums.com/vbulletin/showthread.php?t=722808&highlight=timing
Your car will tell you if you're going too advanced via 'pinging.' You need to understand what pinging sounds like, because its presence means trouble and you need to not let it continue lest you engine destroys itself. You also need to not go too far retarded (there is no benefit to retarding the timing beyond the factory 5° anyway) because it will burn your exhaust valves. With this in mind, do some experimenting, and some searching on the forum.
-MechanicMatt
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