I'm trying to figure out whether my misfire/backfire is fuel or spark related and removed a "locked" distributor and installed a stock one. I then set the spark table to all zeros so that the distributor would control all timing. I set the timing with a light at 10*. So my question is, should my trigger offset also be set to 10*?
MSII, v3.0, 2.89code, was running fuel and spark, but very poorly.
setting spark table to all zeros
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Read the manual to see if your question is answered there before posting. Many users will not reply if the answer is already available in the manual.
If your question is about troubleshooting, configuration, or tuning, you MUST include your processor type (MS-I or MS-II) and code version in your post. If your question is about PCB assembly or modifications, you must also include the main board version number (1.01, 2.2 or 3.0). For tuning/troubleshooting questions, please attached a datalog and your MSQ file to your post.
If you have questions about MS1/Extra or MS2/Extra code configuration or tuning, please post them at www.msextra.com Such questions posted here will be moved to: a temporary MSextra sub-forum, where they will be removed after 7 days
The full forum rules are here: Forum Rules, be sure to read them all regularly.
Re: setting spark table to all zeros
Best to set your entire advance table to 10 and the trigger offset to 10 too; but all at 0 should also work.
But a caution... if MS is doing the sparking then there is no way the distributor can "control all timing"; it will still spark when MS decides. When first installing my MSII, I tried leaving the distributor advance mechanisms in place with constants in the advance table; it was pretty terrible. MS expects the tach impulses to arrive very regularly and gets "surprised" when the distributor sends signals at unexpected times. This messes up its prediction algorithms and I had various problems (e.g. with detonation when starting from rest). It was fine when running in steady state.
Have fun,
Rob.
But a caution... if MS is doing the sparking then there is no way the distributor can "control all timing"; it will still spark when MS decides. When first installing my MSII, I tried leaving the distributor advance mechanisms in place with constants in the advance table; it was pretty terrible. MS expects the tach impulses to arrive very regularly and gets "surprised" when the distributor sends signals at unexpected times. This messes up its prediction algorithms and I had various problems (e.g. with detonation when starting from rest). It was fine when running in steady state.
Have fun,
Rob.
Re: setting spark table to all zeros
Your prior "problem" sounds very similiar to what I'm experiencing now. Just driving down the interstate at a steady speed it runs fairly well, but at high rpm's and/or under load, it backfires/stutters horribly. It also seems to "hit a wall" at around 4500 rpm, the stock ecu would let this exact same engine rev to 7k. Changing the trigger offset from 0 to 10 helped this alot, but still isn't completely cured.
Guess I need to come up with a decent timing table....
Guess I need to come up with a decent timing table....
Re: setting spark table to all zeros
Can you get hold of the original advance curves for your distributor? That's what I worked from to build my table. Car ran well afterwards with electronics doing a better job than old worn mechanicals. I haven't felt the need to tweak it since.
Just to be sure, you did set your entire advance table and trigger offset to 10? If your advance table is all 0 and trigger offset 10, that will retard everything by 10 degrees. If that made it run better, there's something way off. Probably worth giving it another go with the timing light in any case.
What you're describing sounds pretty serious. That adjusting the trigger offset improved things suggests it might be related to advance, but lean running can also get things bucking. Besides, ignition timing should be pretty well fully advanced by 4500 rpm, so it doesn't seem likely that it's purely your advance curve at fault. Hope you don't have your rev limit set to something silly!
Have fun,
Rob.
Just to be sure, you did set your entire advance table and trigger offset to 10? If your advance table is all 0 and trigger offset 10, that will retard everything by 10 degrees. If that made it run better, there's something way off. Probably worth giving it another go with the timing light in any case.
What you're describing sounds pretty serious. That adjusting the trigger offset improved things suggests it might be related to advance, but lean running can also get things bucking. Besides, ignition timing should be pretty well fully advanced by 4500 rpm, so it doesn't seem likely that it's purely your advance curve at fault. Hope you don't have your rev limit set to something silly!
Have fun,
Rob.