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Thread: Ignition timing question
07-02-2008, 04:54 PM #1
Ignition timing question
Ok, here's the deal. My '94 1500 'burb won't pass emissions due to high hydro carbons. The CO content was also high, but within the limits (barely). I was told that this typically means that the engine is running too rich.
One of the things that I've taken a look at is the ignition timing. The sticker
under the hood says 0 degrees BDC, is this right? I've come across other threads on here that have quoted anywhere from 4 degrees to 8 degrees.
At any rate, when I went to check my timing, the mark is so far advanced that it's off the indicator markings on the timing plate. Does ignition advance cause an engine to run rich? Could this be the source of my headache?
07-02-2008, 11:16 PM #2
I doubt that timing is the culprit. It rarely is. How many miles on the odo? Has the cat ever been replaced/.There is no way to happiness....happiness is the way.:yipi:
High Desert SoCal
93 K1500 burb (personal) 350 AT 3" Lift 250K+
02 Honda Civic LX
Looking for a 1990's Miata for an engine swap
07-02-2008, 11:47 PM #3
189,000 on the ticker and I have no idea if the cat has ever been replaced. Anyone want to recommend a good one that won't kill my wallet?
07-03-2008, 05:23 AM #4
Did you disconnect the "computer advance" wire before you used your timing light? I can't remember if it's tan and white, or tan and black. You should see an isolated connector to unplug in the engine's harness at the firewall. The zero advance is intended without the computer's advance. It's like in the old days when you disconnected the vacuum advance before checking the timing at idol.Are we having fun, yet?
07-04-2008, 12:28 AM #5
07-04-2008, 02:02 AM #6
Back in the day, the first step to more power was frequently adding to the initial and total advance. In addition to setting the timing and dwell, we were endlessly changing the advance weights and springs in search of the elusive perfect advance curve. Look in some old fart's tool box and you'll find a tube of distributor cam lube and a few old advance weights and springs. And, there's that little file to recondition breaker points.
07-05-2008, 12:00 AM #7
Ok, I f'd up. I had the wrong wire disconnected. The wire was actually under the glove box, which my manual says is only on the '95 models (mine is a '94). Timing is actually dead on. Now I have to figure out WTF is wrong and making my truck run rich.
07-07-2008, 05:55 PM #8
Does it run rich under load, or just at idol??? If it's just at idol, perhaps a cleaning and re-calibration of your Idol Air Control Valve will get you squared away. It's a cheap thing to check first.
07-08-2008, 01:07 PM #9
According to the readings that the emissions place gave me, the problem seems to be mostly under load between 10-20 mph. I'll check out that IACV though, thanks.
07-08-2008, 01:42 PM #10
- Join Date
- May 2007
high hdrocarbons on an emissions check normally points to the 02 sensor--had the same problem on one of my other trucks--high hydrocarbos--changed 02 sensors and passed emissions with flying colorsI didn't do it. nobody saw me do it, you can't prove anything
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