GM Truck Club
THE PREMIER CHEVY TRUCK & SUV FORUM
Founded in 2004 ~ We're the #1 Chevy Truck & SUV Forum.
Silverado & Sierra | Tahoe & Yukon | Suburban & Yukon XL | SUV & CROSSOVER
Page 1 of 2 12 Last Post byLast Post by
Results 1 to 10 of 14
  1. #1

    Default 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?

    TIA.

  2. #2
    Legend unplugged's Avatar
    Join Date
    Sep 2006
    Location
    High Deserts of SoCal
    Posts
    2,554

    Default

    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:
    http://kx6ijq.blu.livefilestore.com/y1pcOFVNH4ix1hjyGUVyXK5LRfef7qSeWzlZDorpQhIEfkZ2ZA  _vXMYypuKMJFw671uF2ZPhjez_j-atRmcjM2zQKpQi1JSsB75/burb1.JPG
    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

  3. #3

    Default

    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?

  4. #4

    Default

    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?

  5. #5

    Default

    Quote Originally Posted by zippy View Post
    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.
    Assuming that I had the right wire, yes I disconnected it. It was under the fuse relay box under the hood, was tan and black leading into a connector and a different colored wire on the other side of the connector. It also had a bus amp that came out when I disconnected the line. Right line? Maybe this is why my timing looks so off?

  6. #6

    Default

    Quote Originally Posted by ct9a View Post
    Assuming that I had the right wire, yes I disconnected it. It was under the fuse relay box under the hood, was tan and black leading into a connector and a different colored wire on the other side of the connector. It also had a bus amp that came out when I disconnected the line. Right line? Maybe this is why my timing looks so off?
    Sounds like the correct wire. Set your timing to zero with the wire disconnected. Then reconnect it, and you should see some advance at idol. Perhaps, in the past, someone dialed some more initial advance looking for more power.
    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.

  7. #7

    Default

    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.

  8. #8

    Default

    Quote Originally Posted by ct9a View Post
    Timing is actually dead on. Now I have to figure out WTF is wrong and making my truck run rich.
    Okay, it doesn't appear to be a timing problem. Now you know how to check the timing for next time.
    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.
    Good luck.

  9. #9

    Default

    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.

  10. #10

    Default

    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 colors
    I didn't do it. nobody saw me do it, you can't prove anything

Page 1 of 2 12 Last Post byLast Post by

Similar Threads

  1. 82 K10 - 350 5.7L - Timing Question
    By ahobson1 in forum General Chevy & GM Tech Questions
    Replies: 3
    Last: 07-03-2010, 07:44 AM
  2. 91 Ignition Timing
    By 91Burb in forum Chevy Suburban Forum (GMC Yukon XL)
    Replies: 2
    Last: 01-01-2010, 02:47 PM
  3. Ignition timing?
    By Pquiz in forum Chevy Suburban Forum (GMC Yukon XL)
    Replies: 7
    Last: 01-07-2009, 01:22 PM
  4. timing gear drive question
    By 89suburban350 in forum Chevy Suburban Forum (GMC Yukon XL)
    Replies: 6
    Last: 04-29-2007, 05:51 PM
  5. Ignition timing [Expired Topic]
    By Davandy in forum Chevy Suburban Forum (GMC Yukon XL)
    Replies: 20
    Last: 09-14-2005, 12:59 PM

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •