how do i check if i'm running too rich

justinbaldwin · 07-21-2003, 09:51 AM

a while ago, someone pointed out that my engine might be running a bit too rich. i would like to address this and am wondering:
1. is there such a thingy as a good/cheap home DIY machine that tells you this?
2. is there some other conclusive DIY test that will tell me?
3. do i have to take it to a shop where they have the necessary equipment?
4. if i am running too rich can i sort it out myself or again, is this best left to the pro?

many thanks

ps. not sure if my messages mention that i have a 1982 euro SC

Rot 911 · 07-21-2003, 09:52 AM

You need a Gunson Gas Tester. Do a search on here. Lot's of info to be found.

tobluforu · tobluforu's Garage

Gunson I hear is the way to go. Or drive car at certain speed in area that you can pull off. Cut engine, coast to side, pull plug and read it.

Superman · 07-21-2003, 10:34 AM

Well, a quick check would have you just looking at a spark plug. Yes, it is best if you cut the engine during road conditions, but even if you idle into your driveway and shut it off, you'll still get a good idea by pulling a spark plug and looking at it. CIS systems, particularly if your SC is a later model (like '82 or '83), run pretty lean, which shows white deposits on the spark plug electrodes and insulator. A rich mixture will be just the opposite...black soot. A rich mixture will also cause the inside of your tailpipe to be sooty, but be careful, there will be some soot there anyway, even with a lean mixture. For me, the spark plug check is the way to go.

stlrj · 10:43 AM

Even if your plugs are white, your engine could still be too rich.

Try pushing up on the sensor plate ever so slightly while at idle and your idle speed should go up. If it slows down, you're too rich.

Or buy youself a Gunson tester.

Cheers,

Joe

CHILI · CHILI's Garage

Joe,

Interesting technique. What sensor plate? Sorry for the possibly stupid question of the day. Anybody have a picture and or can describe it? I've never checked mine, but I'd like to since it's good to know.

stlrj · 07-21-2003, 12:08 PM

Remove your air cleaner, inside the air box you'll see an arm that is attatched to a plate that goes up. A small mirror should help. When the engine is at idle, a slight touch of the plate upwards should raise the idle.

More accurrate and cost effective than a Gunson tester, IMHO.

Cheers,

joe

Formerly Steve Wilkinson · 07-21-2003, 12:48 PM

You can't tell much from a plug these days, with modern compounded and unleaded fuel, unless you do a serious hot cut after a good full-throttle run. Drive around awhile, pull into the driveway, idle a moment and shut down and you'll see a sooty black plug whether you're rich or lean. Same goes for the tailpipe--no longer a reliable indicator. My plugs and tailpipes are sooty even though the dyno says I'm too lean. It's the fuel.

Stephan

justinbaldwin · 07-21-2003, 02:28 PM

thanks for hte info guys, i'll try the sensor trick and will do a test on my plugs, they are due for renewal anyway.

i did a search on the gunson and found out lots of interesting things except how much they are and where to buy them

thanks for the help as always.

i'm off to visit the enemy tomorrow, to italy for film ferrari!

regards

justin

tobluforu · tobluforu's Garage

http://www.aep.bigstep.com/digital.htm

Superman · 07-21-2003, 04:19 PM

I'm going to respectfully disagree. In the 3.5 years I have owned my car, I have used the gasoline I think Steve is calling "modern compounded and unleaded" in both lean (factory CIS setting with O2 sensor....yes, very lean) and rich (3.5% CO right now) conditions. Regardless of whether the engine idles before shutoff, I get a very clean plug with white deposits when running lean, and a darker plug with no white deposits when running rich. I'll say again that (since I do not have a Gunson tester) my best quick check is to pull a few plugs and look at the electrodes.