What's my a/f ratio?

[iraq_vet_x2]

here's my problem...I think my A/F Ratio might be off, but I don't know how to check it without investing in a AEM Wideband Gauge or something similar. Is there a shade tree way to find out what I'm running?

Stats: '89 258, Carter, (I know "go get a 2100")

 

[Wrangl3r93]

Pull your spark plugs and check them. I have absolutely no experience with this just read it somewhere, drag racers pulling them between runs maybe? I think white means you're running lean and black plugs is rich. Not an exact science though. I probably pulled that bit of information out of thin air so wait till someone more knowledgeable comes along

 

[SteelHeadz]

I have a vacuum gauge on my dash that i use to see where my vac. is at idle along with the proper timing and fuel mixture set at the optimal setting where the engine responds to a wide open throttle and smooth at idle. Like what Matt has suggested , i made several runs on the highway and re-checked the sparkplug condition for the optimal combustion. I use platinum sparkplugs and had to buy 2 sets just in case i have to replace them if i foul them out on the trial and error. I also gapped the plugs @ 0.040 in for the best efficiency.

 

[TerryMason]

I went through this with my CJ7, then with my 914 - I ended up spending $350 on the wideband for the 914...

There are a couple of things you can do:
- sparkplugs as mentioned - white = lean, dirty = rich
- hold a white rag or paper towel behind the exhaust tip. A rich setup will blow out unburned gas that will show up as what looks like soot.
- Does it backfire? Backfires on deceleration normally mean it's lean.
- Does it run hot? normally a lean engine runs hotter.

 

[GaryMB]

Also if you smell gas then it is running rich

 

[Ggg]

There are air/gas analyzers out there besides the UEGO type of a/f gage but they cost even more that the AEM mentioned. For about $250 the AEM it is priced well. The other air/ gas analyzers or diagnostic computers are well over $1000.
Reading spark plugs is an exact science, it will tell you things about your engine you wouldn't believe. But it takes a LOT of instruction, skill, and practice to do it accurately. The small paperback Chilton repair manuals used to have a section of color photos that would show spark plug readings, it was good for general tune up purposes. Here is a link to some good plug reading info;
Spark plug - Wikipedia, the free encyclopedia
IMO reading plugs is the best way to tell not only if your engine is lean or rich, but which cylinder is doing what. I could go much farther in depth about reading plugs but for this thread this will suffice.
Vacuum gage will not tell you if you are rich or lean, it is very helpful in determining engine timing, general mechanical condition, as well as fuel economy. It is a bit of a lost technology sad to say, but still very valid.

 

[iraq_vet_x2]

Hey gents, thanks for all the help! I'm going out of town to Austin for a few days, but when I get back I'll get under the hood and let ya know what I found with the plugs, papertowel, and vacuum readings.
Terry, to answer your question, no, it doesn't backfire nor does it run hot. When it drops to low idle (~700-800rpms) after warm up, it wants to jump back up to high idle after only a few seconds...Like the computer is recognizing that it's about to die, so it steps it back up. Also, my gas milage seems to be going to hell. I just replaced the engine with a new 258 I ordered a couple of months ago and a new 3550 behind that a couple months before the engine, it's been running great ever since....up to now of course. The carb has been working good, my computer works, all my enviro elements work, and all my vacuum hoses are run properly and in good working order.
I'm thinking is I'm either running rich or my timing's gotten off. I'll get under there with my timing light after I get back too.

 

[Ggg]

Just off the top of my head try looking at the o2 sensor(s) they will cause a run rich condition.

 

[TerryMason]

I think that Gregg has a good idea. If the O2 sensor is cheap I'd go ahead and swap it out.

 

[iraq_vet_x2]

Hey, that is a good idea. It's 20 bucks at autozone, I'll pick one up before I head home and swap it out.
I'm sure the wife will love that.

 

[iraq_vet_x2]

Ok guys I'm home, and i swapped out the O2 sensor. There was a pretty bad crimp in the wire of the old one, but the new one didn't fix the problem. Maybe it was already bad and the new problem is just compounding it? Anyway, I let it run with the new O2 sensor in high idle to see if it would kick down to low idle and stay there, but it didn't. It shot right back up to high less than a second after it dropped. I pulled two of the plugs to take a look at their color, and I inserted a pic of them. Maybe ya'll can tell me what you think...

I held a papertowel behind the tail pipe for about 10 seconds, and it was clean. While it's running, its got a real strong gas smell, and it seems to be getting worse.

Thoughts?

 

[Ggg]

Did you check the old O2 sensor before swapping it out? I didn't mean to imply to just start throwing parts at it. It is impossible to properly read plugs from a photo, but looking at the two plugs you pulled those two cyls. are within the ball park for A/F and no oil fouling. If you can take another photo so we can see the other side of the insulator, it looks kinda black toward the bottom. Then pull the others and lets look at them.

 

[iraq_vet_x2]

Yeah, the wire coming out of the O2 sensor was bent over real far, probably not even making a connection. I think when I wrote that last post, it may have been rushed. Now that the computer and the new O2 sensor have had some more trips to work and back to talk, it seems to have fixed the problem for the most part. At least it seems to be happening less and less frequently. I'm about to do the TFI upgrade today. I'll let ya know how it goes.

The other side of the plugs looked the same. I'll get a look at the others while I'm pulling these to open up their gaps.

 

[iraq_vet_x2]

Oops...never mind. My working on the Jeep today just got veto'd by the wife!