grosss

You guys seem to have way more info on this kind of stuff than the people on the truck forums so I once again look to you for good advice!

I made an ALDL Cable (93 Silverado, 5.0L, 459,000kms :-) original everything I think...) and read in the data from the computer to see how my engine is performing using TTS Datamaster.

Long term BLM data is showing that for most of the time it's rich at some rpms/MAP, lean at others, and the fuel trim cell number is bouncing around like crazy. the LTerm counts are around 112 and the box turned red, and STerm counts are all over the place. Watching my O2 sensor voltage, its bouncing all over the place, usually between 40-50 and 800-950mv.

I have a feeling this is saying my O2 sensor(s) are shot, but I have no idea what the data would look like for a perfectly happy engine, so I'm not sure. I'm getting **** poor fuel economy (worse than normal for a truck) and hoping this will give me some insight into why.

I thought the fuel trim cell number is supposed to stay at 0 or 1 most of the time? I'm seeing 4,5,6, 9,10,14, and 18 at warm idle.

Any thoughts?

91chevz71

I think (could be wrong) you onjly have one O2. It's a crap shoot as to whether or not your truck has the heated or non-heated O2. When was the last time you replaced the O2? I take it you have no error codes, you have done all the common sense stuff like filters, check plugs/wires, etc, etc. If you decide to replace your O2, make sure you get the EXACT ACDelco replacement. Call the dealer and get the part number for the O2, then hang up and go buy it online.
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128/128 is perfect. I would say that a +/- 3 on INT and BLM is a good tune.

grosss

Well I bought the truck off a friend's uncle (ok.. more like got it for free) and have been fixing it up ever since, new sparks, spark cables, filter is pretty clean... i've ran fuel injector cleaner, a little bit of seafoam, umm.. bunch of other crap.. new brakes.. and I have absolutely no idea when the last time the O2 sensor was changed...

Yea Canadian Tire (yes I'm in Canada ;-)) has every part for the truck listed on file and they usually have exact replacements, I think it's $20... but I don't want to spend the money unless I have to since I'm on a student budget :-).

I was hoping to get some insight into my fuel econ problem from the ALDL readout so that I can figure out what I need to buy so I don't start spending money on stuff that's perfectly good (Like the spark wires I changed last week that made absolutely no difference)
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Yea I'm nowhere near +- 3 on the INT/BLM, heh....

Ronny

iTrader: (1)

I thought I read when the 02 is kaput there is no swing. steady voltage while in CL.

grosss

I'm pretty sure they're not completely dead, I'm wondering if they are "sluggish" as i've read, sluggish won't throw an SES light, but dead will. Hoping someone can give me a defiinite yes or no on this, or somewhere else to look for poor mileage.

grosss

Ok, so I took a look at the Datamaster results again, I let the truck idle for a good while after it was warmed up and in closed loop, and the STerm was hovering around 128, bouncing up and down every so often, but the O2 Sensor voltage is like 50-80, then suddenly 200, then 850-900mv, kind of cycling through that, and the "rich/lean flag" is on most of the time.

RPMs are somewhat constand at 650, bouncing up to 675 sometimes, and less often falling to 625.