Check Engine Light going on - need some help

[WendyH]

Hi, need some help. I have a 95 5.0 and my check engine light has been going on. There are three codes showing - 172, 181 and 189. I know this has something to do with the engine running lean, but does anyone know exactly what the codes mean? Also, any suggestions on how to fix?

Thanks

[USMC302]

172 - o2 Sensor sensor circuit indicates system lean (right side)
181 - Right side still lean, at richest adaptive limit, during part throttle
189 - Left side still lean, at richest adaptive limit, during part throttle

Definately showing a lean condition so we'll start with the obvious fuel possibilities.
When's the last time you changed your fuel filter?
Do you have any fuel mods, ie injectors, adj regulater, large fuel pump....?
How old are the 02 sensors, may be time to replace them.
Make sure your air filter and MAF are clean, if the MAF doesn't read all of the air coming in, the engine will think it doesn't need as much fuel going in, when in fact the 02 sensors are saying the opposite.
When was your last tune up?
Lsat but not least, have you made any changes at all before this started? Change octane in gas, use platinum plugs, anything at all?

[WendyH]

Hi, thanks for your reply.

I just had the fuel filter changed, platinum plugs put in, etc. I don't have any fuel mods. I also just had a new exhaust pipes / cats done and had the O2 sensors changed. Here is a big issue though, when I bought the sensors from Advanced Auto they said the car needed 4 sensors - 2 upstream and 2 downstream. The H pipes only had place for 2 and the mechanics put in the downstream sensors. Not sure that I have the correct sensors installed and can't find what is correct.

I recently put in a KN air filter, but haven't done anything with the MAF.

I have owned this car for 4 years and have always put in 93 octane.

After having the complete tune-up, putting in the new air filter and having the exhaust system done, the car still didn't pass inspections (emissions).

Any ideas? My regular mechanic couldn't figure out what to do about the codes, so he recommended someone. I'll be bringing the car in next week, but would love to have some more information before I do that.

[USMC302]

Two things I would change....Platinum plugs, throw them out and put in some autolites, next, go back to advanced auto and tell them they gave you the wrong sensors or harness for them, your right about only having 2. If you use a harness for four sensors, the signal will be reporting four a/f ratios and two of them aren't in so they're seeing no fuel now(hence the ECU reporting a lean condition), get the one for just the two sensors. I would bet lots of money that is your problem....

[goodyear1984]

up stream sensors measure fuel downstream are there to measure if the cats are cleaning the exhaust fumes.with out the upstream sensors inthe right spot they wont measure fuel

[USMC302]

Thanks Goodyear, hopefully, she's not still having this problem. lol