Tracked a possible Egr issue.


I got a code 172 system indicates lean bank one on my 93' 2.3. First thing i checked was IAC. Disconnected it and there's no change. Checked vacuum hoses and the green hose that goes to EGR has a faulty vacuum. I feel air vibrating but no vacuum. Checked the red hose at the intake and notice it was broken and mended with a thicker hose. There's vacuum at the intake so somewhere between intake and EGR Valve there's a leak. There's a valve where both green and red hose link. The sticker under the hood says it's an EGR Pole+. I don't feel any air escaping from the hoses. Any ideas?

 

There is no Vacuum at the EGR Valve unless engine is fully warmed up and you are accelerating, so not at idle or even REVing engine, engine must be under a load

Between intake vacuum port/hose and EGR valve hose is the EGR solenoid/modulator, the computer controls this Vacuum Valve
When engine is under a Load the cylinders heat up and NOX(toxic gas) starts to spike, mixing in exhaust gases to intake air COOLS the cylinders enough to lower NOX production
This is the sole purpose for the EGR system and why it was added to engines back in the 1960's and 70's
Some engines don't spike NOX, so didn't have/need EGR systems in those years, most did by 1995 with stricter emission laws


O2 sensors are the only sensors that wear out
12 years or 100k miles
After that they are costing you money in wasted fuel
172 is an O2 sensor code
It means the Computer is adding more than 20% more fuel to the engine but O2 sensor still shows Lean Exhaust
Computer only has O2 sensor to base 172 on, there is no "comparison" sensor
So to "trust" code 172 O2 sensor needs to be under 12 years old or have less than 100k miles of use
If not replace it
See if code comes back, it may, but at least you won't be wasting time if it was just an old O2 sensor code, and your MPG will go UP regardless




Your computer KNOWS it is running a 2.3 Litre engine
So it knows EXACTLY how much air it is pulling in at any RPM, its just MATH, computers are good at math, lol
So it knows exactly how much fuel it should add to get the 14.7:1 air:fuel ratio

There are variables like air weight, air temp, air pressure(valley or mountain), fuel pressure
Computer needs O2 sensor feed back to compensate for these variables
So O2 is "the word of God" as far as computer is concerned, except God doesn't wear out, lol
Computers only defence against a "worn out God" is to set a Lean code

 

Thank you for the information Ron. You're always full of knowledge. I replace the 02 sensor and so far the code hasn't come back.