back again with the same prob, my bronco has been running rich for about 6 months and iver changed the o2 sensor and checked all the vaccumes and the fulepress regulator.. still giving the same code. what do i do?????

 

Leaking injectors? Get a fuel pressure tester and make sure you're not getting any leakdown. I assume that you checked if the FPR was leaking though the vacuum line.

What code are you getting?

 

Even though not getting a code for ECT and ACT I put them in the oven with a good thermometer and checked resistance at different temp. When comparing to the chart both were off quite a bit. I replaced both and it ran better. How dirty is your air filter?

 

Exactly what code are you getting?

 

I'll third that question... which code, specifically?

 

code is, 173

 

173
HEGO sensor circuit indicates system rich (right side)...a KOER test only.

When I replaced mine there was a test to be sure the voltage was at the connection for heating the sensor.

 

See.. that's not an O2 sensor code. Check fuel pressure.. should be 40psi with vaccuum removed from regulator.

Does the truck have dual tanks?

 

I found a cheap fuel pressure gauge at Harbor Freight if you don't have access to one.

 

Code 173 is in fact an O2 sensor code. It indicates that for some reason the O2 sensor was unable to switch readings. The O2 sensor is a comparator and if it cannot differentiate between the tip and the body readings or the computer has reached it adaptive limits to correct for either a rich or a lean condition, this code gets thrown. There are other things that can cause an uncontrollable rich condition. Non-functioning Thermactor solenoids, failed EGR check valves (more likely given you are only getting code 173). Check your vacuum lines to and from the TAB and TAD solenoids behind the coil and to and from the diverter valve behind the right side cylinder head. Loss of Thermactor air injection will cause an intermittent rich condition according to the ECM's internal parameters. Make certain the EGR check valve at the mid-point of the crossover tube between the cylinder heads at the back of the engine is intact and still functioning. These check valves are notorious for failing and/or snapping in half and not letting Thermactor air into the system or worse, letting exhaust back out through the crossover tube.

 

i used a multi meter to test all sensors and such and the egr was way off.. prob maybe?

 

If the EVP sensor is sending incorrect information to the ECM, yes, this can cause a domino effect and trigger a code at the most common denominator so to speak. In this case, a rich condition since the information that the computer is getting from the EVP sensor is most likely still "within the expected range", it is still the wrong information based on the actual operating conditions at the time. This can be true of any variable sensor... which would be most of them. This is an odd condition to experience but not beyond the realm of possibility.

In short, if your reading from the sensor is that far from what it should be, replace it and see if you can clear code 173 and keep it cleared.

 

ok =], i got a new valve and everything on it from a junk yard today and when i took mine off the tube was broken on the area that i guess is suppose to flex... could that be part of it?

 

Any break in the EGR plumbing will potentially cause a rich condition because of the fact that the engine is set up to run WITH the additional air/exhaust mixture coming through the EGR system. Since EGR gasses are "pushed" by the Thermactor (smog) pump, a break in the plumbing will allow the gasses to simply be pumped out the hole(s) in the system rather than being pumped back through the combustion cycle as designed.

 

Not to hijack the thread but I'm having similar issues with my 300 6cyl in my 92 Bronco. I still have a pretty bad exhaust smell but can't seem to locate any major vacuum leaks other than in the white line going to the A/C control. I did the KOEO/KOER test and got these codes.

KOER the first time I got(I Think):31,25,38 or it could have been 312,538. I wasn't sure so I reread the instructions and went back out and did it again. I got 311,411,538 for certain. Also, Later I got: 111

KOEO, I got 522, 553

I drive a plain jane 92 Custom 300 6cyl w/M5OD tranny. It was taken care of very well by my FIL(wife and BIL say he loved it more than them....) who ordered it special and was OCD about maintenance and drove it up until I got it with 75K on the odometer.