Emission HELP Please!

[ulremember]

Hello to all!
I have a serious problem with a 95 Tahoe. I have changed the EGR valve and the O2 sensor. With each change the results are worse when having it checked at our local smog station. Here is what I have:
HC (PPM) max allowed 83, measured at 200 @ 15 MPH.
NO (PPM) Max allowed 477. Measured 1621 ppm @ 15 mph

HC (PPM) max allowed 48ppm. Measured 190ppm @ 25 mph
NO (PPM) max allowed 730ppm. Measured 1516ppm @ 25mph.

I have no clue why it has gotten worse after changing the key sensors and parts. Could it be the CAT(s)?

Any help or information is appreciated by myslef and brother in law. (his truck)

Blessings to all in attendance!
Chuck aka ulremember

[ulremember]

If this helps, the truck does not smoke. It actually runs very good!
It is not a "smoker"
Blessings to all
Chuck aka ulremember

[MT-2500]

Go for a good old fashion basic tune up.
If that does not do it get out the fuel pressure gauge a nd a engine capable scanner.
Get codes and rear out data and complete fuel pressure check.
Post back codes and fuel pressure and out of spec data /sensor reading.
MT

[spytearbite]

Pull All plugs and do not mix them up. Which one is the most sooty? Could be an injector hanging up in that cylinder giving off that much NO/HC.

Air cleaner clean/dirty? Try with zero air cleaner installed. Let the air unrestricted so there is more air than fuel gulping.

[j cAT]

Originally Posted by ulremember

Hello to all!
I have a serious problem with a 95 Tahoe. I have changed the EGR valve and the O2 sensor. With each change the results are worse when having it checked at our local smog station. Here is what I have:
HC (PPM) max allowed 83, measured at 200 @ 15 MPH.
NO (PPM) Max allowed 477. Measured 1621 ppm @ 15 mph

HC (PPM) max allowed 48ppm. Measured 190ppm @ 25 mph
NO (PPM) max allowed 730ppm. Measured 1516ppm @ 25mph.

I have no clue why it has gotten worse after changing the key sensors and parts. Could it be the CAT(s)?

Any help or information is appreciated by myslef and brother in law. (his truck)

Blessings to all in attendance!
Chuck aka ulremember

MAP sensor...check the voltage output at idle should be around 1.5volts dc. also make sure PCV is replaced and hoses to it are in excellent shape...


If the cat was bad it would not cause those very high readings..

[ulremember]

Thank yous to all that replied. Will get on it! I forgot about the MAP. Worked on a car a long time ago, it was the MAP and BARO!
Blessings to all
Chuck aka ulremember

[ulremember]

One question. How do I check the MAP sensor with it on the car. Do I go to ground with my meter, or do I jump across two of the three leads?
Thank you in advance!
I tried from ground to each wire. The highest voltage I got was 1.2 I think on the green lead in the middle

[j cAT]

Originally Posted by ulremember

One question. How do I check the MAP sensor with it on the car. Do I go to ground with my meter, or do I jump across two of the three leads?
Thank you in advance!
I tried from ground to each wire. The highest voltage I got was 1.2 I think on the green lead in the middle

the wires should be ground,5volts d.c. , and the MAP output...3 wires correct... a reading of 1.2 volts dc sounds good..remove the MAP and make sure that the intake rubber gasket is in good shape...

[j cAT]

Originally Posted by ulremember

Hello to all!
I have a serious problem with a 95 Tahoe. I have changed the EGR valve and the O2 sensor. With each change the results are worse when having it

since the MAP appears to read in the normal area now you must check that the EGR passageways are clear ....many times I have had to do this on my now retired vehicles...

usually the intake passageway gets plugged with carbon....as you probably know exhaust gas is sent to the intake manifold by the EGR valve...If this is not done the combuston chambers will get too hot and this then causes high N.O. readings as well as pinging....pre-ignition...

let me know what you found or if you have more questions..

[ulremember]

Thank s j cAT! I really appreciate this. SMOG PROS were gonna charge him 700 dollars for the repairs. Get this, NO REPORT THAT THEY CHECK ANYTHING> Charged him 90 dollars and RECOMMENDED the fix of: CAT EGR (new) (checked with vacuum pump. instructions say do not test with), and possible theromostat missing or stuck open (OH YEAH, they said it would not get to operating temp so they blocked the radiator) Low coolant I found but I know that did not cause it. Sorry to run on, but I thought about the temp. Now back to the blockage. I will check. I put the egr on and did not notice the common build. But I am thinking the intake area to the heads? Maybe you think let me know and thank you VERY much!
Blessings
Chuck aka ulremember

[j cAT]

Originally Posted by ulremember

Thank s j cAT! I really appreciate this. SMOG PROS were gonna charge him 700 dollars for the repairs. Get this, NO REPORT THAT THEY CHECK ANYTHING> Charged him 90 dollars and RECOMMENDED the fix of: CAT EGR (new) (checked with vacuum pump. instructions say do not test with), and possible theromostat missing or stuck open (OH YEAH, they said it would not get to operating temp so they blocked the radiator) Low coolant I found but I know that did not cause it. Sorry to run on, but I thought about the temp. Now back to the blockage. I will check. I put the egr on and did not notice the common build. But I am thinking the intake area to the heads? Maybe you think let me know and thank you VERY much!
Blessings
Chuck aka ulremember

a quick test is to manually force open the EGR with your fingers with engine at idle this should cause the engine to stall...this will indicate if passageways are blocked..


another test is place a vacuum guage in line of the EGR control vacuum line and with a long enough hose take a ride you should see 7-10 inches of vacuum when increasing spend..this ensures that there is vacuum to open the EGR...

this will give you help as to whats bad..

[ulremember]

Hello! j cAT, I just opened the egr with finger, and it stumbled pretty good. I also hooked up the vacuum line straight to the egr. It does pull it open a bit. I also hooked it back up to the control solenoid, and it open slightly when I raise the r's. Could it be the temp sending unit? I otice that the te,p gauge does not show that the temp of the engine is not as hot as it should be. I would say that it is showing about 152 degrees ( line on gauge between 100 and 210).
Well I want to thank everyone that has replied so far, and I hope that I get more sugesstions.
Blessings to all
Chuck aka ulremember

[j cAT]

Originally Posted by ulremember

Hello! j cAT, I just opened the egr with finger, and it stumbled pretty good. I also hooked up the vacuum line straight to the egr. It does pull it open a bit. I also hooked it back up to the control solenoid, and it open slightly when I raise the r's. Could it be the temp sending unit? I otice that the te,p gauge does not show that the temp of the engine is not as hot as it should be. I would say that it is showing about 152 degrees ( line on gauge between 100 and 210).
Well I want to thank everyone that has replied so far, and I hope that I get more sugesstions.
Blessings to all
Chuck aka ulremember

that engine temp sender could very well be the problem as the engine management thinks the engine is still warming up and not providing the correct idle air mixtures too rich...and it can also prevent EGR operation... ECT sender unit replace it..should be 190deg f

[ulremember]

Bless you! I will have brother in law invest in the ECT. It is the one on the side of the head? correct?
Blessings
Chuck aka ulremember

[j cAT]

Originally Posted by ulremember

Bless you! I will have brother in law invest in the ECT. It is the one on the side of the head? correct?
Blessings
Chuck aka ulremember

the ECT on the driverside of engine near #1 plug is the computer ect....on a 5.3l engine ....the 5.7l engine it is near the thermostat..the resistance at 75-80deg should be around 2800ohms and at operating temp 275 ohms...