Racking my brain on this 96

[Busterboy]

The check engine light is on with a low EGR flow code..I have removed the EGR at least 6 times and going so far as to ultrasonic cleaning it...I also replaced all the vaccuum lines. The last thing i did was clean the sensors, valves and switches that are associated with the vaccuum...this was the only thing the allowed the check engine light to stay off for about 3 hours of around town driving....What can this possibly be??? Anyone else have this problem and how did you fix it????? The car runs great...but I'm sure it is in a safe mode and my MPG seems to be suffering alittle.

[TMack409]

Possibilities:

a bad O2 sensor, a vacuum leak, or a condition that allows unburned oxygen to enter the exhaust. Check intake vacuum at idle, and inspect vacuum hose connections.

Do you have a tool to read the signal from the O2 sensors? we need to see .42v average on both pre-CAT sensors.

[Busterboy]

All I have is a volt meter if that will do? I am going to try the propane trick in the morning to check for the vaccuum leak. I am at my wits end on this one. Wouldn't a bad O2 sensor register a O2 code instead of a EGR code?

[new echo owner]

How did you test your EGR system?

N.E.O.

[Busterboy]

All I did was check for vaccuum leak at the EGR solinoid and the accuating diaphram. No leak noted. I did clean it and the valve seemed to be operating fine???? I am open to suggestions.

[new echo owner]

Apply vacuum directly to the EGR valve with IAC disconnected, see if the engine will stall or not. If it doesn't stall the engine or make it run rough, the passage is either restriced or there is insufficient exhaust flow to the EGR valve.

N.E.O.

[Busterboy]

Sounds Like a plan N.E.O. I will attempt that in the morning with the vacuum leak check. I will let you know what happens.....

[new echo owner]

Will await your finding!

N.E.O.

[TMack409]

Originally Posted by Busterboy

All I have is a volt meter if that will do? I am going to try the propane trick in the morning to check for the vaccuum leak. I am at my wits end on this one. Wouldn't a bad O2 sensor register a O2 code instead of a EGR code?

Autoengenuity makes an OBDII tool that you use with a laptop to analyze the O2 sensor. You might get by with a voltmeter if it can produce an average reading, as well as min max readings and has a high input impedance and a filter to reduce the hash inside the engine compartment.

However, I really think you are on the right track with your vacuum leak chase.

[Busterboy]

Went to the local auto parts store and rented a vacuum pump to do the test...Results...with IAC connected and approximately 0.3 on the vacuum gauge the engine started running rough. With the IAC disconnected and approximately 0.2 on the gauge the engine stalled??????
I also did the propane test on all vacuum lines and wasted almost a half bottle of propane with no change to the RPM of the engine.
As far as the tool to check the O2 sensor where could I get one of those. Doubt if they rent those?? Anyway thanks for the help guys I hope we can fix this.... I hate check engine lights, its almost as bad as putting marbles in my frame rails.....
Going to take tester back.....

[TMack409]

On a main vacuum spigot (take off) - did you confirm that the engine was developing a healthy vacuum - in the range of 17 to 21 inches? (at idle)

[Busterboy]

No I did not check the vacuum but the engine does not even shake or indicate any other problem outside of a check engine light? It even accelerates evenly and smoothly?????
As far as checking the vacuum I would need to get another tool...I can take an engine out and put one in in about a day, but I have no specialty tools..Never have I had this difficulty in diagnosing a problem.

[new echo owner]

Which code did you have P0401, or P0402?

N.E.O.

[Busterboy]

This is funny N.E.O. I knew you would ask me that question and I can't remember off the top of my head I want to say it was 401, but my luck in odds has never been with me. I will need to find out one last time and let you know..Thank god for free code reads...

[new echo owner]

It does make a difference on which one it is, one is too much and the other is insufficient.

N.E.O.