Well.. lets see...

I failed my Texas smog test today. Numbers are below..



Ok.. now I just replaced the rubber elbow between the throttle body and MAF today.. it was cracked and sucking air in.. I thought it was making me run richer .. or maybe leaner.. I dunno... it has been running on this condition for quite some time now.....

So was my PCM ( OBDI 1995 ) compensating for this vacuum leak, and store this data in the computer's BLM tables, and since I fixed this issue, the computer must relearn the A/F mixtures?

I replaced the cat about 5 years ago with a magnaflow.
I have no SES light shown, but no way of knowing if I have any DTC's stored as I cant find anyone to scan ( OBDII connector, OBDI PCM )

Should I unplug the battery to refresh the PCM, and return to original values and drive it for a hour or so?

Since I have been running rich ( presumably ) for the last couple years.. could it have fouled my cat?

I really do not want to have to swear and cuss for hours trying to pull off that EGR valve on the back of the motor..

In the last month, I have replaced the Fuel Pump, fuel pressure regulator, filter..
ignition control module, ignition coil..
rubber intake elbow..

5 months ago.. new Optispark distributer with optical sensor...

seems like I am missing some on the bottom end...

Thanks in advance..

 

Why would i fail by almost 3x the limit for NOx? WOW!!!

I took the battery cable off tonight.. and will reconnect in the morning to get some road time... lets see if the PCM will re-learn the new A/F ratios..

If anyone here can chime in.. well...

Thanks so much in advance....

 

Generally, if its running rich, HC and CO will be high, and NOx will be low. If its running lean, NOx will be high and HC and CO will be low. With all 3 over the limit, the cat would be the primary suspect. Or maybe running a bit rich, with a non-functioning EGR system.

With a tear in the elbow between the MAF and the throttle body, the PCM was not getting an accurate measure of mass air flow - it was seeing less than actual flow. So it provided less fuel than was required, the O2 sensors indicated "lean" and the PCM in response elevated the long term fuel corrections to richen the mixture. Repair the tear in the elbow, and its going to run rich briefly. Easiest thing to do is pull the "PCM BAT" fuse for 30 seconds to reset the PCM, then drive it under a wide range of cominations of RPM and throttle position.

But running rich will not cause the NOx disaster you see above.

 

Ok.

I cranked the engine. I reached back to the EGR valve and depressed the diaphram assembly and the engine stumbled and attempted to die.. I released the diaphram and the engine recovered. This is to be expected.

I used a MityVac vacuum pump and connected a run of vacuum line from it and pressed against my thumb and applied pressure.. hose holds vacuum..

I then attached the hose to the EGR vacuum port, and attempted to apply vacuum.. nothing.. engine idle is not effected, and it will not hold vacuum..

So when the solinoid gets a signal from the PCM to apply EGR, the solinoid is allowing vacuum to the EGR, but the EGR is not opening..

Is this a good reason to believe that I have a non functioning EGR system, driving up my NOx?


ShoeBox -----
"Too little or no EGR flow can allow combustion temps to get too high during acceleration and load conditions. This could cause:

Spark knock (detonation)
Engine overheating
Emission test failure "

 

Appears you are indicating that applying a vacuum to the EGR valve did not cause it to open. That would indicate an EGR valve diaphragm failure.

 

Yes, that is correct.

Ok. I took the EGR off, took it to the parts house, and was about to purchase a new one when the guy behind the counter informed me that since it is a negative backpressure valve, just applying pressure will not make it open..

He asked me to get a helper ( the wife ) and have her sit in the car, with the e-brake engaged and with the brake pedal pressed.. then put it in drive and tap the gas pedal to put a load on the engine.. if I felt the EGR valve move, then I would know that the system in itself was working correctly.

Well, that test failed.. I and still do not know why I left my theory of the vacuum test at the parts house counter.. I feel like i should have just bought the damn thing..

I am correct when I assume that if I apply vacuum to the EGR vacuum port, and it does NOT hold vacuum, and it does NOT effect the idle.. then the EGR diaphram is non functionable?

Please help me..

 

Clearly if a diaphragm does hold the vacuum it has failed.

 

I know you meant to say if it does NOT hold vacuum it has failed.

Will it hold vacuum off the car also? i brought my vacuum pump with me to test the new one and it also did not hold vacuum.

I was told, there, that backpressure must be applied to the egr for the diaphram to be capable of being opened using vacuum, wether it be supplied by the intake or the vacuum pump.

 

Well, Mom and Dad.. I brought my report card home again... I hope you are pleased...

oh yes.. after a new Cat, and EGR valve, this is the result..




And.. when I apply vacuum to the new EGR.. it holds... so I guess the diaphram was torn.

The results speak for themselves.

Thanks so much to Fred, and bw_hunter. Moreso for just biting your tongue and bearing with me.

Feels good to have a top running OBD1 car that still passes inspection..

I have another issue though.. but i will post a new topic for it...

Have a great night, and thanks for helping.