Hi guys, I did a complete search and didn't find this anywhere.

My 89 Monty just failed emissions test (NOS extremely high) and I was told it's either the EGR valve or catalytic converter.

When I connect the EGR valve it kills the engine, but when I disconnect it, it runs smooth again. I tested the EGR and it holds a vacuum, so I don't know how to troubleshoot this.

Should I just pull all the vacuum lines except to the distributor or what? Also, if I mess with the distributor, where does the vacuum advance come from when I accelerate.

Sorry for all the questions...

NOTE: I have a Weber installed so not all vacuum lines are needed, but I followed the shop manual and have 90 percent lines correct. <img src="/forums/images/graemlins/confused.gif" alt="" /> <img src="/forums/images/graemlins/confused.gif" alt="" /> <img src="/forums/images/graemlins/scared.gif" alt="" />

You have 90% of the lines correct? What does that mean?

Based on the vacuum schematic on page 25-4, I have all lines attached except for high altitude, throttle-opener, AAP, air control on air cleaner, and to the choke.
http://i1111.photobucket.com/albums/h463/jondanderson/Vacuum-25-4.jpg

In general, EGR valve needs to be connected to a ported vacuum source, (Located above the throttle blade) not manifold vacuum, it should never come on at idle. Usually, there is a thermal controlled vacuum switch to prevent it from coming on when the engine is cold, sometimes a computer controlled switch is present to limit it's function, too.

The test you performed with the valve actuating enough to stall the engine, and the fact that it holds vacuum shows that the valve is working, and the passages in the manifolds are not plugged with carbon.

Do you have it connected to ported vacuum on the Weber carb, or did you have it disconnected because it was stalling the engine?

Do you have the readings from the test? Does a VA smog Test give 5 gas readouts? There is a free online "Lambda" calculator that can tell if your engine is running an air/fuel ratio that allows a cat-converter to properly catalyse the exhaust.

http://www.smogsite.com/calculators.html

Scroll down to the "Lambda Calculator, input your readings and calculate the results. If the mixtures are correct, the EGR is working properly, the timing is set correctly,and your readings are still too high, suspect a Cat Converter.

Another clue to if a high NOX reading is a result of a bad Cat-Con is that there is also a fairly high, yet still passing level of CO reading, as a properly working cat-con is using the CO to convert the NOX back into Nitrogen by stripping the O from it and converting the CO into CO2.

ANY exhaust leaks above the cat-converter need to be repaired. An example would be a gasket that's blown, or a cracked manifold or head pipe. Air getting into the exhaust stream can ignite the CO before the Cat-Con can use it to convert the NOX.

Nice to know. Thanks, Marty.

THe 2.6 has a thermo vac switch, the bakelite thing on the water neck, sticks out toward dside, and every Monty I've ever seen has one nipple broken off, at least one.

Ditto the ported vac on egr. You can spot the ported vac by testing the vac nipples for vac at idle, and finding the ones with out strong vac at idle, then blip the throttle and see which ones have strong vac as the throttle blade opens past the port.

I'd never put on a weber in a emistest state... For that matter, I wouldn't put on a weber in any case unless I was going to use two of them on a new mani.

"...every Monty I've ever seen has one nipple broken off, at least one."

If you have a thermal vacuum switch with a nipple broken off, I've repaired them by using the plastic tube from either a Bic type pen or a straw from a carb spray can, inserted into the remainder of the old nipple and the small hole in the thermal switch, held in with some epoxy or crazy glue.Usually works OK then!

Yep - Slapping a Weber in and then expecting to meet even modest emissions standards sounds pretty optimistic to me.

The whole point of doing the Weber swap is simplicity - Almost all of the vac hoses go away, and there are a lot fewer parts on the new carb to fail. Retaining all the original hoses, vac solenoids and related crap in the hope of meeting the vehicle's original emissions standards negates one of the main reasons for doing the swap in the first place.