DOH! Took my baby in for inspection the other day, and she passed all inspection points, and most of the emissions. NOx levels were almost doubled tho so she failed. Now, I have a pretty good idea that it is the EGR system. I keep gettin codes every so often. I dont think my CAT is bad. Its fairly new. My question is...what else can cause it. Its an 87 305 TPI. It runs perfect. Will the charcoal filter cause high NOx levels? Let me know. I have until the end of next week to get her to pass. Thanks in advance.
Justin

 

High Nox forms mainly from high exhaust temps.. EGR re injects exhaust gasses into the system too cool it down and reduce Nox. Other things like advanced timing, running too lean, missfires and vacume problems can also add to it as well as the Nox bed in the cat. Did you blow threw the rest off the test especially in H.C. ? and C.O. also.. most other symptoms that would cause a failure will also have high H.C.

You should test the EGR like this...

The solinoid below the coil.. Un plug it...

Check for vacume at the solinoid from the plastic tube that comes from the throttle body... Not sure if you need to throttle it up to get vacume there or not. If no vacume repair tube or pluged throttle body.. If vacume is there then....

Reconnect hose to solinoid and disconnect EGR... With engine warm check for vacume to egr valve.. If it's not there and it is probley not.. check wires to solinoid.. If ok.. Replace the solinoid<---- This is probley the cause...

Also besure to apply vacume to the EGR.. Engine should stumble and or die.. If it doesn't.. Replace EGR....

 

The vacume plug that is.....

 

Thanks. Those are pretty much the ideas I came up with. Yes I went right through the CO and the HC tests. Wayyyy under the limit on those. But NOx was doubled. Im almost positive I have an EGR malfuntion. I dont have a vaccum pump to check my EGR, but I might borrow one. Can I check the condition of the valve without a pump??? I have a new EGR setup at home. I.E. a new valve and solenoid and temp sensor. Thanks for the help, I need to resolve this quick cuz in a week my car will be illegal. If I can get away with just replacing the soleniod, that would be awsome. No TPI disassembly this weekend. Which would more likely cause a code to pop up? the valve itself? or the solenoid? Anyway, thanks again. Any more info?...feel free to let me know!
Justin

 

One more question....my timing is advanced about 2 degrees. Its at 8 instead of 6. Will this make a big difference??? Should I even bother retarding it back?
Justin

 

Timing.... If you can get away with 2 degrees off then drop it back to 4 for the test and then put it back up. that 4 degrees can make enough of a diffrence to help insure the your car will pass Nox.

To put vacume to the EGR just disconnect another hose like the one twards the rear of the plentum that goes into the car... Actually if you can get enough hose length to it you can do it yourself with your mouth. It only takes about 6 inches of vacume to make it open.. Good Luck

 

Hey...one quick question. What is a good way to check the wires going to the solenoid? Just visualy check them out? or can I test them with a meter to see whats up. Im not sure where the wires goes...so I dont know where to do a test. Let me know ASAP cuz Im heding home now to start tearing stuff up. Thanks in advance.
Justin

 

The best way to test the wires is to connect a test lamp between the two wires some how. after the engines warm it should light when it;s throttled up

 

Hey thanks alot for gettin back to me so quick. Im about to go outside and start checking things out. Im really hoping at this point that the solenoid is crap. I dont feel like tearin TPI stuff apart. Ill post later on and let ya know what i find out...then hopefully next week Ill be posting about how I passed emissions! thanks again.
Justin

 

Ok, I just got my car re-tested for emissions. Still failed. I replaced every piece of the EGR set up, and retarded my timing a bit. It reduced my NOx level from 2700ppm to 1700ppm, so it must be working. Im still over the limit by a few hundred or so. Is this most likely due to my CAT now??? The guy was a real *** to me today. pulled some huge attitude, it almost got him smacked. So Im really pissed off right now. My inspection is up this week. So my car is just sitting in my driveway til I figure this out. I cant take my CAT off myself, its welded on. So if I get alot of suggestions to change my CAT, Ill probably just do it. Thanks in advance, Im really stumped.
Justin

 

If the EGR is working that would be my next step.. The Cat