PontiacBonnevilleClub.com

Hey guys, I have a 1994 Bonneville (Non-SC) with ~ 130k miles.

I took it in for Texas state inspection, and it failed for the first time ever.

At the advice of the inspection guy, I replaced the catalytic converter. I put about 70 miles on it, and then took it back to get it inspected again.

It failed again.

The inspection place recommended replacing the oxygen sensor. I did that, and took it back to get it inspected again.

It failed again.

This time the guy suggested new plug wires. I replaced the plug wires, and took it back for inspection again.

It failed again.

This time the guy at the inspection place had no suggestions, so I drove it home inspected.

If I can't get it to pass inspection, I am gonna have to get rid of the old girl, which I don't wanna have to do.

Anybody have any suggestions as to what might be causing it to fail the NOx portion of the inspection?

Any help is appreciated....

Any CEL codes?

If you have a Pep Boys nearby, go there, get a bottle of Redline SI-1 fuel system cleaner. Dump that in the tank of a name-brand fuel, and drive it for a few hundred miles.

Also, do the spark plugs, and check for any vacuum leaks.

Check for any CEL codes, too.

Have you tried some seafoam? Try adding some in your gas tank and, if that doesn't work, through your vacuum lines

i am on shaky ground recommending anything in this area but seems like i remember the exhaust gas recirculation system is related to reducing NO. might want to check the EGR valve and associated plumbing.

I agree with that... as well what bran of O2 sensor was used on the car... Is the Cat the original to the car or has it been replaced with an aftermarket unit?

@ petraman: The Seafoam is a good idea. I have heard good things about it.

@ LeSabre in Buffalo: Not familar with the Redline product. Have you tried it?

Would a Pep Boys/Autozone be able to pick up CEL codes with their scan tool, or would I need to take it to the dealership?

I failed to mention, I replaced the spark plugs when I replaced the plug wires, so those are new as well.

EGR valve was next on my hitlist. When I Googled "NOx inspection failure" it was one of the first things that came up. Is that something that would throw a code? Any particular way to check if it's bad or not?

Thanks a million guys.

Jrs3800 wrote:I agree with that... as well what bran of O2 sensor was used on the car... Is the Cat the original to the car or has it been replaced with an aftermarket unit?

I believe the O2 sensor was Denso.

The cat is a universal one put on by a recommended muffler shop...

post up all of your numbers.

Can't find the first or the latest one, but I have the 2nd and 3rd ones:

3/11--------------high speed std/high speed reading---low speed std/low speed reading
HC (ppm)............ 114 / 31 .......... 117 / 44
CO(%)................ 0.63 / 0.29 ...... 0.65 / 0.27
CO2(%)............... XXX / 14.2 ..... XXX / 14.2
O2(%) ................ XXX / 0.2 ...... XXX / 0.2
NOx(ppm) ........... 796 / 1894 ..... 879 / 2103.......FAIL
Dilution .............. >6.0 / 14.49 ... >6.0 / 14.47

3/16--------------high speed std/high speed reading---low speed std/low speed reading
HC (ppm)............ 114 / 12 .......... 117 / 11
CO(%)................ 0.63 / 0.07 ...... 0.65 / 0.08
CO2(%)............... XXX / 15.1 ..... XXX / 15.1
O2(%) ................ XXX / 0.1 ...... XXX / 0.1
NOx(ppm) ........... 796 / 1500 ..... 879 / 1586.......FAIL
Dilution .............. >6.0 / 15.17 ... >6.0 / 15.18

My numbers keep improving, but my NOx is still WAY out of range. I believe on the last one, it was around 1400...

Strongbad wrote:
@ LeSabre in Buffalo: Not familar with the Redline product. Have you tried it?

Would a Pep Boys/Autozone be able to pick up CEL codes with their scan tool, or would I need to take it to the dealership?

I've used Chevron Techron Concentrate and Gumout with Regane with good success. Both have lower concentrations of the active ingredient in the Redline SI-1.

Your car either needs the OBD1 paperclip trick, or a trip to a dealer, to read any codes present.

LeSabre in Buffalo wrote:...Your car either needs the OBD1 paperclip trick...

A "trick" eh? I like the sound of that! LOL!

Please explain...

http://www.pontiacbonnevilleclub.com/fo ... =51&t=8689

gonzo4191 wrote:http://www.pontiacbonnevilleclub.com/forum/viewtopic.php?f=51&t=8689

That is freaking awesome...

I suggest looking at the EGR valve as mentioned above. You can remove it and clean the valve with carb cleaner. I have also disassembled mine and cleaned everthing up and lubricated them up. Just remember where the parts are. There are 3 different sized orifices and they must be assembled in the correct way.

to paraphrase a 96 bonn FSM: the PCM uses info from following sensors to control pintle position of EGR: ENGINE COOLANT TEMP, THROTLE POSITION, AND MASS AIR FLOW. the EGR valve is activated under the following conditions: warm engine and above idle speed.

too much EGR may cause: engine stalls after cold start, engine stalls during closed throttle condition, vehicle surges during cruise, rough idle, DTC 0300 (misfire detected).

too little EGR or no EGR flow may cause combustion temperature to be too high and could cause any of following: spark knock, engine overheating, EMISSI0N TEST FAILURE, DTC 0401, and poor fuel economy.

the 94 may be different especially the DTCs but maybe this will help with diagnosis.

Sounds like the EGR Valve might be the ghost in the machine I have been looking for.

I think I will check the codes, and then will search the forums for some tips on cleaning that bad boy up. Then I will check the codes again and see if that cleans it up.

I think i will give her some Seafoam as well. I usually do Chemtool, but I think I will give the Seafoam a try...

Thanks ton guys.

I will update when I know something...

Found this pic from another thread.



Should help me ID my EGR...

thats a series 2, the position of the EGR may be different

Correct. Its in the front side of the engine, closest to you, but it still looks the same.