Hey,

I have a 1992 F250 heavy duty 4x4 with the 351 and 5spd manual trans. Truck has about 72K on it.

It failed Maryland emissions on NOX. Any ideas on how to get it to pass.

I was thinking:
New o2 sensor
Bump timing up or down (which will help?) - I'm running 12deg base with 87 octane.

Also, since it's granny low, should they be using 1st gear in the treadmill test?

Thanks,
--Bill

 

Was the NOx failure at idle or cruising rpm?

Your timing should be fine, but bumping down closer to 10 should help.

SD or MAF?

NOx failure is usually the result of too high combustion. Normally it is caused by:

Carbon buildup in the EGR and/or intake
Faulty EGR (not opening enough) - Has the truck set any codes?
Overly lean condition

I would probably focus on cleaning the EGR and ports first. If that did not help, I would likely replace the EGR if it was not operating properly.


Good luck.

 

Failed on the dyno driving cycle not idle.

It's SD.

I will check those codes - good idea.

The other thing is, the lady was driving it like granny-low was 1st gear (which it is, but it's obviously not used in everyday situations) - so the rpm's were way higher than they would be in typical driving siutations.

 

Yeah- that's the way these people put the manuals on and try to get the rpms up. Personally, I think it confuses the computer controlled smog stuff.

Nonetheless, since it is SD, if it were running overly lean according to the O2, you would be running extra rich and would probably fail the CO and/or HC.

Therefore, I believe you should focus on the EGR cleaning, check to make sure it is lifting up and down.....

Also, you could drop your timing down to 10 for the test.

After all that, when you take it back, convince the tech that automatics get to at least second gear at cruise, so your truck should be there also.

Don't forget to send your results back into the board after all is well.

 

Thanks man. I read up on egr tests, and I'll do those.

One more question:

There are 3 valves of some kind mounted to a bracket on top of the engine. They are plumbed into the egr stuff. What are these, and can they go bad? After I turn off the engine, one of 'em makes a buzzing noise for a few seconds...

 

Actually, only one of those valves goes to the EGR - it is the EVR (Exhaust valve regulator). It is the component that is used to pass manifold vacuum to the EGR in order to lift it up. The computer opens and closes the EVR to regulate the opening and closing of the EGR.

The buzzing is normal. It is just the vacuum releasing after the truck is turned off.

 

Double post, sorry...

 

I think I figured it out. In the egr system there is an electric valve that controlls the vacuum to the egr valve. This thing (aka EVR) leaks which presents two problems:

1. Vacuum at the inlet port never gets to the outlet port so the egr never opens.

2. It's a vacuum leak.

Also, after I turned off the engine this EVR thing would make a noise as it leaked off the vacuum in the the vac resivior.

I ordered the part from fordpartsonline.com, so I haven't fixed it yet. If I can remember I'll post after I go back to the emissions place.

 

neato5oh; What part of md.? I live in Glen Burnie.

After you replace the EVR go back to the Emissions testing center (puzzle palace) and request to talk to a supervisor. Explain that the tester used GRANNY and not second to start out in. INSIST on a tester that knows how to drive a GRANNY 1st transmission. If they don't have one there go to another center.

I did this with my '87. Numb***s tester insisted there was something wrong with my T-18. 1st gear only 13 miles an hour @ 4000 rpm.

I got the supervisor after she failed the truck for non drivability(how else did it get to the center, Scotty broke the transporter and I didn't trailer it!)????, and explained to him how she started out in 1st which is a compound low gear and not to be used for everyday driving. Treat it like a 3 spd (2-3-4) and everything will be fine. He ended up driving the test over and passed. She ended up getting suspended. This was 3 yrs ago.

BITCH, COMPLAIN, MOAN, AND GROAN! Most of the testers are 2 brain-celled idiots who flunked auto shop and are marking time on State rolls to get their retirement! And all of them are 3-4 bottles short of a case of beer!!!!!! And usually the supervisor have 4-5 braincells (only 2 of which are working at any one time!) Go for the throat if they mistreat your vehicle.

 

Got the new EVR. It leaks just like the old one. Checked the EVR on my 93 5.0 Mustang - it leaks too. Did a net search on ford evr vacuum leak, and found an olf thread from this forum. Apparantly these EVR things ARE SUPPOSED TO LEAK!!!


Ahhhh!!!

 

Next time, do your research BEFORE buying parts!

 

When I first moved to Maryland from out-of-state in the mid-1980s I found the auto inspection processes to be oppressive. The safety inspector tightened a spindle nut too tight on one of my 1980 Chevy Blazer front axles and cost me over $900 to replace a spindle. Maryland's a tough place to own an older vehicle.