Smog problem--EGR fault?

[Mycall47]

Help!!!

I've just purchased a 1990 California SHO that has a problem I'm hoping the membership can help me with. The emissions test paperwork I received with the car showed the following test results:

@15 mph

HC ppm 0014
CO% .2
O2 .3
%CO2 14.8 (All these values are passing ones)
NOX 1148 this value caused test failure


@ 25 mph

HC ppm 0009
CO% .14
O2 .2
%CO2 14.9 (All these values are passing ones)
NOX 1116 this value caused test failure


Max values allowed on NOX are 791 and 730


I have a smog station repair order from the previous owner that indicates "no vacuum signal to egr", and then they replaced the "back pressure transducer to egr" for $125.00

Evidently this did not fix the problem.

In addition I hear a small exhaust leak that is not coming from the main "doughnut" gasket at the Y-pipe or exhaust to head gaskets, but I suspect may be from a leaking EGR pipe. How common is this problem of high NOX (the car has 135K miles on it), and why is the egr pipe listed as a $200 item?.

My other SHO is a 1989 car with almost 200K on it now (a 49- state car) that I have owned for 14 years and I have never had any emission control problems with that one at all.

Thanks in advance for any comments or advice.

Mike

Martinez, CA

 

[Off Road SHO]

It's listed as a 200 dollar item because they can get that much for them. If you think you hear an exhaust leak, make up one of my handy dandy exhaust leak detectors. They can be purchased on the internet for 1,500 dollars but you can make your own for 12 cents.

Tape a piece of tissue paper to a wooden stick. Tissue should be about 2-3" long and an inch wide so it will wave in the wind easily.

Start car, make sure ac is off so fans won't be on. Move the tissue paper all around the back of the motor near the firewall. The smallest of exhaust leaks will move the tissue, and the wooden stick will allow you to reach hard to reach places.

Good luck.

Tom

 

[SHOZ123]

I would inspect the intake manifold to EGR valve passageway. If this is dirty it will impede flow.

Verify EGR flow by applying vacuum to the EGR valve when the car is warm and idling. It should make the engine/motor stumble if it is open. You should also be able to see the shaft on the EGR valve move with vacuum applied.

 

[Mycall47]

Thanks for the tips. I did take the EGR valve off, and checked it with my MitiVac Vaccuum Pump, and the shaft did move and it held vaccuum. Then I sprayed out the valve to remove carbon/gum and it operates smoothly now. Then I took the hex plug out of the manifold, and sprayed Berrymans Carb cleaner until the stuff ran out clean from the egr mounting ******. I also blocked the throttle plate open and cleaned the passages at the bottom of the throttle body bore. Next I took the "de-carbonizing" tip from another guy and with the motor warm and running--- sucked about 12 ounces of Berrymans through the canister port on the downstream side of the throttle butterfly-- let the engine die and sit for 15 minutes---then re-started it and ran about two cups of warm water through the port while working the throttle. So-- the next step seems to be taking your advice with the motor running, and actuating the egr valve with the MitiVac, and seeing if I get the stumbling response you mention. When I bought this car there was a repair order in the glove box showing a "error code" of "no vaccuum signal to egr". I'm wondering if-- after all of this cleaning if I still get no egr action-- I might have a bad "E6AZ-9J460-A" EGT pressure sensor.

 

[SHOman24v]

i know whats wrong.... follow your egr vacuum line on the back of the valve to the vacuum control unit to it, that part opens the valve on the egr, pull the vacuum line off the egr valve and revv the engine, do you feel a slight vacuum on the line, if not the part that the two vacuum lines (one from the intake and one from the egr) go into is bad, trust me, i had that exact problem about 3 weeks ago, pass everything except NOX... its a 29 dollar part btw and it bolts to the driver side engine strut mount

if you take your egr off and it just falls, you have a broken egr tube, you cannot buy that anywere period. id recommend welding it, but you better be accurate or it wont bolt up, remember that tube is solid.

 

[Mycall47]

EGR problem--almost ready to try a pre-test

Thanks for the tip. I did look at that component, and verified that there was vaccuum to it with the engine running. When I put my MitiVac unit to the other port (going to the egr) and revved the engine I saw no reading of vaccuum on the gage. So-- that part was suspect. The only thing I'm kinda worried about was brought up by another member, and that was what if the control signal to that valve was eliminated in the LPM program currently fitted to the car. I'm pretty sure it is a SHO Shop 80mm MAF and LPM fitted, but there are no identifying marks on the MAF. Maybe I can snap a digital pic of both components and post them for comments from you guys.

 

[SHOman24v]

its best to smog when your completely stock...

 

[SHO Dude]

NOX Issue

NOX stands for Oxides of Nitrogen. NOX is produced when the combustion temps exceed 2600 degrees F. As the flame front moves across the top of the piston, if it's too hot, it'll oxidize (burn) the nitrogen in the air mixture. This is what produces the NOX in the exhaust.

There is three way to keep the combustion temps down. You can add EGR, lower the compression or reduce the timing.

The EGR is tough unless you have my SCT programming (I have full control over EGR functions). Compression and timing are equally as tough.

However. You can make a temporary adjustment to pass emissions. There is a plug called a Spout Connector. This is the link between PCM and the DIS module to set timing advance. If you pull this connector, the timing will drop to base and you'll not have any computed timing. This will drop the combustion temps and NOX will fall like a rock.

This plug is located on the back of the intake manifold, near the passenger’s side corner. It's a black connector with a gray plug. Pull the gray plug before you have the car tested, then install the plug after the test.


Hope this helps...


Doug Lewis
[email protected]
Ford Performance Specialists
Atlanta Georgia
770-949-7191

 

[Mycall47]

Spout connector

Doug,

Thanks for the advice. I did find the connector, but then was reminded by a friend out here in California that they do a ign. timing test as part of the smog check. Having moved here 10 months ago from Colorado-- I was not aware of this difference in the test. Anyway-- if the timing is not to spec-- they will fail the car. I put a product from CRC in the tank (to assist in passing smog tests), and drove the car from San Francisco to L.A. this past week (about 400 miles each way). Round trip the car averaged 30 mpg at a mostly cruise control set point of 80 mph. So I guess the 80mm MAF/LPM and aftermarket y-pipe fitted by the PO did increase the efficiency of the engine. I never achieved better than 26mpg with my '89 SHO. I'm going to try a pre-test at the local high school this week to see what the NOX values currently are, and hope all the cleaning procedures I did helped. If not-- I could just bolt-on the stock MAF and airbox out of my '89, pull the LPM from the computer and run it through that way.