Took the Stang into the shop today.

88CougarMan · Dec 30, 2004

I have been having problems with passing emmisions and the check engine light comes on for the EGR/EVAP (code 31). The guy gave me hell about my car being modified and that they might not be able to work on it. I have replaced the EGR pump, and my cats are not that old. Yet I still can't pass emissions. So, I figure it has something to do with that pesky CEL that never goes away. Anybody have any ideas on what my car's problem is in case they tell my they can't fix it?

Thanks guys!

jaidedeye · Dec 30, 2004

get rid of that 160 t-stat......might be keeping your car from warming up all the way

Funanin · Dec 30, 2004

try tuning fuel pressure to lean it out a bit.

4dStang · Dec 30, 2004

How high are your hydro carbons? The o2 sensors could be richening up the engine. You don't seem to have too many smog related modifications in your sig. Some how you are obviously runing rich.

A good way to cheat the smog on a odb1 car is to loosen the exhaust ever so slightly to get a small leak. that will allow less exhaust to come out the tail. I have also seen people put pure o2 into the egr system to add air and lean out the exhaust.

What state are you smogging for? Some are worse than others. Also, here in Illinois, ODBII cars just get a plug in. If you have had any CEL's in the computer, they will fail it. So, loosen the exhaust, remove the battery for a half hour, maybe think about replacing the o2 sensors (they are only good for 50K anyway) and you should pass.

jrichker · Dec 30, 2004

This may be a repeat, but here's the code 31 test path...

CODE: 31 (KOEO) - EVP circuit below minimum voltage. Vref (5 volt reference voltage supplied by the computer) missing or broken wire or bad connection in circuit. Use a DVM to check for 5 volts on the orange/white wire. If it is missing, look for +5 volts at the orange/white wire on the TPS or MAP sensor located on the firewall near the center of the car. Use the black/white wire for the ground for the DVM.

With the sensor removed from the EGR and still connected, press the plunger and watch the voltage change on the brown/lt green wire. You wil have to back probe the wires or take the measurements at the computer.

Pull the passenger side kick panel and measure the voltage at the computer. You will need to remove the plastic cover over the wires and probe them from the backside. A safety pin may prove very useful for this task. Use pin 27, EVR input (brown/lt green wire) and pin 46, signal ground (black/white wire) to measure the voltage. The orange/white wire is Vref and should always be 5 volts -/+ .25 volt. Be sure to measure Vref at the EGR sensor to rule out any broken wires or bad connections.

Daggar · Dec 30, 2004

My tip would be to dump the dumbass that gave you crap about modifying your car. What a tool. Should be legal to kick him in the nuts.

Edit: I know... my post didn't help at all. Get damned tired of the stuff shirt emissions Nazis is all.

*Vent completed*

88stangmangt · Dec 30, 2004

all the cats in the world wont do any good if you dont have a strong tune.......................start there.

MatthewP · Dec 31, 2004

Your EGR valve is probably gummed up. Take it off and use carb cleaner on it to free it up. Make sure it moves freely.

Secondly, I agree with the comment about replacing the thermostat. Put in a 195 thermostat.

As far as your emissions test goes, changing your oil can help. Also make sure that your rotor, cap, plugs, and wires are all in good shape. Finally, some people disconnect the harness from a single injector (usually one that is hard to see like #8 or #4) so that one cylinder is just pumping air. This can make a big difference on the test.

Good luck.

-Matthew

88CougarMan · Dec 31, 2004

The guy called me a little ago and said that he couldn't do anything for me. His only suggestion was bull****, he said that the aftermarket cats were a 1 phase/plain or whatever and the factory ones were 3 phase/plainwhatever...and the factory ones are more effective than the aftermarket ones. So, I asked him if mine were bad, and he said no, just not as good as the Ford factory.

EGR is new and not gummed up at all. You guys think it's because I'm running rich? Do I need to buy a AFPR to fix that? Any dealer won't touch it because it's modified. I asked about a year ago to check the Air/Fuel ratio and they said that since it has exhaust mods and a K&N, they can't touch. I live in a county where they have those dyno emissions machines...any little thing and I'm screwed.

wake · Dec 31, 2004

What are your scores, there was a thread the other day talking about emissions, he said run low octane, move timing down as low as possiple with the idle around 950. He also mentioned some other stuff. I would atleast move up to a 180 t-stat.

88GT17MA · Dec 31, 2004

jrichker said:
This may be a repeat, but here's the code 31 test path...

CODE: 31 (KOEO) - EVP circuit below minimum voltage. Vref (5 volt reference voltage supplied by the computer) missing or broken wire or bad connection in circuit. Use a DVM to check for 5 volts on the orange/white wire. If it is missing, look for +5 volts at the orange/white wire on the TPS or MAP sensor located on the firewall near the center of the car. Use the black/white wire for the ground for the DVM.

With the sensor removed from the EGR and still connected, press the plunger and watch the voltage change on the brown/lt green wire. You wil have to back probe the wires or take the measurements at the computer.

Pull the passenger side kick panel and measure the voltage at the computer. You will need to remove the plastic cover over the wires and probe them from the backside. A safety pin may prove very useful for this task. Use pin 27, EVR input (brown/lt green wire) and pin 46, signal ground (black/white wire) to measure the voltage. The orange/white wire is Vref and should always be 5 volts -/+ .25 volt. Be sure to measure Vref at the EGR sensor to rule out any broken wires or bad connections.

you need to write a book or something man lol, your posts sounds so perfect as if they were rehearsed haha

Mustang5L5 · Dec 31, 2004

jrichker said:
This may be a repeat, but here's the code 31 test path...

CODE: 31 (KOEO) - EVP circuit below minimum voltage. Vref (5 volt reference voltage supplied by the computer) missing or broken wire or bad connection in circuit. Use a DVM to check for 5 volts on the orange/white wire. If it is missing, look for +5 volts at the orange/white wire on the TPS or MAP sensor located on the firewall near the center of the car. Use the black/white wire for the ground for the DVM.
.

The EVP sensor is located on the EGR. He stated he replaced the EGR, but did he replace the sensor? The sensor is what is causing the code...even if the EGR is functioning properly.

I think he should dump the 160 stat and do a full tune up to begin with. Drop timing to 10 degrees, and then disconnect the batter to reset the codes. Then change the oil and go out and get the car HOT before bringing it in for testing.

HISSIN50 · Dec 31, 2004

the computer will adapt to any changes you make (including the FP). if you are running rich, it is from something being out of calibration or spec.
Mike might be onto something - the EVP might not be reporting the actual location of the EGR valve.

good luck with it.

89331SC · Jan 1, 2005

Im a mass inspector and i got a 91 mustang before that would not pass emissions. the guy did everything and could not get the car to pass after 3 times. he also had hi flow cats. he finaly took the hi flow cats off and put the stocker back on and the car passed.

matt17 · Jan 1, 2005

just my 2 cents,might want to check you purge silinoid valve down by the evap canister,i've seen it throw some egr and evap codes! good luck!

88CougarMan · Jan 2, 2005

matt17 said:
just my 2 cents,might want to check you purge silinoid valve down by the evap canister,i've seen it throw some egr and evap codes! good luck!

WHat does this look like, and what does it do? *EDIT* I think I found what you are talking about and it has a freyed wire. Don't really know what to do about it.

Mustang5L5 said:
The EVP sensor is located on the EGR. He stated he replaced the EGR, but did he replace the sensor? The sensor is what is causing the code...even if the EGR is functioning properly.

I think he should dump the 160 stat and do a full tune up to begin with. Drop timing to 10 degrees, and then disconnect the batter to reset the codes. Then change the oil and go out and get the car HOT before bringing it in for testing.

So, I should use a Digital Multimeter to test all the necessary wires; can I replace just the sensor, anybody know where to buy it? *EDIT* I looked up the sensor and it turns out I did indeed replace that part when I replaced the pump. I thought you were talking about the female connector with all the wires attached.
I'm seriously considering dumping the 160 stat, but my CEL comes on even after the car is warmed up. So, I'm not so sure that is the true problem.

89331SC said:
Im a mass inspector and i got a 91 mustang before that would not pass emissions. the guy did everything and could not get the car to pass after 3 times. he also had hi flow cats. he finaly took the hi flow cats off and put the stocker back on and the car passed.

But this doesn't account for the CEL. If I fix what is causing the CEL and I still fail, then I will definetly switch out the cats.

46defense · Jan 2, 2005

The last time I took an emissions test in Milwaukee, the young kids at the test site were really in to my car and dindn't mind taking a couple of extra pulls with it. They thought my KB blower was "radical, dude" Anyway, after it didn't pass with a tube on each tailpipe, they pulled one of them off and just ran a tube on one tailpipe. It still didn't pass! Next, they pulled the one remaining hose off and just held it down about 2 or 3". Hooray, you passed! I was so thankful that it worked out this way. They were really cool dudes, that probably saved me a big headache. I had just been to Anderson's dyno for a dyno tune with my pms, and figured it would be no big deal since all my emissions stuff was intact. Knowing what I know now, I probably would have just needed to get rid of some fuel (lean it out some). They don't floor the car on there anyway. I'm sure it was flunking because of too much unburned fuel coming out the pipe. Anyway, I would also be interested to know exactly where the purge solenoid valve is and what it looks like. I also have a permanent check engine light that never went away with any of the egr valve or evp swaps. It also comes on only when it is warm outside. If the air temp outside is less than say 60 degrees it's not there. I don't know what the exact outside temp cutoff is but it definately knows what the outside air temp is right at startup and either comes on and stays on or doesn't come on. It will sometimes go on and off a little as I drive. I should probably find out what the temp is when this happens because it is probably right around the magic temp. So if anybody knows more about this purge solenoid valve, and why no books i've seen ever seem to mention it as one possible fix for the code 31, I would love to hear it. I would love to get rid of this damn cel light. Thanks.

crunchie12268 · Jan 2, 2005

88GT17MA said:
you need to write a book or something man lol, your posts sounds so perfect as if they were rehearsed haha

I think they are in a book, and he copies and pastes

I would also recommend changing the t-stat, that is really low.

87tbird50 · Jan 2, 2005

Put in a 195 degree thermostat, and make sure your engine is good and hot when they run the test.

notchman90 · Jan 2, 2005

throw the guy a 50 and tell him to take a hike

Took the Stang into the shop today.

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