The other day I took my 88 302 truck to Texas state inspection (sniffer test) for the first time since my [link:brembs.net/cars/maf_conversion/|mass-air conversion]. With new EGR valve and position sensor, new oxygen sensor and new injectors, I figured I should pass with flying colors.
However, after the 15mph test the guy told me it wouldn't pass and if I want to bring it in again later - too many hydrocarbons, he said (it was smelling real rich in the shack, too).
I checked the error codes (so far only memory and KOEO, got some trouble reading the KOER codes) and got the following:

32 (O,M) - EVP signal is/was low (EGR is new, but haven't measured voltage/resistance in the EVP snsor, yet).

66 (M) - Mass Air Flow (MAF) signal low (I backprobed the MAF and the voltage is around 1.1V at idle and increases with depressing the throttle. Looks fine to me.)

67 (O,M) - Park/Neutral circuit fault (it's a manual and it was in neutral. Where do I double check that?)

85 (O,M) - cannister purge solenoid. (1988 trucks didn't have that solenoid. Shouldn't make much difference, should it?)

95 (O,M) - Fuel pump: open, bad ground or always on (I checked the ground from the computer to the chassis, it's perfect. I even checked it from several points in the harness. What other grounds could there be that I have missed?)

None of these error codes seem to tell me why the engine is running rich. Gas mileage is also not horrible (14.5mpg). No oxygen sensor codes at all (I split the O2 sensor signal into the two pins for left and right bank that the A9L computer needs). What else could cause the computer to dump fuel into the engine? If it's running rich, why is the O2 sensor not detecting it? The cat is semi-new (10k miles) and should be fine. The truck starts well and is running strong. After the conversion I expected the truck to run lean, if anything, but not rich.
Any pointers?

 

67 (O,M) - Park/Neutral circuit fault (it's a manual and it was in neutral. Where do I double check that?)

push your clutch pedal down and hold it during the test. This will activate the clutch safety sw.

Disconnect your battery for about 15 or 20 minutes to clear any codes. Run til warm, take it for a road test and recheck for any codes. Some of these codes may have been set during your mod.

 

also check to make sure the injectors match your MAF sensor, unless you bought all stock and brand new, then you'd be fine.

 

I'll check the clutch thing! Thanks!
The codes have been cleared since the conversion.
The MAF and injectors should match (both 19lbs).

 

How about swapping the stock 14lb(or is it 12?) injector's in there for the test

 

Nevermind my last post. I was thinking of the 4.9L

 

Does anybody have any idea what other grounds to check? What could be the reason for the MAF error code? It reads over 1V and I thought the MAF min voltage was about 0.5V??

 

UPDATE: I checked vacuum at idle: just over 18 inches of Hg. I checked the EGR valve position sensor: 4800 Ohms (should be just under 5000) closed, 400 Ohms open (should be about 100). If the EGR is open at idle, engine stalls (it should). Voltage at EVP sensor harness is 5V (should be between 4 and 6V). The EGR valve loses 1inch Hg per about 10-15s if I apply about 5-6 inches Hg (should be about 30s). In short, even though the values are not exactly within specs, they shouldn't cause a 32 error message (hard fault at KOEO).
Triple checked all grounds and connections to various sensors. All checked out fine (between 1.4 and 0.4 Ohms).
MAF error message did not come back.
Still can't check engine running codes (there is no voltage across self-test connectors), so there's got to be a problem somewhere in the wiring. What other grounds are there? The one that gives me the 95 error (PCM to ground) is less then 0.5 Ohms.
Couldn't check fuel pressure (will give the %$^# gauge back to Autozone as soon as I'm done typing).

Does that give anybody an idea what else I could check?
Any help is dearly appreciated!

 

[updated:LAST EDITED ON 24-Nov-02 AT 07:42 PM (EST)]Unbelievable but true! After a long day of troubleshooting I passed!!!

While checking the EGR system out, I sealed the EVP sensor onto the EGR valve with high temperature silicone. That must have made all the difference for the sniffer test, even though it didn't reflect in the engine error codes <shrug>.

However, I didn't pass as well as with the speed density system a year ago (2000 rpm for SD, 2500 rpm for MAF):

Pollutant | Standard | SD reading | MAF reading
HC (ppm) | 170 | 14 | 90
CO(%) | 2.11 | 0.03 | 0.2
CO2(%) | | 14.2 | 13.0
O2(%) | | 0.3 | 13.8
Nox (ppm) | 1677 | NA | 951
Dilution | (>6) | 14.3 | 13.2

Can someone please decipher those values for me??

I also noticed a ping/spark knock at 1400-1700rpm with slight acceleration and at WOT (but not inbetween). Should I change to premium fuel? (Timing is just under 10 degrees BTDC.)

Oh yes and the fuel pressure is just under 30psi for KOEO and KOER. It increases with thrittle opening and it also increases if I unplug the vacuum hode from the fuel pressure regulator.

Thanks so much for any help, guys!

 

Hence your code 95... EGR, EVP problem. Good hunting!

 

>Pollutant | Standard | SD reading | MAF reading
>HC (ppm) | 170 | 14 | 90
>CO(%) | 2.11 | 0.03 | 0.2
>CO2(%) | | 14.2 |
>13.0
>O2(%) | | 0.3 |
>13.8
>Nox (ppm) | 1677 | NA | 951
>Dilution | (>6) | 14.3 | 13.2
>
>Can someone please decipher those values for me??

I looks like you are running too lean. Nox and O2 would be low if it were rich. I suspect that your MAF system is somehow not calibrated just right. I have never heard of "Dilution". Any idea what that is?
>
>I also noticed a ping/spark knock at 1400-1700rpm with
>slight acceleration and at WOT (but not inbetween). Should I
>change to premium fuel? (Timing is just under 10 degrees
>BTDC.)
>

Timing should be 10BDTC. Lean conditions will cause pinging.

Jim

 

I once installed a new EGR valve. I discovered it had a ruptured diaphram after I had replaced the ECM. Lots of screwy codes. Anyway, I got a 95 code during the KOEO tests. I found that the EVP shaft extended too far down because the new EGR diaphram did not come up far enough. I shaved approximately 1/16 inch off of the seating surface of the EVP sensor then sealed it good onto the EGR. I did this after holding the EVP shaft in just a little during the KOEO tests, making it pass.

Good Luck,
Freddie

 

jimandmandy - I'll have to send the MAF sensor inn to Pro-M and get it calibrated again. It is calibrated for the 19# injectors, but for a Mustang. I'll have them do the truck calibration. I was just to cheap to do it so far

LonerWolf99 - that's a pretty nifty trick right there. I'll try to do that next time I pull the codes. The funnny thing is, though, that the EVP sensor shouldn't give error codes as it was below 5000 Ohms fully extended. I'll try it anyway, though, maybe that was all there was to it.

I still wonder if there's anything besides the MAF calibration that could cause the lean condition? Maybe the slightly low fuel pressure? Should I check the high-pressure fuel pump?
Thanks for all your help, guys!