Failed emissions for hydrocarbons (HC)

[sljorge]

The saga continues!!!

So I went back for my retest today after fixing my fuel tank leak.

History: 1st Emissions test and fuel tank leak

The Emissions tech, after the first failure, said the EVAP pressure leak would cause my emissions values to be artificially low. Here they are again:

1st test w/ press failing:
HC = 0.61 (limit 1.0)
CO = 3.90 (limit 12.0)
NOX = 1.23 (limit 2.5)

2nd test w/ press passing:
HC = 1.09 (limit 1.0) FAIL
CO = 10.56 (limit 12.0)
NOX = 1.91 (limit 2.5)

All the numbers went up just as the tech predicted. This is so infuriating!!! I only failed by 0.09 grams/mile!!!! I'm temped to rig some type of remote control vent on the gas tank that I can control while sitting in the pass seat! (just kidding).

Here are some more details on my failure today: I put 91 octane gas in the tank (normally use 87) and drove on the hwy for 15-20 mins prior to testing. Sat idling in the waiting line with a/c on for about 20 mins to keep car warm so I don't think engine temp was a factor.

What suggestions does the team have for getting these VERY CLOSE numbers to pass?


-Nine 100ths of gram over the limit in AZ!!

[hill8570]

Looks like she's running a bit on the rich side. Can you measure the VF terminal of DLC1 under the same circumstances (fully warmed up and idling)? It'd be interesting to see what the ECU is doing to fuel trim when this is happening.

[sljorge]

Is there a post/sticky somewhere to give instructions on this? I'm new to this whole car repair thing (but learning fast).

-Scott

[hill8570]

Originally Posted by sljorge

Is there a post/sticky somewhere to give instructions on this? I'm new to this whole car repair thing (but learning fast).

-Scott

Sorry, thought you were somebody else -- my bad

Not sure about a sticky, but if you open the hood, DLC1 is the little flip-open connector on the passenger side near the firewall. If you flip it open, the underside has the location of all the test points labelled. You're looking for VF (maybe VF1, but I'm pretty sure it's just VF on the 4-bangers). Voltage won't be more than 5V DC, so set scale appropriately. If you need better access to the test terminal, you can always stick an unbent paper clip into the terminal.

[sljorge]

So I read in several places online that a car barely failing emissions will pass by adding denatured alcohol (DNA) to a 1/4 tank of fuel. I put a qt of DNA in my tank and drove back to the air check station (15-20 min drive oneway), paid my $27.75 and watched as my car failed AGAIN:

3rd test w/ denatured alcohol:
HC = 1.02 (limit 1.0) FAIL
CO = 5.06 (limit 12.0)
NOX = 1.80 (limit 2.5)

As you can see, the CO and NOX numbers dropped quite a bit, but the hydrocarbons only dropped a little and not enough to pass. Only 0.02 over the limit.!!!

I agree the car seems to be running rich and am wondering how to fix it. I'm leaning towards troubleshooting/replacing the ECT and O2 sensors.

Any other thoughts out there?

-Frustrated in AZ

[hill8570]

Originally Posted by sljorge

So I read in several places online that a car barely failing emissions will pass by adding denatured alcohol (DNA) to a 1/4 tank of fuel. I put a qt of DNA in my tank and drove back to the air check station (15-20 min drive oneway), paid my $27.75 and watched as my car failed AGAIN:

3rd test w/ denatured alcohol:
HC = 1.02 (limit 1.0) FAIL
CO = 5.06 (limit 12.0)
NOX = 1.80 (limit 2.5)

As you can see, the CO and NOX numbers dropped quite a bit, but the hydrocarbons only dropped a little and not enough to pass. Only 0.02 over the limit.!!!


I agree the car seems to be running rich and am wondering how to fix it. I'm leaning towards troubleshooting/replacing the ECT and O2 sensors.

Any other thoughts out there?

-Frustrated in AZ

Yup, you added extra oxygen to the mix (which is what the alcohol does), and your numbers went leaner.

Just to make sure -- I've been assuming that you had your battery disconnected while you were playing with your gas tank (and so memorized long-term fuel trim info in the ECU would've been reset). If not, I'd recommend disconnecting the battery for a bit -- having the pressure leak surely played hob with your long-term fuel trim.

I'd still like to know what the VF number is -- if it's real low (like, zero volts), that would indicate that upstream sensors are fooling the ECU into thinking that the injectors should be a certain level of rich (or the injectors are leaky...fairly low probability), and then the signal from the O2 sensor is telling the ECU to trim to the lean side -- zero volts on VF means it's trimming lean as hard as possible -- usually a sign that something other than the O2 sensor is at fault. If VF is happily at 2.5V, the ECU thinks everything is peachy, and I'd suspect the O2 sensor. If VF is > 2.5V (like, 3.75 or 5), then the ECU is thinking the mixture is too lean, based on the O2 sensor, and trying to richen the mix -- that's a dead giveaway that the O2 sensor is really doing strange stuff.

[hill8570]

Another couple of ideas: check your air filter...it doesn't seem real likely, but a really, really dirty air filter can give you a pretty rich mix. And, since you just got done messing with the fuel tank, I'd make sure the fuel return line was hooked up and not clogged.

[sljorge]

I finally passed!!! But only after dumping another qt. of 91% (182 proof) isopropyl rubbing alcohol (IPA) into a 1/4 tank of gas. I drove about 20 mins on hwy and, while waiting in line, I idled my car at 2000 rpm until it was my turn--nice and hot! Here are my final numbers:

4th test w/ 91% IPA:
HC = 0.57 (limit 1.0)
CO = 4.54 (limit 12.0)
NOX = 1.13 (limit 2.5)

These numbers were even better than my original ones with the EVAP leak. At least I don't need to worry about the gov't for another 2 yrs.

Now, I still need to work on a few things to get my ride up to par. For example, while at Checker Autoparts yesterday looking at my battery terminals, the tech noticed a high-pitched hiss coming from the engine and said, "you've got a vacuum leak!" We couldn't find it after a cursory overview of the tubes in the back of the engine compartment. I asked, and he confirmed, that a vacuum leak like that could cause the car to fail emissions.

I'll keep you updated...

[freeyellow2000]

any updates? Where was your the vacuum leak.?

[sljorge]

No update, been busy on other things. We let you know soon.