Failed Emission Tests
#1
Well, I installed new cats on my 87 GXL. The engine was rebuilt 2 weeks ago. I have run 1 tank of super unleaded through with additive.
The car did not pass inspection. Interestingly, in the state of Texas they test for 3 gases. Hydrocarbons, carbon monoxide and NOx which I think is nitric oxide but not sure. The NOx is a new test this year. The inspector was really concerned that the car would fail the NOx but it passed that part easy. In fact the NOx was barely detectable. It did fail the hydrocarbons and CO.
Tonight I was trying to figure out what was wrong and I noticed that the shop that rebuilt the engine did not tighten (or maybe it loosened on its own) the lock nut for the crank angle sensor. The timing was off. I reset the timing and the car sounds and runs much better. My question is, could the timing being off cause a failure in the emissions testing? Everything else I have checked, with the help of the Haynes manual seems to be just fine. The timing was off so far that the car could not Idle below 1000 even with the air adjust screw closed all the way. Now the engine idles at 750 RPM, the popping noise in the exhaust is gone and the car has very good power.
The car did not pass inspection. Interestingly, in the state of Texas they test for 3 gases. Hydrocarbons, carbon monoxide and NOx which I think is nitric oxide but not sure. The NOx is a new test this year. The inspector was really concerned that the car would fail the NOx but it passed that part easy. In fact the NOx was barely detectable. It did fail the hydrocarbons and CO.
Tonight I was trying to figure out what was wrong and I noticed that the shop that rebuilt the engine did not tighten (or maybe it loosened on its own) the lock nut for the crank angle sensor. The timing was off. I reset the timing and the car sounds and runs much better. My question is, could the timing being off cause a failure in the emissions testing? Everything else I have checked, with the help of the Haynes manual seems to be just fine. The timing was off so far that the car could not Idle below 1000 even with the air adjust screw closed all the way. Now the engine idles at 750 RPM, the popping noise in the exhaust is gone and the car has very good power.
#3
It does have air coming out even at idle. Haynes manual says air should start flowing at 1500-2500 RPM. I've got air at 750. Does this indicate a bad ACV?
I also did the Haynes manual check of the EGR valve. I removed the vacuum hose from the EGR solenoid valve and I applied a vacuum. Tthe problem was that it would not hold a vacuum. The manual said that the engine shoudl run rough or stall. Nothing happened. I guess that is bad also.
I also did the Haynes manual check of the EGR valve. I removed the vacuum hose from the EGR solenoid valve and I applied a vacuum. Tthe problem was that it would not hold a vacuum. The manual said that the engine shoudl run rough or stall. Nothing happened. I guess that is bad also.
#6
Originally Posted by gazellis' date='Mar 16 2003, 07:24 PM
It does have air coming out even at idle. Haynes manual says air should start flowing at 1500-2500 RPM. I've got air at 750. Does this indicate a bad ACV?
I also did the Haynes manual check of the EGR valve. I removed the vacuum hose from the EGR solenoid valve and I applied a vacuum. Tthe problem was that it would not hold a vacuum. The manual said that the engine shoudl run rough or stall. Nothing happened. I guess that is bad also.
I also did the Haynes manual check of the EGR valve. I removed the vacuum hose from the EGR solenoid valve and I applied a vacuum. Tthe problem was that it would not hold a vacuum. The manual said that the engine shoudl run rough or stall. Nothing happened. I guess that is bad also.
the egr doesnt do any thing, but you should put something in the hose so its not a vacuum leak
mike
#7
I have an update here but still need help. I took the car back to the shop that rebuilt the engine. They checked everything out and found quite a few vacuum leaks but no mal-functioning parts (ACV, EGR, etc...)
They fixed the vacuum leaks. I swear the car runs better than the day I bought it brand new but it still did not pass the inspection.
The first inspection it failed hydrocarbons and carbon monoxide. This time it only failed hydrocarbons. I guess it is getting better.
The rebuild only has about 120 miles on it and the inspectors seem to think that is why it is not passing. I have not been running it hard during the break in period (keeping it under 4000 RPM and such). Maybe that is why it won't pass. I haven't got a clue. I can't really go driving around town all day every day because it is out of inspection. I guess I could risk it, it can't be that bad to get a ticket for out of date inspection.
I took it to be inspected after it had been running for a while. The engine was good and hot (up to temp that is). I have run one thing of additive through the first tank of gas. Maybe it needs another at the next fill up.
Any other ideas? I was assured that the vacuum problem is fixed. It sure does run like everything is great.
They fixed the vacuum leaks. I swear the car runs better than the day I bought it brand new but it still did not pass the inspection.
The first inspection it failed hydrocarbons and carbon monoxide. This time it only failed hydrocarbons. I guess it is getting better.
The rebuild only has about 120 miles on it and the inspectors seem to think that is why it is not passing. I have not been running it hard during the break in period (keeping it under 4000 RPM and such). Maybe that is why it won't pass. I haven't got a clue. I can't really go driving around town all day every day because it is out of inspection. I guess I could risk it, it can't be that bad to get a ticket for out of date inspection.
I took it to be inspected after it had been running for a while. The engine was good and hot (up to temp that is). I have run one thing of additive through the first tank of gas. Maybe it needs another at the next fill up.
Any other ideas? I was assured that the vacuum problem is fixed. It sure does run like everything is great.
#9
It failed by about 90 points on both the low speed and high speed.
I think it maybe running too rich because the inspectors keep making the comment on this. How do you change the fuel mixture to lean it out?
I think it maybe running too rich because the inspectors keep making the comment on this. How do you change the fuel mixture to lean it out?
#10
Originally Posted by gazellis' date='Mar 23 2003, 12:16 AM
It failed by about 90 points on both the low speed and high speed.
I think it maybe running too rich because the inspectors keep making the comment on this. How do you change the fuel mixture to lean it out?
I think it maybe running too rich because the inspectors keep making the comment on this. How do you change the fuel mixture to lean it out?
The ECU controls the fuel mixture for you, it uses the sensors on the engine to select which fuel maps to use, so if it's running rich it can easily be one of the temp sensors or the o2 sensor, definitely check them out.
Introducing a vacuum leak could also help it pass the test, it would help lean it out (kindof funny).
Also make sure the TPS is adjusted properly.