Emission problems

Hawk · 12-29-2007, 10:18 AM

I have an 89 mustang 5.0 and after 19 years it will not pass MD emmissions. I have tested everything and can't find a problem. Any ideas?

mark v · 12-29-2007, 12:34 PM

What do you mean by tested?

How many miles?

Time for a tuneup and or maybe more parts.

ABE · 12-29-2007, 01:23 PM

Quote:

Originally Posted by Hawk

I have an 89 mustang 5.0 and after 19 years it will not pass MD emmissions. I have tested everything and can't find a problem. Any ideas?

In my area of Canada we have to pass an emissions test every 2 years. The test uses a tailpipe sniffer at idle and light throttle in drive on a rolling road. The car must meet minimums based upon its year of manufacture. I have found with 20 year old vehicles in good shape that the cats are the main cause of failure due to the age and types of catalyst.

You cannot test them since they do not have O2 sensors upstream and downstream. Many had drain plugs that you could remove the spent catalyst and put new ones in. My son's truck (before he bought it) had the catalyst removed and not replaced and it wouldn't pass the test, untill I put on a low cost universal cat using the latest honeycomb low restriction catalysts. Cheap (less than $100) and easy bolt on installation.

I am sure that new cats will resolve your problem.

Hawk · 12-31-2007, 11:00 AM

I bench tested the O2 sensors with a voltmeter and they performed in range. I tested the EGR with a vacuum gauge and it was working fine. I did change the position sensor and eliminated the 34 code. I hve tuned it up and changed the oil and air filter. Now I'm pulling a 66 code (Mass Air).

The has just over 34,000 miles and has never failed before. This time it has doubled it's readings of hydrocarbons.

I'm stumped.

ABE · 12-31-2007, 12:27 PM

Quote:

Originally Posted by Hawk

I bench tested the O2 sensors with a voltmeter and they performed in range. I tested the EGR with a vacuum gauge and it was working fine. I did change the position sensor and eliminated the 34 code. I hve tuned it up and changed the oil and air filter. Now I'm pulling a 66 code (Mass Air).

The has just over 34,000 miles and has never failed before. This time it has doubled it's readings of hydrocarbons.

I'm stumped.

The Mass Air Flow (MAF) sensor is a fine wire grid in the air intake air tube which has an electrical connector with about 4 wires on it. The wire grid is heated and the PCM measures the wires' resistance which changes with the amount of air flow over it. If the grid is dirty then the readings are inaccurate or out of range which sets a code.

Remove the sensor and clean it with an electrical contact cleaner that leaves no residue. That should fix your code, and may fix your increased hydrocarbon problem.

Do you have an Air Injection Reaction (AIR) system on your car? This system has an air pump that with some complicated tubing and valves pumps extra air into the exhaust manifold (or heads) and into the cats. The extra air soaks up the hydrocarbons. This is an old inefficient system that is prone to failure, and could explain your jump in hydrocarbons.