tman92

I live in an emissions county and I am having issues with my recently purchased camaro passing emissions test as it is running to rich according to the test. I purchased the car not running and found that the fuel pump was bad. The car had been sitting for two years. I replaced the fuel pump and she fired up but ran horrible. Found the cap and rotor to be bad. Replaced the cap and rotor with a MSD set. Replaced the plugss with N?GK V-Power plugs. The car already had a fairly new set of Accel 8mm wires. Car ran great with no codes.

First emmision test High NOX and High HC.
Came home and found the Egr valve to be bad. Replaced EGR valve, did a 3M decarbon treatment, replace PVC, replaced breather filter, replaced valve cover gaskets (cleaned rear ports on heads), installed K&N air filter, changed the oil and filter, and replaced newly installed fuel filter with a K&N filter.

Second emissions test NOX in range barley and high HC.

Back to drawing board and found MAP sensor voltages reading on the high side. Replaced and car ran a little better.

Third emmisions test NOX in range and HC high. Car was tested at this time cold, hot, high rpm, and low rpm. Was told to drive thecar put some miles on it since it sat for to years. Put 180 miles of fun on it and took it back with the same result four test #4.

Through further diagnosing found some had changed out the fuel pressure regulator with a larger spring (I guess this raises fuel pressure but not sure). Rebulit fuel pressure regulator and flushed coolant system (due to rust in the system ) and installed a 195 degree thermostat.

Test #5 NOX in range and HC high.

At a lost as what to check from here. I have no codes. No black smock. Exhaust is not as smooth as I would like but does not suck to indicate a miss. Car has 184000 miles on it. It is a 305 with a 5 speed. The engine is in time unless my timing light is messed up again.

My temps are a little higher than desired (210 range ). But the car runs great minus the AC compressor issue.

Any help would be greatly appreciated.

RBob

iTrader: (1)

Check/set the base timing with the engine warmed up. Having both high NOX & HC is a sign of too much spark advance.

You likely did change the oil, but if not do that too.

RBob.

tman92

As I put in the above. Timing has been set and oil has been changed. NOX is in range but HC is still high.

RBob

iTrader: (1)

Long posts create an affliction referred to as a 'reading attention disorder.'

Just to be sure the timing for a L03 is at 0* BTDC.

After that, I'd say the cat-con is toast.

RBob.

RBob

iTrader: (1)

To add, an O2 sensor reporting rich may be driving the fuel trims down. This too will cause high HC and NOX.

RBob.

tman92

I will have to check the o2. It has a new magnaflow cat on it. At least the previous owner said he put a new one on befote he let it sit for 2 years.

Will check - thanks

ex-x-fire

Make sure the map sensor is hooked to the proper port. What kind of vacuum is the engine making at idle?
While checking the timing, make sure it advances when you rev it.
When the car is idling, open the egr valve, does the engine stall?
Check the ecm grounds, might be on the back of the heads or near the t-stat.
Check the fuel pressure, might have a resticted return line causing high pressure. Spec is 9-12 psi.

tman92

Car is driving me crazy. I am guessing I need a new timing light or I am missing something obvious. I disconnected the bown wire with a black strip which i am almost sure os my disconnect for timing and the cat idles better. A little doggie at first but runs better.

What am I missing?

tman92

I will check the above and see if i get headway with it.

Converted from racing fords and older chevy's to this so bit of a learning curve for me. Thanks for the info.

ex-x-fire

The harmonic balancer might have slipped on the hub, sbc are known for this.

Schurkey

As alluded to in the earlier post by RBob, a high HC level is NOT from a too-rich mixture--unless it's so incredibly rich that it causes misfire. High CO is a result of too-rich fuel/air mix.

High HC is far more likely to be from a too LEAN fuel/air mix; a lean misfire drives the HC reading high.

Either way, high HC is typically due to misfire (from any cause).

So: All the usual questions:
What does the computer think the engine temperature is? (Not the dashboard gauge.)

What are your O2 crosscounts at various operating conditions?

What are the short- and long-term fuel trims? (Block learn and Integrator)

How old is the O2 sensor?
(a note on O2 sensors: I screwed around with my work truck for about two years--the O2 crosscounts were good at low speed; but I had a lean fuel mix trouble code that set as predictable as the sunrise at highway speed. I checked EVERYTHING, about five times--and then, in desperation, replaced the O2 sensor. Problem solved. O2 tested good (at low speed) but wasn't.)

Will your ignition system properly fire a spark tester?


What is the cranking compression of all eight?

What is the actual fuel pressure?

tman92

Took awhile but issue found and solved. Previous owner replaced the ECM with a 350 ECM instead of one for a 305 and it was running rich and timing was not advancing correctly. Local speed shop was able to reprogram the current computer some how. Do not know what he did but it worked.

Thanks to everyone for their help.