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I think you are misreading the emissions numbers. nj300se's engine is actually running lean. Although it is true that he failedfor slightly higher HC, that in and of itself is not a sign of running rich. A prime example of this is what is known to emissions people as a lean misfire. A lean...

Your CO2 is low. It should be around 15%. Newer cars may even have it as high as 16%. CO2 is an indicator of combustion efficiency. Higher CO2 is always better. Your mixture and O2 sensors are probably OK, otherwise CO (carbon monoxide) would be much higher if you were running rich. Carbon...

Does the Nissan Titan use the newer air/fuel ratio linear O2 senosrs, or does it use the more traditional zirconia "switching" O2 sensors (which we all have grown to know and love . . . )? What about the rest of the Nissan lineup? How do you instrument the newer O2 sensors for testing? I...

Generally, a puff of blue smoke when going off idle is a sign of valve seals in need of replacement. Continuous blue smoke is usually a sign of ring problems. Ironically, your piston soak might have made the rings seal better, creating more vacuum, and accentuating the valve seal problem.

I don't think there is any point to switching unless you are boiling over. Now if you changed your coolant mixture to something like 25% antifreeze, and 75% water, and then went with the higher pressure cap, you probably would see somewhat better cooling. Water conducts heat better, and doesn't...

One clue would be to compare "before and after" emissions results. If NOX is down, then cleaning deposits probably lowered compression ratio. Also HC should be a bit lower too (carbon deposits absorb raw gas, and keep it from vaporizing and burning thoroughly). By the way, your compression...

If you are concerned with fuel pressure, you will need to buy a fuel pressure gauge. To test the regulator, with engine at idle, pull the vacuum hose off the regulator (cover the end of the vacuum hose with your thumb). The fuel pressure gauge should show several psi of increase in pressure...

Hey zstalker, you have it slightly wrong. High CO is always a rich indicator. CO is even a better rich indicator than HC. This engine is running rich. Lean misfire will have low CO and high O2 and high HC. This vehicle is not a case of lean misfire. Mazatrol, this is most likely a carb...

Hey porcupine73, you are correct. It is better to have a tad too much clearance than too little. Too little clearance and the valves won't seal, and the exhaust valve will burn. Over 40 years ago, I was taught how to adjust valves by a really top notch automotive machinist. Allow me to share...

I vote with ChrisW on this. Valves seals are more often a cause of oil burning than ring wear, because the vacuum created in the cylinders very easily sucks oil past worn valve seals.

Most likely the water pump. Impellers are probably shot. Overheating at highway speeds but not at idle is almost always a water pump problem. Overheating at idle but not at highway speeds is almost always an airflow problem--usually a bad fan (or fan control circuit).

Most of the advice here has been right on the money. You are running way lean. If you can make your engine run cooler, you will reduce NOX and it will also run richer which will reduce NOX. Here are some ideas to get you started: Check your ECT sensor, be sure it's in spec. Putting a resistor...

You definitely want to diagnose any problems before replacing the catalytic converter. It would be a real pain in the wallet to replace the cat, and have it meltdown in a couple of weeks. That supercharged Bonneville was a nice car straight from the factory. I don't know what the emissions...

pitzel, I really can't agree with your claim that oil pressure isn't important. The Society of Automotive Engineers (SAE) plainly states in their Internal Combustion Engine Handbook that oil viscosity should be chosen so that a fully warmed up engine has sufficient oil pressure at hot idle. So...

Although this 5w-20 topic has been discussed at much length over the last few years, most of the responses are of the "works for me" nature. One data point which is usually lacking is the actual oil pressure under various ambient temperature and operating conditions. Most cars have idiot lights...

Hey drifter420, the Gumout Regane might have helped. If it cleaned up carbon on the exhaust valves it could help them seal better. It's hard to say exactly what it might have done to the cat; maybe it helped. One other thing that bears mention is that a plugged muffler or tail pipe could cause...

Hey brianl703, I hear you. But another problem is that changing the back-pressure will affect the EGR system. Some EGR systems are very sensitive to this. On OBDII cars you might start seeing P0401 and related codes. Also cars with pulse AIR may mess up the air injection if you mess with the...

The rotten egg smell is caused by sulfur in the fuel. It does not normally indicate a problem. Some catalytic converters have a propensity to accentuate the formation of this gas, notably Toyota converters. It usually occurs under rich mixture conditions such as WOT or cold starts. If you have...

Permatex Stripped Thread Repair works great for these sorts of repairs. Recommended!

Iowanbrick writes: The problem is that refrigerant actually passes through the firewall and enters the passenger compartment as it circulates through the evaporator. A very tiny leak could allow the buildup an explosive mixture of air and refrigerant in the passenger compartment. Static...