Failed Emissions Test

[NobleRogue]

I just took my 97 down for it's first Smog test. As expected, it failed. I got back two coeds. 1. P0400 Exhaust Gas Recirculation Flow. This is a bad EGR valve and or plumbing. This should be easy enough to fix. 2. P0300 Randome/Multiple Cylinder Misfire Detected. I'm hoping that this is nothing more than bad spark plug's plug wires or coil pack. I'm praying that it is not burned valves or bad piston rings. The car does not smoke at all so this gives me hope. Any ideas on how I can easily narrow this down?

[NobleRogue]

So I just spent $200.00 for a new EGR Valve, Plugs, Plug wires and new wiper blades. I had my 16 year old son "help" change the plugs and wires. By help I mean that he did about 90% of the work while i drank a beer and supervised.

I showed him how to inspect the plugs for bad singes like excessive oil, corrosion or physical damage and what each of those things might mean. I also taught him how NOT to over tighten the plugs and told him what could happen if they were over tightened.

He hopes that one day the Miata will be his lol. I told him he had to help work on it if he wants it some time in the future. When we finished with the plugs and wires, I let him start it up. I told him to goose the throttle a bit. lol He taped the pedal and the engine hit maybe 2k rpm's.

I chuckled and told him "you can do better than that!". He floored it right up to 6k before backing off. haha chip off the old block. He then proceeded to do it again and again. I thought I was going to have to drag him out of the car to get him to stop lol. The EGR valve will get done this Thursday when I don't have to work. Only one plug gave me any concern.

There was a bit to much fresh oil on it. This came from cylinder one. I will also be doing a compression test on Thursday for cylinder one. If it comes back bad. What should I look at first? The Valves or the Piston Rings? Pleas someone respond to this question. Valves or Piston Rings?

They both require a bit of work to get to. But I think perhaps someone with more experience with Miata's will know which is more likely to go bad. Thank You every one.

[kung fu jesus]

Just some thoughts, so take them as you will.

Kudos for getting your son involved. :)

For a random misfire, I would check the crank position sensor and the gap. Sometimes crud can get built up down there, the bolt that mounts it gets a little loose, or the sensor is heading south. It may also be as simple as a loose or corroded connection. I remember there was a TSB on the '97s about this, but don't remember the details. Maybe you can find out more about it online?

As for the oil on the spark plug, was it on the electrode side or the porcelain side? If on the porcelain, it's a leaky valve cover gasket. On the electrode side it's a sign of something possibly more serious.

A compression test will tell you the health of your engine, but it won't tell you where the compression is siphoning off at. For that, you need to do a leak down test.

[NobleRogue]

Just some thoughts, so take them as you will.

Kudos for getting your son involved. :)

For a random misfire, I would check the crank position sensor and the gap. Sometimes crud can get built up down there, the bolt that mounts it gets a little loose, or the sensor is heading south. It may also be as simple as a loose or corroded connection. I remember there was a TSB on the '97s about this, but don't remember the details. Maybe you can find out more about it online?

As for the oil on the spark plug, was it on the electrode side or the porcelain side? If on the porcelain, it's a leaky valve cover gasket. On the electrode side it's a sign of something possibly more serious.

A compression test will tell you the health of your engine, but it won't tell you where the compression is siphoning off at. For that, you need to do a leak down test.

I appreciate any and all thoughts, kfj. Thank you. The crank position sensor is on my list for tracking down the misfire, but thank you for bringing it up. The oil was on the threads of the spark plug. I went ahead and did the compression test with my son. I only did the dry but I will do the wet and dry again after I do some carbon clean up. The numbers are promising yet disappointing at the same time. they are as follows 1-4. 160, 150, 150, 145. They are within the 28 psi allowance for variation. but they are low overall. I'm hoping that by doing some carbon clean up with an oil additive and a fuel additive, I can bring those numbers up. It would seem that the oil on the plug probably did not come from a bad valve or piston ring. That is what I find promising. I will be checking the PCV Valve, when I get a chance, to see if the oil is coming from that.

[kung fu jesus]

Well the compression numbers aren't great, but not terrible either. #4 usually takes the brunt because of the cooling system design.

[NobleRogue]

Good News. I have finally had the time to get more work done to pass the smog test and get the car running better. Since my last post on this thread I have replaced the fuel filter and fuel pressure regulator which brought the fuel pressure up to where it should be. My air intake which I discovered to be held together with Gorilla Tape has been replace for a Weapon R Secrete Weapon Dragon air intake. The EGR Valve has been replaced. New break pad in the rear. New PCV valve. Used Sea Foam on the Intake, fuel and oil. Oil change. And lastly I replaced the Valve Cover Gasket. While the Valve cover was off the car I figured I could pretty it up a little and painted it. 144361443714438144391444014441144421444314444 OH! Yah! I almost forgot. I also replace a fuel rail insulation spacer and the oil dipstick. Eli's new compression numbers are from 1-4 (180, 170, 175, 170). Way better than b-4. The car now runs very smooth and feels to have gained at least 20hp.

[NobleRogue]

I got it to pass smog!!! But I still have a misfire. Does anyone have a line on new but inexpensive parts? I plan to get a project block in the future to build up. I'm not sure if I want to do to much after market upgrades on this engine. I just need it to be reliable for when my bike brakes down or the weather is really bad. I'm looking in to possibly having to replace any one or all of the following. The Cam Position censor, Ignition Coil, Mas Airflow Censor, Throttle position censor, so on ans so fourth. I haven't gotten around to testing them yet. I'm just trying to get an idea of how much I'm going to end up spending. Usually I wouldn't worry to much about it. But I was out driving it two days ago and lost my clutch. The clutch grabs wonderfully but I get no pressure in the pedal and cant put it in to gear. My son I bled the hydraulic system. The slave cylinder, despite an extremely slow leek that is only known because of fluid on the lower A-arm, reacts to the pedal being pressed and pushes on the lever like it should. So I'm guessing I have a worn throw out bearing (Clutch release bearing). With all the work and time it's going to take to get to it I'm figuring I should just get a clutch kit and replace all the clutch components. This is going to cost almost $400.00. Not to mention that I'm having some other issue with the cars idle dropping every time the coolant fans come on or when I turn on the A/C fan. I'm running out of funds fast atm and not getting much time to get more funds :(. Any info on where to get good parts cheap will be worth gold to me right about now. Thank you in advance.