9th Oct 2009, 09:36

Update:

Odometer: 150000 miles.

My tug of war with the CEL continues. There is a review of a 1999 Protégé with 130+ comments titled: “Low price, low quality…” I want to thank some commentators there: the guy with the duct tape, the 16 year Mazda mechanic and the guy who posted the content of the shop manual. With their hints and pointers I might actually win this battle.

I used a propane bottle and rubber hose to look for vacuum leaks while the engine idled. No hits. I also inspected the air intake hose again and found some cracks. The cracks did not go all the way through. None the less I wrapped two layers of duct tape around the ripples.

I tested the oxygen sensor and replaced it for lack of trust ($70). I cleared the codes. The light was out for about 340 miles.

I should have done this first: With a high mileage engine there is a high probability that the EGR ports are clogged with gunk. Inspection costs nothing and a fix costs about $10. I got a can of throttle body cleaner, a throttle body gasket and an inspection mirror. I removed the throttle body and looked inside the intake plenum: all black! The EGR portholes were at the 6 and 12 o’clock positions. I poked in there with a wire while using the inspection mirror and flash light to see the upper porthole. I thoroughly cleaned the portholes and also the throttle body while it was off and put it all back together with the new gasket. I cleared the codes. The light was out for about 340 miles.

The engine does run better though. I still feel some hesitation when accelerating, only during the warm up phase. Now this puzzles me: I get the message that the catalytic converter is below efficiency in warm up, but the light comes on after I go for 30 + miles on the interstate. I am way past the warm up and this code pops up. Does the computer not know that the engine is warmed up already? With computer programs it’s “garbage in- garbage out”: the EGR system was completely clogged and no code referring to it showed up. I still feel/hope that the cat is just fine and the ‘dog’ is on the intake side.

Other stuff:

I replaced the passenger seatbelt with one from the “Wrench and Go” for a whopping $7.05.

I replaced the bad Mastercraft rear tires with used ones from the local junk yard. Now I have Kumho Solus KR 21 tires in the front and Bridgestone Weatherforce ($74 for the pair, mounted and balanced) in the back. They have very similar tread design and the ride is much quieter than before. There is now 50% thread all around. I had the front tires balanced too $20).

A guy at the parts store gave me chuckle: “Oh, you have a Mazderati?”

19th Oct 2009, 10:10

Update:

To tame the CEL light, I decided to take off the EGR valve and clean it as well. There is an in and out passage that makes a U- turn. Those passages are about 15 mm in diameter. However, there was a 2 to 3 mm thick layer of carbon on the walls restricting the gas flow. I scraped it all out, sprayed some throttle body cleaner in there as well, and pushed the valve open a few times. I put it all back using a new gasket ($8.00). Again, the engine ran better after this cleaning job. I cleared the codes and the light is off for 450 miles and counting. I will let you know if it comes on again.

The gas station’s pump for regular was not working. So I decided to get midgrade fuel instead (91 Octane and 10% ethanol). That made a huge difference! Immediately, the remaining hesitation was gone and the engine ran quieter throughout its rev range and pulled even from 1200 rpm in second gear. What a transformation!

The manual specifies a minimum of 87 Octane. That may not be enough. The 1.5 L engine has a compression ratio of 9.5 to 1. A little amount of carbon deposits easily can increase it and cause knocking.

I think most Mazda Protégé CEL lights can be extinguished quickly and inexpensively by following this check list:

1. Check and clean the EGR ports and valve, clean the throttle body and use mid or high octane fuel.

2. Check for vacuum leaks.

3. Check ignition parts.

4. Check fuel system parts.

5. Check sensors.

28th Oct 2009, 09:46

Update:

After 610 miles the CEL was bright yellow again. I like the trend. The code read “P1195 EGR Boost Sensor Circuit.”

I pulled the wire harnesses off and put them back on to remove any corrosion. But the CEL returned almost immediately. So I decided to check the vacuum lines.

I pulled off the vacuum tube between EGR boost sensor and manifold. I had to use pliers to get it off the manifold. I poked into the nipple at the manifold to see if the passage is open. In fact there was a lot of hard carbon built up. I fashioned a tool from an old bicycle spoke to drill through the carbon. It takes about 3” of a straight wire with a sharp tip. I cut the spoke with diagonal cutters at an angle and bent the back to a form a small handle.

Next I pulled off the vacuum hose between the fuel pressure regulator and the manifold. I blew air through the hose and found it severely restricted but not blocked. I pushed a strong wire through and some soft gummy stuff came out. I blew again and it was clear. I poked into the nipple at the manifold as well.

Vacuum hose is cheap. I bought 5ft for $3.00 and replaced most of the hoses.

The engine ran fantastic on the test drive: 2nd gear, full throttle all the way from 1200 to 5800 rpm without any hiccups. It acted the same with partially open throttle.

Add to the check list: “Check vacuum hoses and nipples for obstructions”.