RA40

iTrader: (6)

The car is not getting up to good operating temp in 2-3 miles. The car when cool is going to be running rich so the combustion temps have to come up to keep carbon build-up from forming and the cats at nominal temp.

What gas is being run in the car? The ECU will adjust timing for lower octane fuel and this may also impact downstream O2 sensor readings as a compensatory measure. (A properly running O2 is mandatory.) The long term results as far as what I can conclude is that 87 octane is not good for the premium calibrated fuel ratios.

Swap the O2 sensors, ECT, verify a clean EGR pipe, put some good 91/92 premium fuel and take the car for a good hour highway drive.

dicer

You need at least 20 minutes plus of run time to get it up to temp. 10 to 15 mile drive or so.

erubin2000

Car pings with 87, I only use 91 in this car.

I'll be smogging the car on Tuesday. Does the discussion about getting it to operating temp and driving for an hour once help decarbon the car for the smog test. Or should I consider something more agressive along with the long drive. Is it worth trying to decarbon before smogging? Any suggestions how (ATF, very small stream of water into intake while running, snake oil...)?

As for smoging I know a hot cat works best. But please recal my HC and CO are great, I can pass that with a relatively cold car. Will a hot cat help with the NOX. On the flip side I produce more NOx at high temp so where should I shoot between these two conditions? Pull into smog with a super hot engine and cat or just get the car up to operating temp? I can do it either way cause smog is just a few miles away.

Thanks

python

iTrader: (4)

ur car pings because ur egr system is failing to introduce exhaust into the combustion chamber to cool it down. ill bet u have have carbon build as well

erubin2000

Car does not ping with correct gas. High compression engine can ping with low octane. Pinging is not a problem w/my engine. Did I confuse you and in turn you confused me?

erubin2000

Great video Dicer, explaining to a novice like me how a 3 way cat functions. I saw that the first stage of the 3 way cat performs reduction on the N2O to convert it into N2 and O2. Further down the second part of the three way cat performs oxidation where hydro carbons and CO are oxidized. I guess it's not unreasonable to think you can loose optimal operation of one of these 2 sections (in my case the first stage, reduction) and not the other (second stage, oxidation). I wonder if the cat temp is more critical for the first stage to run well and less important for the second stage which appears to work well for me. I made the mistake of smogging after just a short 3 mile drive to the smog shop. I hate to bring in this potential variable (hot but not super hot CAT) but I wonder. Or is it that my engine control is running to lean and that by itself fixes HC and CO but the opposite occurs with NOxs in a lean engine especially with a potentially compromised CAT. 300ppm seems like a relatively large surplus to fix if changing the cat is not an option and the EGR passes functional testing.

I've got my pint of seafoam to squirt into the intake and I'm getting motivated to make time to take off the EGR to clean the passage and new o2 sensor if I can justify the $. Wish I could read the LT trim. Next week I'll prepare for the smog test by getting the cat plenty hot and crossing my fingers.

python

iTrader: (4)

my car doesnt ping on low octane..and no im not confused..u seem to be tho,look at post # 33..clearly states ur car is pinging with 87 octane.
http://forum.miata.net/vb/showthread.php?t=462629
high combustion temps will cause this,also carbon build up in cylinders(adds more compression)...unless u have a code 52,53,55 up.

fixmiester

Let's look at the evidence: Engine pings (yes, your engine pings on 87 octane fuel, and it should NOT )---have you checked your timing? or, maybe you have carbon build up, like Python says!
If so, maybe your EGR tube is blocked, and can't supply exhaust gases needed for NOx reduction. Maybe the tube has holes and sucks air in when the EGR valve opens (which you say is working). And maybe your cat is trying to reduce (but not control, in this car) some of the NOx, but can't overcome the huge amount being generated by the root casuse of a plugged/leaking EGR PIPE.
This has gone on long enough: Check it, Clean it, Fix it.

erubin2000

I think I should let you know what happened: The good news is that I passed smog. Curiously my HC almost caused me to fail this time but NOx was way down.
Here is what I did to get my NOx down:
Cleaned the EGR valve, although it was not blocked it sure had a lot of carbon. You may recall I tested my EGR system before cleaning it and the engine stumbled just as much before as after cleaning the valve (you activate the EGR valve with vacuum). BTW when cleaning the EGR it's best to scrape it out dry first in big chunks then use a solvent like carb cleaner to finish off the job. Just make sure you hold the valve upright so the solvent does not run down over the rubber diaphragm.
Next I ran a whole can of Seafoam in through a manifold vacuum line. Just dont let it in too quick; No point in chancing a hydro locked cylinder. I got the car way hot and let the vacuum suck in 3/4 of the can over a few minutes than I let the Seafoam cause the engine to stall so that the last gulps of seafoam stayed in the cylinders and cooked the carbon. After a 10 minute engine off cook you drive the **** (carbon) out of the car. I think some call it an Italian tune up. Next day did it again with second can. Finally I performed a coolant service with Toyota coolant. I doubt that did anything for NOx but I was overdue for it anyway. Finally I ran the engine hard for 10 miles before going to smog and luckily I had no line to wait in so the cat and engine where at top temp. Never got a straight answer from anyone about the tradeoff between a cool engine and cool cat which may lower NOx on one hand and raise it on the other. Intuitively I guessed that a hot cat is most important for lowering HC but not sure if the tradeoff for NOx follows. Afterall a cooler engine makes less NOx, but that's what the EGR is for. I decided to go to smog with a hot engine and cat which is always the recommendation without specifying the effect on NOx.

Anyway here is a picture of the EGR before and after cleaning and my before and after smog results.

In conclusion I did well not to start looking into a new Cat. Looking for a leak in the EGR tube was a waste of time. A leak there would push exhaust out not draw air in! I had neither an exhaust leak, a putt-putt sound or high O2 out the tail pipe. Thanks for all your input and especially your patience with my countless questions. As always it's hard to qualify free advice but I prefer troubleshooting and planning before throwing parts at a problem and a big part of my research was reading this forum and getting your recommendations.

I feel good enough abot the car to lookminto 3 troublesome problems:
1. Need new driver seat belt,dont care what color. Any good prices on a used one? My is frayed to point of being only 50% of the web.
2. Repair driver door cylinder. Some idiot at my restaurant forced-turn the key trying to unlock it for me without pushing the key all the way in. Only way to unlock it is at the passenger side (the remote lock has long since been
3. The front rod strut bushings are shot again. I bought aftermarket and they only lasted a year. At the time the dealer only sold the entire strut assembly I believe. It would have cost a fortune. These are not the shock/strut bushings but rather the ones attached to the front of the car on the end of a steel rod. They are unique to the first gen Lexus LS400 90-94. They are held to the frame of the car with 3 nuts.
4. Trunk actuator stopped working. Can only open the trunk with the key.

Have not found time to search this yet but if anyone has a good link for me to read that'd be greatly appreciated.

RA40

iTrader: (6)

Glad that cleaning it out allowed the car to pass.

Seat belts check the local upholstery shop. Some have the webbing available and can replace. Don't buy used, hard to say if the tensioners are working. If you need new, Lexus/Toyota has black available. There may bea few colors but you'll have to call. Sub $300.

A new driver door cylinder as far as the 95-97 cost me ~$350.

jaaa

Just fixed my daughters seat belt on her 1991 passenger side. Pulled the whole assembly from a pick/pull for $15. Not that hard to do. Her old belt was almost cut in half, so sure needed to be changed.