LS4me

My '90 LS has developed a persistent ping. I have tried running Chevron Techron fuel additive. Didn't help. I have tried several brands of gas, and up to 94 octane. The car runs fine, aside from the ping. 115k on the odometer.

I took it to Lexus of Portland today, they want to put in a new computer ($1700).

What do you guys think? Would you trust a used computer? I already checked eBay, nothing there at present. Thanks for any help!!

Gene

JBrady

I am very sceptical that it is the computer. More likely it is carbon buildup. Carbon buildup is a combination of driving conditions and fuel quality. I bought a head (for my old Turbocoupe) from a guy in Canada. The car had 50,000 miles on it and the intake ports and valves had a HEAVY coating of carbon. I am talking about nearly a 1/4 inch thick on the back of the intake valves. This type of condition also leads to buildup in the combustion chambers. As carbon builds up the compression ratio increases and the carbon can glow red hot leading to pre-ignition and minor detonation under various conditions.

Now, I certainly cannot check your engine from Texas but you may be able to remove a spark plug and use a bright light to inspect the piston tops. You may want to have someone that knows what they are doing make this check as all pistons will have some carbon deposit. The issue is excessive.

How to fix if it is carbon??? Honestly, the only for certain way would be to pull the heads and clean everything up. On old carburated engines people would pour everything from water to tranny fluid into a running engine with dubious results

There may be some additives that will improve the condition but it would take some run time and most likely many tanks of fuel with additives to do the trick.

BTW, when I inspected the head on my 200,000 mile turbocoupe there was very little carbon buildup on the intake port or valve. Compared to the 50k head there was virtually none. I can only guess it was due to the detergent/cleaner in the gasoline I used vs. the gasoline in Canada. Gasoline has hundreds of formulations and is different in cold climates vs hot.

LS4me

Thanks, JBrady. I am thinking the same thing. If it is carbon buildup, I wonder why. I don't run the car hard, but I don't baby it either. Lots of freeway onramps at full throttle, that sort of thing.

I will continue to use techron additive at every fillup, see if it will break loose.

Gene

Pilot

I use a fuel additive called RXP. It works entirely different than any fuel additive I have looked into. RXP WILL remove all carbon in your engine, but it will take some time. This product works by increasing the temperature of the combustion process, and thus burning off the carbon. This product can be purchased at Wal Mart in red 12oz bottles, located in the automotive area. Visit their web site to see all the testing, which has been done. RXP a small company in Florida, and are starting to make big news with this product, and winning large contracts for commercial uses in Locomotives and other industrial applications. When you increase the flame temperature, you burn more cleanly and also lower emissions. This company started with making an additive for cutting torch fuels, which would increase the temperature of the flame to cut through metal cleaner. They later developed another product to increase the flame temperature inside your car engine. This is not some snake oil like many of the other products. Any serious student of fuels, and additives will confirm this stuff really works.

http://www.rxp.com/master.htm

Pilot

91 LS400
01 RX300

LS4me

Thanks, Pilot. I'll give it a try.
Gene

Pilot

If all else fails, and you want to try what the dealer suggests with a new computer. I have seen used LS400 engine computers on Ebay for less than 50.00. These have been removed from cars which are being parted out. Since these are electronic units, they will work perfect with age, or not at all. I would not worry about running a used computer. Your risk of course with our ageing LS400's, is throwing parts at it in an attempt to correct a problem. I would always stick with a dealer diagnosis, then consider how and who to do the repair. I have a Lexus dealer mechanic, who does work on the side. Its a perfect deal for both of us! If you can get into the shop, you could always ask the first mechanic you see if anyone does work on the side. I would think anyone should understand when you are working on cars that are sometimes 12 years old, that the owner has to find creative ways to cut the cost of repairs. My mechanic insists that I always use factory parts or find someone else to work on the car. He says he cannot afford to have all the com-backs which he claims happen with aftermarket parts. I agreed, and we both have been happy. I get my parts over the internet at lower rates from dealers who sell at discount.

Pilot

LS4me

I found a Lexus shop (non-factory) in the Portland area. The mechanic's over-the-phone diagnosis is carbon buildup, which we already suspect. Anyway, I made an appointment for next week to take the car to them and get it checked as a second opinion.

Money is always an issue, of course. But what I really hate is taking a car, especially a Lexus, to a 'professional' only to have them do a hit-or-miss repair by throwing parts at it. If they wouldn't charge for the parts that didn't fix the problem it would be different. I can just imagine paying $1700 for a new computer only to find out it was a knock sensor (or carbon).

And, I am watching ebay for an ECU. Thanks again,

Gene

bigmac

I don't think it's any carbon build up... I think it's the MAF-sensor. That's the sensor that measures the intake air volume and it sit's right after the air filter.

After some years of use, this sensor will be clogged and it will measure less air, therefore the fule/air mixture is to lean ==== pinging.

This happened to my Lincoln Towncar -97 and I broke the engine! A 7000$ rebuid including 140$ MAF sensor later - it does not ping.

Actually, it was rebuilt, and continued pinging.. hehehe.. was I in a good mood? Anyway, I took matters in my own hands and started doing some investigation, and now it does not ping anymore.

Good luck.

Rgds,

Fredrik

LS4me

Thanks bigmac. Since I already have an appointment with an independant mechanic, I'll have him check the MAF sensor also. Gene

bigmac

Please let me know... ahhh I can feel my ego getting bigger ;-)

JBrady

Good suggestion, a definite possibility. Let us know if you get this resolved.

LS4me

Good news, and bad news. I was impressed with the independent Lexus mechanic I found in Boring, Oregon. He's an ex-Lexus of Portland mechanic and of course knows the car well. After driving and giving my LS a very thorough checkout he pronounced it a "creampuff", in great conditon.

Now the bad news. The pinging is the computer's fault. The mechanic pulled the computer to check the part number, and it is one that should have been replaced under a TSB clear back in '91. Of course, now I will have to eat the cost. The mechanic is locating another computer, so I don't know the how much yet.

He said he would replace my rear CV joint boots for a couple hundred less than the dealer (dealer=$500). Also, dealer said my steering rack is leaking ($1000). Independent mechanic says there is only very minor seepage, nothing to worry about.

And yes, the engine does need a decarbonization ($130). All in all, I think all of this isn't bad for a car with 115k+ miles.

Thanks for the help.
Gene