curiousB

Could be U-Joints in the drive axle. They wear over time and can get sloppy. I would also check engine and transmission mounts. The rubber breaks down on those and the engine might not be held in place as firmly as it once was.

You will coast some with the car in drive as the engine will transfer some torque to the wheels even with engine idling. That could extend your glide distance. You could pop it into neutral and see how far you glide. I like the heat idea better though because if brakes are dragging they're going to get hot. Its simple physics. Energy dissipated as heat.

I just do this car thing for fun. Landar and I are professional engineers. We actually design things that guys like you fix.... So spare us your condescending rhetoric.

Sounds like your serpentine belt has broken and you've lost power steering, alternator, and AC compressor. Easy enough to pop in a new one.

I'm still on the original battery and alternator after 7.5 years. You need a new mechanic. Changing battery and alternator that many times is a symptom the guy doesn't know what he is doing.

Thats what I use. A bargain at twice the price..... very handy tool.

Maybe check as well to see if your brakes are dragging. That would kill MPG too. Go for a 5-10 minute drive on a road where you won't need to brake. Then coast to a stop. Step outside and feel with the palm of your hand if the wheel and brake area is giving off heat (don't touch it as it can get to >>300 degrees). If the brake is dragging it should get good and hot down there.

There is something very wrong with the car based on your MPG. I routinely get around 19MPG in stop and go short trip city driving and high twenties on highway trips. I have been having problems with emissions and one catalytic converter so it has me looking at similar things. An invaluable tool has been an OBDII interface and my laptop computer. I can set up gauges to look at fuel trim, short term (ST) and long term (LT). Look at MAF sensor output. See what ECU thinks engine temperature is. See if emissions system has reverted to closed loop or stuck in open loop. It’s under $100 if you already have a laptop. You need something like this or you will forever be throwing expensive parts at the problem and not having much success. The first thing I would do with such a device is check to see what long term fuel trim is on each bank. If it is very high that indicates the system is sending too much fuel to the engine for some reason. It could be as simple as vacuum leak in the intake ducting so that air is bypassing the MAF. The O2 sensors detect a lean condition and start bumping up LT fuel trim to compensate. In the end you can get a rich condition, poor gas mileage and red hot catalytic converts (which may get permanently damaged). I’d also want to look at engine temperature the ECU sees from the code reader. If the sensor is faulty the ECU may be using the wrong fuel map and sending a very rich mix which isn’t needed. I believe the temp sensor for the dash is different than what the ECU uses. It could be a stuck open thermostat keeping the car from warming up. That will cause ECU to send rich mix… It could be a faulty fuel pressure regulator causing pressure to be too high so too much fuel is shot into the ports. The ECU would attempt to correct this though and you’d see LT fuel trim in negative values as the O2 sensors would be saying the mix is too rich. So it could be many things but you need more data so you can pinpoint the problem better.

Actually for 106k miles they looked pretty good. Maybe slightly wider gap but not significantly so. Also all plugs looked the same so I don't think I have one bad cylinder (running rich and/or missing ignition).

Ok here is my wrte up on changing plugs on a Lexus LS430 wih coil over plug ignition. Changing Spark Plugs on a 2004 Lexus LS430.pdf

I know I am a tad early on the plug change but I've been battling a Catalytic Converter problem and wanted to see if the plugs look clean or do I have one cylinder fouled and contributing to my converter woes. I plan to do a cylinder compression test while I'm in there. I figured if I am going to take the plugs out to inspect them I might as well put fresh new ones back in. Its pretty incredible when you think of it, 120k miles on a single set of plugs. I got the exact Denso plugs for $90 on eBay with free shipping. Seemed a fair price and they came to my mailbox 3 days later.

Any special advice before I go swap all 8 plugs on my 2004 LS430? I just rolled over 105,000 miles. The originals have been their since its birth in summer of 2003. A few questions: 1) Any special methods to remove the Coil Over Plug (COP)? I suspect the plastic COP assembly has gotten a bit more brittle since 2003. Also wondering if the rubber boot is stuck tight to the plug will the COP snap into pieces. I presume gentle twisting action is best but at $100+ per COP I don't want to damage any. 2) What about spark plug socket. Wondering if I should sacrifice a 5/8" spark plug socket and extender and tack weld together so the extender doesn't come off the socket after I torque the new plug in. 3) Dielectric grease on new plug and boot upon reassembly or don't bother? 4) Anti-seize compound on new plug threads?

I'd get it quoted both ways, solenoid only refit and whole new starter. If you're going to have this done professionally, much of the cost is in the labor. For the sake of an extra $100-200 to get a rebuilt complete starter with new bearings, drive gear it might be worth the piece of mind knowing the starter isn't likely to fail anytime soon. If you can do it yourself or have helpers who can tackle this then I might be inclined to just service the solenoid. Its roughly akin to putting in a new water pump while changing the timing belt. The extra parts aren't that much more $$ considering the labor to get at it all.

I'd think twice about not putting too much $$$ in a car worth $3,000 or there abouts. Paint job and rims will cost you more than the car is worth.

They are the same P/N buts its no fun working under there. I'd have to buy another $35 in gaskets and lock nuts & bolts. I'm wondering of the ECU has a measurement issue (noise in ground, amplifier or A/D converter). Maybe I can put an oscilloscope on the O2 sensor outputs and see if it matches the OBDII output (which comes from the ECU). I guess I could maybe spoof the system and wire jumpers from O2 bank2 to bank 1 and vice versa and see if problem moves to other side. Maybe I'll just space the O2 sensor out with one of these.... http://cgi.ebay.com/ebaymotors/Oxygen-sensor-extender-spacer-HHO-Test-Pipe-O2-2-_W0QQcmdZViewItemQQhashZitem27bd00d6e5QQitemZ170674673381QQptZRaceQ5fCarQ5fParts

The plot thickens. Was able to get the flange fixed by tapering the gasket with a grinder and reinstalling. That fixed the flange leak. Then noticed a slight leak in pipe after the O2 sensor. Its under the shield around the pipe so will see if I can get some type of clamp to go over and seal that off. The bad news is it threw a P0430 code so now I'll not sure what's going on. New catalytic converter, new O2 sensor b4 converter. I went for a long drive to see if bank 2 converter was glowing red (due to too rich fuel). It wasn't. I then used i/r thermoprobe and bank2 wasn't any hotter than bank 1. Since I'm at 105k miles I've ordered new plugs but not too hopeful it will help much. The mystery continues.

Well got new catalytic converter installed today. Was more work than it should have been. Rusted bolts. Tight quarters. Oh yeah, I was lusting for a lift again..... The new converter came with gaskets but they didn't fit well in the milled slots and the Lexus gaskets didn't fit either. Chalk one up for OEM parts. I went after market here and it had its challenges. The Lexus converter was $1300 list and I got one on Ebay for $175. Eventually got it in but still a leak on flange joint on exit side of converter. Direct fit isn't quite as advertised. Tried Lexus gasket then switched to one that came with converter. Still leaks and at this point I was fed up with crawling around the ground anymore so just left it with a slight leak for now. Went for a test drive and warmed up the system. Slightly louder due to leak but its a minor leak. Put on OBDII reader with laptop and went for a test drive with O2 sensors in graphs. Clearly my post converter O2 is a lot more stable with the new converter. Still it bounces around more than the bank 1. I reset the P0430 code so we'll see if it comes back in another day. I'll put some fresh eyes on the flange tomorrow or Sunday to see if I can get it better aligned so gasket does its job. Failing that I'll take it to a muffler shop where they can maybe bend the pipe a little or weld in a new flange on the pipe side. The old converter has no visible signs of failure. The honeycomb is intact and all the little holes are clear. I was expecting some visible damage but none found. The O2 test seems to clearly state the new converter performs better. I guess I'll see if I get several days without throwing a P0430. I didn't know these converters wore out so I wonder if mine got contaminated somehow. Equally confusing is that only one bank got damaged. The mystery continues but some forward motion. Once I get a better gasket and improved flange alignment and I will be happier.

could be 1) air leak in manifold or ducts 2) dirty throttle body 3) dirty and sticky IACV

Just makes you wonder why they didn't separate the solenoid from the starter motor given they buried it deep in the V of the engine. The solenoid is a wear out item. Instead of a simple item replacement next to the battery its major engine disassembly. Totally nuts.... "The ultimate pursuit of overly complicated repairs"

Well I think you've called it right. A bolt wasn't tightened properly and/or no locking compound used on the threads. The TB grabbed it and shot it around. There could be some substantial damage inside the housing as this thing probably was launched around for a while before it broke the cover casting. I would get it looked at soon as this is an interference engine so a snapped TB is an additional headache you don't want.

Back from vacation and parts are in. Catalytic converter, O2 sensor, gaskets. Got front of car up on ramps and removed all the covers to get ready for the work. Did I say how nice a lift would be already. Costco has this portable two post lift on sale right now..( http://www.costco.com/Browse/Product.aspx?Prodid=11589445&whse=BC&Ne=4000000&eCat=BC|3960|21277|61837&N=4018446&Mo=2&pos=5&No=0&Nr=P_CatalogName:BC&cat=61837&Ns=P_Price|1||P_SignDesc1〈=en-US&Sp=C&ec=BC-EC22577-Cat21277&topnav= ) for $1900. Wonder how safe it is though. Decided I didn't have enough time to do it tonight all so I just changed the Bank 2 primary O2 sensor today. Will try the catalytic converter on the weekend. Went for a drive to see if the new sensor changed my lazy sensor theory any. Plugged in OBDII module and laptop. Had graphs of O2 primaries against each other. Some difference from before, the new O2 sensor seem a bit more active but still not as much as the bank 1 primary O2. Anyway I reset the P0430 error code and will see if I pop another P0430 by the weekend. I am not too hopeful the primary O2 will fix things because the post converter O2 on bank 2 is still much more active than bank 1 suggesting the catalyst isn't doing its job. The replacement converter looks pretty good. Slightly different design from OEM. Has flange seams down the sides where they weld the two halves together. The mounting flanges look OK but the drilled holes look pretty large. I may need washers for the bolts so then don't bind in the holes. The catalyst looks clean and quite the beehive of passages. No way to tell by looking if it is a robust as OEM. I guess we'll see.

I had the same trouble. New tires at a tire store. Work was done in the evening and they hire high school kids for night shift. Well an 18 year old male chock full of testosterone holding an impact gun and the formula for over torquing is complete. My front rotors were warped within a month. Learned my lesson. I've bought torque limiters for my home shop to avoid this. I always use a torque wrench for final tightening.

Not sure that means heater is a problem. Unless you nulled the multimeter to net out the test leads of the meter and of the harness you could be getting a false reading. Typically heaters (resistors) fail to an open circuit so a failed heater would read infinity or very high impedance. Proper reading is per Lexus manual.

Well not sure I truly qualify as a Guru. That would imply I actually know something...... You make a good point about the O2 sensor and fuel mix. I really don't see a MPG decline. In fact the car is actually getting better with age... I am really not too sure why the converter catalyst is failed (and not 100% sure it has). I did see somewhere the lazy O2 ahead of Catalyst means longer excursions of too lean then too rich. On average about the same as a faster cycling O2 but perhaps the rich cycles do more harm (overheat the catalyst) than the lean cycles. Another theory is the P0420/P0420 error code is determined by the difference between the pre and post catalyst O2 waveforms over time. I guess if the presignal is a little off (not cycling enough) that might undermine the algorithm as much as the trailing signal. Hard to say as they don’t publish the algorithms. I have been burning regular fuel for a couple years and maybe that is a contributing factor as well. All the parts have arrived so once we get a day below 100+ degrees I'll give it a go. Just a little concerned the three bolts on the top end of the converter. They look hard to get at and maybe rusted in pretty good. Crawling under ramps doesn’t make this too much fun. I could really go for a lift.... For a laugh I'll throw the old converter in soapy water and flush it out but won’t reinstall it. I’ll hang onto it in case the new low cost converter is a no go. I notice the non-OEM catalytic converter I bought was for 49 states (hence not legal for California with their stricter emissions). That said the Lexus OEM part didn’t differentiate this detail so I wonder if Lexus just made the entire fleet California compliant rather than have differing models? Might explain why the Lexus OEM converter is $1000+. To meet California they have more rare metals deposited on the catalyst core.

Any error codes in ECU? If crankshaft position sensor was acting up that should result in a code in the log.