curiousB

Very strange. Puzzling for sure. I can't see how it would be MAF because that is common element for all cylinders so it doesn't play favorites. I wonder if it is some strange condition related to propane. What if you just run on petrol for a week or two to see if it heals itself at all?

I wasn't assuming they would just add a solenoid to the existing starter motor. Rather they would come up with a two part scheme with a starter motor that has some Bendix like (or whatever it has evolved into) mechanism that mechanically engages the starter gear to the flywheel upon start up and then retracts after the engine fires. Just get the high current contactor (relay) away from the starter motor and easily accessible for repair. I'm sure cost is driving this. An integrated all in one solution has to be cheaper than a two piece. I'm at 112k miles on the original starter so I guess its not like it is a chronically failing item.

Its pretty easy actually. Just remove the top timing belt covers to expose the camshaft belt pulleys. Then get a socket and ratchet (or maybe a bar)and turn engine to TDC. The cams should align exactly to some marks on them and on the cover behind them. If they don't turn crankshaft ome more full turn clockwise and recheck. It should be obvious if the belt is misaligned. A tooth offset would be about 1/4" error on the marking points.

Yes that is the mechanism. The O2 sensors say the engine is lean and the ecu bumps up the fuel map to compensate. Its the unmetered air which is creating the problem. You can search for intake leaks with a simple propane torch. With the car idling (outside on in garage) run the torch (without flame just gas flowing) around suspicious points of the engine. If there is a leak it will suck in the propane and engine should surge a bit from the hit of fuel. Just be careful because propane is heavier than air so in a still garage it would settle to lowest spot and be an explosion hazard. Hence doing it outside.

I would check for crusted up coolant residue in addition to wetness. As the water evaporates from the leaking coolant some of the residue is left behind. Its pink in my model year but I think was green in older models. If you see that crusting it means its been leaking for a while and a seized water pump is much more likely. Given a seized water pump can snap the timing belt and cause and interference engine to become a disposable chunk of steel and aluminum you probably dont want to risk it. Here are my Top ten pet peeves with the Lexus LS: Water Pump driven by timing belt. High risk of engine damage (if WP seizes) and overly complicated repair (have to do a TB repair to get at the WP. Interference engine. OK I get the performance benefit but the downside risk of a snapped TB is a new engine. Ouch pretty severe. For what 5-10 more HP? Starter motor buried in deep V of engine. Have to remove intake manifold to get at starter motor. Starter solenoid attached to starter motor. If you are going to bury the starter motor how about putting solenoid in the engine compartment so it can be repaired easily. Sealed transmission with so called lifetime fluid. No dipstick to check level and fill/drain ports in most inconvenient location. Limited and tiny jack lift points for working on your car (jack stands and jack points). Silly SST shields on mild steel exhaust Y-Pipe with low quality clamps. A corrosion nightmare. Silly brake wear sensors that cost more than pads and fire off well before pad is done. Sensor not repairable just an expensive replacement item. Poorly designed axle height sensor for AFS system. Water and road grim ruins bearings and device seizes. Expensive and fragile parking sonar sensors. I had to think long and hard to find ten. Some of these are admittedly pretty tiny. So I guess the moral of the story is these are just great cars. Happy New Year to all!

Yes WP driven by timing belt. Serp belt drives PS, AC, Alternator, but not WP...

I would't deviate from oil type. It isn't the reason you have terrible gas mileage. There is something wrong here but it isn't oil. Could be thermostat is stuck open and takes a long time to warm up engine. This maybe why long trips are efficient because the engine gets to steady state warm. You've been struggling with this for a while. I'd go ahead and change the thermostat and maybe the engine temp sensor (ECU one no the dash sensor). This is DIY and not too expensive. If it does;t fix it you're not out too much $$$..

I wouldn’t be concerned with MAF reading when engine not running. I am not sure it is considered a valid state. In any event it is less than 10% of idle reading (which is already small) so not very material. This might indicate a vacuum leak on the +14% side. The ECU is detecting a lean condition at the O2 sensor and commanding the EFI to send more fuel in to compensate. Vacuum leak could be head gasket related, intake manifold leak, injector gasket leaking or maybe a few other areas. My wife’s car had a +14% long term fuel trim. It was due to a sizeable vacuum leak. The root cause was a ruptured vacuum hose to the crankcase ventilation system. With the engine running the leak was significant and quite audible. So I have to think there is something significant going on for a 14% LT fuel trim.

Is the 9 MPG computed with a full tank of gas and then when empty filled back up and then computed on the exact odometer readings vs the exact fuel used? The fact that you get north of 20 MPG on highway says nothing is wrong with drivetrain once engine is warmed up. That means either you do a lot of 3 block trips, you leave the car idling excessively, you are generalizing on MPG computations, or you have a EFI problem where the engine stays in open loop for an extended period when cold ( and intentionally runs richer). The latter could be the engine temp sensor for the ECU but usually when it fails it is a destructive failure so it doesn't correct itself once warm.

This sounds suspicious. Batteries seldom die because the starter motor draws too much current. They simply aren't engaged long enough to make a huge difference. Unless your car has to be crankled several seconds and multiple time to start up each time I doubt this "theory". I would still check the wiring. I don't believe your friendly AAA man is a professional mechanic so you shouldn't take his word as gospel. You still might need a new starter but its not obvious from this diagnosis.

For all the time you have spent cutting and welding I would just go buy an ignition coil for $50-70 and swap it in place for one side. If it doesn't get better swap it over the the other side and replace the first one you took out. An easy test is to pull the high voltage wire off of one coil while the engine idling. If that coil is dead you won't notice any change in the engine (because its running on the other four cylinders). Then try the same test on the other side. If that bank is running the engine when you pull that coil it will die instantly. Probability of an ignition problem being at the root of this >80%, probability of a Catalytic converter being the problem <2%. I know where I would spend my time.

Yes, if that is truly the symptom. click click click is telltale dead battery or bad connections. Fix that first. That doesn't mean the starter or solenoid is fine but you need to get that problem resolved first.

Fix the leak and skip the plastic container. You'll just overheat the alternator and either the regulator or stator diodes (rectifier plate) will fry... Lexus engineers didn't design thermal fins, air circulating fan blade and vent holes just so someone could block them with a bleach bottle.

The tat tat tat is the starter solenoid engaging and pulling the contactor plate to complete the circuit for the starter motor. The motor then is a huge current draw, 120Amps or more, so the battery either isn't able to supply that current (dead or faulty battery) or the wiring has too much resistance (caused by corroded or loose connections). This causes the voltage to drop at the starter motor and the solenoid disengages. The voltage climbs back and the solenoid re-engages, starter motor gets power, voltage drops and the cycle keeps repeating itself. If you can budge a battery connection with your hand it is too loose. These have to be clamped tightly and metal to metal contact or the current can't flow. An old trick for cold winters in Canada was to get a sheet metal screw #6 or #8 and screw it in the gap between the battery post and clamp. This was a bandaid for -40 degree days when all you wanted was to get it running and get out of the cold.... brrrrrrrrr

click click click is a dead battery or bad/corroded connections. Dimming headlights suggest the same thing. I think I'd check battery voltage before ripping open manifold to swap the starter... Your symptoms seem to be moving around, or at least your observations of them are.

good stuff. I think the repair bill for that was reasonable given the effort required to get at these sensors. Happy motoring...

ditto. The fact its running rough and no power and red hot cats leans me towards looking at ignition over fuel to start with. These cars have known problems with the ignition coils failing and leaving the car running on 4 cylinders. That gets a rough ride plus a ton of (unburnt) fuel dumped into the exhaust system to burn up. That is why the CATs are red hot. It will damage them if you let it go too long and then you're getting the checkbook out for another pair of CATs. Could be fouled plugs and bad plug wires too. I would start by checking the coils, plugs and wires and see if you can't get the engine running better.

I think I'd just concentrate on cylinder #1 reading vs its neighbors. If there is a valve or gasket problem it should read significantly lower than the others. I wouldn't get too hung up on the absolute value as this is an engine with many miles on her. Cylinder to cylinder variance is most relevant here. My wife's Lincoln had a problem with bad cylider head (burned exhaust valve). Ford prescribed a cylinder leakdown test instead of compression. I think this is why: Cylinder leakdown test- While a compression test is a dynamic test (engine moving), a cylinder leakdown test (C.L.T.) is a static test (engine at rest). The compression test measures how much pressure the engine can produce while cranking; in contrast to the C.L.T., which measures how much pressure is lost in the engine. In a C.L.T. the engine is placed on TDC of the cylinder in question and using a similar type of connector as the compression test, we fill the cylinder with pressure. The tester then measures the volume of air needed to maintain a predetermined pressure in the cylinder. This reading is expressed in a percentage. Good cylinder leakdown readings should be below 5-8%. The great thing about C.L.T. is that it deals with how well the cylinder is sealing and nothing else. The readings are not affected by carbon deposits, cam timing, or even engine cranking speed. Another great feature of the C.L.T. is the fact that you can hear where the air is leaking out of the cylinder. When a cylinder has high percentage of leakage, first check the oil filler cap. Do you hear a hissing sound? If so, you may have pressure leaking by the rings. Is there air escaping out the exhaust? Is it escaping out the intake system? Then a burned valve may be the problem. If two adjoining cylinders have similar low readings and you hear leakage out the other cylinder, then a failed head gasket may be the problem. Being able to pinpoint the exact source of the compression loss will tell you where the problem is; and not just that you have one. This knowledge will greatly assist you in the next step… the repair. I am not sure how expensive a CLT setup is in the UK but they are reasonable here. http://www.harborfreight.com/cylinder-leak-down-tester-94190.html

I was wondering how they determined misfire in the ECU. I thought maybe some strange property of propane measured differently that the ecu was declaring a fault when in fact none existed might be something to consider. But as you can see they looks at acceleration of camshaft after firing. I think it would be hard to spoof that reading. Either the cylinder fired and sped up or it didn't and it continued to slow down. Seems pretty black and white. Now that you see misfires with both fuels its even more compelling. So I think you probably do have a misfire just not clear on the cause. As for plugs if you had them out to reclean them I assume you liekly didn't put them all back in the same cylinders. If you did its easy enough to swap a couple. Not to likely that is the issue but guess better to be certain than have all these unclosed possibilities floating around. I think you should do compression test as next step per Lexus. You might have a burned value or damaged head gasket. Its easy enough to do especially on cylinder 1. Maybe you just do #1 and a couple other nearest neighbors which are easy to get at.

As military people would say it is a question of asymmetric risk. That is to not do it, and defer the repair, is to put at risk a ruined engine (for the newer interference type) vs. delaying a $800-1,500 repair (not eliminating it, just deferring it). $5-6,000 risk vs. repair bill delayed... So it’s easy to see why it would be biased to the safety side of the ledger, Dilbert manager or not. What is interesting here is the complete lack of cases of report broken timing belts. Given the threads on this subject I would have expected to hear a tough luck story every few weeks. I have yet to hear of a single event. So it looks like these belts are pretty well designed. That said, the empty feeling of those pistons bending all the valves, and the delightful $Repair$ that would entail is not a good risk reward scenario for any of us. Morale of the story, just change the belt when needed and live for another day.

All four have failed? That seems unlikely. I don't think I'd put $300-400 of sensors in just as a maintenance item.

You can evaluate front bears by driving at 15-20 MPH and make a waving back and forth drive down the road (open road with no one around that is). If one of the front bearings is bad it should make more noise when it is loaded. The more the car is leaning to that bearing. When you turn the other way that same bearing will be lightly loaded and shoud be more quiet.

OK didn't realize you were 430. Engine Misfire Diagnosis To monitor misfires, the ECM uses both the Crankshaft Position (CKP) sensor and the Camshaft Position (CMP) sensor. The Crankshaft Position (CKP) sensor is used to measure variations in the crankshaft rotation speed. On the power stroke, the crankshaft accelerates. If the cylinder misfires, the crankshaft decelerates. The Camshaft Position (CMP) sensor is used to identify specific misfiring cylinders. When the engine misfires, high concentrations of hydrocarbons (HC) enter the exhaust gas. High HC concentration levels can cause increased exhaust emission levels. High concentrations of HC can also cause increases in the Three-Way Catalytic Converter (TWC) temperature, which may cause damage to the TWC. To prevent this increase in emissions and to limit the possibility of TWC thermal damage, the ECM monitors the misfire rate. The misfire monitor is designed to detect increases in emissions caused by cylinder misfires, not to reduce driveability concerns. Misfires are counted when the crankshaft rotation speed variations exceed predetermined thresholds. When the temperature of the TWC reaches the point of thermal degradation, the ECM blinks the MIL. If the misfire exceeds the threshold levels, and could cause emission deterioration, the ECM illuminates the MIL and sets a DTC. The engine misfire monitor is a continuous monitor. The catalyst temperature is calculated by the ECM based on driving conditions and percentage of misfire. Use the following steps to diagnose a single cylinder misfire: 1) Duplicate the misfire using Engine Live and Freeze Frame data. 2) Compare the spark plug firing tip of the misfiring cylinder to spark plug firing tips from cylinders with no misfires present. 3) Swap the igniter from the misfiring cylinder to a different cylinder with no misfires present (swap the igniter with cylinder # 4). 4) Swap the spark plug from the misfiring cylinder to a separate different cylinder with no misfires present (swap the spark plug with cylinder # 6). 5) If the misfire moves to a cylinder with a swapped component, replace the component (e.g. if cylinder # 4 begins to misfire, replace the igniter, etc.). 6) If the misfire stays with the original cylinder, check the cylinder compression pressure and fuel delivery. 7) The diagnostic procedure outlined here is for training purposes only and may not be effective for every issue. Always refer to Service Bulletins (SB) and Repair Manuals (RM) for information on specific vehicles and issues.

Since you have changed coil and plug there is not much left for spark other than plug wire and cap. Simple enough to do. Swap the wire and the cap and see if it stays on #1. Off chance it could be a bad wire arcing to chassis or a faint crack in cap that has a carbon trail to ground. I'm not hopeful this is it but at least your can rule out a couple more scenarios.

Its your conscience telling you to slow down… :chairshot: But more to the point it is either fuel or spark. I am temporarily ruling out tranny because it has a lock up torque converter so shouldnt be subject to slippage. If it were fuel I would expect youd see the hesitation at lower speeds, say 50MPH, but with aggressive acceleration (i.e. heavy engine load, thus more fuel demand). Maybe try that next time on a highway. Does it bog down at 50MPH with heavy acceleration? Another test might be to note the RPMs at the time of the hesistation. Then down shift one gear and drive at a speed that you get about the same RPMs and see if engine hesitates there. That might indicate ignition at any speed where RPMs go over __X__. These cars are known for problematic ignition coils so you could try replacing one and see if it fixes it. If not swap the good new coil to the other side and see (Its unlikely two coils have simultaneously gone bad) if the problem goes away. A last possibility is maybe a plugged catalytic converter but I think that is less likely and youd probably see other symptoms.