Mike Floutier

Thanks Guys, Firstly Billy I have dual fuel and the problem is the same on both so that's ruled out. Curious, I have looked at your thread regarding CATs and was wondering whether your investigations were brought on due to a drive-ability issue OR whether it was the P0430. I have a severe drive-ability issue which is: 1) Intermittant - toggles between "hero and zero" fairly often but only when the car is switched off and on again??? and 2. Usually NOT accompanied by the aforementioned codes. I have a question: Does the LS430 have a "Limp-Home" mode? And, if yes, 1. What does it feel like, and 2. What initiates it?

I've been trying to sort out a mis-fire P0301 and flashing CEL for about 15,000 miles but getting nowhere - you may have read the thread. Anyway, I now lose power if I open the throttle too much AND whenever I start the engine it usually stops unless I catch it with the throttle pedal. At first there were no extra codes BUT today I got a P0430 and a P0174 (yesterday I got a 171 AND a 174 - BUT no 430). I have read a few threads suggesting that not every 420/430 is a failed Cat BUT I'm assuming that with: 1) the drive-ability problems, and 2) the longish mis-fire history, the Cat has probably failed - although which one I'm not sure. I guess that all I'm asking is for confirmation of this theory so that I don't spend money needlessly.

Ok, well no joy so far but there have been some additional symptoms:- 1. If I start the engine when it's already warm it starts but often just stops straight away - but usually starts ok the second time. The alternative is that it starts but straight away the revs sink to zero but at the last minute it catches and all is well. 2. Usually I only use a small amount of throttle and very rarely kick-down. Today I needed to put my foot down and was surprised at what happened. As soon as the throttle pedal got half-way down I lost most of the power. I took my foot off the pedal and drove as normal and all was fine. I then experimented with various pedal depressions. With less than halfway it was fine, plenty of power, pulling hard at low revs, easy to get up to high speed. However as soon as I got over halfway there was very little power, hardly any acceleration. Funny thing was that the kick-down was working as normal; the harder I pushed, the more it would change down. The revs would increase a lot, just as normal, as the transmission kicked down BUT there was still no power and no acceleration. If I lifted off to halfway the power would suddenly kick in. Any idea what's going on?? No new codes btw.

Thanks Landar, yes I've read all I can find about seafoam; some swear by it and some swear at it - seems you have to be very careful how you use it. I was curious (no pun intended) to see if any respected loc members had personal experience on the LS430. Anyway, whilst writing a thought occurred to me - would a fractured exhaust manifold or gasket cause mis-firing? I'm guessing this would equate to un-metered exhaust gases which presumably upsets the system. I vaguely remember something like this on my old Ford Scorpio but this was a long time ago so I'm a bit foggy. Any thoughts on this as a possible cause and how would I test it?

Well I did the compression test COLD and the pressure was very slightly lower but not significant. However I am rather put off doing further compression/leakdown tests as I had a lot of trouble getting the tester off the plug hole and there is no way I want that to happen!! Two other thoughts: 1. In my casting around the site I did notice a procedure involving something called "Seafoam" being ingested into a hot engine via a "brake boost" vacuum pipe. Is this something that I could try on the LS430? Is there a thread about this? 2. Also are there any instructions around on cleaning the LS430 throttle body? Thanks again!

Still pressing on, both the Crankshaft Position Sensor and the Camshaft Position Sensor returned good resistance readings so no joy there. My next test will be another compression test on the cylinder with the mis-fire codes. I think I did the original test when the engine was warm (ie. P0301 NOT being set). So I'm going to try it cold and compare readings. If no joy there I think I will do compression tests on the other cylinders to compare. If still no joy I may consider investing in a compressor and a cylinder leak-down tester if they're not too expensive. It's interesting to note that I first observed this problem around 12,000 miles ago and it has not significantly worsened in that time although I think there is a slight but steady deterioration - it's hard to tell???

Hi Landar, I take your point about drivers. The thing with the LS430 is that the transistor that switches on the LT supply to the coil is actually integrated into what we tend to call the COP coil on plug unit. Lexus call this combined unit an "Igniter". It's a 4 wire unit. The wires are, 1. Ground, 2. Battery voltage (constantly live), 3. ECU coil firing signal, and 4. A feedback signal to the ECU confirming that firing has taken place (A P13nn code is set if this misses). I've tried swapping igniters so it's not that. ------------------------------------------------- I'm still wondering about Richard's suggestion about 2 vacuum sensors under the throttle body. I've not seen any mention of vacuum sensors in the manual, can anyone throw any light on that? ------------------------------------------------- My current checking is centering on the Cam and Crank shaft position sensors which I hope to check tomorrow. I see from the manual that their readings are affected by temperature. Since their operation affect ignition timing, and hence mis-firing AND my problem (mis-firing) comes and goes with temperature changes, I'm most interested to see how they shape up.......

Hi Landar, Sorry I may not have been that clear. The mis-firing/blinking MIL starts when the engine is completely cold; any kind of load promotes it and it disappears during coasting. Then, when the engine is warmed up it disappears entirely except for occasional situations of high load, eg. pulling uphill at low revs for a longish period. The problem is the same whether on propane or petrol; they have separate injectors so it's not the injectors. I have considered doing a cylinder leak-down test but I would need to spend quite a bit on equipment that would only be used once. There is little point as in doing this since it would not be economic to repair the cylinder heads. The only value would be the ability to give up pursuing the problem; on reflection maybe that's not that trivial - lol!

The more you look, the more electronic bits this car has! Apparently although it is an IACV, it's not an Idle Air Control Valve BUT rather an Inlet Air Control Valve. In point of fact, it's not even the Inlet Air Control Valve BUT the Inlet Air Control Valve actuator (part of the Acoustic Control Induction System (ACIS) - see attached pic from the manual. A description of the system can be found on wikipedia. I seem to remember reading somewhere in the manual that it opens at around 4,500rpm to give better torque or something. I'm still not sure how the idling is regulated, maybe it's just a function of the Throttle Body. ----------- Thanks Richard, Do you have a link to the thread, I'd love to read it. It certainly sounds interesting. Also I've not heard of Vacuum sensors on the LS430 before, do you know where in the manual I could find them? We were expecting to find a vacuum leak behind the problem because as well as the mis-firing I was getting very high, although slightly sub-code-setting Long Term Fuel Trim readings. I guess a faulty sensor could mimic a vacuum leak.

Thanks Guys, Firstly Steve, I did a compression test on Cyl 1 about 2 weeks ago and it was just over 180psi (the book says 178psi). A lot of folk say that the compression test is not much good and what I need to do is a leak-down test. Now I understand that the leak-down test is much more specific in that, 1. It is not affected by outside issues such as a weak battery, and 2. You can pinpoint the source of the compression leak by listening etc. However, firstly the Lexus manual specifically says a compression test and gives an exact spec. Secondly, since I have a good result (ie. 180psi) there can be no leak, no weak battery and I don't have to detect exactly where my leak is (since I don't have one). I guess my question is - can I have a leak but still get a good compression test reading? Surely if that were the case THEN Lexus would not suggest the test. --------------- Ok Curious, I love your thinking, I'm realizing that I have to start thinking laterally now. A. Firstly I have to be honest and say that my concern is that the cause of the problem is valve seat recession caused by the use of propane as a fuel (no lubricant). I've used an upper cylinder lube system for most of the 150,000 miles I've done on propane BUT it's a single point injection system and the main manufacturer have gone over to a multipoint system leading me to believe that the single point system may be missing some of the valves. The funny thing is that Cylinder 1 (along with 2 ) is the closest to the lube pipe inlet. B. I like the idea of rewiring the knock sensors - but I don't think I'll try that straight away - lol! C. I did wonder about this idea of a false ECU deduction - in your post about the blinking MIL it says "When the temperature of the TWC reaches the point of thermal degradation, the ECM blinks the MIL. " - 1. how does the ECU know that the TWC is too hot, and 2. My MIL starts blinking 10 or 15 seconds after starting the engine from completely cold.??? D. I also liked the idea of the rough idle AND the blinking MIL + P0301 being separate issues - especially since the codes go away after warmup but the rough idle doesn't. Correct me if I'm wrong but I didn't think the LS430 had an IACV - having said that I don't see then how it gets it's air needed to idle and how it's regulated. I've attached a clip from the manual which may be interesting as it shows a pair of narrow air pipes which apparently help reduce emissions (ie. unburnt fuel presumably, which is what we're principally interested in here anyway) AND improve idling stability; also an issue here. Being narrow, could these tubes be affected by gunk after 300,000 miles? Not that I could do anything about it if they were - lol! Finally, is it possible to clean the throttle body at all without removing it?

Ok well I tried running on Petrol for a few hundred miles but it makes absolutely no difference - at least this rules out the physical fuel injectors as a problem source. Next I got a new MAF but again no change. I did consider the knock sensor as I understand this can cause mis-firing but it's so hard to remove that I thought I'd leave that for now - especially as there are no other fault codes. What I'm really looking for is some change I can make to the system that will give some change in symptoms so at least I can get some idea of where the problem might be. I do wonder about WHY the code/flashing MIL go away after the engine is warmed up AND also why the sensation of mis-firing remains AFTER the codes go away.??? It's due for an oil change very soon. I've been using a cheap 15W40 mineral oil up until now BUT I've ordered a bottle of Mobil 1 0W40 for the next change. Will probably make no difference but you never know - it can't have anything to do with the rough idle BUT it may make a difference to the cold starting now that winter temperatures have set in.

I did the same thing recently on an emissions issue I had. Eventually you get tired of developing theories and feel like you have to try something even if it isn't relevant in the end. Closing off theories is helpful too. I know you changed the coilpack for the suspect cylinder to no avail. I wonder if your pulled the connector at the COP pack and spray bother ends with electronics contact cleaner. Plug it together and pull it apart 5-6 times (this is called wiping action and gets fresh metal to metal contact). Then trace wires back to ECU and do same thing at that connector. Maybe you just can a marginal driver wire to the COP and when things warm up it just moved into tighter contact. Just a guess, but costs nothing to give it a go. Thanks, I've tried this already, both ends (including the multiplug at the ECU). I also swapped over the propane system's fuel injector emulator units in case one of them was causing fuel injector problems. Will let you know how it goes over the next week or so. Thanks for sticking with me!

Mmmm, yes I take your point about the MAF not playing favorites BUT my feeling is that some cylinders will be more susceptible to the effects of a poor sensor reading than others and if the sensor problem has just reached the fault threshold of the "weakest" cylinder... Anyway, bearing in mind I spend around £10,000 on fuel each year and the MAF costs £31 I'm going to replace it. The other thing I'm wondering is about the fact the problem goes away when the engine is warm - well the fault codes go away but the rough idle (in drive) remains. Could this be a problem with the coolant temp sensor? Again they're very cheap so if the MAF doesn't work I may replace that next. I know you don't like the "suck it and see" approach but comparing the value of the car to me in my business with the cost of these small items I may press on with this. However, I will do what you suggest and try running on Petrol for a few hundred miles, I've got a bottle of injector cleaner spare so I'll pop that in before filling up.

Ok well I tried a propane torch but couldn't find any leaks - it certainly seems to work ok though as I pulled my upper cylinder lube hose off the inlet manifold and squirted some propane in; you sure can hear the effect on the engine! Anyway I checked the Fuel Trim readings and it turns out that it is Bank 2 that is rather high - it's fairly stable at around +10% (Long term) AND this is the same at a variety of RPMs and Loads (including idle). The problem cylinder is on Bank 1 which is showing around +2% Something I should also perhaps reiterate is that the problem - ie. P0301 & flashing Engine Light ONLY happens whilst the engine is warming up AND, even whilst it's warming up it will go away under a light load. I can't think what else to try. I see you can get MAFs quite cheaply on ebay so I thought, since mine has done nearly 300,000 miles AND suffered my none too gentle cleaning (ie. Brake Cleaner), it wouldn't do any harm to try.

Thanks, sounds like a great idea, I'll try it tomorrow and let you know how it goes.

Thanks CuriousB, to be honest I've only really had a cursory look at vacuum leaks as this is an area where I have no experience at all. I think I understand the theory, ie. the introduction of un-metered air leading to a leaner mixture which the ECU spots via the O2 sensors and compensates for - hence the +14% LTFUEL trim. What I haven't done is identified exactly which pipes I need to pull off and examine. Would I be right in thinking that there is crankcase ventilation pipe for each bank (PCV)? Since bank 2 (btw I'm assuming that Bank 1 is the lefthand bank as viewed from the driving seat) fuel trim is normal, I'm guessing I only need to look at pipes that only serve one individual bank. Finally I should reiterate that by turning off the coil pack to cylinder No. 1, the mis-firing report AND flashing Engine Light stop happening. I don't know how significant this is but my assumption was that it means that the cause of the problem is related to that specific cylinder. I have to say I'm struggling to think this through in terms of cause and effect.

Well I found the engine ECU under the hood and cleaned up the relevant connector BUT no change. I don't really have any idea what to try next. I was looking through the "live data" on my scanner and a couple of readings may give some ideas (hopefully!!) 1. The reading for the MAF with the key on BUT the engine off was 0.56 grams/sec (compared to around 6 when idling). Since the figure obviously ought to be ZERO that makes me think the MAF needs re-cleaning or replacing - I guess it's only a smallish error but I don't have the experience to know how significant it may be - any ideas? 2. The Long term fuel trims were around -3% for one bank and + 14% for the other. That sounds like a significant difference. I read (http://repairpal.com/OBD-II-Code-P0171-and-P0174) that anything over 15% was likely to throw up a code (P0171/174??) So, my reasoning here would be - a) I'm not getting a code because the lean-ness is just too low, B) This level of lean-ness is sufficient to cause mis-firing AND a flashing Engine Light due to unburnt fuel through the engine. I guess I should perhaps look at possible causes of P0171. All ideas very welcome! Regards, Mike

I was wondering about this. My 2002 LS430 is coming up to 300,000 miles and had done 165,000 miles since the last cam-belt change. Also, when the belt was changed at 127,000 miles they didn't change the tensioners OR the water pump so I did think it ought to be done. HOWEVER, I still procrastinated. One thing that made me wait was getting my wife's Volvo V70 D5's belt done at 90k miles - the old one looked perfect; "why bother" I thought. So why did I get it changed in the end, well I'll tell you. Every time I change my oil I look at the serpentine aux drive belt and it looks fine. Then, without warning, it just disintegrates! I can tell you it didn't take me long to arrange to get the cam-belt changed. Yet, amazingly, after 165,000 miles, the old one still looked like new. I guess one compelling reason to get it done is - If I'm going to keep the car for another 100,000 miles I'm definitely going to get the cam-belt changed at some stage SO it makes a lot of sense to do it now; I'll only have to do it once and think about the peace of mind!

Ok, this is taking a little time as I wanted to be certain and I have to let the engine go completely cold between each test which takes around 8 hours. Well I've tested it 3 times - ie. removing the No. 1 cyl coil pack multiplug - and on each occasion I fail to get a flashing Engine Light. Correct me if I'm wrong but the only deduction possible from this is that the unburnt HC (fuel) is coming from No. 1 cyl (ie. when the coilpack multiplug is on). So, what could be the problem? I've read that it's possible for the Crankshaft Position Sensor to give trouble if there is dirt on the teeth of the wheel it reads. My feeling is that this would be unlikely as I've have been changing my oil every 5,000 miles and every other change I've been using engine flush to keep things clean. The other thing that is suspect has to be the low tension electrical supply to the coil pack. As I've said the multiplug and wiring at the coilpack end seems fine and I've cleaned it and refitted it. However, I'm wondering if the connection at the Engine ECU end may be suffering under load. Would I be right in thinking that the ECU is located behind the lower glove compartment (I'm RHD remember)? One thing that I'm also wondering about is, "why does the problem happen when the engine is cold BUT it goes away when it warms up"? What could this be about?

Wow, never heard of that, seems like an excellent idea for pinpointing the source of a cylinder leak. We can get them over here but my problem is lack of easy access to compressed air. Anyway, I did the standard compression test this morning and it was 180psi so it's certainly not a compression problem. I would like to try a diagnostic idea to be certain it's the No. 1 cylinder causing the blinking Engine Light and P0301. Since I always get these two things happening under load whilst the engine is warming up what I thought I would try is removing the multi-plug from the N0. 1 coil pack before setting off. I've got a feeling that IF a P1300 is set (for the coil pack) THEN a P0301 will not be set (even though a separate misfire condition is present on that cylinder) UNTIL the P1300 (coil fault) is remedied. However I'm assuming that, 1. A separate misfire would still be recorded, and 2. A blinking engine light would still occur in the event of unburt fuel getting into the TWC. Also, my understanding is that, if the coil is not firing (P1300 in this case) then the ECU will turn off the fuel injector to that cylinder. Will try that and report back.

Thanks CuriousB, I'm sorry I've just realized I might be at cross-purposes here. When I said I hadn't changed the plugs, I meant the igniter coil multiplugs. I have changed the No. 1 spark plug and also swapped igniter coils around. I'm going to do as you confirm and check the No. 1 cylinder compression next - I understand it should be around 178psi. Will let you know how it goes.

No, I just cleaned them. I have tried to get new plugs but Lexus want £60 each - that's around $800 for the set!! So, no EGR. There do seem to be several vacuum hoses connected to the air intake body but most of them disappear down below so I'm finding it hard to check them for leaks. There is a thing called "VSV for EVAP" which seems to operate a valve allowing/or not a connection from the air intake to the charcoal cannister. At least I can test this fairly easily. I've looked at all accessible vacuum hoses/connectors which seem ok. I will bite the bullet now and test the compression on No. 1. Thinking back 40,000 miles to when I last had a "mis-fire" problem along with flashing Engine Light, I remember that this was accompanied by loads of whitish smoke from the tail pipes which smelt very badly of gasoline. I have had no such symptoms this time. I wonder if it's possible to get the flashing Engine Light without unburnt fuel entering the TWC. I guess you can have a mis-fire code set even though the igniter fires correctly - eg. poor compression. The reason for all my wondering is that I really need to be pragmatic here; my main purpose is to keep the car going NOT to solve all it's problems (it is very old after all). My primary concern, I think, is to avoid ruining the TWC; I can live with a little rough idling for the last year or so of it's life. Anyway, I'll report back when the latest tests are done.

Thanks Landar, as you thought I've already looked at all the plugs. Thinking about general misfire diagnostic, I wanted to check for vacuum leaks and EGR. Would I be correct in thinking that there is NO EGR on the LS430?

Haha Landar, you are so right about the Coil Pack Multiplug problems; I have a funny story about one of mine. My No.2 threw up P1305 soon after I bought the car with 143,000 miles on the clock. I had no code reader in those days and simply went though taking each plug off it's coil, cleaning it and putting it back along with a good wiggle. Obviously I would start the engine as I took each one off until I discovered which one made no difference. As you can imagine, I left good ol' no. 2 until last as it's buried beneath the air intake resonator box (not to mention my propane injector rail and injectors for that bank). Anyway I was glad to discover that no. 2 was the offender (ie. causing the mis-firing). I duly cleaned and wiggled it and was rewarded with 110,000 trouble free igniting. However around 40,000 miles ago it started acting up again and the usual wiggling etc. would only give me 1,000 miles or so until it started missing again. This gap got shorter and I got fed up with all the dismantling just to wiggle the plug. So, I tied a bit of string around the wiring, led it around various bits of the engine and tied it off at a suitable point where I could tension it with a piece of towel which also prevented the string chaffing against the replaced resonator over which it ran. Lo and behold, this constant tension on the plug combined with the ability to remotely wiggle it when failing tension allowed the plug to fail to connect properly has giving excellent service ever since. Still not really sure what is wrong with the thing, ie. is it the connector or the wiring?? Anyway, I'm just agreeing with you really, these things can give trouble. However I'm not sure if any part of the igniter (circuitry) can be implicated as surely any failure would prompt a P13nn code. Also, I've had a good look at the plug and it's wiring and it's in very good condition as it's always been well protected. The wiring is still supple and intact. CuriousB, thanks for the diagnostic info, I have done all the swapping as it suggests so that now leaves the compression test - I guess I can get a standard figure from the manual somewhere. Ok, while I was driving home from work just now I had the following thought:- 1. I am focusing on diagnosing a "specific cylinder" problem - ie. ruling out other cylinder specific causes. 2. My question was, "If I have a general problem (eg. a vacuum leak) that is fairly slight and only justsufficient to cause a mis-fire, then, since not every cylinder's condition (compression, igniting, etc) is exactly the same, it is possible, presumably, that only one cylinder will be bad enough to trigger a DTC. 3. So, let's say no. 1 cylinder is most susceptible to mis-firing and along comes a general problem that doesn't bother the others BUT tips no. 1 over the edge - does that make any sense? 4. So, what would be the general problems that could lead to mis-firing - ie. usually in the "multiple/random mis-fire" section of the diagnostic manual? Anyway,and finally for now Landar, I did have the timing belt and water pump replaced earlier in the week. It had done 165,000 miles and I was only spooked into doing it as my serpentine auxiliary drive belt failed totally without warning the other day. I did hope that the mis-firing would go away with the new belt but it made no difference at all - in fact the old belt looked like new to me although the guy who did it thought it was starting to crack a bit. Ok enough for now, thanks for your thoughts guys!

I have an LS430 like you CuriousB, I guess you may be referring to the Ls400 as I don't think there's anything else I can "swap-to-test" on the ignition front. I suppose there could be a problem with the low tension wiring, that shows up under high load conditions - pity there's no way of swapping that. When the propane conversion was done a wire was tapped on to one of the LT wires to coil 1 for some purpose, I guess I should examine the wiring for any cracking that may be leading to shorting. Apart from that, the only other cylinder specific diagnostic I can think of is compression testing. I hope it's not that as this might point toward valve seat recession which can be a problem with the "lubrication-free" propane.