moira

Any ideas what could be wrong? My car a lexus SC430 is 13 years old and has done about 60,000 miles. It was running fine and is only used for short journeys. it now seems to run out of energy when the engine gets warm and there is a scratching noise from underneath. Any suggestions? it has been regularly serviced and recently.

FatBrian81

iTrader: (2)

You might get more help on the SC430 forum, those cars are pretty different from the 300/400 models.

KahnBB6

iTrader: (5)

^^ Moved to the SC430 sub-forum. I hope you can sort this out, OP. I am not that familiar with quirks of the 1UZ-FE VVT-i engine or its ECU but you may want to check that all the ignition system coil packs are good, that the spark plugs are still in good shape and that your engine doesn't have any excessive carbon buildup due to it only being used for very short trips all its life.

Generally carbon buildup is only an issue seen on direct injection engines (and often not those with Toyota's D4-S direct and port injection system which your car does not have). And just FYI so as not to confuse you, your SC430's engine is *not* direct injection.

But since the car only saw short term use for a very long time like that you may want to take it out onto the highway every so often and actually give it some flat out acceleration occasionally.

However if there is some abnormal issue where it sounds like it is misfiring at idle once warmed up then that would indicate you need to get it looked at by a mechanic to figure out why that is happening.

Also, I am not sure if the SC430 ECU's are affected by failing capacitor issues like older Toyota/Lexus ECUs but if so, consider having Tanin Auto Electronix service your car's ECU *IF* your mechanic has determined it to be causing problems.

But start with the basics first. Diagnose things one by one. Given how the car has been used and how little mileage it has on it I think this may be related to just not doing more with the car than cruising around on short trips for a very long time.

Good luck. It may in fact be as simple as getting the car out for longer drives and letting the engine rev up a bit more in mixed use scenarios. Generally these are very reliable V8 engines if kept in normal service with regular oil changes.

moira

Hi Thanks for your reply and moving my query. I have just joined this site. The car is a second generation model so i believe it should be in that forum and this is a 1st generation forum but don't know how to move it again. Can you do this so my query is in the right forum?
It may be what you suggest but because the engine, once it has warmed up, seems to make a pinging/scraping/clunking noise i daren't drive any further to do as you suggest as it sounds sensible to do a longer drive but i think the engine will just blow up. It seems to be exhausted if that makes sense!
I first thought it was the radiator so drained it, changed the coolant so it is not that. I have also had the brakes looked at. The handbrake/shoes needs to be replaced so I am just not using it at present as you can just leave it in 'P'. The engine oil has been drained, flushed out and replaced. The wheels have been taken off and checked and put back on. The underneath got a branch in it from the road, that was removed and underneath checked for damage and there appears to be nothing significant (that is why i thought it had maybe punctured the radiator!) As it has recently been serviced I would have though the spark plugs would have been checked so possibly not that. Any further ideas as where else to look/consider?

moira

thanks. 2nd generation forum yes?

Harold57

First, welcome to the forum.

Can you expound on what you mean by it "runs out of energy when the engine gets warm" and by the "scratching noise from underneath"?

Before the engine warms up, is it peppy then?
What kind of scratching noise: metallic, plastic, etc.?
Can you make a recording?

Wilson2000

Since you don't mention any check-engine lights/codes, I doubt it is a misfire. Since you had it serviced recently, I would have someone followup and check what parts were replaced. You could have the wrong parts installed, or the person doing the work could have inadvertently caused collateral damage. Sometimes less-experienced mechanics aren't careful and don't pay attention to details when putting things back together. It's easy to knock a connector or vacuum hose lose or break a wire when working in tight places.

Since you ran over a branch recently, you should also focus on any damage to the undercarriage, i.e., the exhaust, O2 sensors, oil pan, tranny, diff, etc..

An abundance of short trips will not only foul up the engine with carbon, but it could also foul up your catalytic converter, although that should result in a check engine light as well. Even without the light illuminating, it would be a good troubleshooting step to check for codes and other critical data at the OBDII port.

If you are hearing strange noises, you can isolate them with a 4-5 foot length of hose. Stick one end in your ear and move the other end around and under the engine bay until you find the area where he sound is emanating from.

If I noticed a loss of power in my SC, I might also suspect some form of fuel issue. Bad gas or the wrong octane could cause knocking noises. The fuel pressure could also be an issue. If all else fails, have it tested.

Lavrishevo

iTrader: (1)

And do the ECU reset trick Harrold posted years ago. It's quick and has solved weird power issues before.

Harold57

It is possible that there is still more branch up in there, stuck around the drive train area causing the scratching noise.

moira

Hi Sorry for the delay in answering all your suggestions and thank you very much for your those. Yes i think in future a long run occasionally would be best and in the future i will do that. For the moment I had the car up on the ramp to check there were no more branches but all good. the fan belt has been changed so got rid of that noise. After it warms up about 6 miles it is at this point it appears to sound exhausted and when i get the pinging noise and scratching metal sound so i got a combustion test of the coolant and it turned reddish so i am thinking it is the head casket. The problem is there are two and it don't know which one to maybe replace. Any way of testing which one it is or is it a matter of trail and error? Whatever it will be an expensive job but obviously some impurities/water has got into the engine I think. I am not sure what the the catalytic converter is but this was mentioned at one point by my mechanic friend (who is an elderly experienced mechanic just can't 'do' anymore) who helped with the combustion test in front of me). Lovely car as you know so don't want to get rid of it!

Wilson2000

Unless you run them out of coolant, which is often due to a radiator or a coolant hose failure, these engines are pretty much bullet proof. If the engine overheated enough to blow a head gasket, you definitely need to replace both head-gaskets, regardless of which one is passing combustion gas into the cooling system. Worst case, you cracked a head or the block, which at that point, you're better off going for a good, used engine from a wrecked, low-mileage SC430 of the same vintage. Either repair will cost you big bucks, but a replacement engine from a reputable source will be more of a sure bet. Beside the head-gaskets, overheating causes all kinds of other problems down the line, i.e., oil leaks, coolant leaks, bearing issues, etc.. So, you might consider the replacement engine irregardless of a cracked head or block. Have the repair quoted both ways and then decide (repair or replace).

A warning to all drivers of all cars...NEVER KEEP DRIVING AFTER YOUR ENGINE BEGINS TO OVERHEAT! You will turn a small repair bill into an astronomical repair bill. Pull over immediately upon the first sign of overheating (temp gauge, warning lights, steam, smell of coolant) and call a tow truck. You'll be sorry if you gamble on making it to the next off-ramp or gas station. Even if you make it, your engine will be toast.

moira

Hi Thanks for all your tips. Just to update you as you have all been wonderful in giving your advice. Took the car to have the head gasket(s) seen to. Just before it went up on the ramp one of the guys noticed one of the exhaust pipes was protruded! This turned out to be what the scraping noise was. NO rust just the exhuast had come apart! Fortunately i had another friend who managed to soldier a bracket to join it up and all sorted. He then suggested trying 'steel seal' for the time for the head gasket. Seems to be doing the trick and it is not overheating so going to just keep an eye on things as it seems to be running fine now and no noises/exhaustion detected. As I don't take it for long journeys hopefully this will avoid replacing the engine or head gaskets for the time being just will keep a very close eye on the car at all times! Will bear in mind your suggestion though if any problems in the future and thanks again, it is such a beautiful car.