Help! Red Hot Cats, Engine Running Very Rough

[Mybikesacx500]

I'm as upset as Chrali at the moment, engine is running very rough, almost no power, got home in clouds of smoke, both cats were red hot and glowing under the car, bit scarry.

I was sitting at the lights, about 1 minute after starting, when the idle suddenly dropped, and the engine went rough. Limped home, and checked the error codes (its a '92 ) 21 and 28, which according to a note I picked up on this or the American board, is both oxygen sensors, and a 63 from the o/d light, which is open or short on no.2 solenoid.

Started the car again, still running rough

I had the same codes 3 days ago, which was the first time I had checked them and I cleared them, so they are not old codes.

I figure the oxy sensor codes could be down to the lpg conversion?

I was on LPG when the problem started, and I switched to petrol for the 10 minute run home.

I had the air cleaner and air flow sensor assembly off today, as I was fixing the leak at the power steering pump. The car started fine and did the 10 minute run out with no problems.

The car is new to me, only had the car a few weeks, so not overly familiar with it, other than reading lots on this forum.

Hopefully someone will recognise the symptoms, any info very gratefully received

[sparkyhx]

I'm as upset as Chrali at the moment, engine is running very rough, almost no power, got home in clouds of smoke, both cats were red hot and glowing under the car, bit scarry.

I was sitting at the lights, about 1 minute after starting, when the idle suddenly dropped, and the engine went rough. Limped home, and checked the error codes (its a '92 ) 21 and 28, which according to a note I picked up on this or the American board, is both oxygen sensors, and a 63 from the o/d light, which is open or short on no.2 solenoid.

Started the car again, still running rough

I had the same codes 3 days ago, which was the first time I had checked them and I cleared them, so they are not old codes.

I figure the oxy sensor codes could be down to the lpg conversion?

I was on LPG when the problem started, and I switched to petrol for the 10 minute run home.

I had the air cleaner and air flow sensor assembly off today, as I was fixing the leak at the power steering pump. The car started fine and did the 10 minute run out with no problems.

The car is new to me, only had the car a few weeks, so not overly familiar with it, other than reading lots on this forum.

Hopefully someone will recognise the symptoms, any info very gratefully received

Sorry nothing specific about these cars this is just general advice

red hot exhaust can be down to running very lean (this will kill an engine) - I alway thought dodgy O2 would mean running rich which is still a problem but generally speaking not catastrophic like running lean can be.

Also it could be the timing is way out. I don't know how timing is controlled on the Lex but it could be a dodgy connection to the crank angle sensor or the sensor itself (assuming these cars have them). - check connection if its running ok.

check air flow sensor connection - clean with carb cleaner - this can cause a lean mix.

Does the ECU have a limp home mode when it detects something bad? Have you reset it - just in case its a phantom problem.

is it running rough on petrol as well?

Personally i'd limp to a garage and get it seen too ASAP. Probably start with LPG guy to rule that out as they know their systems whereas a garage might not want to look at it until the LPG has been ruled out.

[Mybikesacx500]

I thought red hot cat converters were caused by an excess of unburnt fuel, (as opposed to red hot exhausts. caused by a lean mixture) ?

I will try disconnecting the Battery for 10 mins- that is how to reset the ECU?

Yes, it started running rough on LPG, so I switched to petrol, no change, still rough, I drove home on petrol

[chrali]

Ok i take of my hat to you ...... your problems are far more scarey.

Cannot offer anything but my sympathy, a sick car is no fun at all!

[Monster-Mat]

yup sounds like a misfire on a number of cylinders meaning unburnt fuel has entered the cats....and more than likely melted them.

i had the exact same issue on a GS300

[Mybikesacx500]

Just tried disconnecting the Battery for 10 minutes, to reset the ECU, if thats how you do it.

No change, engine starts well enough, but runs very rough, with a strong smell of unburnt fuel.

Both cat converters were red hot last night, so am I right in thinking there was unburnt fuel on both engine banks, so its not like one plug has stopped firing

Keep the suggestions coming, I'm up against it here....

[chrali]

Do these cars have ignition coils that cover more than 1 plug per coil?

If youve got unburnt fuel, then perhaps the place to start is seeing if sparks are getting to each cylinder.

Perhaps your HT leads are broken down, distributor caps, or rotor worn or broken. Time for a little dismantling to check the condition of these.

Just my tuppence from 'ole rusty'

[steveskeggy]

If you have had the air flow sensor assembly off the car, then thats the area that you should start looking at, especially if the car was running ok before.

Did you plug it back in properly? has the plug fell out? could one or more of the wires be broken at the plug? is the plug a good fit? etc etc.

I should think that the hot cats are a result of the fault, not the cause itself and if you look to them then you could be chasing the cat up the wrong tree :D

[Mybikesacx500]

If you have had the air flow sensor assembly off the car, then thats the area that you should start looking at, especially if the car was running ok before.

Did you plug it back in properly? has the plug fell out? could one or more of the wires be broken at the plug? is the plug a good fit? etc etc.

I should think that the hot cats are a result of the fault, not the cause itself and if you look to them then you could be chasing the cat up the wrong tree :D

I would agree about looking at the area worked on recently, although the car ran fine for about 20 minutes afterwards. The air flow plug looks fine, I did leave a big Jubliee clip a bit loose, but cant see that causing my problem. I will be having another look this evening.

Anyone know a good Lexus mechanic in Glasgow?

[steveskeggy]

Anyone know a good Lexus mechanic in Glasgow?

Yes you.

If you can work a spanner and are not afraid to get your hands dirty, then you are the best one to work on your car.

At least you know you wont get ripped off, and you wont take shortcuts or get shoddy workmanship.

[Mybikesacx500]

Anyone know a good Lexus mechanic in Glasgow?

Yes you.

If you can work a spanner and are not afraid to get your hands dirty, then you are the best one to work on your car.

At least you know you wont get ripped off, and you wont take shortcuts or get shoddy workmanship.

I completely agree, unfortunately, I don't know what's wrong with it!

Just back in from re-checking everything I did recently, looked for anything unusual, reseated a few connectors round about where I was working, and it still runs rough and a very strong smell of pertol from the exhausts.

Both downpipes got warm, though, so its not as if one bank has quit. I tjust did this as I was sitting at the traffic lights, beats me, for the moment

[ROYT]

Is the air filter housing located correctly especially at the bottom?

If its' the same as my '94, it's easy to clip together with a gap a the bottom, upsetting airflow.

[Mybikesacx500]

Is the air filter housing located correctly especially at the bottom?

If its' the same as my '94, it's easy to clip together with a gap a the bottom, upsetting airflow.

Agree it is fiddly, but when I initially got it, there was no filter at all, and extra holes drilled in the filter housing and it ran fine!

It's one of the things I re-checked tonight, still got my fault

Thanks for responding

[steve2006]

Hi,

I take it you have a single point LPG conversion fitted this is probably the reason why the air filter had been removed and extra holes made in the housing as they are prone to blowback through the induction system.

If this has occured it may have damaged the airflow meter ( karmen vortex type) giving the results you have or with no filter fitted it may have sucked in debris causing damage as they are reliable in general but very sensitive to damage.

[Mybikesacx500]

Hi,

I take it you have a single point LPG conversion fitted this is probably the reason why the air filter had been removed and extra holes made in the housing as they are prone to blowback through the induction system.

If this has occured it may have damaged the airflow meter ( karmen vortex type) giving the results you have or with no filter fitted it may have sucked in debris causing damage as they are reliable in general but very sensitive to damage.

Spot on, it is a single point conversion, that's good to know, it was the LPG installers- I thought boy racers had been at it. Not impressed with setting a car up with no filter. There were a fair few bugs caught in the matrix in front of the AFM, but I cleaned it and fitted a filter, about 6 days before the engine started running rough

[steveskeggy]

Just had a look on E-Bay to see what the price of a new sensor is, they aint cheap.

However the one that is fitted to the LS400 looks to be the same as a few other Toyota cars, such as the Supra Turbo and the Camry

Just type in LS400 maf, and you will see what I mean.

They results are from the USA and the prime supplier lists some of the symptoms of a bad sensor as:

-Loss of torque/horsepower (Doesn't pull like it used to).

-Misfires (lean).

-Some jerking motion when accelerating.

-The engine shakes and may rattle.

-The engine shuts down when idling.

-Sometimes the check engine light comes on or blinks.

-Low gas mileage!

Sound familiar?

May be a good idea to find the part number get on the phone to the local scrappys to see if they have one, More likely to have one off a Toyota than a Lexus.

If you can get one cheap and it works, then you can always make the decision to get a new one, instead of shelling out for a new one and finding its still the same.

[Mybikesacx500]

Just had a look on E-Bay to see what the price of a new sensor is, they aint cheap.

However the one that is fitted to the LS400 looks to be the same as a few other Toyota cars, such as the Supra Turbo and the Camry

Just type in LS400 maf, and you will see what I mean.

They results are from the USA and the prime supplier lists some of the symptoms of a bad sensor as:

-Loss of torque/horsepower (Doesn't pull like it used to).

-Misfires (lean).

-Some jerking motion when accelerating.

-The engine shakes and may rattle.

-The engine shuts down when idling.

-Sometimes the check engine light comes on or blinks.

-Low gas mileage!

Sound familiar?

May be a good idea to find the part number get on the phone to the local scrappys to see if they have one, More likely to have one off a Toyota than a Lexus.

If you can get one cheap and it works, then you can always make the decision to get a new one, instead of shelling out for a new one and finding its still the same.

All good stuff, not quite my symptoms, the car runs very, very, rich, and the cats were glowimg red hot with unburnt fuel

just had a good look at the American forum, top of the list is an HT coil failed

Feels like it is running on 4 cylinders, and apparently this problem will cause both cats to overheat- ECU must get confused

Thanks for responding

[sparkyhx]

Just had a look on E-Bay to see what the price of a new sensor is, they aint cheap.

However the one that is fitted to the LS400 looks to be the same as a few other Toyota cars, such as the Supra Turbo and the Camry

Just type in LS400 maf, and you will see what I mean.

They results are from the USA and the prime supplier lists some of the symptoms of a bad sensor as:

-Loss of torque/horsepower (Doesn't pull like it used to).

-Misfires (lean).

-Some jerking motion when accelerating.

-The engine shakes and may rattle.

-The engine shuts down when idling.

-Sometimes the check engine light comes on or blinks.

-Low gas mileage!

Sound familiar?

May be a good idea to find the part number get on the phone to the local scrappys to see if they have one, More likely to have one off a Toyota than a Lexus.

If you can get one cheap and it works, then you can always make the decision to get a new one, instead of shelling out for a new one and finding its still the same.

All good stuff, not quite my symptoms, the car runs very, very, rich, and the cats were glowimg red hot with unburnt fuel

just had a good look at the American forum, top of the list is an HT coil failed

Feels like it is running on 4 cylinders, and apparently this problem will cause both cats to overheat- ECU must get confused

Thanks for responding

good luck and keep us posted with the fix when you suss it. Nothing worse than a board full of half fixed problems.

[Mybikesacx500]

Do these cars have ignition coils that cover more than 1 plug per coil?

If youve got unburnt fuel, then perhaps the place to start is seeing if sparks are getting to each cylinder.

Perhaps your HT leads are broken down, distributor caps, or rotor worn or broken. Time for a little dismantling to check the condition of these.

Just my tuppence from 'ole rusty'

Sorry Chrali, didn't realise I hadn't acknowledged your reply, Yes, I thing pull leads and hook up a spare plug and see if all cylinders are sparking, hopefully its a duff coil or something equally simple to understand and fix

[chrali]

No worries .... also found this on seaching for 'coils'.

As well as the coils there are the 'igniters' 1 and 2 .

Also number 1 and 2 cam position sensors send signals to the ECU, which calculates the ignition timing

and sends a signal to the igniter.

Whew!

The crank position sensor detects the crank angle, and the number ! cam position [ for left bank] and no 2 cam position [for right bank] sensors detect the CAM angle.

Have you got that?....[ Wish I had]

At a wild guess I would suggest the sensor for your 'dead' side may be faulty and not supplying the signal

needed to trigger the igniter on that side...

Might all be Bull..it but worth a look if your stuck....

Bit more info

Turn on ignition and check for Battery voltage at the coil + terminal

Resistance of coil [cold] Primary 0.41 - 0.50 ohms---Secondary10.2 - 13.8 ohms

Sensors 950- 1250 ohms

Keep us all updated!!

[Mybikesacx500]

No worries .... also found this on seaching for 'coils'.

As well as the coils there are the 'igniters' 1 and 2 .

Also number 1 and 2 cam position sensors send signals to the ECU, which calculates the ignition timing

and sends a signal to the igniter.

Whew!

The crank position sensor detects the crank angle, and the number ! cam position [ for left bank] and no 2 cam position [for right bank] sensors detect the CAM angle.

Have you got that?....[ Wish I had]

At a wild guess I would suggest the sensor for your 'dead' side may be faulty and not supplying the signal

needed to trigger the igniter on that side...

Might all be Bull..it but worth a look if your stuck....

Bit more info

Turn on ignition and check for battery voltage at the coil + terminal

Resistance of coil [cold] Primary 0.41 - 0.50 ohms---Secondary10.2 - 13.8 ohms

Sensors 950- 1250 ohms

Keep us all updated!!

Wow, Thanks for that Chrali all good and relevant

info

I have got as far as checking the "top" coil secondary, because it is easy to get at- 11K, so OK.

I tried unpluging the HT lead, and the car still started and ran the same, so thats pretty inconclusive, one test says ok, one sugests not

I have to go varnish a floor this weekend, its killing me walking past the car and not working on it, but I will get to it and I will get back with results

Thanks all

[Mybikesacx500]

Chrali,

I will finally be working on the car this weekend, can you tell me where you got all that info, I have been searching my eBay CD and it seems to cover later models, with separate ign. coils, what I need to find is a CD for the '92 model, back to eBay, I suppose.

Thanks to all you replied, I will be posting updates. Is getting the distributor caps off involved?

[Mybikesacx500]

Here's an update of the work I did today:-

R/H bank (drivers side)

HT coil lead 3.8k, ok

HT coil 12 k , ok

HT coil low tension 0.4 ohms, ok

12v. on black and orange wire. ok

cam position sensor 1079ohms, ok-- but the wire from the connector was almost cut through where it had been rubbing on the serpentine belt

GREAT!, I thought, its been shorting out, how can this not be my problem, so I soldered away and rerouted the repaired cable, put it all back together , jumped in, fired it up and- still running on 4 cylinders

Disapointed.

OK, had a read at the new manual I bought last night at

http://www.tunerselect.com/Lexus-LS-400-19...al--100908.html

"Pull the HT lead from the coil of the distributor, turn the car over, and check for a spark" it said

so I did, big fat spark, and the car didn't start.

Plugged lead back in, and car did start

SO, the other 4 cylinders must not be firing.... But I remember last week pulling this lead from the coil end and the car did start, must be an intermittent fault?

Over to the L/h side, HT coil lead 6.28k, ok HT coil 6.14k NOT ok, should be 9 to 15 k GOTCHA!

This coil failing has been the cause of my symptoms, as reported on the American board, so its looking hopefull

I have one ordered from that nice chap Maurice, and its in the post, but it's a holiday weekend, isn't it, and its not here yet

Hopefully that will be it fixed. It was a right bugger to get off

[Mybikesacx500]

FIXED! its fixed! WHUahh haa haaa :D

What a relief, it was the left hand HT coil pack, changed it tonight, and normal service is resumed

The original pack coil resistance was 6K, which was out of spec., and this coil failing was mentioned quite a few time on the US site. I guess 17 years living next to the exhaust manifold is what does them in. 17 years and it goes 2 weeks after I buy it...

Thanks to all who offered suggestions, the moral support really helps.

Next step is to see if I still have the O2 sensor error codes...

[chrali]

Glad you got it sorted mate :D