What's This Judder - Almost A Stall?

[johnmckellar]

Hi Guys,

Hoping that the wider US audience might help throw some light onto this problem. 1990 LS400 142,000miles. Recently started to judder at 40mph after running for 15 minutes or so & having accelerated OK. Had plugs changed. Air filter. Petrol additives to clean jets etc. No change. Sent to garage. Diagnostics showed code 41 so new throttle position censor fitted. Worse!

The diagnostic also showed Codes 25 & 26 ( air fuel ratio lean / rich respectively ) but garage said that was related to need for replacement cat at OUCH! cost. I don't want to be paying big bucks for new cat if that isn't going to solve the judder problem. But will, if it's the problem.

The judder was so bad today at 40mph car almost stalled. Revs are OK at idle. This problem doesn't happen till car has run for awhile so garage wasn't able to feel it.

Advice please before going back to garage & becoming much poorer!!

Thanks in advance.

JM

[leximus]

I would try changing the O2 sensors first. Why spend it on cats when it may not be them? I just would like to save you some money.

I had issues with emissions and they told me everything was wrong...from the cats to the MAF. Cost me 3200 (US) dollars. 4 O2 sensors, 3 cats, and the MAF, plus labor. What's worse is they only secured the cats with 2 bolts instead of three causing me to replace 2 of the O2's just replaced. No doubt that this caused my next problem (code 71 - EGR malfunction) because it was running too too lean. And also TRAC codes 13 and 51 (also looking for help on how to resolve these). You fix one thing and 2 weeks later, it never fails, something else rears it's ugly head....

Good luck.

[johnmckellar]

I would try changing the O2 sensors first. Why spend it on cats when it may not be them? I just would like to save you some money.

I had issues with emissions and they told me everything was wrong...from the cats to the MAF. Cost me 3200 (US) dollars. 4 O2 sensors, 3 cats, and the MAF, plus labor. What's worse is they only secured the cats with 2 bolts instead of three causing me to replace 2 of the O2's just replaced. No doubt that this caused my next problem (code 71 - EGR malfunction) because it was running too too lean. And also TRAC codes 13 and 51 (also looking for help on how to resolve these). You fix one thing and 2 weeks later, it never fails, something else rears it's ugly head....

Good luck.

Thanks Leximus - have noted your suggestion & will add it to others when I visit the mechanic.

Cheers,

JM

[SRK]

If it was an O2 sensor the code would have been O2 sensor specific. The rich lean could just be the ECM hunting for the correct fuel mixture. The convertors of course react to the swinging mixture, and the rear O2 sensor would trip a code.

Sounds to me like you have an ignition coil going bad.

I know you were looking for a US audience, and as I am from Canada you can ignore this post if you think it outside the specified zone.

[LScott400]

+1 on the coil. Change 'em both. Careful with the connectors. They may be pretty brittle by now.

[johnmckellar]

If it was an O2 sensor the code would have been O2 sensor specific. The rich lean could just be the ECM hunting for the correct fuel mixture. The convertors of course react to the swinging mixture, and the rear O2 sensor would trip a code.

Sounds to me like you have an ignition coil going bad.

I know you were looking for a US audience, and as I am from Canada you can ignore this post if you think it outside the specified zone.

Hey, SRK my abject apologies! Didn't mean to negate the great Canadian nation especially given that all of my family live there from Toronto to Calgary. many thanks for your suggestion.

Cheers,

JM

[UCF3]

If it was an O2 sensor the code would have been O2 sensor specific. The rich lean could just be the ECM hunting for the correct fuel mixture. The convertors of course react to the swinging mixture, and the rear O2 sensor would trip a code.

Sounds to me like you have an ignition coil going bad.

I know you were looking for a US audience, and as I am from Canada you can ignore this post if you think it outside the specified zone.

No: I had to change my all of my o2 sensors when I got the Code 25 and 31 especially for a car with so many miles.

I'm also thinking it's bad ignition coil or fuel.

Any hesitation during startup, e.g bouncing needle?

Any chance of stopping by a Toyota Dealer or locating a Certified Toyota Master at an aftermarket store?

[johnmckellar]

If it was an O2 sensor the code would have been O2 sensor specific. The rich lean could just be the ECM hunting for the correct fuel mixture. The convertors of course react to the swinging mixture, and the rear O2 sensor would trip a code.

Sounds to me like you have an ignition coil going bad.

I know you were looking for a US audience, and as I am from Canada you can ignore this post if you think it outside the specified zone.

No: I had to change my all of my o2 sensors when I got the Code 25 and 31 especially for a car with so many miles.

I'm also thinking it's bad ignition coil or fuel.

Any hesitation during startup, e.g bouncing needle?

Any chance of stopping by a Toyota Dealer or locating a Certified Toyota Master at an aftermarket store?

Thanks guys. No hesitation at start up. Car runs fine & gets good acceleration but once speed drops, the judder kicks in. Will go for the cheaper options first: O2 censors, fuel filter, coils. I'm not convinced about Cat replacements especially since in UK they're not compulsory on a car this age.. Thanks again for all thoughts. Any further always welcomed.

Cheers.

JM

[SRK]

My further thoughts are then these:

It can't be all of the O2 sensors at the same time - so don't replace them all. One might fail (they are very reliable after all) but not all four.

It could be the fuel filter, and as that's a routine replacement item, go ahead. However as you get good acceleration, it probably is fine.

It may very well be one of the two ignition coils, they are known to fail, and one can be easily checked against the other to confirm primary circuit resistance. Replace the one that is bad.

A part throttle misfire is also a symptom of a bad ignition wire or two. Ignition wires don't throw a code, but the result of the misfire can and does, normally a cat code, or O2. Just like a coil.

In any event, do one thing at a time, and note the change. Don't throw parts at it ( a common piece of advice from me, because I am cheap, and like to know what the actual problem is before spending money).

[johnmckellar]

My further thoughts are then these:

It can't be all of the O2 sensors at the same time - so don't replace them all. One might fail (they are very reliable after all) but not all four.

It could be the fuel filter, and as that's a routine replacement item, go ahead. However as you get good acceleration, it probably is fine.

It may very well be one of the two ignition coils, they are known to fail, and one can be easily checked against the other to confirm primary circuit resistance. Replace the one that is bad.

A part throttle misfire is also a symptom of a bad ignition wire or two. Ignition wires don't throw a code, but the result of the misfire can and does, normally a cat code, or O2. Just like a coil.

In any event, do one thing at a time, and note the change. Don't throw parts at it ( a common piece of advice from me, because I am cheap, and like to know what the actual problem is before spending money).

Thanks for all the help. Have ordered 2 replacement coils from a breaker & have arranged for new fuel filter too. My mechanic ( not Lexus! ) says that the Cat can simly be removed if it's failed tho' he doesn't think this is the cause. If it's ot the coils, I'll have Lexus look at it again but it's value ( despite my love of the car) doesn't merit throwing too much more cash at it. Keep fingers crossed.

Cheers,

JM

[SRK]

I don't mean to beat this to death, and I may be mistaken about the 1990 LS, but if it has four O2 sensors, then the post cat O2's are there to check the performance of the cats. If you mechanic "removes" the cats, the post cat (rear) O2's will throw a code instantly, and it won't go away. It ain't that simple - although your mechanic may be..... :whistles: Tell him to get over the idea of removing the cats as some sort of solution.

[HomerTHX1138]

Is this the issue where the car hesistates, bumps so to speak? Particularly at low RPM around 40 mph?

My 93 Ls400 has the same thing. I wonder though because if turn off O.D. the problem goes away.

The plugs, wires, caps and coils, fuel filter and air filter have all been replaced. The only thing in this thread NOT replaced or examined are the O2 sensors. The car also gets pretty bad mileage - 16.5mpg in city with air.

[johnmckellar]

Thanks, Guys. Car goes in this week for replacement coils / petrol filter. Homer, will try turning off the OD & see if that makes any difference. SRK - I'm not in favour of removing the CATS since they're there for a reason though I'm open to all suggestions to get the problem sorted. Will certainly point out the O2 censors to my mechanic as well.

I'll let you know what ( if anything ) happens.

Cheers,

JM

[NIALS400]

I have a similar problem, did anyone get theirs resolved. Did the coils rectify the situation? Thanks for the update.