Car, was sputtering and shaking when idleing and I just took it into the dealership today and they said that there was a 25/26 Code, and it was missing from idleing on up to high RPM'S, does anybody know what this could be? Thanks

 

Could be an exhaust leak as well as bad engine mounts causing your sputtering and shaking--

Mine ran absolutely perfect and smooth, until the exhasut gaskets burned out the same day, and then the motor seemed to shake and got a lot louder under the car naturally--

A big exhaust leak can cause the engine to seem like it misses, and bad mounts can amplify this problem..

1) Check your engine mounts-- How? Put the car in drive, stand on the brake, and give it a good bit of gas, if the motor "stands up" on one side, repeat this in reverse, it should lift up considerably on the other side-- IF it does this -- you need new mounts-- common problem on these cars-- mounts can go out in 60k miles....

2) An exhaust leak will be pretty audible under the car at higher rpms, but almost silent at closed loop idle (500 ~ 600 rpms) so rev it up a bit and you'll hear it -- or not

Missing can also be from a bad injector, bad plugs, bad cap/rotor, bad plug wires--

A general tuneup is in order on a car that age anyway-- so I would start with those steps first to see if it cures...

 

I believe code 25 and 26 are lean/rich conditions. I dont think it's engine damage, and I definitely don't think it's engine mounts or an exhaust leak. Exhaust leaks can mess with the O2 sensor, but it usually doesn't frak it up that badly, and only hurts gas mileage or makes the car louder.

If you started shuddering, sputtering, and shaking out of nowhere, something got disconnected. Very few parts on the car just go bad like that.

Since it's rich/lean condition, that means something is not firing right. Easy things to check would be that the MAF sensor (on the intake) is properly connected. Next, check that your spark plugs and wires are properly seated. A spark plug wire that becomes loose commonly causes the 25/26 error code.

Cap and rotor don't usually fail disastrously, and typically wear out.

 

I figured it could've been plug/wire problem--

I just wasn't clear on the codes or exactly what type of shaking was going on--

 

Yeah I wasnt sure I'll make sure to let the guys at lexus know, because they couldn't figure it out either. Anybody else know of what could be the problem.
Thanks for the help

 

What's scarier is that they "didn't know" what it could be. Just be careful that they aren't trying to take you for a ride. It sounds like a simple problem-- crossing fingers that it is.

 

2nd that-- The guys you most likely talked to were the service writers [ie: commissioned salesmen, they get paid to sell you a load of bull****e, the more you buy by the shovel, the more food they can eat when they get off work] Alot of these guys can make $70k plus a year, I used to sell and thought about doing it.

When they say "We don't know what it is", it could possibly mean, "We don't want to pin it down to one thing, because we may be able to get you to pay for several things"

I think the plug wires and plugs would be a good place to start, normal tuneup items, --------- IF the stuttering still exists after you replace plugs, wires, cap/rotor, ---- Look into fuel injection problems----

The seating the plug wires is a free place to start--- The plugs are under the black covers on top of each sides valve cover-- It looks complicated enough but it's not-- Also check the wires at the dist. cap on each side too---

A cracked cap has made this happen before a time or two also-- on a side note....

If you reseat all the plug wires on the cap end and the plug end and the problem doesn't subside, pull each wire one at a time, the car should run noticeably rougher with a bad miss each wire you disconnect, so disconnnect and reconnnect each plug wire one at a time (easiest to disconnect at the cap obviously) -------

Once you go through all 8 wires, there should be one wire that when pulled didn't add to the miss-- meaning that is the cylinder misfiring-----

Bad plug wires cause misfires, as do fouled plugs, as do dead injectors, the previous 3 instances are in listed most likely to least likely -- but don't rule out a distributor cap being cracked-- but you would be able to most likely see the damage if it's causing a misfire....

One of those wires will lead you to the missing cylinder------ And though it is easier to disconnect/reconnect at the caps, you'll be able to tell which cylinder it's at much more easily by doing this test on the spark plug boot end of the wires (in the valve covers)

This is really easy to check, so I hope I didn't make it seem complicated.

It's just trial and error-- and can help you eliminate more expensive problems, but changing a fuel injector wont be expensive or difficult either, just don't let it spray gas in your eyes if/when you remove the injector [fuel pressure]...

 

I agree with MJHSC for 2 reasons. 1) it is probably the plugs/wires . I'm experiencing the same issue very recently and that's what I'm going to check out. We have such a big engine that when it's missing (or whatever), it SEEMS like something's shaking... and #2, he is very , very wise to say start with the easy, inexpensive stuff and his problem solving method recommended to you is sound. Most of the time the easy stuff is what goes wrong and you save lots of time and $$$ by checking/replacing/fixing that stuff first.

On another note that I'll surely get flamed about, this isn't exactly the best list for getting good maintenance info. From my sig you can see I have 2 Lex's and try to do as much as I can. Most of the talk on this list is about tires/intake mods, and "how do I lower my Lex" and other stuff like that. I've been looking for tips on replacing the plugs/wires and the best post on replacing this on our SC400 is from a dude who WATCHED someone else replace the plugs/wires. (I still appreciate his post, though)

It should be mentioned, however, that these are pretty complex cars and a lot harder to work on than older, less sophisticated cars so there's certainly a smaller amount of dudes who have done their own maintenance than , say, a Supra or Tacoma..

 

IMO,

You shouldn't diss the Lexus service department. No, they are not sure, but either is anyone here. Many things need to be checked.

And from a mechanics point of view (I am a Toyota tech), I wouldn't spend who knows how much time trying to figure the problem out for free. If you’re willing to pay the diag time, and be sure that one of the "good techs" has your car, I'm sure the problem can be found without throwing too many parts at it.

Anyway, I had a 25 (lean code). The light would come on the first time I came to a stop after warm up, and then went back off after going down the highway for awhile. I used a scan tool to look at my front o2's and found the waveforms to be quite lazy. And, if I snapped the throttle open, then closed, they would flat line at 0 volts (lean) for 20 seconds or more before recovering.

Put new sensors in, and so far so good. Waveforms are now perfect.

My car did not have any noticeable drivability problems though.....

I do have an occasional mis at very light throttle that I think may be crap in the gas tank, or fuel pump related, gets worse when I'm low on gas. But this problem is still there even after sensor change.

Well, good luck!

Notes:

If your wires (should have the production date on them), plugs, caps, rotors are more than 5 years old, replace them. Good idea regardless. I would reccomend only using Lexus parts. I have seen many problems caused by people using aftermarket parts, mostly plugs.

Same with T-belt. Unlikely it is off time and causing your problem (fairly easy to check while your doing the wires ect), but it is possible and should be changed anyway if its due/over due.

Check for vaccum leaks.

On OBD II controled Toyota's, P0171 (too lean) is almost always the mass air flow sensor. Have seen this code set by water in the gas tank once on a 3.4 tacoma.

jpw, if you need info on a tune-up on your car, let me know, happy to help as much as I can.

 

Thanks KC !
I appreciate the offer. I was just about to buy some NGK Plugs before I read your post. At the risk of starting a plug thread, which brand/type are stock for the SC400? I do trust NGK wires so I'll probably stick a set of those in...

 

I had code 25/26 and my mechanic was like "dude, you have to change O2 sensor"... and then, I did Seafoam about couple days ago and my check engine light went away...

Do some research...

 

jpw,

NGK or Nipondenso are factory reccomended. If you have an owner's manual, look under engine specs and you should find part numbers.

Nothing wrong with aftermarket wires, if they fit well. I put factory wires on mine for ease of replacement + they are not that much more expensive than aftermarket.

If your doing plugs and wires, you should also do caps and rotors. Again, not too expensive from Lexus.