Intermitant Check Engine Lamp

[Lucifer]

Hi guys, recently got a clean '94 SC400 w/ automatic about 80K miles. It was owned by an older female and ran kinda flat until I cleaned out the exhaust ;) It seems to run pretty good now but the engine lamp comes on occasionally, only after a really hard acceleration. The lamp stays on about a day then goes off if I drive it normally. It seems worse if I run low grade fuel instead of the top grade so I was thinking possibly a misfire detection in the computer since the light never comes on during easy driving. I also noticed that I'm hitting the fuel cut off at about 6500 if I let it shift in auto. Has anyone had any similar experiences and what did it turn out to be? It's not as much fun if I have to keep my foot out of it....

[AWJ]

You have a high compression motor. Do yourself a favor and use the good gas. Give me your e-mail addy via pm and I will send you the diagnostic procedure tomorrow. It could be anything from a dirty air filter to a bad catlytic converter.

[brucelee]

I am having my mechanic run down a interm. check engine light right now. It is not the ECU nor the distributors, which have been replaced.

I will let you know what he finds.

Its a 94, stay off the redline and use decent gas for Gods sakes. It is a LEXUS, not a Scion.

[SPORTcoupe300]

Lexus = Toyota = Scion no?

[Lextech2k3]

actually the order is Toyota->Lexus->Scion

but yeah it's all the same stuff....hey if i were you i'd just take the thing to autozone or the dealer..they will both read that code for free.

btw what did you mean by you "cleaned out your exhaust" i've never heard of that.

the most common problem we see on those cars are the O2 sensors going out...don't skimp on this item..buy it from the dealer...they charge you out the nose but it is important that it gives the computer an accurate reading...if not your engine could go lean (less fuel than usual) and literally cook itself.

you should know that only about 1 in 10 of the O2 sensors are intermitent so there is still a good chance of there being other problems.

good luck with it,

Tyler

[brucelee]

Here is my story.

Replaced dist caps and timing belt. Did the water pump while we were at it.

Seems to be the remedy.

Ouch, 104K service items hurt big time.

[advan7]

The SC needs and requires premium gas as evidenced by the cluster and the sticker on the gas lid, so I wouldn't put anything less in it. When I got my car whomever had it used mid grade and once I switched over to Premium car runs so much better. Just my 2 pennies.

[AWJ]

Low grade gas could very well be the cause of the intermittent mil.

[Lucifer]

What I meant by "clean out the exhaust" is that I drive it like it was designed for.... to it's full potential.... Gas pedal all the way down on the floor ;) The power seemed a little flat for the first couple of days after I got it, then it came to life. I know it was driven by a 50+ female for all it's days. Probably some carbon build up in the cat or whatever ehhh ?

Yeah, it does run better with the premium fuel and thats all I put in it now. I've had it since July and this problem with the check engine lamp started about 3-4 weeks after I got it.

I'm in California where we just had the mondo fires. I replaced the air filter with a K&N since the fires clogged up most of my other cars filters too. That made a huge difference in the torque and intake noise got throatier too. I found out the air filter door popped open and that was the majority of the drone. When I closed the access door the torque dropped off quite a bit. That air intake tract forward of the air box must be a sizeable restriction. I was thinking about doing some stealth surgery, since we have to smog check every other year here.

I wanted to change the fuel filter, but when I looked it didn't present itself. Where are the darn things? I'll probably throw in an O2 sensor too just because of the miles, but I agree I don't think that's the problem. Usually an O2 will set a hard code, and the light will stay on. I used to wrench for a living about 12 years ago, mostly OBD1 stuff but lost touch if you know what I mean. I don't have any manual for this beast yet. AWJ, Thanks, I'd appreciate any diagnostic procedure or specs info, pm is on it's way.

Hey, someone said these little beasts have timing belts???? I thought it was a chain? It doesn't look like a T-belt system from the front of the engine...unless it's totally buried. Was I squinting and holding my tongue wrong or something? Ok, I give up.... Chain or T-belt?

[AWJ]

Got your pm. I will try to send you the procedure on Saturday. It is not available currently. There have been a few tests on the SC400 intake induction OEM and aftermarket. It was found that any modification of the tubing caused a reduction in torque. In fact, for best performance, the stock airbox was modified. It is called the BFI and has been discussed here in the past. There should be link in the faq. It was developed (at least in testing and invention) by a guy in Australia. Peter Scott I think. That is your best bang for the buck. I will have to consult the manuals to get the location of the fuel filter unless someone else here knows off hand. Your motor and all lexus motors (I think) use belts. Your timing belt is behind the serpentine belt and timing cover. I though I posted a pic from the FSM in one of our gallerys but I can't find it, so maybe I didn't. All I could find was the 2jz pic. I'll be in touch. Good luck.

[SPORTcoupe300]

If I recall correctly, the fuel filter is chillin somewhere next to the rear left wheel in the SC300 so I wouldn't be suprised if it's in the same location on the SC4.