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Intermittent Misfiring


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Hello all,

I have a 93 es300 with about 185000 on it. Recenting I was on a trip

cruising at about 70 when something just didn't feel right. I got off the

next exit and stopped at a service station. While I was sitting there

the engine was running rough at idle. As I increased the rpms the engine

ran more roughly. It almost seems like its misfiring. I had 2 more hours

to get back home so I decided to chance it. It never got worse. I got about 30 miles

from my house and it smoothed right out. At first I hoped it was just bad gas, but

it wasn't. Its been doing it off and on ever since. As a matter of fact it started doing

it again today when I went to the store. Funny thing is I shut it off and started it again

and it ran smoothly. Any help would be great.

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It could be anything in the ignition chain like, Spark plugs, Ignition wires, Distributor, etc. BTW: How many miles do you have on your spark plugs? Maybe a good old fashioned tune up is all you need. :rolleyes:

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In addition to the previous suggestions, check the air intake hose for cracks or small holes. This is the large black accordian type tubing going from the airbox to the throttle body. They tend to dry out over 10 years and can form small cracks or holes that will let excess air into the intake. Air that isn't compensated for by the MAF sensor.

good luck.

steviej

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Hey Steveiej,

My car has developed the rough idle as well, so I want to check out the air intake hose. Just a question: if the air intake hose is indeed cracked, do you need to replace it with a new part or can you simply seal up the cracks with silicone or something?

Thanks!

Bryan

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when in doubt swap it out. :D

I don't know if the silicone would hold up to the extreme heat that the tubing will endure. It does sit right next to the plenum and quite close to the rear exhuast manifold. Last thing I would want is silicone getting into the throttle body.

There is always the indestructable duct tape. :lol:

If it were me, I would just get a new one, especially if you plan on keeping the car for a few more years.

steviej

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Speaking of the throttle body (this goes for anyone who has an idle problem at engine start-up), you should check inside the TB and see how dirty it is. It can get gummed up with carbon and fuel vapor over time, and a dirty throttle body is especially seen on high mileage ES's. I used to have the dreaded idle problem in my '01 ES many months ago (which went on for several months because I tried different methods to correct the problem). I finally took the car to a Toyota dealership (in last month June), and they did some magic to clean up the TB. Now my car starts up great every time. No hesitations or anything like it :)

Note to self: When in doubt, bring the ES to Toyota for service work. Sometimes they can be smarter than Lexus service, and do the work cheaper :D

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Hmmm . . . duct tape sounds like an intersting fix for a student budget :P

With regards to the throttle body . . . maybe I have a rough idle because I tried to manually adjust my idle at the throttle body about a month ago. However, it wasn't until about 2-3 weeks later that the problem appeared. Do you think it could be my adjustment that is causing me grief?

Regards,

Bryan

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bdonker, I think I know what manual fix you're talking about in attempts to correct the rough idle problem. I would have to say that that fix is just a temporary fix (so bring that "fix" back to factory spec if you can), and that the real culprit may be underneath the throttle body. Read my earlier post on what to look for inside the TB ;) :)

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the rought hot soak idle problem is only on 97 and up 1mzfe engines as per new emmision controls regulations making it run hotter with more open egr time as well as the temp causing engine gelling also.

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Well, first I am going to get off my lazy butt and adjust the idle back to where it was before. I think I adjusted it quite a bit, which makes the computer have to compensate for my overadjustment.

Hopefully this is my problem. I just hate going to a dealer more than the dentist! :P

Regards,

Bryan

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