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My 1993 Es 300 Is Not Shifting Correcty


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I just recenlty bought a 1993 es 300 for $3400 with 105,000 miles. The guy that I brought it from always got his car serviced at Lexus. He told me that the Idle speed control valve needs to be replaced and so I did that and it cost me about $650. My car was jerking and it doesnt pick up right away when I push on the gas. Also when Im in traffic or stopped up the hill my car turns off. I always have to step on the gas coz when I stop then go my car is jerks. After I got the idle speed control valve replaced it is still doing the same thing but not as much and it still turns off on me. The check engine light is not on, but my mechanic said that now that we replace the valve everything opened up and now they saw more problems which now I have to replace the TPS.

So my mom drove my car and she said after what I spent how come its not fixed? So she called the shop and asked them why my car is still having the same problem and the manager said that I have to fix the air flow something and the transmission is not shifting correctly and it will cost me about $2000 to fix everything.

How come my mechanic didnt tell me about this?

I'm not really sure what's wrong with my car. Should I get a diagnostic test? Because Im starting to doubt these people

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There is no clean answer to your question. On the intake of the early '90s ES300's there is an exhaust return tube, and over years it leaves the air intake system just nasty and gunky! It clogs so many things, and goes for the Idle Air Control Valve first (usually, and that's something that you can clean... you probably didn't need to actually replace it, although most shops will suggest you replace it). The IACV shows up as problematic when you try to start the vehicle, but it can also show up as lurching and jerking when accelerating from idle.

The symptoms you describe could come from many things, like an air-leak somewhere in the intake lines, or the throttle position sensor (doubtfully), or the MAF (mass air flow sensor), or faulty injector, or a coil pack giving you problems. If the check-engine light is not on, then that means all sensors are reading/functioning in spec, so it's not an electronic piece/sensor that has outright failed... I'd say you've got an air leak somewhere (crack in your intake duct, crack in one of your vacuum lines, etc.). These things show symptoms that are more pronounced when the engine rpm is down around idle. This is something a trained tech/mechanic will need to search and hunt for... sometimes they are hard to find.

Just for a reference, a coil pack failure, even slight, will trigger the check engine light.

An injector failure could be causing the problem, but will usually trigger a lean/rich code and the check-engine light will come on.

A faulty MAF could run in spec, but cause problems without triggering the CEL (check engine light). I would pull that sensor and spray it out with automotive electrical cleaner (the sensor is easily removed, the spray cleaner can be purchased at your local auto parts store, and just be sure not to touch any of the sensors elements (they are deep in the housing) and wear gloves when using the cleaner... it's nasty stuff.

Unfortunately, it's an older vehicle and components under the hood could be fatigued... you'll need someone will skill to diagnose the system (skill meaning great experience and intuitive automotive troubleshooting... not someone who can just read a diagnostics system reader).

If I had the vehicle, I would clean the MAF and see if that makes a difference. If not, then check the vacuum lines and the main air duct for cracks/splits. I wouldn't let your mechanic just start replacing stuff unless he can be sure what the problem is. If the CEL is not on, then the car is running fairly decent and you've got a little gremlin in there somewhere that needs to be tracked down. Again, I'd go for the MAF and/or hose lines first.

Good luck.

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Ok, first of all does the check engine light come on steady when you turn the key on, some unscrupulous people have been known to either remove the CEL (check engine light), or just break it. First check all the vacuum hoses, they should be soft, not hard and brittle. Then check for vacuum leaks, make sure that the large hose clamps on the big air hose are tight. Once the intake system is air tight, so all the air getting into the engine is coming through the Mass Air Flow sensor, (the big box on top of the air cleaner), then the next thing to look into are the plug wires, they have a tendancy to arc down iniside the sparkplug tubes. I had all these problems on mine, which is 93 ES also. Once I got the CEL working I found that that I had a bunch of codes.... I fixed them one at a time. The o2 sensor codes were being caused by a massive misfire in cyl. # 5 because of the bad wire. As for the tranny, don't believe them, until the engine is running right, its going to buck, snort and drive you batty.... so put the engine back together exactly as the fine Toyota engineers designed it to be...it should idle soooooooooo smooth that you can barely feel it..... then if the tranny still doesn't shift, check the trans. for codes too, the O/D light will tell you some of the important things going on inside the A/T. This is a pretty sophisticated engine, but the injection/emission crontrol system is not that complicated. Once you understand it, its pretty straightforward to troubleshoot. The key is air/fuel mixture and this is determined by the computer, based on how much air is getting to the engine along with temp, throttle position, etc etc.... so if the intake system is not tight, your *BLEEP*ing up a rope, to put it into the vernacular. Find a mechanic that really understands the injection system, and emissions systems and make him your best friend. Good Luck .... if you need any other advice drop me a line..... I basically had to restore my entire system from the air cleaner to the exhaust and everything in between, including the computer. Most of this I learned the hard way, by having to figure out what was happening to my car. Fortunately I have many years of experience and training on mechanics and electronics... thanks to the USN.....go Navy


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