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93 Ls400 Misfire?


AimHer3
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how u doin guys i just picked up my lexus about a month ago didnt really have any issues with it until i took it on the highway ive been gettin this heavy shaking around 65 mph and then after that its been shaking at 45 and 65 now almost like it was a stick and i was about to stall out u guys have any idea what might cause this?

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how u doin guys i just picked up my lexus about a month ago didnt really have any issues with it until i took it on the highway ive been gettin this heavy shaking around 65 mph and then after that its been shaking at 45 and 65 now almost like it was a stick and i was about to stall out u guys have any idea what might cause this?

Do you have any service history on the car? What's the mileage on the car?

What year is it? Has anything been replaced recently? Do you get this

problem at any speed or just the range you mentioned? How does it idle?

Is it smooth and what's the rpm? Any problems starting? Get the idea?

We need more info from you. You need to help us in order for us to help

you.

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sorry guys for the lack of info its like the whole car shakes...uhh its a 93 Ls400 mileage is like 135K there isnt any problems starting at all it idles a little rough like it feels like its skipping when it idles dont really know the rpm when it idles but its not past 1g and it is only at certain speeds just the ones i mentioned 45 and 65 u go past or below them the rides smoother

i was thinking i am in the need of a tuneup could it be the plugs and wires?

and i got brandnew tires put on cuz the old tires were shot.

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sorry guys for the lack of info its like the whole car shakes...uhh its a 93 Ls400 mileage is like 135K there isnt any problems starting at all it idles a little rough like it feels like its skipping when it idles dont really know the rpm when it idles but its not past 1g and it is only at certain speeds just the ones i mentioned 45 and 65 u go past or below them the rides smoother

i was thinking i am in the need of a tuneup could it be the plugs and wires?

and i got brandnew tires put on cuz the old tires were shot.

A warm engine should idle at 650 rpm +/- 50. Rough idle could be coolant temp sensor, incorrect idle mix,

Vibration could be out of balance wheels, loose wheel nuts, alignment, wheel bearings, loose/worn suspension components.....tie rods, control arms, ball joints. You should read some recent threads with discussions and suggestions for similar problems to yours.

Here's one: http://us.lexusownersclub.com/forums/index...showtopic=43613

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Regarding the title of your thread, if there was a regular misfire, the Check Engine Light would probably go on as I have seen codes in the ODD II which come up if any one of the spark plugs doesn't work. Hold on., you have a 93. Maybe the OBD 1 also has similar codes???

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  • 2 weeks later...
How does coolant temp sensor cause rough idle?

Ecu uses the sensor reading to adjust mixture. I would also check the ISC. The valve could need cleaning. Another check would be for an intake leak say between the air flow meter and the cylinders. If you have a bad slope in the fuel curve near idle from erratic air flow, the ecu would search to correct mix errors. Going from overly rich and starting to stumble/stall to overly lean and upping the revs. Rough idle.

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  • 1 month later...
sorry guys for the lack of info its like the whole car shakes...uhh its a 93 Ls400 mileage is like 135K there isnt any problems starting at all it idles a little rough like it feels like its skipping when it idles dont really know the rpm when it idles but its not past 1g and it is only at certain speeds just the ones i mentioned 45 and 65 u go past or below them the rides smoother

i was thinking i am in the need of a tuneup could it be the plugs and wires?

and i got brandnew tires put on cuz the old tires were shot.

I have the same mileage and symptoms that kicked a missfire code on 5 and 6. Code PO305,6. I also had a flashing Trac off and engine light. Both occured after I washed my engine. I had the Lex dealer read the code for $115 just to be sure. They quoted $850 for 2 caps, rotors and new wires. I ordered new caps and wires (powermax) from Rockauto. The change took two days but was worth the effort. I recommend you drill or using a soldering iron melt a small hole in the cap cover to access the lower cap screws. To do the job right, you would have to remove the belt and upper radiator hose. The good news is I found a knicked wire and lots of build up on the cap and rotors. Definitley a do it yourself job with basic metric tools. Following the change out, she ran normal on start-up. I drove to Autozone for a free code read and to clear the stored errors. All clear...All good. I also run Pri-G in the fuel. Wife finally let me out of dog house. 95LS400 :D
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