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Climate Control Issue-Went Dumb, Engine Bucking


Greg5OH
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the climate control decided to stop aknowledging the interior temp ithink. i set it to 18 and ita still pumping hot air. try to keep jusy the front defeoster on and it gets too hot even eith fan off. Put it to auto, it takes the fan speed to max and im sweating buckets-what the hell! Its worked fine last week!

And then the engine bucking. while crusing or lightly acceleratong it will buck HARD. Can see rpm dip down a few hundred, then resumea normal operation. ita pretty violent feeling. can be on a perfectly smooth road and will still do it. Its random, somwthimea will do it a few times in a few mins, sometimes once an hour.

Could it be a failing tps? im going to use my fathers good multimeter to do the ripple test-see of its the ecu caps

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IMO, you should be telling people every time you start a thread about all the problems you have had due to lowering your car so much that a tire chewed into a critical wiring harness.

There are a number of interrelated components in these cars as a friend of mine found when I fixed the long-dead radio in his 1999 LS400 by bypassing an ECU in his trunk.

Some of your new problems may be related to your chewed wiring harness. For example, the wire for the outside temperature sensor behind the front bumper may run through the same harness that your tire chewed up. It is, of course, connected to your HVAC (climate) control module above your radio head unit.

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Oh ease up ya grump.

The harness has been fixed.

Greg, that kind of response to 1990LS400 is not warranted nor going to help your situation. I, for one, do not appreciate your attitude toward him. Jim is a venerable poster on LOC and has made many, many valuable contributions. He also makes a good point. Just because you think you have the harness patched back together, it could still be an issue. Your engine bucking could be due to an intermittent connection somewhere. You have to consider all potential sources of root causes. Ya, we do have a lot of 'grumps' on this forum(including me) but we are some pretty smart and experienced grumps so it would be wise of you to listen up and learn. Please tone the attitude down or go try your luck on another forum.

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All we ask is that you show some respect for those who take the time to try to answer. We are not always right but we are trying to help. As a young guy, you need to know when to refrain from lashing out. If I ever get into that mood, and I do occasionally, I step away from the keyboard and let it go for a little while. Usually when I come back, I am calmed down and can answer in a more civil manner.

I don't 'hate' on lowered cars. It is just that you really have to be careful that a mod is well designed and thought-out before applying it. Whoever slammed your LS should have thought about the wiring harness getting chewed up before it actually got chewed up. If you are careful about the mod, it could be ok but many are not well thought-out and lead to other failures of the car. The Lexus engineers spent many, many hours doing tedious design work and you cannot expect to come in and just modify some aspect of that careful design without some consequences.

So, back to your issue. Try scanning for codes as a first step. If the engine bucks on a fairly consistent basis that will give you a good opportunity to do some testing. You are going to have to divide this into an ignition or fuel issue. Then go after the root cause. I could just see some chaffed wire touching chassis ground causing your problem.

I see you are 'working' both forums on this one.

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