Lose Of Power Around 80 Mph Fine Before And Fine After 85

[JosephT]

Well now a new issue has arised. I noticed this when I was coming to work this morning. I was on the highway and at around 75 / 80 mph the car started to buck, no knocking noise or any noise at all but just like lose of power then it was fine after 85, and be4 75.... any ideas?

[91LS400vgb]

perhaps you should test out your throttle position sensor (tps) with a meter or sensor tester while turning it

[914lps]

Had something allng this lines with my 91. I took a chance and changed my fuel filter (it was way past due). Touble never came back. So when was fuel filter last changed in your car?

[JosephT]

Picked a fuel filter up last night and was going to install after work today. A buddy of mine recommended. I don't know when the fuel filter was last changed. I just bought the car 2 weeks ago. Thanks!

[nc211]

Do yourself a favor Jo...do a search on this proceedure as I have heard it is one hell of a messy job! I think Lexls.com has it up on his site. I can't remember if you want your gas tank as low as possible or not.

[91LS400vgb]

Yes, it is quite a messy job. Unlike other cars I worked on, the fuel did not stop flowing while I had the filter disconnected, so make sure you are as prepared as possible. It will help to plug the fuel line, especially if you need the time to swap the bracket from the old filter to the new one. I would recommend getting a filter that comes with the bracket already installed to save you time.

[JosephT]

Thanks for the advice guys, I already read the procedure and i'm having a buddy of mine that is very good w/ cars help me out w/ it. Lets hope this fix's the problem =)

[teamer]

Thanks for the advice guys, I already read the procedure and i'm having a buddy of mine that is very good w/ cars help me out w/ it. Lets hope this fix's the problem =)

Also I highly recommend that you install a LEXUS OEM part. I bought an aftermarket one and tried to install on my 91 LS and it was a nightmare! The threads were not exactly matched and after an hour of fuel spilling onto my arms and shoulders I ended up putting the original back on and having to buy another filter. It was truly a nightmare.

ALSO - HIGHLY RECOMMENDED- before you try to remove the old filter, REMOVE the GAS Filler CAP!!! This will release the back pressure from the fuel so that it does not continually shoot out when you try to install new filter!!!

Best Wishes and let us know how it came out!

[914lps]

Hope it works for you.

When the guy did mine I watched.

Defanitly take your gas cap off. And when you take a wernch to the fittings you are going to get gas leaking out. Tie a rag around your wist. It will soak up the gas and stop it from going down your arm.

[SKperformance]

I can't see how a fuel filter is a problem only at 80-85 mph by its nature it cleans gas.

So by it name it can reduce pressure if dirty ,right?

Well if it reduces pressure it will cause a problem under a certain load . Now what load is changed between 80-85mph?

I don't know of any changes. So by ways of reasonable deduction a fuel filter cannot cause this problem.

A tps is more likely although not the first thing to look at either.

What does you tranny fluid look like when is the last change?

possibility of a TC lockup problem is much more probable than anything as well as a speed sensor.

[914lps]

SK you know more then me. But if he has no idea when it was last changed can't hurt to do it now. When my car acted up it would not stay running under load, and acted up in park. Then seemed to be fine after I reset the computer. To play it safe i did the fuel filter. It was past due antway. Car has been fine. Have driven over 3,000 miles. I know a resent could have fixed "something" ells.... But I have seen a fuel filter act crazy at only a certan fuel flow.

[SKperformance]

Ahh the main difference is yours would do it in park also which means there is no load and still has a problem.

So yours points more to the fuel filter or bad gas.

I do agree changing it may be needed anyway .

Funny part is my LS filter is smaller than my ES one which is in the engine bay and is not even stocked at a dealer as it never goes bad unless you get really bad gas.

[Jeffrey Davis]

Well now a new issue has arised. I noticed this when I was coming to work this morning. I was on the highway and at around 75 / 80 mph the car started to buck, no knocking noise or any noise at all but just like lose of power then it was fine after 85, and be4 75.... any ideas?

This may not be directly applicable but i had a similar problem with a 93 Q45 and it turned out to be the Mass Airflow Sensor. I think it is the proper name, it is the sensor in the line between the air filter and the manifold.

Jeff