Loss Of Power In Heat Wit Ac On

[problemsolver]

Hey All, good day. I have a 91 lexus ls 400 and it drove fine until the summer came thru. I noticed that when i turn the AC on and drive it for about 45 mins in 90deree weather, the car starts loosing power. It starts jerking forward and backwards and sometime stops. But am always able to start it up and keep moving with continues jerks and the rpm revving up and down.

This only happens to me in extreme heat with the AC on. If i drive my lexus without the AC it is fine.

Please advise.

thank you

[RFeldes]

Sounds like your compressor is on its last leg. If it goes you may have a mess of shavings throughout your system.

[wwest]

Hey All, good day. I have a 91 lexus ls 400 and it drove fine until the summer came thru. I noticed that when i turn the AC on and drive it for about 45 mins in 90deree weather, the car starts loosing power. It starts jerking forward and backwards and sometime stops. But am always able to start it up and keep moving with continues jerks and the rpm revving up and down.

This only happens to me in extreme heat with the AC on. If i drive my lexus without the AC it is fine.

Please advise.

thank you

A couple of possibilities...

As the A/C clutch is engaged and disenaged a HUGE electrical SPIKE hits the 12 VDC eelctrical system. That spike has been know to cause on-board engine ECU's to execute the wrong instruction stream.

With the A/C on the airflow into the engine compartment will be substantially HOTTER then otherwise so any solid state device sensitive to heat to be intermittent of fail.

You can alleviate a bit of this last effect by making the A/C substantially more efficient thereby less heating of the radiator and engine compartment via the A/C condensor airflow.

To do so use MAX, 65F, cooling, recirculate mode, and the lowest blower speed that will maintain your comfort level.

MAX COOLING...?? Counter-intuitive, right..??

Not actually.

MAX cooling bypasses the Lexus climate control's REHEAT/REMIX airflow path allowing fewer cycles of the a/c compressor. Better FE too. You can improve the A/C efficiency even more by disconnecting the reheat/remix servomotor actuation cable from the hot water flow valve (top/center of the firewall in the engine compartment) and tying the valve into the shutoff position.

[problemsolver]

Thank you, but another thing is that once it starts jerking back and forth and I turn the AC off, the car still wont move until the weather cools off.

Why is that? And the Air blows real good at least.

Sounds like your compressor is on its last leg. If it goes you may have a mess of shavings throughout your system.

[problemsolver]

wow am confused. In lay man terms please explain what i should do again. thank you.

Hey All, good day. I have a 91 lexus ls 400 and it drove fine until the summer came thru. I noticed that when i turn the AC on and drive it for about 45 mins in 90deree weather, the car starts loosing power. It starts jerking forward and backwards and sometime stops. But am always able to start it up and keep moving with continues jerks and the rpm revving up and down.

This only happens to me in extreme heat with the AC on. If i drive my lexus without the AC it is fine.

Please advise.

thank you

A couple of possibilities...

As the A/C clutch is engaged and disenaged a HUGE electrical SPIKE hits the 12 VDC eelctrical system. That spike has been know to cause on-board engine ECU's to execute the wrong instruction stream.

With the A/C on the airflow into the engine compartment will be substantially HOTTER then otherwise so any solid state device sensitive to heat to be intermittent of fail.

You can alleviate a bit of this last effect by making the A/C substantially more efficient thereby less heating of the radiator and engine compartment via the A/C condensor airflow.

To do so use MAX, 65F, cooling, recirculate mode, and the lowest blower speed that will maintain your comfort level.

MAX COOLING...?? Counter-intuitive, right..??

Not actually.

MAX cooling bypasses the Lexus climate control's REHEAT/REMIX airflow path allowing fewer cycles of the a/c compressor. Better FE too. You can improve the A/C efficiency even more by disconnecting the reheat/remix servomotor actuation cable from the hot water flow valve (top/center of the firewall in the engine compartment) and tying the valve into the shutoff position.

[mjrav]

Hey All, good day. I have a 91 lexus ls 400 and it drove fine until the summer came thru. I noticed that when i turn the AC on and drive it for about 45 mins in 90deree weather, the car starts loosing power. It starts jerking forward and backwards and sometime stops. But am always able to start it up and keep moving with continues jerks and the rpm revving up and down.

This only happens to me in extreme heat with the AC on. If i drive my lexus without the AC it is fine.

Please advise.

thank you

Hi,

I've been experiencing similar problems with my 91 LS400.

I had a diagnostic check done and there were indications of an igniter problem.

I haven't cured it yet - it's intermittent - seems temperature related.

Today I put a plastic bag of ice on the igniters and in a few minutes the problem went away. Then later, in the heat of the afternoon, the problem never came back......?