Weird issue

[TREYFIGGS]

I have a 1990 ls400 and is idling really low and wife said other day it totally lost power out of nowhere. And when it was dying the RPMs seemed to really be lulling. Amy help would be greatly appreciated. Thank you

 

Trey

[sha4000]

Welcome to the forum. At this point all of these cars idle low just due to their age. Is the check engine light on? ?How many miles and when was the last time the car was tuned up?

[TREYFIGGS]

Only owned it about a year. Haven't done a tune up. I just put new fuel filter in. No check engine light. Car has just over 200000. Drove it yesterday and seems when is in great under a load it wants no like surge. Thank you for any ideas.

[Spartan0536]

Sounds like it could be the throttle body, it is a mechanical throttle, and my old Camry had that issue before (1995 Camry LE). How old is the battery, and is the Alternator holding up?

The reason I ask about the alternator is that it's a common issue on LS400's with over 100K miles to have power steering fluid leak onto the alternator and kill it.

[Exhaustgases]

Lots of things can cause strange problems in these cars. There is the ECU problem, IAC motor, broken cracked vacuum lines, Engine coolant temp sensor, and other sensors. Not easy to track down lots of these problems on an OBD1 system. Trying to read codes is a good place to start, and a code can be set with the check engine light not being on.

[TREYFIGGS]

1 hour ago, Spartan0536 said:

Sounds like it could be the throttle body, it is a mechanical throttle, and my old Camry had that issue before (1995 Camry LE). How old is the battery, and is the Alternator holding up?

The reason I ask about the alternator is that it's a common issue on LS400's with over 100K miles to have power steering fluid leak onto the alternator and kill it.

Replaced alternator recently...because of the poor design...tested the electrical today. Battery and alternator perfect. 

[TREYFIGGS]

1 hour ago, Exhaustgases said:

Lots of things can cause strange problems in these cars. There is the ECU problem, IAC motor, broken cracked vacuum lines, Engine coolant temp sensor, and other sensors. Not easy to track down lots of these problems on an OBD1 system. Trying to read codes is a good place to start, and a code can be set with the check engine light not being on.

I was told with the OBD1 that of I don't have a check engine light on it won't give any codes? I'll use a jump wire tomorrow, hopefully it gives me something. Thank you