HELP!! 1991 LS 400 Engine Dies When Turning
11-01-18, 10:22 PM
#1
Driver School Candidate
Thread Starter
HELP!! 1991 LS 400 Engine Dies When Turning
This is crazy! I had the engine replaced in my 1991 LS 400. I now have about 3000 miles on it. Runs great, EXCEPT that it occasionally dies without warning when I make a sudden stop, when I am making a left turn or U-turn to the left, or when I am slowly going up a hill in traffic. The left turn issue is the most frequent. Does not happen every time. It starts right back up and runs fine after every occurrence. No engine warning lights or anything like that before it just quits. Runs and accelerates perfectly smooth otherwise. Had fuel pump and sock replaced when engine was replaced. Always has more than 1/4 tank of gas. Almost got hit turning onto a freeway on-ramp last night, so I really want to get to the bottom of this. Any help would be appreciated.
11-01-18, 11:40 PM
#3
Moderator
Is your car lowered?
11-03-18, 05:29 PM
#6
Driver School Candidate
Thread Starter
Actually, I corrected the trunk wiring issue a month ago. The symptoms from that were 'Reverse' indicator light came on every time stepped on the brake; premature dowmshofting, and a few other dash light issues that I cannot recall right now. BUT, now I am getting ramdom Oil Level, Check Engine, TRAC OFF, and TRAC lights coming on and going off at completely random times. My highest priority is to solve the random engine ****downs. Meanwhile, I will re-check the trunk wiring to eliminate that as a possible cause. Will also follow up on another suggestion to replace some capacitors.
11-03-18, 06:44 PM
#7
Driver School Candidate
Thread Starter
I'll give it a shot. Hope it works.
Trending Topics
01-17-19, 06:33 PM
#8
Driver School Candidate
Thread Starter
The nightmare continues! First, I want to thank all you you all for the advice on resolving my '91 LS400 issues, BUT...the nightmare continues. I sent the ECM to Module Masters in Idaho (one of the places suggested in the "All My Crazy Lexus Problems Solved..." thread) to have the capacitors replaced. I sent them a description of the problems and included the capacitor information in this thread as reference material. They said that they only used Panasonic capacitors, and would only warranty their work if THEY obtained the capacitors. They advised that they have had no issues with Panasonic, and have done this kind of work before. The tech was aware of the specific capacitor manufacturer / model# concerns, but advised that those were no longer concerns, as the industry has resolved those problems. Well, they know more about this than I do, so I went with it. Got the ECM back in installed it. Still have the problem with random warning lights coming on and going out, and the engine still cuts out randomly without warning as described in my original post. However, the problem does not occur as frequently as it used to.
Now the car is at an independent shop in Southern California for further diagnosis. So far they found a code for the Throttle Position Sensor, so that was replaced. They are still driving the car to see if the problem continues. Any ideas, while I am waiting for results? I HAVE to get this car running right, as I am giving it to my sister, so it has to be safe to drive.
Thanks!
Now the car is at an independent shop in Southern California for further diagnosis. So far they found a code for the Throttle Position Sensor, so that was replaced. They are still driving the car to see if the problem continues. Any ideas, while I am waiting for results? I HAVE to get this car running right, as I am giving it to my sister, so it has to be safe to drive.
Thanks!
01-18-19, 11:02 AM
#10
On the "turning" ...
These cars have a problematic feature, the idle up air valve on the power steering pump. It is a valved air path from the air intake to the intake manifold (bypasses the throttle body). When the PS system needs to turn while the engine idle is low (e.g., when parking), this valve opens up, allowing some extra air to flow to the intake manifold, increasing idle speed to provide more PS power and prevent the engine from dying.
So that's what's supposed to happen. Great system, but the valve will leak after a while, allowing PS fluid to enter the intake manifold, causing white smoke on start-up due to that PSF burning off all at once. Replacing those valves is a commonly needed thing. Some people instead save some $$ and just replace it with a plug that stops the leaks but removes the feature. First thing I'd do is look for that valve and those hoses: air intake-to-PS-valve and PS-valve-to-intake manifold. White smoke on startup? PS fluid needing constant refilling?
So maybe you've got a combination of issues - there is something that makes your idle a little on the low side, and also there may be a problem with your idle up air valve, which causes it to die when trying to turn. Even if the idle-up valve is fine, consider this an explanation for why the turning causes some extra load on the engine (due to the PS), which may cause an already low-idling engine to die.
Sounds like you're doing a lot of good things to improve the engine. I expect this problem is a minor one and you'll get it solved.
If analyzing the RPM, I'll advise to not necessarily believe what the tach says - it can easily be off.
These cars have a problematic feature, the idle up air valve on the power steering pump. It is a valved air path from the air intake to the intake manifold (bypasses the throttle body). When the PS system needs to turn while the engine idle is low (e.g., when parking), this valve opens up, allowing some extra air to flow to the intake manifold, increasing idle speed to provide more PS power and prevent the engine from dying.
So that's what's supposed to happen. Great system, but the valve will leak after a while, allowing PS fluid to enter the intake manifold, causing white smoke on start-up due to that PSF burning off all at once. Replacing those valves is a commonly needed thing. Some people instead save some $$ and just replace it with a plug that stops the leaks but removes the feature. First thing I'd do is look for that valve and those hoses: air intake-to-PS-valve and PS-valve-to-intake manifold. White smoke on startup? PS fluid needing constant refilling?
So maybe you've got a combination of issues - there is something that makes your idle a little on the low side, and also there may be a problem with your idle up air valve, which causes it to die when trying to turn. Even if the idle-up valve is fine, consider this an explanation for why the turning causes some extra load on the engine (due to the PS), which may cause an already low-idling engine to die.
Sounds like you're doing a lot of good things to improve the engine. I expect this problem is a minor one and you'll get it solved.
If analyzing the RPM, I'll advise to not necessarily believe what the tach says - it can easily be off.
01-28-19, 01:39 PM
#11
Driver School Candidate
Thread Starter
On the "turning" ...
These cars have a problematic feature, the idle up air valve on the power steering pump. It is a valved air path from the air intake to the intake manifold (bypasses the throttle body). When the PS system needs to turn while the engine idle is low (e.g., when parking), this valve opens up, allowing some extra air to flow to the intake manifold, increasing idle speed to provide more PS power and prevent the engine from dying.
So that's what's supposed to happen. Great system, but the valve will leak after a while, allowing PS fluid to enter the intake manifold, causing white smoke on start-up due to that PSF burning off all at once. Replacing those valves is a commonly needed thing. Some people instead save some $$ and just replace it with a plug that stops the leaks but removes the feature. First thing I'd do is look for that valve and those hoses: air intake-to-PS-valve and PS-valve-to-intake manifold. White smoke on startup? PS fluid needing constant refilling?
So maybe you've got a combination of issues - there is something that makes your idle a little on the low side, and also there may be a problem with your idle up air valve, which causes it to die when trying to turn. Even if the idle-up valve is fine, consider this an explanation for why the turning causes some extra load on the engine (due to the PS), which may cause an already low-idling engine to die.
Sounds like you're doing a lot of good things to improve the engine. I expect this problem is a minor one and you'll get it solved.
If analyzing the RPM, I'll advise to not necessarily believe what the tach says - it can easily be off.
These cars have a problematic feature, the idle up air valve on the power steering pump. It is a valved air path from the air intake to the intake manifold (bypasses the throttle body). When the PS system needs to turn while the engine idle is low (e.g., when parking), this valve opens up, allowing some extra air to flow to the intake manifold, increasing idle speed to provide more PS power and prevent the engine from dying.
So that's what's supposed to happen. Great system, but the valve will leak after a while, allowing PS fluid to enter the intake manifold, causing white smoke on start-up due to that PSF burning off all at once. Replacing those valves is a commonly needed thing. Some people instead save some $$ and just replace it with a plug that stops the leaks but removes the feature. First thing I'd do is look for that valve and those hoses: air intake-to-PS-valve and PS-valve-to-intake manifold. White smoke on startup? PS fluid needing constant refilling?
So maybe you've got a combination of issues - there is something that makes your idle a little on the low side, and also there may be a problem with your idle up air valve, which causes it to die when trying to turn. Even if the idle-up valve is fine, consider this an explanation for why the turning causes some extra load on the engine (due to the PS), which may cause an already low-idling engine to die.
Sounds like you're doing a lot of good things to improve the engine. I expect this problem is a minor one and you'll get it solved.
If analyzing the RPM, I'll advise to not necessarily believe what the tach says - it can easily be off.
01-31-19, 08:56 AM
#12
regarding power steering pump air up valve:
https://www.clublexus.com/forums/ls-...ing-bible.html
more here as well, referenced here as an IAC valve:
https://www.clublexus.com/forums/ls-...ystem-diy.html
https://www.clublexus.com/forums/ls-...ing-bible.html
more here as well, referenced here as an IAC valve:
https://www.clublexus.com/forums/ls-...ystem-diy.html
Thread
Thread Starter
Forum
Replies
Last Post