KBH2

I got a 91 LS400, car will start but dies after 2 seconds, it will fire right back up and then dies. I can keep it running by consistently blipping the throttle. If I hold it steady state it will die.

Changed the ECU capacitors, cleaned the IAC valve.

Someone mentioned jumping the fuel pump resistor but I couldn't find it.

Any ideas?

thanks

Yamae

It sounds like an inhibit mode to me. Hope the link below may help you to find the root cause.
https://www.clublexus.com/forums/ls-...ml#post9073825

dicer

Do Yamae's link first.

Resistor is just behind the fuel pump relay that is behind the airfilter. It is bolted to the innerfender on the passenger side.

KBH2

I had to change engine check bulb in gauge cluster trim. Finally got 2 codes 52 and 55.

KBH2

Thanks Yamae and Dicer.

KBH2

52 - No. 1 knock sensor signal

52 - No. 2 knock sensor signal

dicer

So either its both knock sensors, the connections, the wires, or ecu circuits. Who changed the caps? Did they use ESD precautions? Solder joints were made correctly?

Spark goes to max retard with those codes.

KBH2

I did the caps. Yes to ESD and solder.

But wouldn't you also get knock sensor issues if there was a problem with the EFI?

Would retarded timing make it run, almost die, run, almost die etc...

Are the codes a symptom or cause of problem?

Sometimes it will run, almost die, then run, almost die, then run, etc... it can go for 10 cycles of this. But when you turn the key over it will again start right back up and sound normal for 2 seconds and either die or cycle.

Thanks for the responses.

dicer

I have seen codes set that have nothing to do with the problem on some cars.
I would be looking at crank position sensor. Its part of what Yamae's post is about.
If you know what esd is then you might know how to use a scope, you could trace the various signals.
And normal diagnostic stuff, check fuel pressure etc.

aptoslexus

+1. Might be fuel pump issue was my original thought.

DoktorYes

Had same problem, I changed the fuel filter, and it helped with problem. Check last time your fuel filter was changed. Good Luck

RA051823

You can put a fuel pressure gauge on the fuel rail and see what kind of pressure you are getting.