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BangEmBoy

Ls400 Firing Issue

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Hello everyone, my name is Randy aka BangEmBoy; and I just want to say hello and introduce myself into the community ......

On another note, I have a problem that I need desperate help with .... Earlier in the year, I bought a 1992 Lexus LS 400 that had been sitting up for a few years . The owner couldn't get a firing problem solved (right bank kept needing a new coil every other month), so they parked it and bought another . I had the car towed home and stared diagnosing the problem .

The first thing that I did was try to get the computer in diagnostic mode, and found out that it didn't have a computer, so I bought one . Further diagnostic revealed that the fuel pump wasn't working, so I changed it and all the filters as well, then I found out that it wasn't firing on the right bank (passenger side), so I replaced the coil, as well as gave the car a complete tune up (plugs, wires,rotors and caps) . Then I changed all the fluids .

After I was done with my maintainance, the car cranked right up, and I drove it for about two(2) weeks . Then on my way to work one day, I noticed white smoke coming from the back of the car . I pulled over and checked it out, and found out that the pressure switch on the back of the power steering pump was bad and that the power steering fluid was being sucked back into the intake manifold . I blocked off the lines and drove to work . On the way home, the car started to loose power, and I noticed that a yellow light that looks like a bird cage with a ball on top of it came on . I parked the car and had it towed home . The next day, I cranked the car up, and it drove fine, so I decided to drive it to work again . The same thing as before happened, it started loosing power .

The next morning when I cranked the car, it idled just fine, but when I gave it gas, it died, and wouldn't start back . I pulled the plugs to see if any were fouled, and when I replaced them, the car cranked and idled just fine; but died once again when I gave it gas .

I decided to find out what was really going on so I did a compression check, a leak down test, fuel pressure test and ignition (spark) test's . All test were within specs except for the leak down and compression test's on cylinder 8 .(160 lbs of compression) . Knowing how stout the LS engine is, experience told me that that wouldn't account for the symptoms that I was getting from the car . Since the car sat for as long as it did, I decided to to change the timing belt and the water pump; when I finised I rediagnosed the car; and foud out that the injectors are not pulsing . They have fire (12.78 volts) going to them, but no ground signal .

I put the computer in diagnostic mode, and codes 24 & 31 showed (I had forgotten to plug the air flow meter) . I plugged the air flow meter in, cleared the codes, and tried to start the car with the same results as before . Just to be on the safe side, I once again entered diagnostic mode, no codes, but the check engine light now constantly flashes .

Can anyone help me out with what I am going through ? Thanks .

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You seem very knowledgeable so I suspect you'll have no problem solving this.

The white smoke from the PS fluid getting dumped into the intake manifold is a very common problem. You can either fix it with a new ACV (air control valve) or plug the lines. Lots of posts here on this problem. It might take a while for the fluid in the intake chain to dry out but it eventually will. You can take the ducting out and clean up with rags and cleaner if you want to speed up the process.

The low compression on #8 can't be enough of a problem to cause the poor running. I'd park this issue to the side for now.

A dead fuel pump (or broken fuel pump relay) will explain not starting. A weak fuel pump (or dirty fuel filter) will explain loss of power at higher engine loads. Rev'ing an engine in neutral is not a heavy engine load so I am doubting you have a fuel pump problem.

The injector electrical isn't overly concerning. The ECU provides a switched circuit to ground to power the injector. The constant +12VDC (switch ignition) is expected and its easier to design the ECU to pulse the signal to ground instead of the +12VDC side.

To me it sounds more like ignition. These cars are famous for coils failing and losing 4 cylinders and just running on the remaining four. You can tell this is happening because CATs will glow red in darkness because unspent fuel is getting burned in CATs. The ECU is not able to detect problems with coils so it won't pop a code.

I am not sure why you have a CEL yet no codes. Usually when you clear codes the CEL is reset. One thought may be that there is a problem coming and you have a pending code that hasn't been written to the ECU log yet. See if it does pop a code in the next couple of days.

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Thank you all very much for your input and help . Here is an update on my Demon Spawn lol .......

Just got in from working on the 92LS . I switch the igniters, TPS, MAF and ECU from my 91LS . The car still runs the same . I installed the listed components from the 92LS on the 90LS and the d$m thing still runs like a champ . I did find one(1) problem though, the trunk wiring harness had a broken white/black wire that I soldered back together .

After installing the parts on the 92, I let it run for a while and then kicked the computer into diagnostic mode; no codes were found .

My mind is telling me that I have a blockage somewhere in my exhaust system, but since I'm no Lexus expert, I would like some feedback concerning this . ALL thoughts, help and advice will be taken VERY seriously; therefore feel free to voice whatever you think .

Once again, thanks to everyone for your help concerning this matter .

(Note : Have checked the firing repeatedly, and all wires are firing on both banks, even under the small reving that I can do before the car shuts off. Don't know if I mentioned it before, but once the car dies after I try to rev it, the onlt way that it will resart is if I take a spark plug out .)

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Was this issue ever resolved  and what was it? I am trying to figure out a sc400 that is only firing on the drivers side. All new ignition, ignitors been swapped, injectors pulse disconnected the cat to check for restriction.  ECU? 

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