PureDrifter

iTrader: (10)

while the AFM from a '91 will probably work, the ECU will not due to mid-gen changes from the 89-92 and 93-94 model years.

deanshark

My mistake, I haven't owned this car long enough to do too many repairs yet, I don't know why but I was thinking 91 - 94 ECU were the same.

StevieA

OK, So I get the AFM & they took off the MAF module only. Looks dirty so right in the lot I give it a few shots of electrical cleaner and let it sit in the sun & breeze while I take mine off my car. Install the '91 MAF and take off (late for an app't & had my 3 year-old with me) hoping if the MAF didn't dry in the sun it would on the 30 min drive home at 120kph.

So it worked no better.

5 min later engine and TRAC lights come on.

Performance seems to be a bit better further I go but still doesn't have the pull at 3,000 to 6,000 like it should. Still surging and starving for something.

When I get home I check the codes:

25 - Air Fuel Ratio Lean
31 - Air flow meter signal

22 - Air bag warning light (from me missing the ports in the TDCL diagnostic port in the dark last night I think)

51 - TRAC - Problem Engine Control SYstem.

Going to go clear the codes and go for another spin hoping the MAF needs more time to dry - doubtful though. May post a video or two.

Plan is tomorrow return the MAF and get the ECU to try it - they also have a '94 there junked with higher mileage that I'll try the ECU off of.

StevieA

Took it for a drive after I cleared the codes. 20 minutes or so and the lights didn't come back on. Although performance isn't where it should be it did seem better. A little confused now, not sure if my old MAF was no good or not.

Here's a few videos showing tonight's performance

1st kickdown into 1st gear

http://www.youtube.com/watch?v=ErUnO3wRqAo


Now 0-60 in 11.93 seconds

http://www.youtube.com/watch?v=3ME6XjVFT_Y

Now kickdown at highway speeds - notice the bog/hesitation when I nail it

http://www.youtube.com/watch?v=fblNVFHx6OA

Och

iTrader: (3)

Stevie, thats about the same as mine performed. It also ran 11-12 seconds from 0 to 60. I even invested in a bran new MAF and that didn't help either.

When running 0-60 from dead stop, listen to your engine at around 2-2.5k RPM. Can you hear slight pinging? Sometimes it helps to park next to a wall, open your window, press on the brake, put the car and drive and let the RPMs climb to around 2-3K. You should be able to hear the slight miss. Its very very quiet, not violent at all, and not likely to cause any damage to the engine, but it was there in my car.

As far as the codes that you are getting, the TRAC light will go on every time the Check Engine light is on, so thats nothing to worry about. And these - 25: Air Fuel Ratio Lean
31: Air flow meter signal, you were likely getting them because you cleaned the MAF and didn't let it dry enough. If I understood your posts, you no longer have any codes after the MAF dried off, so its fine. If your buddy's car runs fine with this MAF, that means MAF is not the issue.

Looking forward to you swapping the ECUs and testing it out!

StevieA

Och

Now that you mention it, I do remember slight pinging around 2,500

Brother, I just read your WHOLE THREAD holy ****! Sounds like you bought the car as a slouch. Yes, mine was sitting for two years but for the 1st two-three months I owned it there were no performance issues.

For example, there's a steep hill leading to my house. I used to enjoy punching it at about 50kph down into 1st and letting it rev out and into second. The wave of torque after the shift into second was mildly disorientating - it was awesome, would set you back in the seat and scenery would blow by.

Then suddenly, in one day, it was a slouch. Where it used to pull harder as the rpm's increased (like 3,000-6,000) like a HEMI or mildly like a two-stroke engine, it now seems to pull less as the rpms increase, often with the feeling of obvious surging, like its starving for fuel or something.

You know, a plugged catalytic converter really makes sense in my mind based on what I'm describing above.

So anyway, the catalytic converter is on my list to investigate however after reading your thread I want to satisfy some curiosity of both yours and mine and I'm going to try the ECU off the '94 that's junked with I believe high 200k's on it and report back. Should have time to do it tonight. $25 non-refundable :-p vancehanesautoparts.com

If you read this how about throwing some hints on removal/re-installation of the ECU?

Thanks

Och

iTrader: (3)

So basically your symptoms and mine are exactly the same. I suspect that most of these 1st generation LS400's that are still rolling around suffer from the same issue, but most people don't even realize it, they think that this is the way they ran from the factory.

Look at top gear police challenge, where one of the car they used was our first gen LS400. Scroll to the 4:06 mark of the video, and see the way it takes off - it bogs just like ours. http://www.youtube.com/watch?v=DtTnfFH2Hjc

In any case, I doubt if it has anything to do with cat converters, because mine usually ran much better with MAF disconnected, although the idle sucked and the car would sometimes stall. You've mentioned that you tried to disconnect the MAF, but the didn't help any. I just remembered, when I disconnected the MAF, I would reset the ECU and then it would run great. If I didn't reset the ECU it kept running like crap. Try it out.

Now, with the MAF disconnected obviously your car is relying only on O2 and ECT sensors to calculate air/fuel ratio. It might even ignore O2 sensors I'm not sure. So of course the A/F ratio isn't very accurate like this, and sometimes running with MAF disconnected I would hear a very distinct ping, and after that the car starts running just as bad as it did with MAF connected. My guess is that once the ECU detects a ping, it retards timing and that makes everything even worse. Its also probably the same thing thats happening with MAF connected, there's ping caused by incorrect A/F ratio, yet ECU thinks its because of timing, and by retarding timing it makes things go from bad to worse.

One thing that I always wanted to try, but never got to trying, is to disconnect knock sensors, and put in a resistor that would fool the ECU into thinking that knock sensors are there but not detecting any ping.

As far as removing the ECU, its relatively simple. Open the glove department door, and there are two plastic tabs on it, one on each side, next to the levers that hold it. Snap these tabs off and take off the levers - now you can take off the door. After you do that, you can pull out the glove department lining, and then you'll see three or four 10mm bolts that hold the lower panel to the dash. Remove them. The snap off the most bottom panel, and I believe you should see more 10mm bolts, that hold the lower panel - remove them and the panel comes off. There you'll see your ECU.

deanshark

AWESOME video. When the LS4 took off he it didn't bog down, he just gradually left. Anyway, when you unhook the AFM, from what I understand, it also bypasses the O2 sensors. That's why I was saying test them if you only changed one of them. I have my AFM unplugged and it runs 95% better. One of these days I'll get to fixing that. (when I can afford it)

StevieA

Hey guys, for the record. I just unplugged MAF to no avail - 2nd attempt

Steps:

Engine off.
Unplugged MAF
Removed EFI fuse for 10 seconds
Replaced Fuse
Started & went for a drive - engine light illuminated. Worked like garbage.

Shut off
Re-plugged MAF
Removed EFI fuse for 10 seconds & replaced
Started & engine light gone, performance back to normal - which is better than without MAF but still not what it was a month ago.

blunden

Some of those codes you may have gotten because you unplugged the MAF sensor. If you clear the codes, try running the "Test Mode" diagnostics (see attached). Let me know what codes come up and we can look at the manual procedures.

StevieA

Travelled 30 min on the highway with my MAF installed to junk yard to pick up used ECU. On the way back, at same point in the trip as the other day, engine and TRAC came on. Got home & they showed same as the other day (with used MAF) all except code 31 - Air flow meter signal


25 - Air Fuel Ratio Lean

22 - Air bag warning light (from me missing the ports in the TDCL diagnostic port in the dark last night I think)

51 - TRAC - Problem Engine Control SYstem.

So I cleared all but airbag codes and began installing used ECU see pic below used on right mine on left



Result? performance no better, still *******y

Bit different though, now off the line it's worse, 0-60 around 14 seconds, but stab it anywhere after 40kph and works almost half decent

sigh

next steps - if I get a chance at my uncle's garage, I'll unhook the exhaust before the catalytic converters & see if that does anything - I have beennoticing a slight "whurrr" or "whizzz" sound from under the floor like a slight supercharger whine....hmmmmmmmm.......

Other than that, nearest Lexus dealer is 160km away. I'll be working that way in a few weeks so I may leave the car with them.

Or I may just accept my fate as a low-budget cruiser that no longer gives thrills.

Och

iTrader: (3)

If its an ECU from an old car, it probably suffers from the same issues. Unless you can find someone with the same car that runs properly and swap ECUs, don't bother with junked ones.

Your other option would be to buy a whole new ECU for $900-1200, or get an aftermarket standalone ECU. I was toying with the idea for a while, just never bothered to.

Honestly being that the car is 20 years old, you're better off saving your money and just accept it as is.

StevieA

Thanks Blunden! - gonna give that a try, may be a day or so.....

But do I need special tools? What's an SST? I've just been connecting one wire to two terminals like Te1 and E1 for example.....

deanshark

That's all you need is the wire. SST stands for "Special Service Tool". It's just that the dealer has special tools for every specific job.

StevieA

Too bad cuz now I'm married with a 1 and 3 yr old & single income so all my "adrenaline fulfillers" have been sold cuz I can't afford anymore. Used to have CR500's that I woould catwalk up and down the road for a release. And three snowmobiles one was a big bore 1,060cc triple PSI motor in an Arctic Cat chassis that would haul the skis to 85MPH.

So now my thrills were coming from my 6km drive to and from work in my 250HP , $2,500 Lexus.

but now it's down to only about 150HP and I'm cruising a slow old man's car and my fun is gone again - LOL

I NEED A 750HP something