Easy tuning question....I hope

[roach]

Hello I am a new member here and have a problem with my fathers 1990 LS400 that was taken to the dealer and supposedly fixed.

Problem symptoms: Check Engine Light; Rough idling; No Power during acceleration.

Dealer says the check code was a lean condition caused by one of the spark plug wire leads shorting out. Dealer ended up doing a basic tune up, replacing the wires, dist. cap/rotor, plugs. That seemed to fix the problem and the car drove/ran great.


That was 4/5 years ago that the LS400 was taken to the dealershi; but due to my fathers old age, it has only been driven approx. 2000miles since. AND the same symptoms have came up again. The car is rough idling, no power, and smells like unburnt fuel.


I checked the code and it gave me 25 (lean condition); which stumped me as I could smell the unburnt fuel. Checked the plugs and they were all black and fouled. I checked everything else I could (this is my first time ever touching this motor) and I thought I found the problem.
The left(driver side) ign. coil broke at the connector and was barely holding on. This coil was a major pain to remove (I still couldnt get the 14mm bolt back in yet). I exchange it with the right side coil (because it is much easier to get to) and rig it up temporarily to see if that was the culprit. So I put everything back together and start up the car.

Problem is still there (no check codes though). Please give me some suggestions on what to do next. The wires, dist. cap/rotor, plugs are basically new (only 2k miles). Also, Where is the cheapest place for me to purchase an ignition coil. thanks.

 

[KDog]

I don't think you can get aftermarket ignition coils for the 1uzfe. Toyota OEM may be your only option. IF the coil isn't running properly then it would be the cause of the engine running rich due to unburt fuel. It is your most obvious fault.

Are you sure the error code 26 indicating rich condition?

The previous error should have given a rich condition as well. Unless the factory manual has mixed up the labels of the error (which is possible). The only other explaination is that the oxy sensor is dead.
Take the easy option, replace the coil and see if that fixes the problem.

 

[roach]

Im sure it was a code 25 lean condition. (I was stumped at why because I could smell the unburnt fuel; thats why I pulled the plugs)


But looking at the work order sheets that my father got from the dealership it seems that the code 25 was the same code they pulled and supposedly repaired because of shorted plug wires. (Could it be that the ecu sees lean and tries to dump more fuel; fouling the plugs?)


I pulled the wires today and checked the resistance and they were all under 25kOhms and checked the sensors and they were all within spec. I also checked the coils resistance and they were fine. I am almost positive that the coil is working fine.

Im am going to change the plugs, since they are all fouled but what else could I check? Is there a way to test the O2 sensor?

 

[KDog]

If your are positive the coil is fine (some coils will meaure the correct resistance and still be faulty) then it is more likely the oxy is dead, although it should show an error code if the main or sub oxy sensors have a problem.
Don't replace the plugs, just pull them out and burn the residue off with a cigarette lighter.
I don't know of any way to test the oxy sensor other than to monitor its output whilst monitoring the true A/F ratio. You can measure the resistance of the heater coil in it though to see if that is OK. It should be between 5.1Ω - 6.3Ω.

edit: just in case you don't have the specs for the coil. The primary winding should be 0.4Ω - 0.5Ω and the secondary winding should be 10.2KΩ -13.8KΩ

 

[Lextreme II]

Lean condition means you are running less fuel and it sounds like your car is running rich and your spark plugs are blacken. If the O2 is bad, the code OBDI code reader should show up too.

If you want to spend some money. We are getting some custom Nology Hotwire for the 1UZFE. Expensive but much much better than stock.

 

[roach]

hmm, when I measured the coils, I got 12.XXKΩ and 0.8Ω.

They both measured the same so I figure they were good. Do you think the 0.8Ω is a problem? I figure that 0.3Ω is within tolerances of the multimeter?yes/no? (I used a $49.99 sears multimeter) What do you guys think before I got out and spend money on two coils to replace two that are possibly good?


Also, how do you test mode the ecu? Do you jump E and T2 OR do you jump E and T1 and T2? thanks.

Thanks lextreme, but I am not looking to spend money as this is my fathers car and all he needs is to get to point B. The OEM wires that the dealer replaced are approx. 2k miles and measured good with my meter. I am very hesitant to spend money on the coils.

 

[KDog]

Roach,
You are correct. Thoose measurements should be fine for your meter, the contacts of the probes can cause anything up to a few ohms resistance.

Have you measured the main oxy sensor heater coils yet? This should probably be your next step seeing though the car is running rich but is giving a lean error.

You should connect TE1 and E for when the igntion is on for normal testing. And readout fo error codes.

For more advanced testing you can use TE2 and E but the is and order for which you must do things as the the test functioin is more complex.
For this the Battery must have more then 11v.
Throttle valve must be closed, AC switched off, car in neutral.
Ignition off, connect TE2 and E1.
Turn ignitioin switch on. Check light should flash.
Start engine.
Try and simulate the error, I would guess just driving a little bit should do this.
When finished read the diagnostic code by connecting TE1 and E1.
Remove all connections of TE1,TE2 and E1.

 

[roach]

I got a chance to go to the Auto parts store to get new plugs. I went looking for the non-platinum NGKs (1.99) but they didnt have eight. I went to the next cheapest plug they had eight of. (I went cheap because the plugs will probably foul again) Changed to new Bosch Platinum +2 plugs.

Car is running good again. I still dont know why the plugs are fouling.

I did not check the O2 sensors as the plugs seem to cure the problem for now. If the plugs foul again, that will be my next step. How many O2 sensors are there on the LS400 motor? I assume that since it is pre-OBD2 that it doesnt have sensors behind the cat? thanks again.