BigRon239

My 93 LS with trac runs really rough, almost like it was just running on 4 cylinders, but it goes back to normal when its about a 1/4 warmed up. It's pretty bizarre to me why its doing that. I get a check engine light for code 13, which is rpm signal #2, but i seriously doubt its the cam sensors that are doing this, or the timing is off. Once the car is warmed up it starts up and goes without any problem. Any suggestions or comments would really help! Thanks!

LScowboyLS

code 13 is G, NE signal circuit (No. 2)

this is normally either ECU, cam or crank sensor or else jumped time (usually on just one tooth of one cam)

failing ECU capacitors would usually be the culprit in the case of an ECU issue

you may want to also check for a dirty AFM (MAF) - clean it with gentle compressed air and possibly a super soft dry clean cotton or chamois cloth

do not use commercial MAF cleaners!

also check Engine Coolant Temp Sensor (the one with two wires) that can cause bad running when cold

BigRon239

I'll clean out the AFM tomorrow, but I have a feeling your right with the Engine Coolant Temp Sensor, makes more logical sense. Thanks a lot!

python

iTrader: (4)

cam sensor/connector or timing jumped..how many miles on the car and when was the timing belt/water pump done? a bad afm would not have the symptom when its cold then clear up when warm..besides ive never heard of someone cleaning an afm/maf because a check engine light has appeared then it fixed the issue

LScowboyLS

oh yes, that is precisely what could happen, the AFM is a type of Kármán vortex MAF, the MAF provides data to the ECU which is used in conjunction with the feedback from the pre-cat O2 sensors and the ECTS, TPS and rpm information to calculate air/fuel ratio, but because the O2 sensors use fuel trim to adjust air/fuel ratios in normal operating conditions called "closed loop", a dirty MAF can be disguised better on a warm engine than a cold one, because the O2 sensors, though heated to speed up the transition to closed loop, are not accurate during warm-up and therefore not relied upon by the ECU until they have reached approximately 350 degrees, this results in higher reliance on MAF information being accurate during warm-up when the ECU must utilize its map along with the MAF information to adjust the fuel to the injectors without the fine tuning of the O2 sensors, (this period before the O2 sensors are completely warm and are ignored is called "open loop", much like wide open throttle (WOT) is also open loop, as you want a more powerful fuel ratio at that time that the narrow band O2 (lambda) sensors would allow.)

python

iTrader: (4)

http://us.lexusownersclub.com/forums...s-400-code-13/
http://us.lexusownersclub.com/forums...shows-code-13/
and finally joes thread
https://www.clublexus.com/forums/ls4...code-13-a.html
been on this forum as well as lexus owners club for over 5 years...any code 13 that has come up has always been cam sensor or timing belt related...
the coolant sensor would make sense for the idle problem but not the code he has

BigRon239

Timing belt and water pump were done 25k ago, and I only have 140k on the car, I'm going to try with the Engine Coolant sensor later today or tomorrow and let you guys know. I don't get the code when the car gets hot so i'm ruling out any timing issues until I have tried everything else.

LScowboyLS

jumped time or defective cam position sensor doesn't tend to straighten out when the car gets warm, if the cam position sensor was intermittently working only when warm, then maybe

python

iTrader: (4)

code 13 isnt a afm related issue
https://www.clublexus.com/forums/per...on-issues.html
if it was code 24,31,32..then i could see it possibly being a afm..anyways..good luck with this and keep us posted,possible ecm?

BigRon239

UPDATE: I changed the Engine Coolant Sensor, and the car does run better when its all warmed up but still has the same problem when starting up. I am going to swap the ecm with my old one that had the hesitation problem at 2,000 rpm but started up fine. Will keep you guys posted.

BigRon239

Update #2: Ecm is not the problem, I'm thinking it might be either distributors or rotors now.

paulybear

I know it's an obvious check but there could be an intake, injector or other vacuum leak? While car at idle and cold, you can spray some carb cleaner around all the intake, throttle body, injectors and vacuum hoses (anything related to your intake system and vacuum). I'm sure that if you have a pretty good leak, and the car runs bad enough cold where the carb cleaner check wouldn't change the idle much you could also check it warmed up. I've had vacuum leaks cause various idle idle issues at different temperatures and idle speeds depending on what part of the engine has the leak during temperature expanding and retracting. Also the iac valve can cause idle roughness if not working correctly. I just dealt with both the vacuum and iac problems on this ls400 my step dad recently bought. The vacuum leak check is a cheep and easy test to preform thankfully. In my case it looked like the previous owner replaced the starter and on reassembly of the intake didn't bother using new gaskets :-[. Hope this helps. Paul

paulybear

Also with the vacuum leaks the car would run ok once warned up.

BigRon239

Yes, the timing belt indeed did skip a tooth. Reset the timing and its working perfectly now, no more ce and trac off lights!

python

iTrader: (4)

lol,figured as much..anyways glad u got it resolved.