I feel like I am all over the place with this car! Well, I looked over my previous post and did some lookin thru old posts. the car does not have erratic idling when I first start it. It starts to occur once the car starts to warm up.

My question is, according to past post the ecu shuts off the maf during warm up. once the car is warmed up it begins to use the maf. this would match my situation.

so, i am going to buy a used maf to see if i get a different reaction out of the car. also, i am going to a non k&n air filter.

As I mentioned before, the car gradually became like this after I cleaned the throttle body, changed to k&n filter, and replaced the maf.

 

It's good that you're getting rid of the K&N filter, I heard bad things with them in the Lexus. Before you go spend money you don't have on a different AFM check the one you have with an ohm meter to see if that is the problem. Idk off hand what it's supposed to read but you can search for it. Did you try unplugging the AFM to see if there is a difference? If you do try to clean it, make sure you are very careful with it and use the correct cleaner on it, they are very sensitive.

 

I'll try to find out what the afm should ohm at and test it. I will also unplug my current afm and see what happens. thanks for your help. i already ordered a used one off of ebay for $48. it has a return policy, so if it is also no good i will return it. I hope it works though. it is frustrating to improve the car by bringing up the maintenance just for it to have more problems.

 

i unplugged the afm and there was no change in the car's behavior. so, it still warmed up without fluctuating then as it warmed up it started to fluctuate and when i put it in drive it fluctuates more erratically. so, I will try the different afm and see what happens.

any ideas as to why the seafoam made the erratic idle go away for a short time?

 

should have the afm/maf monday or tuesday, will update then, if that does not work will try ignition coils and fuel pump.

 

got the afm today.. no change in rpm stuttering problem. so, i decided to take it to advance auto for a battery/alternator check. my batter is just below 12v. it is 11.8. considering the battery was bought in july 2010. will get a replacement then go on from there.

 

the wrong battery size was in the car. got the correct battery (27f & 710cca). also had the alternator and starter checked, they are good. I will swap the throttle positiion sensor with a used one to see if there are any changes. If that does not work will try new ignition coils & fuel pump. I am going to wait until jan to take it to the dealer. until then I am just going try to figure it out on my own.

still confused as to why seafoam cures the problem while it is being burned thru the intake and exhaust, but as soon as it mostly burned off the erratic idle and stumbling returns.

any ideas would be appreciated

 

Dude...change your Engine Coolant Sensor... your problems will vanish. I did everything under the sun...Caps, rotors, plugs,wires, FP, FP filter, MAF, TPS...the last thing I did was Temp Sensor and presto.. The improvement and overall power range was off the Chart!!!
ECT- Autozone $18

see this thread...its the one i used:
https://www.clublexus.com/forums/ls4...ange-pics.html

 

Thanks for you advise. I changed the coolant sensor when I did the wires and plugs. there was a huge power difference. the car actually feels fast now. the car stalled for the first time yesterday. started right back up. on friday, i will switch out the ignition coils to see if that works.

the car just has a bad stutter at idle and when pulling off. I tried a different tps and no change. also while driving there is a drop off but the rpms come back right away.

these problem do not occur when the car is cold and is first started. when it is cold, it drives like it should. by the time it gets to the first temperature line, problems begin and get to its worse when the car is fully warmed up.

what could this be?

 

Did you ever check the AFM with an ohm meter? I know you changed it with another but it could be bad and still not throw a CEL. The reason I say this is my car does the exact same thing when it warms up and I know my AFM is bad with NO codes. I just unplugged the AFM and it runs beutiful but bad MPGs. The AFM also works in conjunction with the o2 sensors. Your first post says you changed one, you could have another bad one. I think you should have brought it to the dealer and had it diagnosed b/c now you're just throwing parts at it with no results.

 

thanks, i just signed up for alldatadiy.com. got the specs for testing the afm. will do that later today. If the afm is good then, i will try the ignition coils tomorrow. if that does not work then coils will be returned.

and you are right, i am probably wasting money. it just feels like that i am one or two parts away from getting it diagnosed on my own.

I am going to check the egr too. it seems like that could be my problem as it is temperature controlled and affected by seafoam (i think) when i run it thru. too bad i cant keep a trace amount of seafoam coupled with keeping the car in its cool state at start up. I would have no issues.

 

Perserverance has WON for now...

After signing up for alldatadiy.com and checking the resistance of the afm and ignition coils, I found my problem.

The afm that i just bought was very borderline with its ohms, so I checked the previous afm and it ohmed perfectly, so swaped that out. then i checked the ohms for the ignition coils. the driver side ohmed within spec. the passenger side was below spec. I swaped out the passenger side ignition coil and presto! the car now idles perfectly. in park it idles at 650 and in drive it idles at 600 without any fluctuation!

So, to recap just in case other people have my problem..

the car idle would be fine when the car was cold. as it warmed up it started to miss and idles would drop from 650 down to 300 sometimes. pulling off too there would be hesistation and stuttering. and cruising speed it would hiccup every now and then.
did seafoam, changed the wires, plugs, coolant sensor, afm, change battery,cleaned iacv, stil not change, bought a fuel pump. once i did the simple and proper thing which is testing the ohms on parts that are affected by temperature. i found my problem and the car is fixed. I have spent a few hundred dollars when I all I needed to spend was $50.

I did crack the ignition coil connector, so will go to the junk yard find a good one and have it spliced in.

thank you for all your help and advice. this forum and lexls.com is worth their weight in gold! To any one having problems, it is a must to sign up for alldatadiy.com

 

Nice!!! An ohm meter is one of the "must have" tools that should be in everyones tool box. Like you said, you should have checked it all out first. (before throwing parts at it) I hate to see people spend hundreds, and sometimes thousands, of dollars that they didn't have to. When you get your timing belt done in January are you going to do it yourself? You got Alldata now, ya might as well. You can save alot of money that way.

 

you are right. I see how to do the timing belt. but to be honest my confidence is so low when it come to major services like that. So, I am going to try to save money on the parts and just pay the dealer 5.6 hours of labor at $105 per hour. so, total i will probably pay $1000 -$1200 for the timing belt job.

 

Dude if you are going to pay the dealer the labor to do the timing belt you might as well have them install their own Lexus parts and have them charged out on the service invoice. This way if something does happen to the parts then both the parts and labor are covered under the 12/12 warranty. If you supply the parts and something happens with the new belt or tensioner that you bought aftermarket then it is going to be very hard to have the aftermarket parts supplier pay for the labor to the dealer to put the warranty parts on. Hope that made sense the way I wrote it.