///MDex

During my recent 55k service, I asked for my TPS to be replaced due to the low idle issue while in D that has been discussed here at length.

I got a call from the tech, stating they had checked all parts including the TPS, 02 sensors, and all were operating to spec, but here is what they found.

When they placed their hand over the filter on the intake, the low idle in D ceased.

This leads me to believe that there may be a mis-mapped variable somewhere in the piggyback ECU.

Now, I didn’t have time to personally verify this, and I bet, if the dealership wanted to make $150 installed for the TPS, which they had on hand, they would have.

The TPS switchout soulution has worked, but not sure if those drivers had your intake.

I have not modified the intake or heatshield in any manner.

You guys have any light to shed?

You have my number if you'd like to reach me.

Thanks.

lexlyf

Interesting & strange at the same time. If I had another customer's similar experience to draw from...I would have a ready answer for you, but this is a first.

I've put a call in to the Guru & just waiting a return call so that we can diagnose possibilities on the phone.

I'll hit back as soon as I get some answers. I'm also expecting your boy...DaveGS4... a little this afternoon/evening.

///MDex

Thanks Marken for the timely reply.

I know - I await Dave's comments and dyno graphs for my purchase / swap decision on the new ECU.

///MDex

Actually, see if you can get Dave's to do it today, because he gets the low idle too.

lexlyf

We'll take a look, as Dave is suppose to here around 6/7pm est.

Mo & I talked at length about your car & could not derive as to why the low idle you are experiecing.

We did determine that the only reason for the idle pick up after your tech put his hand over the filter was b/c he is actually creating a more lean scenario (your car's engine is starving for air because of the restriction in the air path) & thus to counterbalance that, your ecu increases the idle.

Mo & I will take a closer look upon Dave arriving, but once again we could not determine any problem associated with the SRT piggy-back Ecu.

///MDex

So its rich without the 'hands', right? I thought the PB-ECU modified the 02 levels. That's why I tied it into the intake.

I guess the ECU modifies the 02 levels higher up the RPM range then, right?

lexlyf

Without the hands it's normal, neither rich or lean.

The SRT Ecu's do not do anything with the O2 sensor, as it only really has to do w/ the mass airflow readings, which effect the air/fuel mixture.

"That's why I tied it into the intake.">>>>> Not sure what this means? What did you do?

///MDex

What I meant was, I was under the impression that the PB-ECU adjusts the fuel/air mapping, SO, the rich or lean situation is caused by ("tied to") the intake and associated PB-ECU.

fever

Before I installed my old piggyback SRT ecu I had that weird idle at around 500 in drive. It's as if it's thinking about stalling out on you but never does. My guess is this is for emissions and helps Lexus gain an overall edge in fuel efficiency/emissions with the Feds.

lexlyf

Dex: Without divulging the exact mechanics of the SRT piggy-back Ecu, you a more or less correct.

Fever: That sounds like a definite possiblity. In fact, that was one of the concepts that Mo & I kicked around when addressing Dex's question.

///MDex

I cannot buy that this ultra low idle issue is built in from the factrory; why else would replacing the TPS eliminate it?

Anyhow, I'm convinved it is not suposed to be there, and I know absolutely positively it didn't behave this way when I purchased the car.

So fever, I am confused by your statement:

"Before I installed my old piggyback SRT ecu I had that weird idle at around 500 in drive."

So now that you have installed your old PB-ECU, your wierd idle is gone?

Anyway, I'll wait and see what happens today at SRT, then I may replace the TPS anyway.

And if I have my OEM intake re-installed, and the low idle goes away, we'll talk further.

lexlyf

cool.

tmasta

hi marken, i too have this problem. i had my TPS replaced .. and a little after i installed the SRT intake my idle was once again very low, and it actuallyed stalled on my twice. could this be related to the intake at all? thanks!

Tony
(white gs4, came in with chris with black gs4)

DaveGS4

iTrader: (2)

Unfortunately I didn't see this post until now (after I'm back from my race ECU install - more on this later after I get a bit of drive time).

I do have the same issue, but it isn't constant. It usually happens when my AC is turned OFF and at a stoplight after driving (so not when cold).


Maken - I happened to go the wrong way on 495 (just following habit going home to my old place in Annapolis) so I drove out of that storm and into a dry area @ Braddock Road. I pulled off and gave it a little what for a few times before the rain caught back up.

Butt-o-meter definitely tells a difference. I'll drive it a bit longer to make sure it's not just the ECU reset - but it's the first time since my LSD install last weekend that I lit up BOTH tires .

lexlyf

Good to hear that you're enjoying the race ecu. Lit them both up...huh?!

I'm really glad that you had a chance to visit the facility & meet some members of the crew. Can't wait to see how your pix turn out.

I didn't get out of the meeting til around 10:30-10:45pm & there was a wreck on inner loop 495 @ route 50, so I got home way after 11pm est tonight. I'll give you a buzz before you leave town.

Dex: Mo & I closely observed Dave's idle prior to swapping ecu & his idle was purring w/o fear of cutting off. Both before & after the swap, Dave's idle between dyno runs stayed consistently around 750 rpm.