Oldsig

So.... my '06 started perfectly like it normally does but as I was putting my seat belt on and grabbing my sunglasses, suddenly it started to feel like it was going to stall. I watched the tach shaking and going lower and lower. Suddenly it jumped back up and idled as it should.

I backed out of the garage and let it warm up a little. Rev-ing the engine sounded and felt perfect.

I decided to take her for a drive... as I was pulling out of my development, she felt like she was going to stall so I pulled over. Just like before, the tach suddenly jumped back to where it should be.

I turned around and headed back home. Part way home the same thing happened but this time she stalled. I restarted her and put her in the garage...

There is no check engine light on and per the battery maintainer, it was fully charged before discontinued it and started her up. Fresh tank of gas the week before this happened and she drove find after that.

Has this happen to anyone else?

DshngDaryl

My guess is one of your vacuum hoses cracked. Look under the hood and see if you see anything. google "site:clublexus.com sc430 cracked hose" and you can get a better idea of the problem I think it is

Oldsig

Sorry, I forgot to mention that since that seems to be the standard reply for certain issues, I had already looked them over and did not find any cracked hoses or anything else obvious. Was there a specific hose you were thinking of that would cause this issue?

DshngDaryl

All the hoses age at about the same rate. I had a cracked hose that was obvious and a P0440 code. I replaced the hose and a couple days later I got another Check engine light. I ended up replacing all the hoses.

Since you do not have a CHECK ENGINE LIGHT, it maybe something else, like a bad MAF sensor.

Your best bet is to have your car scanned for codes and go from there. Though you may not have a check engine light now, the computer may have PENDING codes you can read.

Let us know what you find

Oldsig

It's been at my local Toyota dealership for 2-days now. I got a call late in the day from them. They confirmed there are no codes. They also didn't find any cracked vacuum hoses (either).

They mainly called to see if I had anymore information on what's happening. It's a fairly short and simple story so all I could do was to tell them again and remind them I left a writeup sticking out of the center console.

The only good news is they haven't given up yet!

Oh, BTW, they can't duplicate the stalling or RPM dropping and suddenly popping back up to where it should be... that's the worst type of issue...

DshngDaryl

This is just a stab in the dark and probably not worth having them check it, but maybe your alternator is failing.When my alternator was going out, I was driving down the street and then my radio shut off, my car would seem to coast and then everything came back. BUT the only difference was my car died totally 2 miles later.

Possibly your alternator is intermittent. If it is the alternator, it does not leave a code. (mostly because it kills the power and your ecu resets)

GmanSC

Before the alternator dies, the battery warning light will start to blink or steady lit.

Oldsig

I just got off the phone with the Service Advisor. He may have misspoke previous because now he says that it is "acting up" for him when he took it for a drive and for the Technician while he's doing debug. He thinks that it's worse or only does it when the engine is cold.... hmm...

He said there are no codes and they see nothing when it's acting like it's going to stall. I confirmed again they looked for vacuum leaks and did smoke tests (what I call them) but they found none.

The Technician found something online that it could be throttle body related. They cleaned and recalibrate it (and admitted that the voltage range was already correct) and the issue continues.

They now want to give up on it and said that maybe a Lexus dealership could find the issue. I explained that they would start by doing the same scans and maybe the same debug all over again. I also reminded them that I can't safely drive it anywhere and the closest Lexus dealership is almost 2 hours away.
He said they have a higher level Technician that can look at it in a few days so that's what I asked him to do...

Anything else I should suggest for them to look at?

Bgw70

when you say “voltage range was already cottect” do you mean the throttle body voltages?

if so, then you might want to keep monitoring the battery & alternator.

if you have TechStream, you could hook it up and watch the alternator voltages

SGB4570

Side thought... You said you just filled it up with fresh gas, I'm thinking bad gas or water in the gas maybe. You say it ran fine after the fill up, how far did you drive it? It'll take a bit to get from the tank to the motor. Again, just a thought.

GmanSC

I'm with you. It could be very well that water in the gas.

Oldsig

Yes...
It's still at the dealership and although I do not have 100% of the information, they said that they "are monitoring everything while it is running and they see no changes when it acts like it is going to stall". In the same conversation multiple times they mentioned Techstream being connected.

Oldsig

This tank easily has 100 miles on it before this started. That was a mix of highway and city. It was parked for ~week in my garage with a battery maintainer connected before I drove it again (and this started happening).
Keep the thoughts and ideas coming 🙂

Bgw70

How about the IAC (Idle Air Control) located on the power steering pump?

Someone028

Intermittent fuel pump low pressure?