Car stalls when accelerator pressed hard

DGPIKE

MEMBER
1994 LEXUS LS 400
V8
RWD
AUTOMATIC
180,000 MILES

Car runs normally but stalls when accelerator is pressed hard and when accelerator is released car starts immediately on its own. This has happened three times recently. The OD1 codes are:
Code 25 = Air Fuel Ratio Fault. Does this indicate an Oxygen Sensor (about $35)?
Code 41 = Throttle Position Sensor. I'm told that this may lead to the Engine Control Module.
New oem is $800
Rebuild current one (about $200+)
Code 42 = Vehicle Speed Sensor Fault (About $70)
I'm retired, spending is an issue, so here's my question. I've driven this car over 20 years and hate to give up on it but I can't afford to have a mechanic try to figure it out at $100 per hour. What do you think might be wrong? Is it one of the mentioned problems or could it be a problem as simple as a clogged fuel filter or defective fuel pump? How do I zero in on this?

Thank You,
Dave

5 Replies

RIVERMIKERAT

MECHANIC
6,110 POSTS

Find a place that will either lend you a fuel pressure gauge or will check fuel pressure for free.

This is the full diagnostic tree for the O2 sensor(s).
Www. Dropbox. Com/s/pvy5kdpou8fixag/Lexus%20TPS. Pdf?Dl=0

Our reference shows nothing for the Code 25.

And the Speed Sensor diagnostics tree.
Www. Dropbox. Com/s/tt6ltxlmdln0x3z/Lexus%20Speed%20Sensor. Pdf?Dl=0

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Tuesday, September 15th, 2015 AT 11:04 AM

DGPIKE

MEMBER
3 POSTS

Thank You for your feedback. Is it fair to assume from your response that you don't feel that code 41culprit would be the engine control module?
Do you know of anyone qualified who does side work in the eastern Massachusetts (cape cod) area?

Thanks again,
Dave

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Wednesday, September 16th, 2015 AT 5:31 AM

RIVERMIKERAT

MECHANIC
6,110 POSTS

No. To be honest, it means that I was so tired that I forgot to include it with my reply.

Www. Dropbox. Com/s/pvy5kdpou8fixag/Lexus%20TPS. Pdf?Dl=0

No, sorry I don't. You could head over to a couple of the more reliable shops in the area and quietly ask the techs if they do. I know most of us did when I was actively turning wrenches.

Do a search for "Cape Cod Lexus Club" and check out the results.

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Wednesday, September 16th, 2015 AT 8:20 AM

DGPIKE

MEMBER
3 POSTS

Can I pick your brain again? I found a certified mechanic who was willing to work on car as a side job.

Due to distance and the requirement that the car had to be towed a distance we pre ordered parts he recommended.

He replaced the vehicle speed sensor and the throttle position sensor but my problem is still present. Tech tells me that I need to replace the ECM that it failed the (voltage?) Diagnostics.

Any thoughts on what type of ecm to use: a junker? Rebuild current one? If I go with a rebuild could you recommend a place to have it rebuilt. Oem is $800 plus and to rebuild mine about $200.

Once again thank you for your time and courtesy.

Dave Pike
dgpike@hotmail. Com

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Sunday, October 11th, 2015 AT 6:02 AM

RIVERMIKERAT

MECHANIC
6,110 POSTS

IF the junkyard can guarantee that the junker unit is good and IF they give you a guarantee and IF the price difference is good enough, I'd go with a junker unit.