Throttle Problem

[Jhawk]

Hi,

I'm new to the board.  I'm, the original owner of a '99 21' closed bow Epic.  The boat has been perfect until now.  I have approx. 240 hours on it.  Live on Lake Norman, NC.  The dealership I purchased boat from is no longer in business.

The problem is when I push the throttle down it won't accelerate until it's almost 3/4 of the way down.  The boat goes into gear immediately but no acceleration, either forward or reverse, until about 3/4.  I've taken to two dealerships and they checked the obvious, stretched throttle cable, etc.  They tell me it's probably computer related and they don't have proper diagnostic equipment.  One suggested I take it to a Lexus car dealership.

Any suggestions?  Any contact info. for Toyota Marine support?

Any help would be appreciated.

[cyclone]

hmm, that sounds like the throttle position sensor. Assuming that the throttle is moving from the cable.
Capt. rick might be able to help, and I think there is a test for that sensor in my engine manual. It shouldn't be too hard to diagnose. Let me look in the book.

Pete

[cyclone]

There are three components that I would check first. I have the procedures in my engine manual, I would suggest that you get this manual before proceeding. Look in the TMS parts section of the site. You can order it from Atlanta Marine.

There are resistive checks that can be performed on these components with a multimeter. The Toyota handheld diag tool is not required.

The three components are:

The Accelerator Pedal Position Sensor, which senses the position of the shifter assy. It is the round gizmo with wires coming out that the throttle cable attaches to, on the drivers side of the intake manifold at the engine.

The Throttle Position Sensor. The throttle plate (butterfly) is driven by a stepper motor, and the actual position of the throttle plate is sensed by this sensor. It is on the passenger side of the engine opposite the throttle cable.

The Throttle Control Motor w/clutch is located next to the throttle position sensor on the passenger side of the engine opposite the throttle cable. It is the aforementioned stepper motor that actually moves the throttle plate.

There are adjustments required when replacing these components, I would bet a paycheck that they are the same parts as on a 99 or 00 Lexus automobile. If you go to a Lexus dealer, they could probably check these components for you.

My scanner isn't working, or I would scan the docs for you. Really, you should have the entire manual as there is more info in there than I could scan.

[wakejunky]

We see this occasionally at the dealer. Most likely the accelerator position sensor. Sounds like its in "limp in mode". During normal operation the throttle cable moves the sensor and the computer moves the throttle plate via the throttle control motor. During "limp in" after the sensor has gone bad the throttle cable will open the throttle but only 25% at full throttle so you can get back home so to speak. Just to see how it works you can remove the intake tube and watch the throttle plate as you move the cable. this will show you how the limp in mode works. Highly doubt its a computer or throttle postion sensor. TPS is mainly used for transmission shifting on the LS400. don't replace the entire throttle body its very expensive like $1200. If Toyota marine doesn't offer it separately just go to the Lexus dealer there about $300 and are very easy to change out. Any OBDII scan tool will pull a code. But I'm betting its the accelerator position sensor, sounds way to familiar.

[cyclone]

See the attached doc for pics, it is from the engine drawings on the site. If you disconnect the connector and look at the pins on the sensor itself, you will see four pins in a row. With the oval shaped connector oriented so that the latch part of the connector (two ridges) is facing away from you, test the resistance between the two left hand pins. You should read 1.64 to 3.28 Kohms.

[Rambling Wreck]

Unbelievable - from the description of a problem until diagnosis, pricing of the repair and pictures to boot in under 2 hours. A dealership would have taken longer than that.

You guys are priceless - and are officially forbidden to ever sell your Epics and leave this place.

[Bitzco]

So, I was going to suggest that you do exactly those same things. Too bad the know it alls on the site got to you first I would also suggest that before you spend the $300 bucks you stand next to the boat, kick the tire and trailer, do the hokey pokey, and turn yourself around. That usually fixes things for me. Welcome to the site.

For everyone else out there, I'm back from a horrendous several weeks with tonsilectomy. My clueless, disjointed, nonrelevant posts have returned. I'm takin the boat in today to get dewinterized and am going to freeze my pieces parts off on the lake friday. It should be a balmy 53 degrees or so in the liquified heaven.

[cyclone]

Water was 65 deg today:)

[Rambling Wreck]

Bitzco, a tonsilectomy as an adult is supposed to be a rough experience. I see that you can now confirm that. Hope you are doing ok. It is great to have you back.

The forum is starting to kick up again now that people are sticking their toes (and boats) back in the water. People are asking questions and getting rapid responses that rival the best dealership or tech support. We need your input to remind us why we stay at Holiday Inn Express many nights.

[Bitzco]

The tonsil action ain't so bad so long as you like no talking, no ability to work your job, copious bleeding, and hellish pain for a couple weeks. At least you get gobs of Percoset.

[toyotafreak]

Studs!

[ScarabEpic22]

Glad to know about the TPS issue, mine seems to kinda accelerate quickly in reverse.

And, I should be back for the season, but I need you guys to stick around and help me!

[lesman01]

MIne does the same thing. Always has. Accelerate fast in reverse. I've gotten used to wher it engages. Once it engages it seems to automatically ramp up the rpms. It has not gotten any worse in 3 years, so I'm not sure that's the way it's suppose to work??? No problem for me since I'm use to it, but when someone else drives it, they always slam it in reverse.

Anyone else have this issue and know how to fix it?

[epic_toy]

I have the same issue in reverse. Always have. Could the jump in RPM have to do with cavitation? I really have no idea...

[bullet1w]

Cyclone,
Just curious as to how much your noggin weighs?  My guess is somewhere between 500 and 10000 lbs.  I misplaced my ohm meter somewhere.  I think it may be next to my anti-matter gun.  You guys are awesome man...