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View Full Version : What did I break this time?!!!


Skipper
03-11-2011, 09:01 PM
1995 Prostar 190
Standard Indmar EFI engine
1:1 Hurth transmission
625 hrs

Yes, it is probably something that I did wrong. At the end of the season last year I installed a throttle body spacer in the hopes of gaining some horse power. But, I never started the engine after the installation.

I tried to take advantage of the beautiful spring weather. Installed the battery, impeller, hoses, and belt. Hooked up a 5 gallon bucket fed by the garden hose. The boat started after a few cranks.

But when it started it jumped to 3000 RPM. The throttle was closed. Yes, I am sure. But the throttle body was spraying like gas was only a dollar a gallon. I poked and prodded but I don't know what the heck I am looking for under the motor cover.

Why is the throttle body pumping at nearly wide open throttle when the throttle is closed. For those that still doubt...just to be sure I pushed the throttle down and the throttle opened. I pulled it back to neutral and it closed.

Help please. I need to go skiing.

aquaman
03-11-2011, 09:14 PM
check the throttle linkage.....was it altered?

Skipper
03-11-2011, 09:28 PM
check the throttle linkage.....was it altered?

Not the throttle linkage. I did a smashing job of constructing a new bracket to hold the throttle cable in proper alignment with elevated throttle body. But like I was saying, the throttle is 100% closed.

WilliM1940
03-11-2011, 09:32 PM
Look for an air leak. Perhaps one you caused installing the spacer plate.

JimN
03-11-2011, 09:33 PM
Not the throttle linkage. I did a smashing job of constructing a new bracket to hold the throttle cable in proper alignment with elevated throttle body. But like I was saying, the throttle is 100% closed.

Did you remove the throttle cable from the throttle lever? If it still wants to do 3000RPM and the throttle plate is closed to the idle position, you have a vacuum leak. Did you remove the PCV hose and not put it back on?

Skipper
03-11-2011, 09:52 PM
Yes, I disconnected the throttle lever so I could work the throttle by hand. It still wants to go to 3000 RPM and the throttle plate is in the idle position. That is one heck of a vacuum leak? The PCV hose is on.

Where else do I look?

How does a vacuum leak cause the throttle body to pump all of that fuel like that?

Thanks Jim.

j.mccreight@hotmail.com
03-11-2011, 10:11 PM
Is the tps plugged in or loose, if its disconnected the rpm's will increase to keep engine running.

JimN
03-11-2011, 10:18 PM
Yes, I disconnected the throttle lever so I could work the throttle by hand. It still wants to go to 3000 RPM and the throttle plate is in the idle position. That is one heck of a vacuum leak? The PCV hose is on.

Where else do I look?

How does a vacuum leak cause the throttle body to pump all of that fuel like that?

Thanks Jim.

Pull the PVC hose off and cap the stub. If it drops back to normal, you probably have a crack in the hose or a leaky PCV valve. Otherwise, leave the flame arrestor in place and wrap some plastic sheet around it. If the RPM drops, the IAC may have stuck open and in that case, you'll need to shut it down and look at the hole where the IAC pintle should be visible. If it's not, did you make sure to plug the harness in when you re-installed the throttle body? Does the spacer have a gap where the IAC is?

If you have a vacuum leak under the throttle plate, the MAP sensor doesn't know that it's not the throttle plate that's opening, it just knows that the vacuum reading has decreased and that it needs to deliver more fuel. The throttle acting normally is just a controllable vacuum leak.

Check for codes- use a paper clip to connect terminals A and B in the DLC, turn the key to ON and watch the check engine light. If yours doesn't work, look at terminals E and F, measuring for voltage on terminal E. If you see intermittent voltage that seems to have a pattern, connect a test light to terminal E and ground the other end so you can watch the flashes. It should flash once, short pause, twice, short pause and repeat the pattern (this designates 12) three times before showing any codes. If it only flashes 12, you have no codes. However, you may see 21 (TPS low) because the RPM increased and the MAP decreased so much. If the TPS had increased by an amount similar to the MAP sensor, the ECM wouldn't think there was a problem because it can't tell why the RPM increases, either. All it knows is that the RPM increased, the MAP changed and the TPS didn't. If you do see a TPS fault, don't worry about it- it would be a false code because the throttle hadn't moved. If the TPS moves and the voltage doesn't change, you would have a bad TPS.

Also, the way these are programmed, the ECM switches engine control to the MAP sensor once the TPS passes 2%. Below 2%, the ECM thinks it's idling unless the RPM increases and that's why it will probably show a code. Above 2%, the main triggers for the ECM from the TPS are: >20% increase (short time period) causes acceleration enrichment and >20% decrease (short time period) causes deceleration enleanment (basically cuts off fuel delivery so the RPM decreases rapidly.

If the TPS fails or is unplugged, as mentioned, the RPM will increase to keep the motor running but in the event of a total TPS failure, the ECM will default to 12% and any acceleration/deceleration will be caused by the MAP sensor and actual changes in vacuum.

Skipper
03-11-2011, 10:26 PM
Thanks Jim. I'll try tomorrow.

thatsmrmastercraft
03-11-2011, 10:35 PM
I would take the spacer out and go back to where you started. Sell it to someone on craigslist. That spacer won't give you any performance gain.

Skipper
03-11-2011, 11:59 PM
I would take the spacer out and go back to where you started. Sell it to someone on craigslist. That spacer won't give you any performance gain.

That is my plan...minus the craigslist thing. Pretty simple philosophy states that if everything was working fine before you screwed with it but afterwards something is wrong, then whatever you did is probably the cause. Should be on the water by noon.

thatsmrmastercraft
03-12-2011, 12:03 AM
That is my plan...minus the craigslist thing. Pretty simple philosophy states that if everything was working fine before you screwed with it but afterwards something is wrong, then whatever you did is probably the cause. Should be on the water by noon.

Might be needing new a gasket. Good luck.

east tx skier
03-12-2011, 12:23 AM
Sounds like when I added the intake to my old 351. Took a while to get everything working. You've got different problems though. Mine was just the linkage getting bound up from being in uneven alignment from the height difference.

1redTA
03-12-2011, 11:48 AM
In the search for more power on a tbi engine I would run a Holley tbi performer manifold and maybe if i had $ to burn a 454 throttle body. Spacers may help on a wet design intake manifold with plenum volume but I doubt the motor needs it.

milkmania
03-12-2011, 12:11 PM
I love the title !
It cracked me up!!!!!
I didn't read everyone's posts, kinda in a hurry.
I know when I had a cracked gasket on my 1995 suburban, if it was in gear, it would IDLE AT 15 MPH
So, I sprayed carb cleaner around the base, and learned I was sucking air around the base gasket... one "mechanic" wanted $300.00 to "rebuild" the throttle body ! But, he was going to save me money and do it "on the side" at his house.... away from his boss's shop :rolleyes:

3 bolts, pulled out old base gasket, slid in new base gasket, 5 bucks and 5 minutes! didn't disconnect anything.

JimN
03-12-2011, 12:21 PM
In the search for more power on a tbi engine I would run a Holley tbi performer manifold and maybe if i had $ to burn a 454 throttle body. Spacers may help on a wet design intake manifold with plenum volume but I doubt the motor needs it.

The Holley manifold probably won't improve performance much on one of these, although the Vortec manifold does flow more freely. Still, it's not going to be substantial. Porting and polishing the heads would probably make more improvement but if the heads are coming off, I would switch to Vortec heads with roller rockers/cam and do the porting and polishing on those. IIRC, that would be good for about 35-40HP and a definite improvement in torque. The Predator with Vortec heads is rated at 310HP and that hasn't had the ports enlarged or polished and we all know that if it breathes better, it goes faster.

Skipper
03-12-2011, 12:22 PM
I am back in business. Had to construct a new gasket for the throttle body. Scrapped the spacer. Turns out that the auto version of the throttle body and the marine version require different gaskets.

Aside from installing an OJ shaft seal this was the only time I have ever modified anything on the boat. There is a reason for that. Should just leave well enough alone.

Now that I am ready to go again, the clouds are rolling in. Go figure!

Thanks for all the responses. Yesterday my wife was giving me that "you did it again" look. When I closed the motor cover and put the boat back in the garage she asked "what now?" I told her that now I put it up on the Mastercraft site and we wait. I got another one of those looks "like that is going to help." Now the only look I got from her was when I said I need to fill up the truck before we head to the lake....$3.75 a gallon for diesel.

Jim you are like one of those characters on a spy movie. Some guy comes and puts an "x" on a street pole and the hero appears out of nowhere to save the day.

east tx skier
03-12-2011, 01:36 PM
I am back in business. Had to construct a new gasket for the throttle body. Scrapped the spacer. Turns out that the auto version of the throttle body and the marine version require different gaskets.

Aside from installing an OJ shaft seal this was the only time I have ever modified anything on the boat. There is a reason for that. Should just leave well enough alone.

Now that I am ready to go again, the clouds are rolling in. Go figure!

Thanks for all the responses. Yesterday my wife was giving me that "you did it again" look. When I closed the motor cover and put the boat back in the garage she asked "what now?" I told her that now I put it up on the Mastercraft site and we wait. I got another one of those looks "like that is going to help." Now the only look I got from her was when I said I need to fill up the truck before we head to the lake....$3.75 a gallon for diesel.

Jim you are like one of those characters on a spy movie. Some guy comes and puts an "x" on a street pole and the hero appears out of nowhere to save the day.

skipper, if you want to swing over to my part of TX, my local dealer has a MPI GT40 for sale. Completely remanufactured and ready to drop in a boat. MPI and 310 hp. I'd bet they could make it fit a MC!

Skipper
03-12-2011, 11:00 PM
Made it to the water. The boat ran fine. Thanks for all of the help. I'll be sure to stick to regular maintenance in the future. No engine swaps, gadgets, or anything like that for me.

I was excited to try out my new to me 2009 D3 Nomad RCX with brand new D3 bindings. I forgot to pack the binding lube (shampoo). I managed to get into the bindings. But when it was time to get out I thought I would be trapped forever. Had to make a run to a local store and get some shampoo.

Air temp was 72 and the water was 64. It is water skiing season boys!!!!

mattdda
03-12-2011, 11:21 PM
Glad to hear you made it! I'm still waiting on cooperative weather!

east tx skier
03-12-2011, 11:58 PM
Got out today as well. Air 74; water 60. Good times. Enjoying the Strada boots more and more.

mattdda
03-13-2011, 12:07 AM
ah. you guys are making me sick.

André
03-13-2011, 11:16 AM
ah. you guys are making me sick.
You're not the only one!Still 2 feet of snow on top of another 2 feet of ice!

Doug,are those boots on a Strada now?
If not,you should try one and pick up a few bouys extra!

Skip,we all learned something from your story.If it ain't broke...:D
Glad it was running fine after1

TX.X-30 fan
03-13-2011, 11:53 AM
Got out today as well. Air 74; water 60. Good times. Enjoying the Strada boots more and more.




Just board shorts stud??............:D

psychobilly
03-13-2011, 12:51 PM
Just board shorts stud??............:D

Heck yeah! I got my boardys on today!!!! SWEET TEJAS WEATHER!!!!!

mattdda
03-13-2011, 09:21 PM
I wore some around the house today...

H20skeefreek
03-14-2011, 07:56 AM
skipper, if you want to swing over to my part of TX, my local dealer has a MPI GT40 for sale. Completely remanufactured and ready to drop in a boat. MPI and 310 hp. I'd bet they could make it fit a MC!


Any idea what they want for it?