1997 sport nautique code 23 (throttle position out of range) boat will not start

[Mike Boles]

Hi, I have a 1997 sport nautique 630 hours, recently I removed the intake manifold to repair a oil leak at the rear of the manifold, after the repair I have been unable to start the engine. this is a fuel injected 351 ford gt 40. this engine has run excellent until the end of this season when it started to stumble when coming off the throttle and the starting was not a crisp as it always has been. During the inspection of the stumbling problem I found the leaking intake manifold and decided to fix it, at the same time I bought a new air bypass solenoid thinking this was the stumbling/hard starting problem.
After I reassembled the intake manifold, the plenum and all of the other things that had to be moved to repair the intake manifold.
Ie
wiring harness
fuel injectors
fuel rails
water and air temp senors
vacuum lines
throttle Assembly
lucky for me the distributor did not have to be moved.
This sounds like a lot but it really isn't a problem and it all went together really smooth. on the first start the engine started right up and went to a high rpm, around 2500 + and I shut it down right a way to look for the problem. it hasn't started again.
I have spark to the plugs
I have purged the fuel rails
Engine will not start on starting fluid
The only code I get is code 23 the throttle position sensor out of range, I have replaced it and still get the same code.
any help I could get is appreciated, I'm new to this site and will try to respond asap. thanks
As I am reading my post I realized, Could I have jumped time at the timing chain? but why am I getting the code 23?
Mike.

[Mike Boles]

let me add to my question, Are the codes used for a ford automotive instalation the same in a boat instalation? I have a ford ODB1 reader for a car and a manual for a car. Does PCM use the same codes?

[Lewy2001]

Yes code 23 is a TP sensor error on the PCM OBD1. The codes should cross over there maybe a couple of unused codes in the PCM application.

Did you need to remove the TP sensor ?

[DanielC]

"engine started right up and went to a high rpm, around 2500 + and I shut it down right a way to look for the problem. it hasn't started again."

Take the flame arrestor off, and look at the throttle plate. Is it closed, with the throttle handle in neutral? If it is, the TPS should also be in the idle position. At idle, the throttle plate is closed. the idle speed is controlled by the Idle Air controller motor. I do not think the IAC can open far enough to run the engine at that high of an RPM, but I could be wrong. You might still have a vacuum leak.

You can down load the GT-40 service manual from the downloads section of Planet Nautique. Go there, and do that.

[Mike Boles]

Thanks DanielC, when the engine started at high rpm, I found the throttle cracked open somewhere near 1/3 throttle. I returned the throttle to the closed or idle position and tried to restart. No luck, I also tried to start with the throttle at 1/3 again but it will not start.
Today I checked to see if the timing was correct by testing for the compression stroke at #1 cylinder and then looked at the distributor it also was pointing at #1 cylinder at the distributor. everything looked ok.
I am tracing the vacuum lines to see if I have any leaks, and also checking for proper routing. I see in a vacuum diagram that there is a canister with a directional arrow on it. the arrow points in the opposite direction of vacuum flow. I have mine set in the same direction of the vacuum flow. I will be changing this in the morning and I will get back to you.
Also in the meantime I will download a copy of the GT40 service manual to see if there any clues.
Thanks again for the feedback about the service codes, I still have no clue why I have code 23. I'll read the service manual, let me know what I should look for next.
Mike.

[Mike Boles]

Thanks Lewy2001 for the feedback about the codes and the service manual. I'll look there to see if there are any clues.
Mike

[dfoster]

Note: I have a newer MEFI-IV engine... but wanted to share my experience as it may help

Definitely check the TPS. On my MEFI engine when I had a problem I had a TPS code that I had to "Reset" by putting the engine in "Service Mode" and then running the throttle from idle to full throttle, so it could reset the range. The EFI "learns" as things go out of calibration, but when things break or you replace a sensor it can throw an error because the range changes.

The manual gives a chart that shows the voltage range for the TPS. You can double-check to make sure your new TPS is operating in that range and then see if you can find a reset procedure. I have it for the MEFI, but not for yours.

I had to do the re-calibration so that the engine would run full throttle on the new TPS.

The high idle is a bit odd, as the manual says that once it gets an error it holds the idle at 800rpm, which is no where near 2000+. So you may want to also check that the IAC didn't get stuck. In the manual it says that it doesn't store a code when that fails, so it may be stuck. But EFIs can behave a bit weird when one sensor goes bad and they try to quickly compensate. You may have turned it off before the EFI could have brought the idle back down. Or it is stuck wide open which now is keeping it from starting.

Other possible issue, but it should have prevented starting the first time and throw a code is the PIP signal from the distributor. Double check that is solid.

Good luck... just remember to only change one thing at a time and keep track of it. Lots of stuff changed when you pulled it off, so check for vacuum leaks or loose connectors even on stuff you didn't think you touched. I did my TPS issue when moving something out of the way for an alternator installation.

[Mike Boles]

Thanks Dfoster, I gave up and sent my boat to the local Nautique dealer for service. they sent to back to me saying I had loss of compression in all but one of my cylinders. some of the cylinders were reading as low as 50 psi with only one cylinder at 125 psi. they sent it back to me to save me some money and only charged me 150.00 for the diagnostic check. I went on to try to find out why I lost compression on so many cylinders. If I add oil to any of these cylinders I get the compression back to 130 psi. My theory is, I possibly washed the oil from the cylinders during the issues I had with the TPS and if I add oil to the cylinders I may get the compression back and that will allow the engine to start.
During this process I discovered some rust in one of the cylinders and on an exhaust valve, at this point I have the exhaust manifolds off and can see possible problems caused by the exhaust manifolds being left with water in them and rusting the exhaust valves, not bad but a possibility of the loss of compression.
I now have the engine out of the boat and am going to rebuild the heads and short block, at the same time I will replace the exhaust manifolds and install some means of draining the water from the manifolds during storage.
When I get this all back together I will post all of my findings, I haven't ruled out the TPS, I did replace it and have no codes but I don't know if I need to go into a calibration procedure to set it up. and if I do, how do I do that?
one thing is for sure when I get done I will have a brand new motor and manifolds and can eliminate that from the list of things that could be wrong.
I need to add. when cranking the engine I measure as low as 8 VDC at the starter and the engine turns over slower that I would expect. I removed all of the spark plugs and still get only 10vdc. this with the low compression is why I have elected to pull the engine. the cables are good and the starter was rebuilt buy a reputable shop and then checked twice. the dealer thought the motor turned over rather slowly and placed a new starter from PCM and came up with the same results. all grounds have been checked and polished to a shiny finish.
I'm running out of things to check. I will re post when I get done, maybe we can all learn from this and help someone down the line.
Keep in touch.
Mike

[Mike Boles]

Ok here is the update, when I removed the pistons from the block the rings and connecting rods were rusted from water entering thru the exhaust valves. the problem was caused by not changing the exhaust manifolds on a regular intervals, I hear that it should be done every 5 years mine were original. the connecting rods were rusted to the point of 0 or very limited movement I'm sure this caused the high current draw when trying to start the motor.
I sent all of my parts to the local machine shop and had to bore the block 30 over and recondition the connecting rods the crank and cam shafts were on good cond.
I had the heads reconditioned and replaced the pistons and rings and all gaskets and seals this cost me 1650.00 I also replaced the exhaust manifolds 725.00 all of the labor I did myself with the help of a friend who is a really good ford mech.
After the install back into the boat and with the timing set to roughly TDC #1 cylinder the motor only cranked a few times and fired right up and went to a idle. the fine timing was set and I have completed the first few hours at the lake.
All this could have been avoided if I had changed the exhaust manifolds every 5 years, I guess there is no way to tell if they are failing.

[s_kelley2000]

Excellent to hear that you got her back running!

[jtryon]

is this true that exhaust manifolds need to be changed every 5 years?? mine are original on my '88 supra.

[bhectus]

is this true that exhaust manifolds need to be changed every 5 years?? mine are original on my '88 supra.

I've never heard that either, nor do I believe it to be true. Maybe if you're running in salt water? I'm suspecting he had a bad riser gasket that leaked water back into the exhaust manifold and into the engine which would have definitely caused the problem he experienced. It's not that uncommon for it to happen. If you see evidence of water leakage from your riser gasket onto your manifolds, chances are it could be leaking on the inside too. Guess where that goes?