rebuilt motor hiccup?

[jeffkuk]

hello everyone, I had to rebuild my 351 FI in my 1998 SuperSport. The motor was rebuilt due to water getting into the cylinders. Almost everything was replaced, new plugs and cap and rotor, in line fuel filter, idle sensor, idle control valve, etc. The motor was bored .030 over to clean everything up, everything else was factory stock parts. The boat idles fine if maybe a little rough, and runs great once underway, however when just engaging the transmission from neutral if you don't quickly get in to the power, the boat will hiccup and sometimes stall. Anyone have any ideas? I've tried two different computers as well and still no improvement. Thanks for the help in advance!

-Jeff

[Mazza]

Fuel problem??

Sounds like a fuel problem?

is it a EFI or carb model ??

[Mazza]

Fuel problem.

Sorry posted to fast.

can se it is a EFI.

Have you tested the fuel pumps, had similar problem with mine. turned out to be the low pressure fuel pump that was starting to go bad.

Mine happend when it had been pulling for some time at a constant speed, suddenly it would start doing hic ups.

checked the back flow of petrol to the tank, at idle. it was not a steady flow, change the low pressure pump first, that fixed the problem. So no need to change the high pressure pump. a 100 dollar fix her in Denmark. Most likely cheaper in the US

[scuff97]

The ECM calibration will not allow for the change of the 30 over pistons. I have seen this several times. The max you can go is 20 over. Unfortunately i don't know of anything you can do to over come this

[core-rider]

The ECM calibration will not allow for the change of the 30 over pistons. I have seen this several times. The max you can go is 20 over. Unfortunately i don't know of anything you can do to over come this

Not saying this isn't the case, but it doesn't make any sense. You're talking about a very small difference in engine displacement. I would tend to look at the simple stuff first... Timing, firing order, fuel delivery, fuel pressure, engine vaccume, etc.

Also you mentioned a lot of sensors were replaced. Did you replace the TPS (throttle position sensor)? I'm not completely sure about the PCM computers, but Ford engines want to see a voltage of 0.65 - 1.25 VDC VDC at 0 throttle position. This voltage is read between the black and green wires on the TB side of the sensor. The -lead of the meter should be on the black wire and the +lead on the green wire.

[scuff97]

It never hurts to check all of those things. i have had multiple attemps replacing parts and checking all parameters without success on ones that have been bored. Ford does not recommend with their calibration anything over the 20 thousanths

[AirTool]

I'd have to think through this a bit more....but maybe a Daytona style restrictor plate might work.

If someone steals this idea and makes millions....I get part of the take.

[jeffkuk]

Thanks for all the info guys. I had heard something about the 30 thousands over issue, but I just can't really swallow the fact that it can't adjust for that, especially since it runs great everywhere except just off idle. I did replace the TPS, so when I get up to the boat I'll try check that as well. This is quite frustrating.

Another thought I had when thinking about car modifications, is why can't someone make a "chip" or rewrite software especially considering the simplicity of this motor. Anyone have any info on this?

Thanks again everyone

[teamseal]

http://www.amazon.com/Billet-Adjusta.../dp/B0011FLAQG

This "may" help your problem. If it dont then at least it looks cool!

[AirTool]

I'd have to think through this a bit more....but maybe a Daytona style restrictor plate might work.

If someone steals this idea and makes millions....I get part of the take.

Scratch this idea. The plate only works at higher engine speeds.

[jjgag60]

Rebuilt 351

My motor is also rebuilt and is 30 over. It took purchasing the "star tester/ code reader" for the ECU to find I had a problem with one of my sensors. Remember after you replace a sensor, you have to disconnect the negative battery cable and let the computer sit. Our ECU's are very smart and will "self learn" and it takes them several cycles to relearn once your replace a bad sensor with a good one. I don't like to say this, but you need to get your boat into the dealer that can check out your ECU, by hooking up a coder reader to make sure all the sensors are working. The star tester actually runs a test of most all of your sensors to make sure they are working. After mine was rebuilt, it would not idle and "hunt". When you put it in gear it would die sometimes. Resist playing with the idle adjustment, there is a reason why there is a red cap over the screw. It also would flood and not start. I replaced all my sensors including the temp sensors ACT. That solved my problem. 90 percent of our problems with the gt-40 are fuel related. Boat ran great last season.

[horkn]

The Ford EEC IV engine control setup has no problems with oversize bores and can compensate for a wide variety parameters. The ford computer is not the issue.

It's more than likely a sensor issue. The TFI module is a known weak spot on the EEC IV, and a relocation of that away from the distributor will usually clear that problem sometimes without even changing the TFI module.

There's some really good articles on the ford EEC IV diagnostics for problems if you look on mustang forums.

[jeffkuk]

Okay, I know someone at Lake Norman that should be able to get me access to that code reader. I'll have start there I guess. Thanks again everyone. Also, forgive my acronym ignorance, but what is the TCI module?

Jeff

[jeffkuk]

My motor also hunts for an RPM when in neutral and idling, but it will idle. It sounds like it has a big lobed cam in it, which is not the case. I'll have to go back and see if I replaced the ACT or not. Thanks.

[core-rider]

Okay, I know someone at Lake Norman that should be able to get me access to that code reader. I'll have start there I guess. Thanks again everyone. Also, forgive my acronym ignorance, but what is the TCI module?

Jeff

I think he meant TFI module (Thick Film Ignition). It's the rectangle piece on the side of the distributor with a wiring harness plugged into it. They do have a tendency to go bad and cause some strange things to happen. Since you said you have replaced the TPS sensor I'm almost certain that is going to be your problem. Either the voltage is out of range at low throttle or it is installed wrong. Get the code reader and find out what it says before wasting anymore money chasing gremlins though.