2004 Malibu still backfiring... found something interesting

[Ilivetoski]

So we still have some backfiring issues with our 04 LXi. The other day while on a public lake my dad decided to try something. He wanted to try to turn the boat before we get into the course, like what we have to do on the private lake instead of going straight into the course. Every single time that we turned the boat left it backfired. It gets weirder. It wont backfire if there isnt a skier behind the boat. It hesitates, then backfires while turning left with a skier behind it. Any ideas?

[oldjeep]

Fuel pickup issues so the pump briefly sucks air? How much fuel are you running with? Is the same thing happening with a full tank?

[Ilivetoski]

@oldjeep fuel pump has been replaced, most other things in the fuel system has been replaced.

[oldjeep]

It wouldn't be a fuel pump issue, I'm just wondering if the pump is sucking air due to a bad pickup/low fuel level.

[Ilivetoski]

@oldjeep this has been going on for 2 years. Been in the shop about 6 times. I dont think its a low fuel issue. Not sure about a bad pickup.

[9400]

Backfire through exhaust? Perhaps some unburnt fuel igniting in the exhaust. Does it idle ok?

[Ilivetoski]

@9400 idles perfect.

[nzwaterski]

Sounds like an ignition problem . Maybe ignition leads .

[Ilivetoski]

@nzwaterski we have replaced the entire ignition system.

[gregy]

Did you replace the distributor? If its backfires through the intake it a timing issues. If its missing could be fuel, maybe vapor lock.

[oldjeep]

Which engine? My FIL's 04 has the black scorpion.

[ozski]

Electrical issue I'm thinking, something is lose / broken / earthing out perhaps..

[TylerR]

I second @gregy‌ 's post. Also check all your wiring sometimes a loose wire in that area can cause all sorts of mischief

[DmaxJC_ski]

Leaning toward wiring also, check rub points on PCM harness and visible arc burns, I had a duramax with the same problem, $2500 in labour only to find the injector harness rubbing on a bracket (myself).. A bit of RTV silicone and a piece of rubber.... Problem solved

[gregy]

If it's a wiring problem I'd expect it to be worse when crossing wakes from the jarring. But you never know. Inspect the wiring harness. If you don't find anything start the boat and move the harness around and see if you can duplicate it. We had a fairly new distributor cap end a good ski day last week.

[SDNAH2OSKIER]

Backfires are unspent fuel cooking off in the exhaust system. Bad plug, plug wire. Per Gregy, see if you can duplicate, if you can get it to duplicate you can systematically pull plug wires and see if you can isolate a cylinder. Could be a bad head gasket, I have not heard of this prob with indmar and think it is more likely fuel/ignition, but it is a possibility.

[kdeupser]

I saw where you stated "in a left turn". Have you tried taking the motor box off and the floorboard behind the engine. While idling at the dock turn the steering wheel full left and full right. Any backfire's? I'd be looking for the steering linkage pinching something or rubbing something. Maybe simulate a pass through the course with someone watching the fuel lines and electrical with motor box off?

 

Good luck,

Ken

[Monkstr6100]

Fuel pick up issue I would assume as well. Splice in a short section of CLEAR FUEL line on the fuel intake line by the engine. Then with the motor box off have someone SAFELY sit next to the engine and watch that line for air bubbles running through it during your left turn. Just a way to at least rule out an option.

[gregy]

Does that boat have the fuel pump inside the tank or external? If its external you could disconnect the line and run it into a gas can or something similar.

[Ed_Obermeier]

The boat I owned previous to my current '05 RLXI, a 2000 Supra Legacy, would cut out and sputter when the fuel level was below about 1/3rd tank when I'd do fairly hard turnarounds to the left. Didn't do it turning right or when the tank had more than 1/3rd tank. We assumed from that it was a fuel pickup issue. Don't recall it backfiring but don't really remember. I'm tending to agree with @oldjeep and @Monkstr6100, sounds like the pickup sucking air. FWIW have never had that issue with my '05. I'm wondering if perhaps the pickup is flopping around loose in the tank? Or if possibly there is debris in the tank (i.e. pieces of plastic from drilling connections into the tank that were never cleaned out on assembly) occasionally blocking the pickup momentarily. I've heard of that as well.

[DanE]

@llivetoski Please share with us what the fault was when you do solve it.

[JayG80]

Might want to follow current planetnautique.com discussion on 2007 Excalibur misfire

 

 

[Ilivetoski]

I am coming home from school this weekend sadly to ski... I think the water will be below 60 and since we cannot replicate the problem without a skier... Sucks for me. We have replaced the basically the entire fuel system. New pump, new lines, everything. We did replace the distributor, it does backfire but what it does every time is a hesitation. I must not have been clear on that, but when we give it gas it just dosent want to get up and go right then.

[rayn]

Two things other things to look at - Thermostat (My boat would run cool under 130-140 and that would cause hesitation) - Computer - sometimes it gets jammed up and you have to replace(Mine was caused by having the key in the on position and putting the battery in-gave the computer a good shock). You need a dealer with the right cable and computer or you could get the winky blinky from skidim.com - Good Luck

[Dano]

Sounds like a vacuum leak or maybe a bad sensor (MAP, TPS, or MAF). Maybe low fuel pressure or faulty injector. Bad gas could possibly cause this as well. I would start by double checking the timing. Then checking for vaccum leaks. Can check the sensors with a multimeter and google search for the parameters. Check fuel pressure to make sure it's where it's suppose to be. If all checks out it should be running.

[Winston]

I agree with Dano try running engine with engine cover open then spray carb cleaner along each side of intake between heads and intake if change in rpm possibly you can tighten intake manifold bolts then do the same around carb or throttle body

[thager]

Did you change the "distributor cap?"

[Ilivetoski]

Backfiring is fixed. It was a clogged fuel injector. Hesitation is there. We are switching the servo motor for PP... Wont know the effect until spring.

[LeonL]

I thought you had already replaced all the injectors!

[GregHind]

@Ilivetoski‌ pretty easy to tell if PP servo motor is causing problems. Hesitation isn't how I would describe what it could cause though. Surging is possible but not hesitation.

it is a

If you do linkage tests and servo tests you will see if something is binding. Set your hand throttle at different positions (with the engine off) and run the tests. As the servo winds, you should expect perfectly smooth movement. If the dacron cord (on the servo knob) is catching on the glue which holds it to the knob, it can cause surging. Check to see any jumps there and any binding of the black servo cable plus the engine throttle linkage.

 

Other possible reason is weak return spring and low voltage to the master module.

 

It doesn't sound like a PP problem to me, but the test is so quick and easy you might as well eliminate it. Post a video here if you want me to check it.

[Ilivetoski]

@LeonL He only replaced the one that had a clogged filter. He did that last week. As a result, I had to ski on Saturday (53 water temp) to test it. We cannot replicate the issue without skier load, that is where I came in sadly. More sadly, that was not the fix. He thinks this is the last thing it could be. That said, we have had about 10 things that "could be the last thing"... If this is not it I am pretty sure my dad is going to finally take it somewhere else.

[oldjeep]

What is a "clogged filter" on an injector?

[LeonL]

About time you took it somewhere else. You needs to demand that Dusty reimburse you for most all of that parts hanging and all his labor.

[Ilivetoski]

@oldjeep all I know is that there are small screens in the injectors and when one got clogged it caused the injector to drip gas instead of spray a mist, causing it to build up and backfire.

@LeonL That is up to my dad. I am sure that has crossed his mind.

[Andre]

Injector was clogged without a skier and while turning left too.Why no symptoms then ? Load ?

I think it's spark related more then fuel issue...

Good luck!