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1999 Response Hesitation and Backfire


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I have a 1999 Response with a 325 hp Indmar Monsoon. Boat runs great except that there is a hesitation (like the engine is about to die) and occasional backfire when the throttle is pushed down relatively quickly (like when initially pulling up a skier). It doesn’t seem to do the same thing when you don’t have a skier and the throttle is pushed down a little more gradually. Once you get past that initial hesitation the boat runs great and has plenty of power.

Any suggestions? Is it a timing issue? I couldn’t find a prior post about this same problem, sorry if there is one that I missed.

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Check the cap in case you got a lot of moisture in it over the winter.

I'd also see when that fuel filter was replaced.

Last thought, does the boat have fresh gas in it?

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I'll check the cap.

Fuel filter was replaced last summer.

There is fresh gas.

No one has mentioned this, but is it not a timing issue?

Thanks.

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My first thought was moisture in cap as well. Also, are you sure you got all the plug wires in correctly? You mentioned you replaced the fuel filter last summer. Did you do both the one mounted on the engine and the one behind the trunk panel that is just after the fuel shut off valve? Remove approximately eight screws to get panel off. How many hours on engine?

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Fresh gas for you may not always be fresh gas for the station you purchased it at. I'm guessing it's your gas especially if your in a hot humid environment right now. Some states are still using winter gas and that doesn't work so great in a hot humid environment. Humidity and Ethanol just don't work well together.

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I also have a '99 Response with the 325 HP and have been solving the same issues by reading and following the suggestions in another thread "engine trouble" by SHREDPOWER.

Changing both of my fuel filters solved this hesitation and backfiring problem and the boat has been excellent since. A simple change of the TPS also solved my intermittent high idle.

Whole new boat now.

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Stumble & backfire on take off with a carb boat is a sign of lean condition and typically means the accelerator pump needs to be adjusted/replaced - been there, done that.

On fuel injected boats, I've seen similar when the fuel filter was going - took off OK, but stumbled/bogged at 2500 - 3000 RPM, then ran fine. It was OK when accelerating slowly and ran up to regular WOT RPMs with no further symptoms. Could have gotten some dirty gas or similar into the tank & it's starting to slightly restrict the flow during the hard accelerations. Does it also stumble when you punch it without someone in tow?

It could be a timing issue, though if you didn't replace/move the distributor, timing shouldn't be off. You need to put the boat into service/cal mode - there's a few posts about how to do that around.

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I have a 1999 Malibu Sunsetter LX with a 350. I have been searching and reading all posts.

I did complete tune up,fuel filters (both) and it won't even idle for more than a few seconds.

If you give it gas it pops thru the throttle body and dies. It gave me a #42 code I checked the ICM and it is fine.

I think I will change the gas tomorrow and see what happens. This is getting aggravating!

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I have a 1999 Malibu Sunsetter LX with a 350. I have been searching and reading all posts.

I did complete tune up,fuel filters (both) and it won't even idle for more than a few seconds.

If you give it gas it pops thru the throttle body and dies. It gave me a #42 code I checked the ICM and it is fine.

I think I will change the gas tomorrow and see what happens. This is getting aggravating!

What does the 42 code reference?

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Human Hammer: carb or EFI? Engine Hours? How was it running prior to tune-up?

MPFI 300 hrs It was cutting out at 3000 rpms and stalling. Today I called Indamar and asked a few questions. I ended up taking the distributer out and changing the pick up coil in the distributer . Then put the fuel line in a 5 gallon gas can with new gas same issue surging and stalling and backfireing. Then when warmer It was running great no problems dropped it back in the water ran good for 5 mins then stalled and would not restart. I checked the tps and it was fine also there was good voltage to the IA sensor. I am stumped! No new codes. thanks for the help but I might go to the dealer tomorrow.

Edited by Human Hammer
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A common issue I have ran into with this on a buddy's boat is if it is a Multi port injection engine, then it has some kind of freshwater cooler that is supposed to keep the fuel cool and and not vapor lock. He had replaced the original fuel pump with a universal pump that met the pressure demand, we rerouted it to bypass the fuel vapor seperator and went straight into the inline filter and then into the fuel rail, it should have a vacuum operated fuel regulator that will regulate the pressure in the rails by itself. but the kicker here is that we had to run another line that used to go back to the vapor seperator as a return and make it return back into the tank in order to keep fuel cool enough to not vapor lock. His boat is a 1995 malibu echelon with the 350 MPI MAG engine. might look into it and if any questions or comments feel free to e-mail me at [email protected]

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The fuel injected engines will usually not backfire due to timing issues because they are advanced and retarded by the ecm. it will usually adjust for any wrong settings. If the engine is out of time you will usually notice either poor power and getting hot. If the engine is backfiring out of the intake on the fuel injected engines it is due to lack of fuel either to fuel pressure or vapor locking.

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Stumble & backfire on take off with a carb boat is a sign of lean condition and typically means the accelerator pump needs to be adjusted/replaced - been there, done that.

On fuel injected boats, I've seen similar when the fuel filter was going - took off OK, but stumbled/bogged at 2500 - 3000 RPM, then ran fine. It was OK when accelerating slowly and ran up to regular WOT RPMs with no further symptoms. Could have gotten some dirty gas or similar into the tank & it's starting to slightly restrict the flow during the hard accelerations. Does it also stumble when you punch it without someone in tow?

It could be a timing issue, though if you didn't replace/move the distributor, timing shouldn't be off. You need to put the boat into service/cal mode - there's a few posts about how to do that around.

The boat is fuel injection. It will stumble most of the time when you punch it, even if you don't have someone in toe.

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Human Hammer: carb or EFI? Engine Hours? How was it running prior to tune-up?

EFI, about 500 hours, had some hesitaiton problems prior to the tune-up, but the tune-up solved them until now.

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Human Hammer: carb or EFI? Engine Hours? How was it running prior to tune-up?

EFI, about 500 hours, had some hesitaiton problems prior to the tune-up, but the tune-up solved them until now.

Did the tune up include new plug wires and coil wire? Have you tried running the motor at night to see if you are getting any ignition arching from any of the wires? Your descriptions and code sound like an electrical short and are you sure all the plug wires are in the correct position?

Edited by awilco
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how are you reading codes on that engine?

Here is the link for code reading http://www.themalibucrew.com/forums/index....showtopic=17763

Could be a lethargic MAP sensor.

That is what I was thinking!

Human Hammer: carb or EFI? Engine Hours? How was it running prior to tune-up?

EFI, about 500 hours, had some hesitaiton problems prior to the tune-up, but the tune-up solved them until now.

Did the tune up include new plug wires and coil wire? Have you tried running the motor at night to see if you are getting any ignition arching from any of the wires? Your descriptions and code sound like an electrical short and are you sure all the plug wires are in the correct position?

Yes it included wires and coil wire. The firinfg order is correct I triple checked. The dealership just called and said its the fuel pressure regulator but I disagree. When running fine it has 50 psi when it messes up and won't run it shows 80. But they are saying it should be 29 PSI. I thought it is suppose to be between 40-60 PSI?

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My 2000 Response with the Hammerhead 365 used to hesitate on take off if you gave it pretty hard throttle. Sometimes it would even backfire. The dealer checked it and found no problems. Last year I installed a 180* thermostat and that fixed the problem.

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