Jump to content

 

Welcome to TheMalibuCrew!

As a guest, you are welcome to poke around and view the majority of the content that we have to offer, but in order to post, search, contact members, and get full use out of the website you will need to Register for an Account. It's free and it's easy, so don't hesitate to join the TheMalibuCrew Family today!

SkiPablo

LS1 Stumble

Recommended Posts

SkiPablo

Hi All,  i have a 2002 LS1 engine.  It has always run great but I have noticed off and on this year it will stumble when pulling up a skier.     Just happens right when I start giving it gas and will clear up in 1/2 second.   Seems to be only the 1st 2 pulls or so. 

Plugs are less than a year old.  I pulled one just to look and it looks great.     Wires are approx 7 years old.   Coils are original.

No other issues - ran up to 48 mph yesterday with 3 people in the boat.

Edited by SkiPablo

Share this post


Link to post
Share on other sites
NHolladay

I would start with fuel filters and water seperator if you have one.  Maybe a miss but likely fuel delivery.  Maybe try running some sea foam through it.  Do you use ethanol fuel?.

Share this post


Link to post
Share on other sites
MadMan

The throttle position sensors main purpose is to let the engine controller know that the throttle is moving.  If it's not functioning correctly the result will be stumble you describe.

Share this post


Link to post
Share on other sites
SkiPablo
9 minutes ago, NHolladay said:

I would start with fuel filters and water seperator if you have one.  Maybe a miss but likely fuel delivery.  Maybe try running some sea foam through it.  Do you use ethanol fuel?.

i put a new fuel filter in last spring.    I use Premium that is 10% ethanol.

Share this post


Link to post
Share on other sites
SkiPablo
4 minutes ago, MadMan said:

The throttle position sensors main purpose is to let the engine controller know that the throttle is moving.  If it's not functioning correctly the result will be stumble you describe.

is there a way to check the TPS ?     the problem doesn't seem to happen later in the day

Share this post


Link to post
Share on other sites
MadMan

Engines are more prone to stumble, from being too lean, when cold.  This is the reason carbureted engines had a choke. 

You could measure the resistance of the TPS, but I'd just go ahead and buy a new one.  You can usually find one cheap at the local auto parts store for a car, with the same engine, a couple years older than your boat.  Indmar was always a couple years behind the OEM (GM).

Edited by MadMan

Share this post


Link to post
Share on other sites
formulaben

TPS is an easy swap.  I went to the auto parts store and asked for one for a 1999 Chevy Suburban 350 and it appeared to be a perfect match.

 

Share this post


Link to post
Share on other sites
justgary

Before you start throwing parts at it, get the throttle body clean.  You can use a can of spray carb cleaner.  Get the edge of the butterfly where the gunk builds up and the tiny bypass passages near there.  Also get some into the side port that goes to the idle control, air flow, etc.  Open the throttle wide with the engine off so you can get to everything. 

If you get it clean and it still has a miss, then start changing parts. 

Share this post


Link to post
Share on other sites
SkiPablo
1 hour ago, justgary said:

Before you start throwing parts at it, get the throttle body clean.  You can use a can of spray carb cleaner.  Get the edge of the butterfly where the gunk builds up and the tiny bypass passages near there.  Also get some into the side port that goes to the idle control, air flow, etc.  Open the throttle wide with the engine off so you can get to everything. 

If you get it clean and it still has a miss, then start changing parts. 

Thanks Sir,  I did clean the throttle body a few months ago - it was so clean it didn't even get the rag dirty.  

I wonder if my idle is supposed to be 600 or 650 - i could have sworn it was 650 at one point but i might be confusing that with my friends boat.  Right not it fluctuates from 590 and 600.   Although I don't think this adjustable.    

Is there anyway to read codes from a MEFI-4 engine ?  we have a ODB2 reader in the garage but I don't see anywhere to plug 'er in.

Share this post


Link to post
Share on other sites
justgary

I wouldn't use a rag to clean the throttle body, but let's assume it's clean.  It sure sounds to me like either the butterfly seat in the throat or the IAC is cruddy. 

Yes, you can adjust the idle stop.  It may be just a tiny set screw, possibly with a Torx socket instead of hex.  The monsoon wants 650 in neutral, yours may be similar.  Small adjustments....

Share this post


Link to post
Share on other sites
MadMan
11 hours ago, SkiPablo said:

 Is there anyway to read codes from a MEFI-4 engine ?  we have a ODB2 reader in the garage but I don't see anywhere to plug 'er in.

You can make your own code reader (OBD2 doesn't work)

https://www.pirate4x4.com/tech/billavista/MEFI/

 

Share this post


Link to post
Share on other sites
SkiPablo

here is a picture I took when I cleaned it - I think the top is the IAC and the bottom is the TPS ?    Thoughts ?

IMG_7640.thumb.JPG.05dc6bab38734cc6d96f83b5a9341d55.JPG

 

 

 

Share this post


Link to post
Share on other sites
MadMan
9 minutes ago, SkiPablo said:

 the top is the IAC and the bottom is the TPS ? 

Yes.

Share this post


Link to post
Share on other sites
justgary
1 hour ago, SkiPablo said:

here is a picture I took when I cleaned it - I think the top is the IAC and the bottom is the TPS ?    Thoughts ?

IMG_7640.thumb.JPG.05dc6bab38734cc6d96f83b5a9341d55.JPG

 

 

 

Yup, those are them. 

See the crud in the throat where the butterfly touches it?  Also in the two large passages in the upper left. Shoot some carb cleaner in there.  Open the throttle to get the butterfly and throat. 

Share this post


Link to post
Share on other sites
SkiPablo

that picture was before I cleaned it.   i verified that mine runs at 600 rpm idle - looked at a video from last summer to be sure.   I can't image the IAC is dirty but I suppose taking it off and cleaning is the next logical step.   The stumble feels electrical to me though but I know that's hard to judge.

Share this post


Link to post
Share on other sites
SkiPablo

just updating my thread with the fix.  I changed all the spark plug wires and I believe the issue is gone.  I also noticed more pull getting up on my ski both times yesterday

Edited by SkiPablo

Share this post


Link to post
Share on other sites
Nitrousbird
On 10/21/2019 at 12:31 PM, SkiPablo said:

just updating my thread with the fix.  I changed all the spark plug wires and I believe the issue is gone.  I also noticed more pull getting up on my ski both times yesterday

The wires Indmar used on these motors (LS1, not LS-1 FYI) were junk.  I ended up doing a 8.5mm cut-to-fit wire on mine.

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Restore formatting

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


×
×
  • Create New...