1986 E140TXCDC 140hp v4 Misfires are low rpm's?...

[Rscardina]

Hey all...hope you are having a great summer on the water.

I'm back with a little bit of a head scratcher..or at least it is to me..

Issue: At low RPM's the engine seems to missfire..and I start to get a wobble as if I am dropping a cylinder or 2.. However, once i give her a bit of juice, she seems to pick up and get cranking along..very smooth, no wobble.. If i could run all day at WOT that would be great but as you know wave and water conditions sometimes force you to throtle down a bit... if I bring her back down she again sounds like she is bogging and the wobble comes back..

My question is ..What would make an engine miss at low speed and work seemingly fine at high speed? One can easily notice when the other pistons engage..the boat just flies out of the water..its night and day..

Some history: Last year with the help of JonesG we changed plugs, powerpack, coils wires, and rebuilt carbs...

I just got back so I have not checked the usual: spark, fuel and compression.. will do that tomorrow.

Any suggestions on this???

Thanks!!

 

[Rscardina]

Re: 1986 E140TXCDC 140hp v4 Misfires are low rpm's?...

Anyone.....???....Ideas...

Thanks

 

[archcycle]

Re: 1986 E140TXCDC 140hp v4 Misfires are low rpm's?...

Probably start with spark, fuel, compression

There's no good direction to go in until those are covered. Also try putting it on the muffs and pulling one spark plug wire at a time and see if it affects the idle.

For example I have spark on all 4 but when I pull the bottom SB plug nothing changes. I'm heading out there right now to see if it has a clogged bleeder orifice/low speed jet.

Need to have the basics first!

 

[Rscardina]

Re: 1986 E140TXCDC 140hp v4 Misfires are low rpm's?...

Thanks. I have to do that when the rain stops!! My only concern is doing damage. What baffles me is why at WOT she picks up all 4..its very noticeable...and then when she is at 1/4 or 1/2...she misfires..
The other thing that I noticed as well was after getting home I put her on muffs to clear out the salt water...purred like a kitten!!! no noticeable pops, sputters, or anything...
Lastly, thr roller that rides the throttle arm has a flat spot..it was timed last year at the boat shop, but I am curious if the roller spins to the round side is that much difference going to throw it slightly off of time?...
Guess I'll start with the basics and move from there.. just odd to me...

Thanks Again

 

[Rscardina]

Re: 1986 E140TXCDC 140hp v4 Misfires are low rpm's?...

...

 

[archcycle]

Re: 1986 E140TXCDC 140hp v4 Misfires are low rpm's?...

That roller is a replaceable part and it should be round so that the cam follower rolls smoothly as the throttle arm moves. Mine was missing. It was only like $4 at the dealership.

As for the performance differences, you have an idle bleed orifice, an intermediate orifice, and a high speed jet. They are utilized just how they sound. It may still seem to idle just fine if those idle and intermediate are partially clogged or one is even fully clogged.

Then again it could be spark. A next step really needs some diagnostics.

 

[blimp]

Re: 1986 E140TXCDC 140hp v4 Misfires are low rpm's?...

I would replace that roller, but also would pay attention to those carbs. the low/idle jet may have some obstruction and you would be running lean at lower rpms. You can cover up the carb openings one by one to determine which carb is lean, but if you are going to clean one you might as well clean them all.

 

[Rscardina]

Re: 1986 E140TXCDC 140hp v4 Misfires are low rpm's?...

Great advice guys.. I'm heading out now to start sniffing around a bit. I'll follow up with more as I find something..

Keep the advice coming..any suggestions or tips are greatly appreciated.

 

[Rscardina]

Re: 1986 E140TXCDC 140hp v4 Misfires are low rpm's?...UPDATE

Re: 1986 E140TXCDC 140hp v4 Misfires are low rpm's?...UPDATE

UPDATE:

I finally had time to play with the engine a bit. I started with fuel... Seems my water/fuel seprator had 2 inches of water at the base and started rusting.. this pulled brown fuel up into the carbs. I kept sniffing around and also discovered that my primer bulb had a small pin hole leak in it. Not enough to see without removing the hose and draining into a bucket. Thats when I heard gurgle and found the hole. The cool thing is that I read with VRO if you introduce air into the fuel system, she will add more oil than need be..and it all clicked when I recall that this year she smokes way more than she did last year.

So...I'm gonna grab a new sperator, new fuel line that showed cracking, new bulb and then....tackle the carbs since the brown water had floaties in it.. probably sucked something up there.. will probably throw new plugs in for good measure..

Thanks for the help guys!!