225 Promax - rough idle and no warm start

[I/O to O/B]

I have a 1996 engine that was running pretty decent until it suddenly started idling very rough and on up to about 3000 rpm. On a cold start, it roars to life instantly, killing all airborne life with a huge plume of smoke (50 to 1). Past 3000 rpm and right up to the limiter she runs great. If I stop after running, there's about a 60% chance she wont start. I am almost sure it is flooding / too rich. If I wait about 30 minutes she fires up. Based on reading, maybe the TPS got out of whack. If so, can I adjust it myself? Is there any other way of leaning things out a bit at the lower rpm? Thanks - John.

 

[njj502]

Could be several things but don't go adjusting the TPS out of spec b/c it'll lean it out on top too. Sounds like a switchbox.

 

[M.ALEXIE]

I would check the map sensor hose first (blocked, cracked or off).

 

[njj502]

^ Very good point.

 

[TBuck2003]

As stated check the hose first, if nothing there sounds like a TPI

 

[dragmerc]

leaking injector???

 

[mdevrow]

leaking injector???

Bad Injectors will cause a stumble and then cleanup and Run, But still be Fat and need attention!!

 

[chad202]

The tpi on that engine works from idle to 3k. At 3k and above its maxed out. Could be the low speed side of the stator. All what Todd said.

 

[njj502]

^ What? If we're talking about the throttle position sensor it's in full effect from 0 to a gagillion rpm. All is is monitoring is throttle position and nothing else.

 

[I/O to O/B]

Thanks for the input guys. Can someone point me to a diagram of the hose in question? I've come up with the sensor, but can't find a pic of any hose....

http://www.marineengine.com/newparts/part_details.php?pnum=MER889575&ptype=&Engine=&Model=


Thanks again.

 

[njj502]

The hose comes out of the back of the ECM to a little fitting on the intake manifold. It's shown on bottom right of this photo.




That sensor you found is a temp sensor. What we are talking about is the MAP sensor in the ECM. The MAP sensor uses that hose to sense the pressure within the intake manifold and adjusts the fuel map accordingly. MAP = Manifold absolute pressure.

 

[I/O to O/B]

Perfect - thanks for taking the time. Is the tube supposed to be perfectly empty?

 

[njj502]

Yes it doesn't carry anything other than air into the ECM. It's normal to have a tiny bit of oil/gas in it but nothing more than probably a drop or two.

Nick

 

[I/O to O/B]

Thanks Nick. It'll be great if this is the problem.

 

[njj502]

No worries. Hope all this helps.

 

[whipper]

I also have a 96 and mine also did the exact same thing before. Idle sucked and couldnt even get on plain hardly. Like a dummy I had spare switchboxes and stator so changed them all out problem solved. Witch one fixed? Probably the switch box..Everyone was telling me TPs but I have my tps diconected with the ACU. i always suspect the diaphram pump when i loose power also because it has coused similer problems 3 or 4 times over the years. Idle rough would be very low fuel level in the vst and then when ya try to get on plain it just cant keep up and drains. A good test for that is pump up the ball filling the vst with engine off. start the motor then hit it. Might run up to wot throtle for sec then stumble out of fuel. Then back off idle for a sec then try again. If you cant get on plain the vst didnt fill up enough to handle the demand so soon. Thats the diaphram pump for sure then.

 

[whipper]

http://forum.allisonowners.com/showthread.php?t=3646&highlight=stator+issue

 

[chad202]

On a promax(not 225x), with the butterflys closed, the tpi(tps) will read .268-.288(roughly). As you increase the throttle imput, voltage will increase till it gets to 7.3-7.5(roughly) volts which happens at the 3Krpm range. From 3k up it still reads 7.4ish. If you slowly press the hotfoot, the voltage should increase slowly. If they jump around and erractic, it should be changed.

 

[whipper]

Mines a 96 225 promax also not X i have an X sticker on an aftermarket cowl if ya were refering my 225 Chad.:big grin

The link to the old thread had all the same type of possabilitys. In the links thread my problem turned out to be a plugged fuel filter or bad gas. So start with the cheepest way and work your way up.:shock:

 

[whipper]

I have a 1996 engine that was running pretty decent until it suddenly started idling very rough and on up to about 3000 rpm. On a cold start, it roars to life instantly, killing all airborne life with a huge plume of smoke (50 to 1). Past 3000 rpm and right up to the limiter she runs great. If I stop after running, there's about a 60% chance she wont start. I am almost sure it is flooding / too rich. If I wait about 30 minutes she fires up. Based on reading, maybe the TPS got out of whack. If so, can I adjust it myself? Is there any other way of leaning things out a bit at the lower rpm? Thanks - John.

After reading this again it sure sounds like classic diaphram pump not keeping up? She takes of fine from the get go because at idle it can still fill the vst enough to make a run to wot. Because the motors cold you idle longer before ya take ask for the demand. Then you back off and shut down. because the engine still warm you start up after depleteing the vst on the last run but take off wot sooner than you did from the cold start but the week spring didnt have as much time to fill the vst this time and presures not there for idle then you take off and it just doesnt have the fuel to meet the demand the second time around??

I mean you can also do as Chad said. Before I got the Bruacto ACU and used the TPS Ive checked that thing and it was jumping around on me. Thats when I bought the Brucato acu so I could eliminate the tps as the brucato unit does that for me.

Also fuel issue. I would drain the tank change the filters and plugs replace the diaphram pump. Swab the tank if theres any particals in there also with a rag tie strapped on the end of a coat hanger. Then try her again. That way at least you eliminated fuel as a problem also.