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Bf 150 Rough Idle Skipping a beat

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barracuda88

Member
Hi Guys Been reading posts for ages on this site, but this is my first.
I bought a BF150 2006 vtec, did oil,plugs,gear oil, low &high fuel filters. cleaned IAC as best as possible.
All cylinders have even compression, spark. fuel pumps are working, fuel lines are solid.
It will start run good on Idle at 1000rpm for 20sec then sound like it skips a cylinder, it will continue to run like this through the rev range
back to idle at 1000rpm
any help would be great thankyou
 
Not sure what you mean by rev range. Are you throttling up beyond 1000 rpm? Or is it that it idles lower, then jumps back to 1000 rpm?

The idle in neutral for that engine should be around 750 plus/minus 50 rpm.


Mike
 
Yes thanks, ok it is in idle neutral and sits at 1000
if I take the revs up still in nuetral it runs a little better but still not sweet.
And when I back down to idle it does not go below 1000 rpm and runs rough
thanks
 
So I have cleaned the injectors, pulled apart the vst. both all clean.
So the IAC valve doesn't move if I take it off and turn the start key, in fact it doesn't move even if I start the engine.
However the engine wont run with it unplugged. the ohm on the iAC is 14 and it is getting power to it.
 
I am thinking you may have a couple things going on....

You did not say what the compression was....only that it was even. If overall, it is somewhat low, you may need to decarbonize the engine. (It does seem like that has been the go to answer for many of the threads lately) However, I have seen this first hand....engine missing like crazy after a short while running.....compression even, but a little low...decarb and valve adjustment fixed the problem.

The valve clearances may also need to be adjusted. If you do that....only do it after you do the decarb. At the same time, you can check the timing marks to see if maybe the timing chain has jumped a notch or the adjuster went bad.

Before you get to that, remove the IAC and take a couple of small jumper wires and run 12v to it intermittently. Give it a little exercise. You should be able to see if the IAC is moving. If it is only moving a small amount, you might get it going better.

If you want to be adventurous, with the IAC off, check to see the two holes in the intake that it covers. I can not remember off the top of my head, which one, but the air is fed to the IAC from one and the IAC controls the air going into intake through the other. Figure out which the "other" is.

Connect the IAC electrically(so you do not get an alarm), but do not install it on the motor. Have someone start the motor.....it should start with a very high idle. You should be able to take your finger and put it on the "other" hole and when you vary the amount that you cover it, it should vary the idle speed. You are now the IAC.. If you can get it to idle smoothly that way, the IAC or IAC circuit is definitely an issue.

As always, make sure you are using NGK spark plugs (no substitutes)

Mike
 
Ok great thanks, I would be in trouble without you
ok so Iac connect to 12v does open and shut.
The finger job I had a hard time still getting it to idle properly
i cleaned the intakes and throttle body.
I will give it the Yama ring free treatment I think you suggested
and compression test it again. What should it be? I think I saw 200?
when I changed the thermostats I notice a lot of salt build up and muck around the two water temp sensors, would these be a cause?
 
Book says compression should be 222 - 250 psi at 200 rpm.

I wouldn't think that the salt buildup would be a cause....but you never know.

You might also check the map sensors for any debris.

Mike
 
ok so its at the mechanic and he is also at a loss as to how to fix it, compression 230 even
tried switching sensors with a block he had there, nothing seems to fix it.
idles at 1000rpm and once warm seems to skip a beat (drop a cylinder even - then pick it up again repeat repeat)
also after 3minutes on the muffs overheat alarm goes off
 
I don't know the 150 at all, but something to check would be the VTEC control valve. If that is stuck in VTEC mode (where timing is different and intake valves are supplying more air than normal, that could explain what is happening. Just a SWAG.
 
The vtec test is normally done when there is a vtec code. Clearing code and running motor at 4500 rpm to see if it returns. Also checking resistances, etc. It is a little more than that for the actual test.

If the mechanic is a Honda tech, he should have Dr. H to look at to see what the ECU thinks the VTEC solinoid is doing. Of course, it could be mechanically stuck and the ECU would not know that it is on.

You really have to pump a lot of water (full force) to the engine on muffs (good muffs that cover and seal well) to keep it from overheating on a hose. You still will not be able to run it for a long time.

Mike
 
You probably have done this but not said....

Have you plumbed in a small tank of fresh fuel? If not, drain the vapor separator after it is plumbed in and flush the fuel system.

It could just be bad fuel.

Has anyone check those valve clearances yet?

Mike

Mike
 
Hi Mike yep did all the easy stuff,
the mechanic is going to try a new fuel regulator
the thing is if I pinch the return line from the top of fuel rail back to vst, it idles smooth
 
Ok so regulator changed nothing, all sensors even injectors and different ecu changed nothing
mechanic is leaning towards high pressure fuel pump first or maybe throttle position sensor. Could not try a different one cause he had none.
Fuel pump had 33psi
any comments welcome as a new one is expensive
 
yes I had a look but could not seem to remove the plastic sleeve where the pump slides in to
so I cleaned it out with throttle cleaner and rinsed off with petrol
pulled all the vst and pump apart where possible for a clean.
does seem to run a bit worse now after playing with the pump
 
I had similar issues on my 200s. The screen in the vst is vital. Make sure you get to it and clean or replace it. Also a hidden culprit, which really racked my brain until I figured it out, is the screen that is in the fuel rail near the fuel pressure regulator. That bastard had me stumped. Once I cleaned it my fuel pressure dropped to "normal" range and has no idling issues.
 
Skooter - can you provide a link to a site that shows that darned screen in the fuel rail near the pressure regulator on a parts diagram? I've never been able to find it.
 
ok so update, pulled fuel pump and vst apart again, managed to get to the screen underneath the pump and gave it a good clean it had a bit of dirt on it.
cleaned the other filter screen behind the pump. decarbed the engine with ring free, changed oil and filter cleaned spark plugs a bit. no change.
now here's the real question if I remove the fuel regulator hose from the intake manifold it runs sweet
part number 7 http://www.boats.net/parts/search/H...F150A4 XA/INTAKE MANIFOLD INJECTOR/parts.html
can I just continue running it with this hose off?
 
WOW, that's weird. Earlier, you stated that if you pinched the vacuum tube, it idled fine and now you're saying that if you remove that tube it idles fine. And the fuel regulator is new? I cannot think of any explanation for that type of problem.

Mike???

Scooter - thanks for the link.
 
Ok thanks so to clarify- If the return fuel line from the regulator to VST is pinched it idles smoother
if the little air line from regulator to intake manifold is unplugged runs near on perfect

the fuel pressure regulator was changed out but made no difference so the original is back on (according to mechanic)
 
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