Engine not idling right

[rene]

has the engine and OMEX 600 run together before ?

because it is you ignition that is wrong when it is firing in exhaust and inlet

what signal patten do you run for you crank trigger ?

is stat_SYNC = on ?

[Jezza_hr]

rene Wrote:has the engine and OMEX 600 run together before ?

because it is you ignition that is wrong when it is firing in exhaust and inlet

what signal patten do you run for you crank trigger ?

is stat_SYNC = on ?

Yeah, it was running on this engine previously on this very map with no problems. The Stat sync is on, I've also adjusted the crank trigger sensor to be sure that it was in the right spot to be supplying the correct signal to the ECU. Omex has also assured me from the log I sent them that the crank trigger sensor is fine.

[Jezza_hr]

Ok, I've done some more tests today:

- Cam belt is all perfectly aligned

- Spark plugs are perfectly fine, look strong and arc nicely (although spark total in the MAP screen does jump, which might be down to the engine having to adapt the engine's run speed)

- Fuel quality should be perfect, I fully drained the tank and gave it brand new fresh fuel. The fuel that came out did look pretty nasty.

- Adjusted the fuel trims and timing in the MAP screen with little to no noticeable changes apart from a raise in engine speed

- Return fuel line is working and not blocked. I squeezed the pipe which caused the engine to stall. can also hear bubbling in the tank if blown into

- Engine is fully grounded all around, so it shouldn't be a bad earth.

Things to note:

- There is no real change in the engine operation when removing any singular HT lead

- There is also no noticeable change in the idle when removing the brake booster line, but the engine drops out when removing the vacuum line to the FPR

- The engine still wants to keep running after switching it off, popping out of the intake as it splutters to a stop

- The spark plugs do have a fair amount of carbon deposits on them, leading me to believe they are getting sufficient amounts of fuel. Plus the distinct smell of fuel coming out of the exhaust.



I think this covers most of the things I can think of. If anyone can deduce something from this, to give me more of an answer as to what else I should be checking, then please do.

I will be checking on the brake booster tomorrow (to see if the pressure is released in the pedal when I switch on the engine) for air leaks and I will do some more tweaking on the fuel trims. If I can get a proper fuel pressure tester to see if there is something wrong there, I will.

Anything I could be missing?

[jondee86]

Jezza_hr Wrote:- Adjusted the fuel trims and timing in the MAP screen with little to no
noticeable changes apart from a raise in engine speed

By how much (%) did you trim the fuel ?

- There is no real change in the engine operation when removing any
singular HT lead

Would tend to indicate auto-ignition is taking place.

- There is also no noticeable change in the idle when removing the brake
booster line, but the engine drops out when removing the vacuum line to
the FPR

If you remove the hose between the check valve and the booster, it has
no effect on the engine. If you remove it between the check valve and
the manifold, it should jump your idle substantially.

Taking the hose off the FPR will cause the rail pressure to rise, and the
engine will run even richer.

- The engine still wants to keep running after switching it off, popping out
of the intake as it splutters to a stop

Tends to indicate that you have a lot of unburned fuel in the manifold and
in the combustion chambers, as both ignition and injection should stop
immediately you turn the key OFF.

- The spark plugs do have a fair amount of carbon deposits on them,
leading me to believe they are getting sufficient amounts of fuel. Plus the
distinct smell of fuel coming out of the exhaust.

Tends to indicate a rich condition.

I'd be inclined to experiment with taking more fuel out with the master
trim control. Try 20% or 30%... see if it cleans up.

Cheers... jondee86

[Jezza_hr]

Thanks for that Jondee, I'll have more of a toy around with the fuel trims. I did reduce them from 38 down to 32, so closer to 15%, but it seemed more like the engine was being starved for fuel when I got down that far. I will keep toying with them and see how it works out.

One other thing I can think of, is that the carbon deposits have built up in cylinders so much that they're still causing auto-ignition from the old fuel. Maybe a good carb cleaner could help out here?

Also, going over the brake booster once again. I removed it between the check valve and the engine and there was no change in idle. I also put my finger over the vacuum line on the manifold to test if the check valve was knackered and there was still no change.

[jondee86]

OK... there a few things not making sense here

The standard AE101 manifold has two connections for brake vacuum. One
off the first throttle and one off the last throttle. I would expect them to let
in enough air to jump the idle at least 200-300 rpm when you disconnect
the booster hose.

Can you feel the engine making vacuum at idle off any of the connections
to the common vacuum rail ?

How does the engine get idle air ? Are you using the OEM ISCV ?

Have you had a timing light on the engine to see if the actual spark timing
matches to the timing indicated by the ECU ?

Cheers... jondee86

[Jezza_hr]

Keeping in mind that the engine appears to be hunting, the removal of the vacuum might have a negligible difference to the idle. Saying that, I can't notice much of a vacuum on any of the lines when putting my finger on them.

The engine gets idle air from the throttle bodies themselves, there's no iscv attached. They haven't been tweaked in any way.

I haven't had a timing light on it yet, that's on the list of things to obtain to carry out the test. But the timing was spot on with this map previously and nothing has been touched, so it seems unlikely.

[jondee86]

You need to get the idle up to around 1000 rpm and see if it stabilises. You
can do that by winding the main throttle stop (between the centre two
throttles) up a turn ot two. At 500 rpm the engine is unstable and on the
verge of dying.

Are you sure you have your water temp sensor plugged in ?

If we assume that timing is good, and the ECU has the same settings as
worked before, there has to be some simple matter that you are not seeing.

Cheers... jondee86

[Jezza_hr]

One simple matter I have resolved is the engine run on. The ecu was getting a constant feed instead of an ignition feed which kept everything running. After adjusting that it now stops instantly. When getting the idle up to a consistent 1000 rpm, it still wants to move a couple of hundred rpm in either direction. I tested this by keeping the pedal at a steady height.

I did check the water temperature sensor and it's giving a reading, so everything is okay there.

[jondee86]

Can you compare the fuel map that is in the ECU now with the map that
was in the ECU when it last ran correctly ? Just to make sure the map has
not become corrupted for some reason.

As in, do you have a saved map that you could re-load if necessary ?

Cheers... jondee86