sprouts-car
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| posted on 18/5/15 at 02:49 PM |
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Engine running again but am I doing damage?
Afternoon all,
Following on these two threads with an update
Engine starts but won't run. Help! and
WTD: 1.8 cvh ecu
I've got my engine running!
The cure (which I discovered in the process of swapping ecu's, thanks again jimmyd) was just to remove the vacuum tube from the inlet to the
ecu.
Now as cures go, it was satisfyingly effective but I'm worried about what damage I might be doing.
I assume that the vacuum tube is used to tell the ecu what the engine load is. So the ecu then adjusts the timing accordingly.
So would breaking this feedback mean that I'll have a hotter exhaust when under load and might damage valves and things?
C
Build blog
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Davedew
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| posted on 18/5/15 at 04:20 PM |
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By disconnecting the vacuum connection the ECU won't be sensing engine load. So the timing wont advance and retard as needed, so you will be
loosing power.
You probably wont do any damage as it will basically be running in limp home mode at a fixed 10 degrees I believe.
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sprouts-car
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| posted on 18/5/15 at 04:25 PM |
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quote:
Originally posted by Davedew
By disconnecting the vacuum connection the ECU won't be sensing engine load. So the timing wont advance and retard as needed, so you will be
loosing power.
You probably wont do any damage as it will basically be running in limp home mode at a fixed 10 degrees I believe.
That's good to know.
What could the problem be though? As soon as I plug the vacuum tube back in it dies. Completely repeatable.
Build blog
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MikeRJ
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| posted on 18/5/15 at 04:29 PM |
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Did you block the vacuum hose after you disconnected it from the ECU?
The ECU advances the ignition under high manifold vacuum (i.e. low engine load) which gives a significant improvement in fuel economy. Removing the
vacuum hose means the ECU will be running the ignition timing permanently at the WOT value, which is perfect if your throttle is wide open, but
clearly not optimal anywhere else. This could result in the engine running hotter at part throttle and will definitely make it thirstier, but is
unlikely to damage it.
However this is a workaround, not a fix. Without knowing the actual cause of the problem there's no way of telling if it's going to let
you down again in the future, so it's well worth persisting.
If you have the engine running, and apply a vacuum to the ECU port (e.g. attach a bit of pipe and use a syringe or even your mouth) does the engine
cut out like before?
[Edited on 18/5/15 by MikeRJ]
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rusty nuts
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| posted on 18/5/15 at 05:24 PM |
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If the same thing happens with 2 ECUs then I think I would be looking at what could affect inlet melt manifold vacuum starting by checking the valve
timing
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Angel Acevedo
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| posted on 18/5/15 at 05:26 PM |
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MAP sensor out of calibration?
Maybe sensor is feeding ECU wrong pressure...
Beware of what you wish.. for it may come true....
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sprouts-car
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| posted on 18/5/15 at 06:02 PM |
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quote:
Originally posted by MikeRJ
Did you block the vacuum hose after you disconnected it from the ECU?
The ECU advances the ignition under high manifold vacuum (i.e. low engine load) which gives a significant improvement in fuel economy. Removing the
vacuum hose means the ECU will be running the ignition timing permanently at the WOT value, which is perfect if your throttle is wide open, but
clearly not optimal anywhere else. This could result in the engine running hotter at part throttle and will definitely make it thirstier, but is
unlikely to damage it.
However this is a workaround, not a fix. Without knowing the actual cause of the problem there's no way of telling if it's going to let
you down again in the future, so it's well worth persisting.
If you have the engine running, and apply a vacuum to the ECU port (e.g. attach a bit of pipe and use a syringe or even your mouth) does the engine
cut out like before?
[Edited on 18/5/15 by MikeRJ]
I've blocked the tube after disconnecting it. No change, its definitely the ecu reacting to the low pressure.
So I guess next things to look at (based on what people have said here) is:
* check crank sensor and wheel for misalignment.
* check that the timing belt hasn't jumped a tooth.
Anything else?
Build blog
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MikeRJ
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| posted on 18/5/15 at 09:54 PM |
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Stick a strobe on it and see what the actual timing is at idle, and how much it changes when vacuum is applied to the MAP sensor.
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rusty nuts
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| posted on 19/5/15 at 05:54 PM |
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The 1800 CVH engines suffered with the timing belt tensioners failing . I would check the valve timing before starting the engine , check the water
pump as well
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