2.5 dse auto Power loss..?

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Baiman

Baiman

Member
Posts
27
Location
Devon
Hi folks,
Hope you're all well.
My 1997 2.5 dse auto (alloy intake) has just begun loosing power, simmilar to limp mode, but will rev above 2000rpm when pushed. It starts and drives fine, then (usually after a gear shift) looses all thrust and just plods along. Now, heres the odd bit... when it happens if I take my foot totally off the throtle pedal for 2 seconds and re-apply power the problem is gone, boost and power return for a short while before it happens again. Doesn't seem to make a difference wether engine is hot or cold. Ohh, also when it happens applying more fuel via right foot (to the floor) doesnt activate kick down and it feels more like the old 10J engine.

I'm guessing 4th injector perhaps, or maybe the throtle position sensor?

Any advice would be greatly appreciated.

Paul
 
Check the rubber turbo pipes inside for delamination, another thing to check is the map sensor bolted to the fuel filter housing which has the spill pipe from intake manifold to it, check that is connected and not gunked up at intake end, to check sensor unplug and try car if it is worse it is working if no change sensor may well be defunked.
 
Check the pipe to the MAP sensor (bolted to top of fuel filter) has no splits or leaks in it. Check that it is clear with no obstructions at either end. Clean out intercooler, check for turbo pipe leaks. If you have no MIL lamp coming on it will not be number four injector.
 
MAP sensor seems okay, pipe in A1 condition, clear and connected.
Intercooler was removed and soaked in kero overnight before being flushed about 6 weeks back.
All silicon hoses for turbo circuit, no splits I can see.
No MIL lamp on dash...
 
Baiman said:
MAP sensor seems okay, pipe in A1 condition, clear and connected.
Intercooler was removed and soaked in kero overnight before being flushed about 6 weeks back.
All silicon hoses for turbo circuit, no splits I can see.
No MIL lamp on dash...
Click to expand...

Check that turbo hose from intercooler to manifold goes hard when engine is revved. Maybe difficult with silicon pipes but squeeze it together on tick over it should swell and push your fingers out when revved. If that is ok take another look at MAP pipe check nipple to manifold is not blocked. If ok there is only the MAP sensor it'self left to look at. Check electrical connections to it and that it is not blocked. Don't poke anything in it other than very carefully. Spray in some carb cleaner and blow out with airline several times. If that does not sort it you maybe looking at a new one. Also check connections to inlet air temp sender under front of manifold that effects fuelling, but should not give you your problem..
 
How much fuel have you got in the tank? If it's down much below half full, a failed in tank pump can cause those symptoms as can a badly blocked fuel filter.
 
wammers said:
Check that turbo hose from intercooler to manifold goes hard when engine is revved. Maybe difficult with silicon pipes but squeeze it together on tick over it should swell and push your fingers out when revved. If that is ok take another look at MAP pipe check nipple to manifold is not blocked. If ok there is only the MAP sensor it'self left to look at. Check electrical connections to it and that it is not blocked. Don't poke anything in it other than very carefully. Spray in some carb cleaner and blow out with airline several times. If that does not sort it you maybe looking at a new one. Also check connections to inlet air temp sender under front of manifold that effects fuelling, but should not give you your problem..
Click to expand...
My project car ran quite happily with a duff MAP sensor, the spigot had broken off so no connection to the manifold. I was surprised, so I took the pipe off the MAP sensor on my other P38, that ran quite happily too. Both are later cars with the plastic manifold.
 
Datatek said:
My project car ran quite happily with a duff MAP sensor, the spigot had broken off so no connection to the manifold. I was surprised, so I took the pipe off the MAP sensor on my other P38, that ran quite happily too. Both are later cars with the plastic manifold.
Click to expand...

Don't see how it can, the MAP sensor tells the ECU the manifold pressure and the ECU increases fuel to accommodate the extra air giving more power. Without the MAP sensor there can be no increase in power, they will run but not properly..
 
Mine is the same year as OP and currently has no map sensor fitted that is on another car stuck in Belgium atm but that's another story there is a thread on that car awaiting a turbo atm and mine is as flat as pancake if you try and drive its like the turbo is not there:( I am awaiting a replacement sensor.
 
brianp38dse said:
Mine is the same year as OP and currently has no map sensor fitted that is on another car stuck in Belgium atm but that's another story there is a thread on that car awaiting a turbo atm and mine is as flat as pancake if you try and drive its like the turbo is not there:( I am awaiting a replacement sensor.
Click to expand...
That is a different situation, with the MAP electrically disconnected, the car will not run properly, with an electrically a working sensor but no pipe, both my P38's run normally.
 
wammers said:
Don't see how it can, the MAP sensor tells the ECU the manifold pressure and the ECU increases fuel to accommodate the extra air giving more power. Without the MAP sensor there can be no increase in power, they will run but not properly..
Click to expand...
I'm not going to argue, but the fact is I have 2 P38's that run with the pressure pipe disconnected, no noticeable difference when the pipe was replaced.
 
Datatek said:
I'm not going to argue, but the fact is I have 2 P38's that run with the pressure pipe disconnected, no noticeable difference when the pipe was replaced.
Click to expand...

You cannot be serious. Without the MAP sensor there can be no turbo boost. Plenty of air but no fuel to increase power. It is not possible that there is no difference to power when MAP is disconnected. Now come on be sensible.
 
wammers said:
You cannot be serious. Without the MAP sensor there can be no turbo boost. Plenty of air but no fuel to increase power. It is not possible that there is no difference to power when MAP is disconnected. Now come on be sensible.
Click to expand...
So I have 2 cars that do the impossible, I can't argue with the facts. The MAP was electrically connected.
Perhaps you should try it.
 
Datatek said:
So I have 2 cars that do the impossible, I can't argue with the facts. The MAP was electrically connected.
Perhaps you should try it.
Click to expand...

It would seem so, without a working MAP sensor there can be no turbo boost therefore the car will lack power. Disconnecting the MAF sensor won't make a difference but disconnecting the MAP sensor will.
 
wammers said:
It would seem so, without a working MAP sensor there can be no turbo boost therefore the car will lack power. Disconnecting the MAF sensor won't make a difference but disconnecting the MAP sensor will.
Click to expand...
It's only the pipe that is disconnected, not the electrical connection. Makes no discernible difference.
 
Datatek said:
It's only the pipe that is disconnected, not the electrical connection. Makes no discernible difference.
Click to expand...

There is something wrong with both your P38s then. The pipe takes pressurised air from the manifold to the MAP sensor the ECU then receives a signal indicating manifold pressure, it will then increase fuel as required subject to throttle power demand. If it does not get a signal it doesn't increase fuel to meet throttle power demands beyond the standard fuel map. Simple as that. How can a MAP sensor send a signal to the ECU if the pipe is disconnected and there is no pressure to change it's state.
 
Thanks for the assistance guys, have the day off tommorow so will investigate further based on your advice and report back :)
 
wammers said:
There is something wrong with both your P38s then. The pipe takes pressurised air from the manifold to the MAP sensor the ECU then receives a signal indicating manifold pressure, it will then increase fuel as required subject to throttle power demand. If it does not get a signal it doesn't increase fuel to meet throttle power demands beyond the standard fuel map. Simple as that. How can a MAP sensor send a signal to the ECU if the pipe is disconnected and there is no pressure to change it's state.
Click to expand...
Nothing wrong with either car, no faults recorded either.
 
Datatek said:
Nothing wrong with either car, no faults recorded either.
Click to expand...

Sorry Keith don't want to fall out with you but what you claim is not possible. With the Map sensor pressure pipe disconnected there will be a significant power loss and throttle response lag above 2000 RPM.
 
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