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Topic: Failing EGR system..:-? (Read 369 times) |
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kanor
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I'm a YaBB newbie!
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Failing EGR system..:-?
« on: May 8th, 2006, 1:48pm » |
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Hi.
I own a Scorpio 95' with a 2.0 16V engine and manual transmition. Since I baught it I have noticed that it starts to hesitate and behave poorly on part trottle when engine is at normal running temperature. Runs fine while cold.
I have swapped the MAF, but same problem, so I started to sort out other problems.
When disconnecting and plugging the vacuum hoose to EGR valve it runs 100% ok! so It seems to me like a EGR problem. Checked EGR pipes for leack, but seems ok.
Has anybody had problems with the DPFE-sensor and is there a way to test if it's failing before buying a new one ? 
Also have to mention: The car had a blocked catalyst when I baught it that I had to replace. Is it possible that this blocked cat has damaged any parts of the EGR system ? 
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bootiful-scorpios
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ex 2.9 24v
Posts: 560
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Re: Failing EGR system..:-?
« Reply #1 on: May 8th, 2006, 5:53pm » |
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blocked cat could you tell me how if it affected your car ? as im wondering if mine is blocked . sally
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kanor
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Re: Failing EGR system..:-?
« Reply #2 on: May 8th, 2006, 10:20pm » |
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Mine did hardly run since exaust was nerly totaly blocked. I asume that the symptoms may warry on how broken the inner parts of the cat is. Also listen for ratling sounds as mentioned here: http://www.fordscorpio.co.uk/faults_rattle.htm
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sector-9
Senior Member
No scorpio anymore
Posts: 1069
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Re: Failing EGR system..:-?
« Reply #3 on: May 8th, 2006, 10:36pm » |
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With the EGR valve open it will run poorly and hesitate - that's not a malfunction, just a side effect of introducing exhaust gases into the induction which is deliberate to lower combustion temperatures.
As far as I can work out, the EGR valve should only open when the throttle has been closed from an open position and when the engine is above a certain speed (on the overrun for example, where engine performance isn't critical) and it should have closed by the time the engine gets to idle speed so that the ECU can maintain that. Incidentally on the diesels the EGR valve can stay open at idle since the air inlet isn't throttled therefore has little effect at idle. In all cases the EGR valve should close when you press the accelerator more than a slight amount.
I found on my diesel that the EGR valve was staying open until I put my foot about half way down (way too late); was simply an incorrectly adjusted throttle cable which meant that large pedal movement hardly moved the 'throttle' (or more importantly, the TPS which tells the ECU you've floored it and to turn off the EGR system). With the cable correctly adjusted the EGR now closes as soon as I put any useable pressure on the accelerator pedal.
I'm not sure what you mean by DPFE sensor - I presume this is the differential pressure sensor connected to the EGR pipe either side of the venturi? If so, this is to tell the ECU that gases are flowing through the EGR pipe and therefore that the valve is working correctly. I believe that this is now a requirement so that the ECU can detect a fault with the EGR system. The way it works is that with the EGR valve closed the same air pressure exists either side of the venturi in the EGR pipe. When the valve opens the pressure drops on the inlet side of the venturi and the sensor detects that gases are flowing. Unfortunately I don't know what type of signal the pressure sensor generates so can't guess at how to test it. In any case, if it's faulty it should generate a fault code which an OBD scan will reveal...
Darren
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