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  #1  
Old July 30th, 2010, 09:31 AM
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James Pierce
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James Pierce Jr.
1995 D90 SW #314, 59 SII 88 HT
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Surging

I have a 95 D90 SW with 110k that is surging (for lack of better description) between 1500 and 3000 rpms.

It does not do it when idling or under full throttle. When sitting still you can rev the engine and the issue is present.

The check engine light is not on and there are no codes.

It does not seem to be spark or ignition related more like fuel metering.

A strong electrical load on the system, such as turning the ac on or turning the fog lamps and head lamps on at the same time, seems make the problem worse.

What I've done so far:

Cleaned the Mass Air Flow Sensor
Cleaned the IAC Valve
Checked the engine wiring harness for loose connections / damage.
Wires Cap and Rotor look good.

Any helpful input would be greatly appreciated!
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  #2  
Old July 30th, 2010, 09:41 AM
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Jason England
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Do you notice this when trying to drive in traffic in 2nd gear?
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  #3  
Old July 30th, 2010, 09:57 AM
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James Pierce Jr.
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It is more noticeable in 2nd and 3rd vs 4th and 5th. However it is still present in all gears. If you are cruising or accelerating lightly it is worse than standing on it. If you let off the gas to coast it goes away.
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  #4  
Old July 30th, 2010, 03:04 PM
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Jason England
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Have you checked all the air pipes for leaks ...anytime I have 'fuelling' problems it's always the air that's the issue ... generally a leak or loose pipe. Having said that I still have minor surging in 2nd gear ... but suspect this is due to exhaust leak near the header which I need to get round to fixing.
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  #5  
Old August 1st, 2010, 11:26 AM
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'95 D90 ST 2.8L TDi #2050
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For me, the fix was a new alternator. It seems that my old alternator had a bad diode that was causing the similar surge issue you described. Good luck.
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  #6  
Old August 1st, 2010, 08:54 PM
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James Pierce
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James Pierce Jr.
1995 D90 SW #314, 59 SII 88 HT
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Quote:
Originally Posted by Chris Vitale View Post
For me, the fix was a new alternator. It seems that my old alternator had a bad diode that was causing the similar surge issue you described. Good luck.
I wondered about that. When checking the back of the alternator I get 13.94 volts. I will take it off and have it tested.
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