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ENGINE HESITATION, FUEL PRESSURE, WHAT DO THESE CODES MEAN? V70-XC70 1999

posted by  someone claiming to be Mark on  Thu Aug 19 15:02 CST 2004 [RELATED]

Hi, this is my first post. My 99 V70R developed this annoying engine stumble under high boost/load, principally above 3000rpm. Under normal driving conditions the car drives fine, gets respectable mileage and doesn't use much oil. When the problem first appeared at about 49000 miles, I replaced the spark plugs, fuel filter, O2 sensors,cleaned the throttle body and checked the fuel pressure, 58PSI @idle. I subsequently went on vacation, logging an additional 4000+ miles. The condition remained constant. When I returned, I took the car in for a very rare trip to the dealer to see if they could figure it out. The tech, after finding no codes stored, took the car on an extended road test (100 miles+), and determined that the fuel pressure was falling to 48 PSI under full load, and got the ECM to kick out codes 260A, 3502 and 3503.
As far as I can tell, 260A is some sort of MAF sensor fault, so he checked perfomance at idle, getting 14KGH at a throttle module reading of 4%, supposedly within specs. 3502 and 3503 are cylinder specific, I think, but no explanation was offered.

So here it is. The tech said the fuel pressure should actually increase slightly under load to 60 some-odd PSI. He suggested replacement at an estimated cost of $2100. I hit the brakes.
So, is 48PSI really too low, and does low fuel pressure support the codes that were stored in the ECM?. Can a MAF sensor operate satisfactorily at idle, but fail when gulping the large volumes of air that this engine demands?

Thanks for your patience with this,

Mark





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