Ken2004llbean Posted April 5, 2019 Share Posted April 5, 2019 Some background: Wife's car is a 2004 Outback LL Bean with H6-3.0, automatic, 153K. A sudden, massive coolant loss destroyed the original engine. Since a mechanic installed a used, replacement engine (with 100K) three months ago, the check engine light has remained on, with persistent codes P0519 and P0507, no matter what I've tried (see list below). Idle speed also high (1,000 rpm in park, 850 rpm in drive), and idle speed also sometimes surges/hunts, both in park and drive, which causes car to buck. Idle speed in park has sometimes gone as high as 1,300 to 1,500 in park, when engine is hot. Also, car does not always start on the first crank, but will always start on second crank. Surging rpm and hard starting have happened both with cold or hot engine. Anyway, I downloaded the factory service manual and followed procedures for checking codes P0519 and P0507. The most likely suspect for high/surging idle is vacuum leak, but neither I nor the mechanic have been able to find a vacuum leak (I used the carb cleaner spray method, he used a smoke test). Steps I have taken so far, with no change in solving the problem: - Replaced following parts with Subaru OEM parts: throttle position sensor, idle air control valve, PCV valve (old was was gunked) and PVC and air box breather hoses. - Removed EGR valve to check valve and passageway on intake manifold for carbon buildup/blockage, but found no blockage. - Adjusted throttle and cruise control cables. - Replace throttle body gasket and cleaned throttle body. Replace air filter (old one dirty). - Replaced ECM with unit from salvage yard. - Cleaned all ground connections I could find, and checked for loose electrical connectors. - Tested for voltage and ground at various sensors (MAP, TPS and IAT) The past few days, I have monitored live data from my basic scanner/code reader while driving, and I noticed one pattern: whenever I let off the throttle (whether from cruising speed, or acceleration), the car goes into open loop briefly and bucks, then returns to closed loop. Also, when I experience surges in rpm, the ECM is in open loop. Another pattern I've noticed is if I put the car in park, and press the throttle, I will get the surging rpm problem between 1,000-1,100, and also around 1,700-1,800 (very specific, reproduce-able ranges). I don't know if the open loop is causing these surges, or is the effect of these surges. The P0519 and P0507 codes; going into open loop going on and off the throttle; and surging rpm come back after resetting the computer by disconnecting the battery. Since I get the surging when rolling on or off the the throttle, I used a DVOM and backprobed the TPS connector. I get 0.7 volts at full closed throttle, and 4.5 volts at full open throttle, with smooth increase in voltage as throttle is opened. I don't know if it's the throttle position, or a certain rpm range, as described above, that's sending the car into these open loop spasms. Took the car back to the mechanic today to see if his expensive Snap-On scanner could reveal any smoking guns than my $40 scanner could not, but he said nothing jumped out at him, and that the fuel trims looked good to him. The car cruises and accelerates smoothly and powerfully. It only acts up when first letting on and off the throttle, in addition to sometimes hard starting and the always-high idle. One other thing maybe worth mentioning: my scanner shows emission monitor readiness status, and in the past several weeks of tinkering around with the car, the monitor for EGR has never entered ready status. My mechanic thinks it may be worth replacing the EGR valve, although I hate to keep throwing parts at the car at about $100 a pop, even though my labor is free. I've spent hours searching online and under the hood, and am growing beyond frustrated. This car is consuming me. -Ken Link to comment Share on other sites More sharing options...
RumbleRumble Posted April 5, 2019 Share Posted April 5, 2019 Do you have a exhaust leaks at the headers? or even possible vacuum leak? Link to comment Share on other sites More sharing options...
Ken2004llbean Posted April 9, 2019 Author Share Posted April 9, 2019 No exhaust leak I'm aware of. Have performed carb cleaner spray test to check for vac leaks, none found. Mechanic did smoke test to check for vac leaks, and he could find none either. Link to comment Share on other sites More sharing options...
RumbleRumble Posted April 9, 2019 Share Posted April 9, 2019 Did you adjust your TPS when you replaced it? you can check with a code reader. I'd find someone with a good one that check to see what monitors are ready and which ones are not. Link to comment Share on other sites More sharing options...
Ken2004llbean Posted April 10, 2019 Author Share Posted April 10, 2019 Unlike the H4 engine's TPS, the TPS on the H6 engines are NOT adjustable. Also, all my monitors, including the previously stubborn EGR monitor, are in ready status. I did some highway driving after my last computer re-set, and that seemed to do the trick (my basic code reader also tests for I/M readiness). Link to comment Share on other sites More sharing options...
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