DamageINC Posted January 6, 2010 Share Posted January 6, 2010 Ok fellas, I have a good one here for ya. Got a solid hour into it now and am running out of ideas.. ..96 Taurus/Sable, 3.0 Duratec. Comes in running rough, only code is P0174 (bank 2 lean). Feels almost EXACTLY like the EGR is stuck open a little.. Low RPM/idle is when the concern is around, anything over 1,000 rpm and it runs mint. Looking at the PID data, my LT fuel trims for BOTH banks are pegged at +33, and my shorts are at +25 so it's adding fuel like crazy and still not happy. I don't hear any obvious vacuum leaks and the first thing I do is eliminate the MAF. Boom - idle jumps up and runs smooth for a good 5 minutes with no MAF. A few restarts with no MAF and it seems fine. Order up a new MAF, clear the KAM and install it - same issue as before. Root through my toolbox, find ANOTHER known good MAF and stick it on there. Same problem. Hmm.. Ok, well, my upstream O2 data shows both sensors at a VERY low 25-30 mv. However, when you snap the throttle and bring up the RPM's, the O2's come alive and read normal values. And with the MAF unplugged, they will read anywhere from 200-900mv cycling back and forth like normal. Here's the funny thing - even though the fuel trims show that it's DEAD LEAN and adding fuel like crazy, it runs better when I add even MORE fuel by taking the fuel pressure regulator line off and spraying brake cleaner into the intake through the regulator's vacuum line. O2's light up and read rich almost instantly. I block off the EGR by placing a piece of cardboard between the valve and intake. Problem still there. DPFE voltage (1st thing I checked) is at .81 KOEO and KOER, and it DOES respond to EGR flow. Fuel pressure is about 36-37psi running and the fuel looks like it's good, clean gasoline. TPS voltage is at .9 and reading C/T when idling. This car DID, however, come in with some gnarly noises in the timing cover and they went away, magically, after I added 4 quarts of oil to it. I fear that I may have a base engine timing issue, almost, but my gut tells me that the driveability concern and lack of oil are not related. I hope I'm right, lol... ..Anyone got any thoughts? Dave Quote Link to comment Share on other sites More sharing options...
DamageINC Posted January 6, 2010 Author Share Posted January 6, 2010 Nevermind. Found the hugest vacuum leak in history and somehow it was inexplicably inaudible, NOR did the 2 cans of brake cleaner I fired on the engine get anywhere near the leak, apparently. Love it! Thanks anyway guys Dave Quote Link to comment Share on other sites More sharing options...
Cetane Posted January 6, 2010 Share Posted January 6, 2010 I am no gas engine expert but I just did diagnosed one with similar symptoms and it ended up being some cracked rubber just under the throttle body/upper intake. I think it was the something to do with the PCV but the guy I diag'd it for actually replaced the part. Quote Link to comment Share on other sites More sharing options...
Aaron Posted January 6, 2010 Share Posted January 6, 2010 some cracked rubber just under the throttle body/upper intake. My pop's car did this, his is a 24v. Kicked my ass for a little bit, the hose had sucked itself flat and the leak was on the back side of the hose, so it was not visible, and I don't bring the smoke machine home from work, typically Quote Link to comment Share on other sites More sharing options...
eastendpowerstroke Posted January 6, 2010 Share Posted January 6, 2010 I chased a lean code on a 24v taurus for a while. I found the plastic elbow on the vac hose to thebrake booster was cracked and would open up and leak when the engine torqued back on accell but would't leak when it was in the bay. Quote Link to comment Share on other sites More sharing options...
mchan68 Posted January 6, 2010 Share Posted January 6, 2010 If you are referring to the vacuum hose where it connects to the intake just ahead of the throttle body on the firewall side, those are pretty common to swell up on a lot of 24V Duratecs of that era, and get by some of even the most seasoned driveability techs. Quote Link to comment Share on other sites More sharing options...
Aaron Posted January 6, 2010 Share Posted January 6, 2010 Little short hose that went from the bottom of the intake right behind the throttle body to the plastic hose that ran under the intake, on mine. Quote Link to comment Share on other sites More sharing options...
DamageINC Posted January 6, 2010 Author Share Posted January 6, 2010 No, the VMV feed line out of the valve was all crispy and completely deteriorated off the nipple behind the valve cover on the passenger side. Never seen that one go bad before! Usually it is the line you're talking about.. Dave Quote Link to comment Share on other sites More sharing options...
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