GP1138 Posted February 18, 2012 Report Share Posted February 18, 2012 Took a snapshot of my system on an OBDII scanner today, just for curiosity's sake. ECT: 176 -- STFT B1(%): 12.5 -- LTFT B1(%): 16.4 -- MAP(inHg): 10.0 .. This was just the first screen but I was pretty much just interested in the fuel trims. I'm also throwing a very intermittent P0171 code. I'm going on a trip in March, so I pretty much want to nip any fuel problems in the bud before they become larger. I copied the values above exactly as the scanner showed them; I took a picture of it. Anything I need to worry about here? This was probably taken at idle. Also, any FREE way of pulling ABS codes?? Quote Link to comment Share on other sites More sharing options...
95 vert Posted February 18, 2012 Report Share Posted February 18, 2012 Definitely adding fuel. Bad 02 sensor, vacuum leak, weak fuel pump are things I can kick off the top of my head. Anywhere between +7 to -7 is the general rule for normal. Quote Link to comment Share on other sites More sharing options...
Night Fury Posted February 18, 2012 Report Share Posted February 18, 2012 Anywhere between +7 to -7 is the general rule for normal. This is good to know! I always wondered what was normal Quote Link to comment Share on other sites More sharing options...
Cutlass350 Posted February 18, 2012 Report Share Posted February 18, 2012 Sounds like a vacuum leak. FWIW: That's what my car showed when the brake booster went. In my Olds, it's pretty obvious when a brake booster dies. Olds seems to like very over boosted brakes. Quote Link to comment Share on other sites More sharing options...
GP1138 Posted February 19, 2012 Author Report Share Posted February 19, 2012 I've replaced the actual pump on my fuel pump -- when I did this, somehow the little plug that keeps gas in the catch-can fucked up and it all leaks out when I let the car sit after driving, so I have to let the pump prime and then start it or it'll crank for ages. Could this be emptying while driving and causing problems with fuel pressure? It seems to take a little while to empty, if I go into a store and immediately come out it'll bump start, but if I take 20 minutes it'll crank awhile. I'll check the MAF, I've read that can cause this as well. No holes in my exhaust that I can tell -- I do have a hole in the resonator but I "patched" it with a flat steel panel wrapped around and clamped. Once we get our tax return, I'm going to tune it up. Quote Link to comment Share on other sites More sharing options...
alec_b Posted February 19, 2012 Report Share Posted February 19, 2012 You missed a couple critical data points... Speed and Load. Are those idle readings? Look for a vacuum leak. If those are on-road readings, especially under load, look for fuel starvation. Bad pump and/or clogged fuel filter. Quote Link to comment Share on other sites More sharing options...
Cutlass350 Posted February 19, 2012 Report Share Posted February 19, 2012 You missed a couple critical data points... Speed and Load. Are those idle readings? Look for a vacuum leak. If those are on-road readings, especially under load, look for fuel starvation. Bad pump and/or clogged fuel filter. He likely looked at the trim values at idle, or with the car in park. Under those cases, if the trim was that bad at idle in park, then a bad pump, clogged fuel filter, leak, etc would be so bad they car wouldn't even make it up to 20mph. There likely aren't that many vacuum sources from the engine. It's easiest to plug them all up (except for the fuel pressure regulator if the car has one). Off hand, with the engine already warmed up, there shouldn't be any need for vacuum sources as long as the car stays at idle. If it was a vacuum leak, the trim values will start to come down within ~10 secs after the engine goes into closed loop - in other words withing ~1 min after the warm engine is started. IMHO, the hard part is then trying to hunt down exactly where the vacuum leak is. For ~$2K, a "leak-test smoke machine" can be bought. The better dealers have them and use them. Otherwise, one problem in hunting down a vacuum leak is trying to disconnect the hard vacuum lines without making a new leak (or one in the future). For my Mustang, I said ****** it and bought new hard lines and hose connectors. IMHO, not worth the risk of a poor fitting making a vacuum leak. Plus, at over 20 years old, I think it's earned at least new vacuum lines. Quote Link to comment Share on other sites More sharing options...
95 vert Posted February 20, 2012 Report Share Posted February 20, 2012 That's not that bad for fuel trims. Yes, it's adding fuel to compensate, but at those trims, it would still idle, maybe a little rough. It would certainly still be able to go over 20 mph and most likely driving conditions would be normal. Now, fuel trims 20+ in long term and/or short term can cause driveability issues. Power loss, cut out, etc. 30+ and now you may not go over 20 mph. Quote Link to comment Share on other sites More sharing options...
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