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171-174 codes

May 19, 2013
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My trusty '96 LongRanger started thowing P0171/174 codes recently and I was finding the truck a little down on power and harder to get good mileage. Now back in my younger days, my engines alway had a "lean code" because I drove Mopar slant sixes and 2.3 Vauxhalls -but that was before the days of OBD codes and all. The long and short term enrichments were both pegged - 40 and 25 on both banks. I also had a small exhaust noise which Ihad been putting up with for some time. Ends up the EGR tube was cracked off at the flare inside the nut on the back of the exhaust manifold. What a miseable SOB that was to get off with 378000Km and 26 years of extreme heat!!!The bolts holding the EGR valve on (starting out as 10mm) werer almost as bad as the tube nuts. One came off with a 3/8 inch 6 point socket after heating it and the valve red hot several times with the aceylene torch - the other was burned round and I was fortunate to have a set ot rounded nut remover sockets - I drove the little one on with the bolt almost dripping and managed to get it out too.I should have replaced all thet when the engine was out last fall!!!~ getting the new one on was, if anything, more challenging than getting the old one off - no room to swing a wrench ANYWHERE. ANyway - I got it back together - it was nice and quiet but no difference AT ALL on the fuel trims - and if anything it idled worse. Luckily I had the foresite to order a MAF sensor from Rock Auto along with the EGR parts (I had tried another "experienced" one previously - it made no difference but I wasn't convinced). I put in the new MAF and cleaned up the idle speed control valve and the trims dropped like a stone - and it hasn't run as well in several years.
ent for my test drive and NO VSS and NO SPEEDO!!!!!
I pulled the speed sensorout and checked it - no problem. Checked for signal at the ECU - nothing. I checked the bottom (transmission) harness - no problems -so I opened up the top (engine) harness looking for any damage and found where the grey and black wire exits the enbine compartment to the speedo and confirmed the splice in THAT wire wasn't the issue, then connected my continuity tester (beaper) to the engine harness pink/orange wire and the wire at the sensor - no beep - - -and to ground - also no beep - so SOMEWHERE there is a break in the ground circuit. I just spliced the pink and orange wire to the black ground wire wires in the harness up by the ECU there they bolt to the firewall, taped everything up and went for a ride. HALLEUJAH!!!!. All fixed.

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