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1998 Plymouth Neon Highline
2.0L DOHC 5 speed manual
2 door 129,000 milesJust got this last Friday (one week ago today). Tested everything with my Snap On MT2500 scanner before I bought it and it tested OK. Coolant temp seemed a little low and a couple of other things weren’t quite right but I could live with it.
I drove it home and it seemed to be fine, except that the cruise control kept cutting out. I fixed that and then when my wife drove it in to work on Monday it came up with the P0140 and P0171 codes and it it has an intermittent loss of power which comes back when cruising around 50 mph. It works fine on the highway at 70 mph.
Haven’t had a chance to really check anything out yet because she drives it every day to work and doesn’t get back until after dark and this is the first day since Tuesday that we have had commercial power back on (lost it due to high winds from Sandy blowing down trees, reported winds of 1 mph less than Hurricane strength here in Michigan on the shore of Lake Huron http://www.clickondetroit.com/weather/High-winds-slam-Michigan-communities-along-Lake-Huron/-/1719236/17199700/-/t24mut/-/index.html ). Weather permitting will be working on it tomorrow. Looking for things to check first that don’t cost anything before spending money on parts. Have a supply of spare parts for the 1996 Neon Sport which I may be able to use also. II don’t even know whether it has a stock exhaust system with CAT and up and down O2’s guess I’ll find that out tomorrow. Will change the topic icon to a smiley face when problem is solved and keep thread updated in the meantime.
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Both codes are for an O2 sensor so I suppose the first step would be to hook that scanner back up and see what the O2 sensors are doing. If it doesn’t show activity then move to the visual inspection and if you see that everything is hooked up the way it should be you might consider replacing it.
Update –
Put the scanner on the vehicle this morning. After resetting the codes last Thursday the only code today was the P0171 Lean code, the P0140 has not returned. Live Scanner Data indicated Lean only (no changing between Lean Center Rich). Upstream O2 0.06V then down to 0.04V Downstream O2 remained constant at 0.47V The highest I got the engine temp up to was 174 F at 170 F it dropped down to 163 F then went up to the 174. STFT 24.8 LTFT 24.8 This was all checked at idle.
Haven’t run it up on the ramps yet to check the underside will try and do that this weekend unless I can get the wife to take the 1996 Dodge Neon to work on day this week and leave the 1998 with me for a day (when it’s not going to rain as all my work is done outside in my parking area (no driveway here and garage is too full).
I plan on doing a coolant exchange with a thermostat replacement and if I can get them out a change of both upstream and downstream O2 sensors.
Will update as the work progresses
Update
Replaced the downstream O2 sensor. Was quite surprised at how easy it came out. Checked vehicle with scanner and found that there was voltage activity with the downstream sensor now but only 0.04 to 0.10 activity on the upstream with no change between RICH CENTER LEAN still LEAN only. Replaced the upstream sensor and the scanner now showed activity on the upstream sensor between 0.1 V and 0.9 V and the LEAN CENTER RICH were now changing. I think my P0140 and my P0171 code problems are solved. Haven’t really taken it out for a test drive yet but my wife will do it tomorrow. Hopefully the intermittent power loss will have disappeared with the codes. Reset the trouble codes as well as the adaptive trim. Now the STFT is down close to zero +- and the LTFT is at zero while idling. Will wait to see what happens in the next few days before I change the icon for this post to my smiley face “I got it fixed I’m HAPPY”. Thanks to everyone replying with helpful comments to my post.
John
Forgot to mention the low engine temp I had was a missing thermostat fixed it with a new one and new gasket. She’s got heat now!!!!
Still have to install an ignition key cylinder holding bracket and an engine roll damper. Hopefully this weekend. Wife drove it in to work today, said no SEL codes no overheating still loves me so I guess she’s happy. Having to pay $234. to have someone else put in a new radiator (that I could have bought for $61. with a lifetime warranty and easily have done myself) with only a 2 year warranty really sucks though.
Changed icon to smiley face. It appears that after over 300 miles of driving the codes and sudden intermittent power loss problems have been resolved with replacement of both the upstream and downstream O2 sensors. Thanks for all the helpful replies to this thread.
John
Was told that the mileage has improved substantially since the new O2 sensors were installed to fix the lean condition of the P0171 code.
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