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need major help with a 98 mystique with the 2.5 v6

11-20-2014, 05:09 PM
well here is the problem as it has happened. it belongs to a female friend. she been having to use a battery charger to start in mornings when it got cold. so she went and got a new battery at auto zone and they also ran the code checker cause it has check engine light on. the codes are P1150, P1151, P100, P1130, and P0171. she went and topped off fuel tank, and added heat. 3 blocks after all of this it would die when she came to a stop. she had to keep engine reved up to keep it running. she said that once before it did this and someone replace the O2 sensor, so I thought and seen codes for both O2s and so I replaced both.
no help:headshake. start it up and dies. hit throttle twice and start up it revs up high, then it dies. saw a vacuum hose that was getting bad. replaced it. still the same thing.:banghead:
now for the kicker of all of this, I have told her about keeping up the maintenance, but she thinks just by adding oil when needed, that is good enough. she is a doe doe.:screwy:
so my question is what does anyone think this could be, with out spending a crap load of money. she don't make a lot of money. I have known her most all my life.
myself I think it should go to a junk yard, but she need the car to get to work.
so please if anyone has an idea, it would help.

changed out fuel filter and air filter, and still go to start, it will rev up to 2750 rpm then die. hit throttle pedal, and it will stay revved up, but when u leave the pedal alone, it will die.
I have ordered the idle air control solenoid, will see if that fixes it. but would still like any help, please

11-23-2014, 05:43 PM
well changed out the IAC and it would run, but, would go to hi idle then down, and up and down. called someone i know that works at ford dealer, he asked a tech, they said TPS, so i went and got a TPS, and plugs. put the TPS in and Plugs, then started it, started out with the up and down of RPMs, so i hit throttle and help at 2 to 3000 rpm then released throttle, and it started to stablize. she drove it last night to work and home and it is working.
best note is when it acts up real bad, take to a dealer and get it on their diagnostic computer. with the new systems, that is the best way to get an ide4a on what needs fixed. in all, the hit and miss has cost her about a couple hundred in parts.
next time, a stick of TNT will go in the tank, and that will be it for the car.

11-30-2014, 03:32 PM
I have a 98 Mistake too and have had many problems. I have replaced the IAC valve, repaired a vacuum leak on the brake hose, two bank 2 O2 sensors, and now had problems where it would not start all the time. Found out that the fuel pressure regulator was bad. The codes it shows are not always easy to read, they can mean multiple problems are possible but only one of them is causing the fault. I'm a pretty good mechanic but sometimes the problem is hard to track down. Buy a good manual and go through all the steps to diagnose it, it is a pain sometimes but if you follow the manual and have the tools it can be repaired without just swapping parts.
The p0171 code is what mine was showing, it says lean condition but what was happening if that the pressure regulator was bad allowing too much fuel pressure that would flood the engine so the PCM would switch it to lean mode to try and compensate. Some cylinders were flooding while others were lean so the engine would not start. I tested the fuel pressure to find this.

12-04-2014, 10:42 PM
as i told her, it was a pain in the rear. thank goodness for her sons friend that worked at the ford dealership and info from the head mechanic.

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