i own a 98 neon DOHC w/ 75k miles. the car has been backfiring on left hand turns for the last 7k miles. The car runs much better with a full tank of gas, but once the gas hits about 3 quarters it starts acting up to the point of breaking down, and backfiring in the front. the car also seems to be burning up oil, about 1-2 quarts a month. I have replaced the spark plugs, and wires, pcv valve, air filter, battery(which surprisingly did alot of good.), i put 3 different coil packs in, and have tried various additives/cleaning sprays you name it. the car has also had a very rough start since i have had it, but lately (now breaking down often) it will almost always chug up to a start, and take forever to idle.

today i pulled off my throttle body to take a look at the idle control valve, and TPS sensor. once removed i noticed how black and disgusting my throttle body was, along with the ICV. i cleaned all this to the best of my ability with throttle body cleaner, put everything back together, and voila, with only a quarter tank of gas the car seemed to be running decent (by this i mean not breaking down with so little gas), still came to a rough start, and bogs and chugs whenever i turn the wheel to the left. if i were to replace the TPS sensor, and install a new ICV, would this fix my problem? or is this only part of my problem?

the car has spit out many many many diff codes, i dont remember them all but this is the best i can do at the moment...

CODE 72** Catalytic converter efficiency failure.Catalyst efficiency below required level.
CODE 43** Multiple cylinder misfire detected.Peak primary circuit current not achieved with the maximum dwell time.
CODE 25** Idle air control (IAC) valve circuits.A shorted condition is detected in one or more of the IAC valve circuits.Or a vacuum leak has been detected.

sorry these are so vauge, i plan on getting it tested again sometime this week, but i would like to try a few more things first.

some things others have told me it could be, and things i think it could be...

something shorting out (backfiring and bogging down only on L hand turns)
fuel pump (seems to sound louder, and very wierd sometimes, than other cars)
fuel injectors (injector cleaner does nothing)
fuel pressure regulator (built in filter)
TPS/ICV
Bent valves due to bad timing belt
Cracked head/bad gaskets (burning or leaking oil, white foggy smoke)
bad alternator (new battery helped a ton, seems to be getting weaker)
bad wires (were bought brand new within last 5k miles, is it possible to buy brand new wires which are bad out of the box?)

im just looking for the best possible explanation for all those symptoms, anyone who could give me any advice it would be greatly appreciatted. any mechanic i have talked to, or has looked at the car tells me something different.

please...anyone....help!

thank you.

 

Holy freaking hell you have so much going on I would look the other way and strip the damn thing and sell it for parts. Thats just me...Truthfully to be compleatly honest with you its going to be hard for anyone to help that much due to so much going on... your going/have spend alot of money getting it running correctly again. Butit sounds like you know quite a bit just by saying heyI have allready torninto it, so dont get discouraged ifno one answers your question. Stick around and welcome to our forum.
oh after reading threw your post again I would try switching out your fuel pump first before doing anything else..Then the Cat...hell cut it out for christ sake gain a few hp...Bent valve soundsconsistant with the crap in your intake. I bet you anything if you take off your intake manifoldand unbolt the bottom of the manifold it has at least a 1/4th inch of oil sitting at the bottom of it if not more...might as well switch out the ICV its fairly cheap....(im going threw your post and disecting it sorta) take your throttlebody off and check the vacume port. it may be cloged if not go threw every single vacume line and switch it out shouldent cost more then 20 bucks, sincecode 25 is present i wouldent even deal with checking everything just replace it its cheap...do a good leak down test to find outif the valves are bent or not would leak"up" if that was a problem. Any noticeable leaks under the car or on the block??? Hope you can make it threw my rambleings I'll shut up now....

 

nothing under car, ever. think i will try new vacuum hoses, and new ICV tomorrow. see what that does for me.

 

Ok I wouldn't go getting rid of the car, heres some things I would try,

I would fix the things it says are wrong in the codes or you can unplug your battery for 10 minutes then rehook up, and what this does is erase the codes and hopefully reset if the problem has gone away which is unlikely but worth a shot.

To meit sounds fuel pumprelated maybe your Fuel Pump pickup is fkd up, as a last resort I would pull the pump out and replace it with a Walbro 255 or 155 fuel pump direct replacement and cheaper than the Mopar direct replacement and better. Also You could replace your PCM with my Known Working DOHCPCM which I'd sell you for $40 (same price I paid) but if you like you can just pay for shipping and I'll give it to you and if it fixes your problem give me $40 or whatever seems fair I have no use for it anymore.

Things I would look at before sending it away would be.... Vaccum hoses, Fuel Pump Assembly, Map Sensor/IAT Sensor, O2 Sensor both up and down stream sensors,PCM Injectors and Fuel Pressure. Not exactly in this order but...

And if you like I have a Extra ATX CLEANThrottleBody and DOHC PCM which you can throw me an offer for the pair.