Exhaust Problem Leads To Odd Idle
 

Ok, I personally have NO clue why my car is doing this suddenly, but it sure as hell is baffling me.

I took a turn onto a street and went WOT. Right now I have an offroad X and a Mangaflow Catback without the tips on (I havnt had the chance to adjust the exhaust and put the tips on yet). As I went WOT, my car decided to backfire with 6 loud pops. I let off the gas to make sure the car wasnt going to die, and then continued to drive normally. I came to a stop at a stoplight and watched my revs and theyre not acting like they should. I come to a stop in first, the revs go from 2000 to 1600, stays there for a moment, drops to 1400, stays there, and then hovers around 1050. My idle before this was around 800-950. I have no clue what is causing this at all. I checked my pipes and all is well underneath there, no leaks (that I could see, its kinda dark outside), no broken connections, no nothing. Got gas, started up the car and the idle acts normal as I start up the car, but if I drive it and stop it starts the 2k thing again.

Any ideas as to whats has caused this and what could be the culprit? Im hoping if I let the engine cool to relieve the pressure in the lines and start it up tomorrow everything will be ok. Is this a baseless hope?

Thoughts?

Sounds like your runnin rich or your not getting complete combustion. If you have a header or manifold leak, sometimes that will cause a backfire. You have CEL? You checked for codes?

you sure the loud pops was from the exhaust backfiring? I know it'll have a sound like that if the timing is off. Have you added a tb, plenum, or u/d pullies?

I am going to make an educated stab at this....try replacing your TPS with one from another Mustang. I bet that fixes it. I have seen multiple bad TPS cause this hanging idle and a rich condition. I don't know why it happens, just that it does. It is as if there is abad signal from the TPS which causes the IAC to open when it is not supposed to. Because of the bad TPS signal, the car thinks it is supposed to add more fuel then it is supposed to and you get your back fires.

Does the exhaust pops happen when you hit the gas, or after you take your foot off? If it happens after you take your foot off, then I suspect the TPS. If it happens as you hit the gas, then I am not sure. Before you buy a new TPS, I would try to get a bud to allow you to swap one over to your car first.

BTW, while it is at idle, try unplugging the TPS. What happens when you do that?

My TPS actually broke.. before it completely died the idle was hanging pretty bad. It was jumpy like you described.. I'd be stopped at about 900 rpms and it would jump to like 1500. This was going on during the 3 hour drive to get my car dyno tuned. It actually broke completely when it was on the dyno. A spring inside seem to have gave up on me. It was extremely weird. After they loaded the tune it acted like 4th gear was gone, it wouldn't accelerate at all. So they put the stock tune back on and it wouldn't go in any gear. It was dead at that point and we took it apart and saw the spring was gone. Put a new one on it and all was well.

How much is a throttle position sensor going to run me? Can I get it at any Pep Boys or am I going to need to head over to Ford so they can PIIMB and overcharge me?

Whoops, I take that back, looks like that TPS is cheap as hell (15.15 for a motorcraft one). lets see if I can find it anywhere close :)

I got mine from Ford for $45-50

Here we go!! New problem!

I was driving on I-76 yesterday doin around 70 and I look at my battery meter and its at the end of normal (low end) I wonder if it is just a bad sensor or something. Then the needle dips all the way down to the redline and suddenly my tach drops to 0. Bad news. Im stuck in the left lane, theres a wall of traffic to my right, and theres a slowdown ahead. I tap the brakes and downshift, and thats when my car starts to studder. I hit the gas to try and keep moving, but the car doesnt accelerate. Whammo. My car dies and im stuck in the left lane. I try to get it to start back up, but no dice. No clicking, no nothing. The car just dies.

Im thinking its the alternator. I looked at my battery gauge every once and a while to see if anything happens, but no dice, the battery is dead. I got a check engine light thrown, but I wasnt able to read it because I didnt have a code reader on me.

Anyone else thinking alternator? Any other ideas?

I'm thinking alternator also

Yup, on the plus side I created a 3-4 Mile long backup in traffic :P

okay let's see my idle on mine dropped after cleaning the imrc's....o2's will do this.... check your mils if you have them..... as far as it dyin i'm saying alt... but check your grounds

u suk @ teh mustangz

O2's are disabled, no MIL's. I Seafoamed, but I didnt actually crack open the IMRC's to get in there and clean. I could also afford to clean the IAC's probably. Goddamn alternator.

the seafoam probally helps but it won;t cure all your o2's are not disabled the front two could be bad....

No, just the rears. Sorry I should have been more clear on that.

WHOO SHES BACK UP AND RUNNING!!

New alt w/ a recharged battery, and shes runnin like she should. No more idle issues either :)

yayy now get back to bein a pimp and ull be right at home again

Chris:

I have heard of battery/alt issues causing bad idles before. Sorry about that. I forgot and should have mentioned something to you.

IF anyone needs a TPS . . .http://cgi.ebay.com/ebaymotors/ws/eB...MEWA%3AIT&rd=1

i'm not selling it, just trying to help somone out.

It was my positive wire going to my alternator that failed. It rubbed up against one of the bracket bolt mounts and ended up ripping into the wire. Once it ripped in all it needed to do was touch metal and voila, the alternator shorted out.

Its all fixed now, new alt, recharged battery, and were back in motion.