New H pipe now car hesitates and check engine light comes on.

[Rusty88]

Hi,
Have a 95 GT mustang. Just had a new H pipe w/ 2 cats put on. Now the check engine light comes on after a few minutes after start and the car is hesitating on acceleration. I haven't checked the codes yet.
Thanks

[fordtrucksonly]

hmm well if it wasnt hessitating i would say 02 sensor but hmmm check codes.. sounds like she might be lean.

[351wStang]

The o2's may not be getting enough heat with the new exhaust causeing a lean/rich reading.

[fordtrucksonly]

yeah i'd say that sums it up. Oh btw 351Stang, you have any new pictures of your ride?

[351wStang]

I made a thread a few days ago in the mustang talk section. Latest update on my street car. Just finished painting the roll cage today and got the carpet back in. The turbo kit is supposed to be here this week so hopefully I'll get to put the motor back in this saturday. Its coming right along!

[Rusty88]

Originally Posted by fordtrucksonly

hmm well if it wasnt hessitating i would say 02 sensor but hmmm check codes.. sounds like she might be lean.

Read the codes and came up with 172 "Heated Oxygen Sensor indicates lean condition right side" What causes this? vaccume lines are fine. Can it be a bad sensor? Thanks.

[351wStang]

Faulty o2. You can try mil eliminators but they probably wont work for very long.

[Rusty88]

Originally Posted by 351wStang

Faulty o2. You can try mil eliminators but they probably wont work for very long.

Thanks, will change the O2 sensors. Wondering if a leak where the manifold connects to the H pipe would cause any problems with the sensor? The guy who put the H pipe on was afraid to tighten the bolts too much because the manifold's bracket were pretty rusted. I can smell exhaust at idle in the car and hear a thwapping sound coming from the area...not good. cars going back in next week.

[351wStang]

Yes and no. If the sensor is close to the manifold connection then it could. I know with wideband O2's it will. I'm not sure about the stock narrow band O2's. If the sensor is way down stream of the manifold connection then I doubt it is causeing your problem. Stock O2's are finicky. I know a friend of mine just changed his mufflers on his Dodge pickup and it wiped out his stock O2's. He replaced them with universal O2's from Advance Auto and no more problems. He tryed mil eliminators and they worked for about 2 days. Then the check engine light came back on.

[Rusty88]

Got the car back...no more exhaust smell, hesitation or check eng light. Says he tightened up the H-pipe/mani connection and changed the O2 sensors. Running great so far.