Thread: New exhaust work: now my performance SUCKS!!!!

As you may see I am new to the forum. Wednesday night I puchased a 2000 GTP with 16300 mi. I couldn't resist the price! There really wasn't a ton wrong with it, but I began having it worked on IMMEDIATELY!!!. I had to replace the intake and supercharger gasket, belts, fluids, plugs, and thermostat. RAN LIKE GREASED LIGHTING!!! I knew that it had an exhaust leak, but it was a bad donut at the flange where the converter and the resonator meet. I took the car to the guy that normally does all of my exhaust and suspension work (needed new front struts and springs) and I let him talk me into replacing the exhaust from the downpipe back.

Every thing is replaced w/what I believe is 2.5 inch exhaust ( I didn't measure it), but now my car runs like crap!!!! It sputters, hesitates, fuel mileage sucks and it has cut out on me! The problems showed up IMMEDIATELY. There is no guessing that the change in exhaust caused the issue.

NOW:

There is no bend coming out of the convertor into the resonator as before, so there is less back pressure, could that be an issue,

OR:

Is it possible that something needs to be recalibrated to make up for the change in exhaust,

OR:

Is it it possible that I have been dupped and have cheap or undersized components (Convertor) on my car, (my vote)

OR:

Possible O2 sensor problem when the convertor was installed?

Er you mean 163,000?

New plugs - is it re-wired in proper firing order, are the plug wires good, no cracking and routed proper.

I had a plug wire routed wrong burn itself on the manifold just enough to short out, made it run like complete anus(i think it took out both cylinders on that coil) until i pulled over at a truck stop routed it proper and taped over the crack with electrical tape.

Other than that - Make sure your crank sensor is good, my old 91 olds crank sensor started going bad and threw the timing to hell.

Exhaust
Almost sounds like the cat is clogged....did they mess with EGR on the exhaust work?

PCM / 02....
If the rear 02 is dicked its possible its gone into the catalytic converter diagnostic mode which would make it run rich and suck fuel but i dont think it would cause it to behave poorly....dunno tho only read about it.

Is it stock from the previous owner or was it modded / demodded.

changes in the exhaust short of a big header/manifold leak will not affect performance. its something else.

Originally Posted by GeeBee

Er you mean 163,000?

New plugs - is it re-wired in proper firing order, are the plug wires good, no cracking and routed proper.

I had a plug wire routed wrong burn itself on the manifold just enough to short out, made it run like complete anus(i think it took out both cylinders on that coil) until i pulled over at a truck stop routed it proper and taped over the crack with electrical tape.

Other than that - Make sure your crank sensor is good, my old 91 olds crank sensor started going bad and threw the timing to hell.

Exhaust
Almost sounds like the cat is clogged....did they mess with EGR on the exhaust work?

PCM / 02....
If the rear 02 is dicked its possible its gone into the catalytic converter diagnostic mode which would make it run rich and suck fuel but i dont think it would cause it to behave poorly....dunno tho only read about it.

Is it stock from the previous owner or was it modded / demodded.

Everything was stock. Performance was okay when I purchased it Wednesday. Worked on it Thursday and Friday morn. Thats when the new plugs etc. went on. Performed like a champ!! Ran it Friday night no sweat. Saturday morn, no problem. Changed exhaust Saturday afternoon...turdjuice.

Don't know about the EGR though...but you are correct, it is behaving as if it has a plugged/clogged convertor. Someone else suggested to check the fuel pressure regulator, but that just seems to iffy!

do you have a vacuum leak? I am with bio......short of a major leak or a big time obstruction........the exhaust is not your culprit.......start searching......does it have trouble idling? any other info that we should be aware of?

good luck....

#!@# him on the crank sensor, he prolly broke it in the first place ($15 part btw) I know it was possible to move the crank sensor on my series 1 which would throw it off timing - dunno about series 2/3 tho. Either way i'd tell that guy to !@#@ off on it and tell him he broke the EGR on the exhaust install and to fix it.

so your EGR is leaking?

Originally Posted by Billy Low

Diags show that it's the EGR and Crank Sensor. Dude asked to repair it for me for the low price of $620....


Unbelievable.

did you have the same place that did your exhaust do the diagnostic analysis? If so, they should fix it as they broke it........if not then contact the people who did do your exhaust and see what they have to say....

yes.........wait for your regular mechanic and make sure it is someone you trust.......I hate dishonest shops........my worst pet peeve in the world......?

what type of plugs did you put in?( which model) not platinum I hope.........

ummm the crank sensor isn't too bad if i remember right...

get it jacked up and you should be able to reach it from below...i think you can re-align it without having to take anything apart.

Think you undo the set screw and push it towards the harmonic balancer and use a feeler gauge to set the gap.

If you actually have to replace the crank sensor its a good idea to do the harmonic balancer at the same time since its a PITA to pull and the rubber can go rot / tear and break free causing the inside to turn independantly from the outside making funny noises when you turn the wheel / run the ac....

i'm not sure but i think the EGR valve is the butterfly just behind your throttle body, but thats a guess..

If your harmonic balancer is bad it wont throw off your timing since that is run off a magnet mounted to the center not the outside, but your accessories and supercharger wont turn proper.

Changing the crank sensor req's pulling the harmonic balancer off so...If it looks like its dry rotted or can see stress marks in the rubber its $100ish part to replace which is less than the labor will prolly be if you have a shop do it.