hey everyone,
wanted to present a problem to see if anyone has opinions...didnt find much after searching.

had my local muffler shop put on a true dual exhaust for my 88 2.8 FI blazer this weekend. when we left the shop it drove pretty well, but as i got closer to home it started sputtering/missing when accelerating. just a few blocks away from my house i had to just coast home because it was missing so bad i couldnt even get it to rev over 1000 rpms...now the car starts but dies right away.

if i take off the air filter cover and spray starter fluid while pressing the acclerator, it revs up like a dream. this led me to believe it might be a fuel problem so i replaced the old fuel filter (the pump was replaced two months ago) but still no luck. i have checked for vaccum leaks or loose connections with no luck.

one thing i did notice was they re-located the o2 sensor and removed the catalytic converter...could this really cause it to run so poorly?
the car ran great before the dual exhaust was on.

thanks in advance!

 

The O2 Sensor very well could be your problem, when the engine is cold it is in open loop where the exhaust does not come into play with the fuel/idle. Once the engine is warm based on the temp sensor for the computer the car will switch into closed loop for the fuel mixture. If the O2 sensor is faulty or not connected you could have all kinds of problems. I would make sure that you do not have a broken/grounded wire to your O2 sensor, then I would try a replacement sensor. If they relocated the sensor did they have to splice the wire?

 

#1 problem is that the "muffler shop" violated federal law by removing the catalytic converter and can be fined quite a bit and even shut down for such an offense.

#2, why even bother with a true dual exhaust on such an anemic motor?

How does the fuel spray out of the injectors look? Is it spraying at all? The next step would be a fuel pressure test. For a TBI motor, you should see 8-10 psi.

 

The "relocating" of the oxygen sensor sounds suspicious to me (also the cat thing). Did they have enough slack in the sensor wire or did they cut and splice?

 

mr.vls:
i agree the o2 sensor could be at fault, and this would explain why the car ran well until it was warm. however, why would it continue to run poorly after we got it home? even now, if we try to start it the engine fires up and dies. feathering the gas makes it stay alive longer, but it sounds like it is running on two cylinders.

swartlkk:

yes, i know it is illegal to remove a cat. this is my nephew's car (17yrs old) and he really wanted dual exhaust. i am just trying to help him fix it.

as far as the fuel spray, it looks pretty light to me, even sputters a bit. a fuel test is next in the diagnosis project.

bandidolenny:

it appears that they had enough slack in the o2 sensor wiring, so i dont think they messed with the wiring, but i haven't ruled this out.

thanks everyone for the responses, at this point i am investigating all things related to the exhaust system installation, since the car ran well before that.

someone else suggested to check the timing, but i find it hard to believe the muffler shop would mess with that on purpose...

 

You may want to take it back to the muffler shop and let them assess the situation. You paid them to do a job and they F'ed it up, seems to me they should figure this one out, sounds like they caused the problem, they should fix it. I wouldn't be suprised if they have run into this same problem in the past, they should have a solution. Make sure you talk to a manager and act a little pissed off, they'll take care of it.