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Extremely poor acceleration and 5.4 MPH
Dear Sirs, I inherited a 1993 Chevy Lumina Euro with a FI 3.1 V6 eng and auto trans. 102,000 Miles. It had not been driven for 16 years and stored in a garage. It had problems from sitting,,, the usual, brakes tires battery. No mouse damage! The car looks Great, almost NEW! I replaced the Spark plugs and spark wires, got a mechanic to check ignition coils and for computer codes, there are none. Yet I have a VERY strong smell of unburned fuel from exhaust. EXTREMELY poor acceleration, and getting only 5.4 miles per gallon. Checked eng. compression it's fine. No eng knocks or noises. I have never seen anything remotely similar! I am loosing it over this problem! Will you help Please?
Thank you David Comstock Sr.
Re: Extremely poor acceleration and 5.4 MPH
just a suggestion of something to try, an exhaust back pressure test. measure the exhaust pressure between the cat and the exhaust manifold. you might have a plugged exhaust.

If the exhaust pressure is withing normal specs, drive around with the scanner graphing the data stream and see what the fuel trims are doing.
Re: Extremely poor acceleration and 5.4 MPH
carriedi wrote:just a suggestion of something to try, an exhaust back pressure test. measure the exhaust pressure between the cat and the exhaust manifold. you might have a plugged exhaust.

If the exhaust pressure is withing normal specs, drive around with the scanner graphing the data stream and see what the fuel trims are doing.


I did think of that. Yesterday. I took the old girl to the local Muffler and exhaust shop and had the entire exhaust system replaced. Unfortunately there is no change in how the car runs! I really hate this! This car was given to me by a very good man that has past on. I would like to see it running well and use it as he wished! I am open to any idea's!
Re: Extremely poor acceleration and 5.4 MPH
most places, when they talk about replacing the exhaust system, do not include the catalytic converter. But if you had that replaced also then I would drive it with a scanner on the vehicle and see what your computer is seeing. Your oxygen sensors, fuel trims, MAF, coolant temp... See what they are doing as you drive under normal conditions. this way you can see if the engine is trying to add fuel or it may be taking away fuel. You can see if the ESC is seeing an engine knock (ping). See if the TPS is working normally.
Re: Extremely poor acceleration and 5.4 MPH
carriedi wrote:most places, when they talk about replacing the exhaust system, do not include the catalytic converter. But if you had that replaced also then I would drive it with a scanner on the vehicle and see what your computer is seeing. Your oxygen sensors, fuel trims, MAF, coolant temp... See what they are doing as you drive under normal conditions. this way you can see if the engine is trying to add fuel or it may be taking away fuel. You can see if the ESC is seeing an engine knock (ping). See if the TPS is working normally.

did replace a cat converter, but I'll try your suggestion. Lord knows I'll try anything. At this point anything is better than nothing! This problem has me nearly exhuasted!
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