Vette will not start after after removing O2 Sensor and putting it back

[Randy from NY]

Hey guys. Hope someone can point me in the right direction. I have an '84 Vette with 48K original miles. The car is all original and has always been cared for...before buying it this spring, it spent the last 9 years in a garage witg a little over 600 miles put on it in that time. So heres the pronlem..as soon as I got it, the car was sluggish and would stall after only about 5 minutes driving. I replaced the fuel filter, wires, plugs, cap and rotor and ignition module. The car seemed to run great (for two days). then I started feeling the car get sluggish again after about 20 minutes of driving (220 degrees). Each time I took the car out, the trip would get shorter ad shorter and the car would become sluggish at lower and lower temps. I also noticed that the car would go into overdrive (Automatic trans) quickly and at low speeds. I considered replacing the fuel pump replay switch and a mechanic mentioned to me that he felt that it was the catilytic converter. He said to remove the O2 sensor and if the car ran without hesitation, that would tell me for sure. I removed the O2 sensor, started the car up, it ran rough for about a minute, stalled and could not be restarted. I reinstalled the O2 sensor but car would not start (only cranks). I let it sit overnoght and tried again the next morning..it started, ran rough for less than a minute and stalled. Got it to start again, it stalled and that was it. I tried agan the next moring, again it started, ran for 3 seconds, stalled and again could not be started. Up until I removed the O2 sensor and started the car, It always started on the first shot. Does anyone have any ideas. I am not a mechanic, just learning as I go. I would rather fix this myself, learn whats wrong and how to fix it rather than flatbed it to a mechanic and have them charge me for something I can learnand do myself. Thanks

 

[vetteoz]

a mechanic mentioned to me that he felt that it was the catilytic converter. He said to remove the O2 sensor and if the car ran without hesitation, that would tell me for sure.

Never everheard that one.
Usual test for blocked convertor is to remove it and see if engine runs different.
Disconnecting the O2 sensor just means car stays in open loop tune; if cat is blocked exhaust would still be restricted so no change to how it runs

I reinstalled the O2 sensor but car would not start (only cranks).

Engine will start and run with no O2 sensor , just get crappy fuel economy.
You have other problems.
Back to basics; fuel and spark
Have you tested fuel pressure? pump may be on its way out ( or dead )
If sitting for that long did you flush tank out, all sorts of things could have happened in there
Even though you have new parts have you confirmed you have strong spark at plugs when cranking?

 

[Randy from NY]

Reply to VetteOZ re: vette won't start after removing O2 sensor

Thanks for your insight..I have not tested the fuel pressure yet. I found it strange that the car started right up every time until I removed the O2 sensor so I figured that by removing it and then replacing it was the cause of the car not starting. Before doing this, starting the car was never a problem. This all started when I went into a local auto parts store with the fuel pump relay switch in my hand looking to replace it. The guy behind the counter suggested the cat converter and told me to test it by removing the O2 sensor..now it will not start

Never everheard that one.
Usual test for blocked convertor is to remove it and see if engine runs different.
Disconnecting the O2 sensor just means car stays in open loop tune; if cat is blocked exhaust would still be restricted so no change to how it runs



Engine will start and run with no O2 sensor , just get crappy fuel economy.
You have other problems.
Back to basics; fuel and spark
Have you tested fuel pressure? pump may be on its way out ( or dead )
If sitting for that long did you flush tank out, all sorts of things could have happened in there
Even though you have new parts have you confirmed you have strong spark at plugs when cranking?

 

[BigJimZ16]

Well if nothing else, that proves how little your parts man knows about the vehicles he sells parts for... I'm thinking fuel myself. Check pressure, look at the plugs (are they wet?) what is the condition of the fuel??
Listen to the voice of the FSM, not the guy who makes money selling you parts...

 

[djsroknrol]

My bet is the fuel pump is going south....I had the same thing happening with my '84, and 45 minutes and a new fuel pump later, I had a smooth running 'vette again. They're really easy to change and the best part is, you don't have to drop the gas tank

 

[John Robinson]

600 miles in 9 years = a lot of junk in the gas tank. If the car was stored all that time with a partial tank of gas the tank became a miniature tropical forest. I would bet if you pull the fuel pump you will find a lot of rust and the fuel pump pick up screen will be clogged. Think about it when you turn the key on the pump primes the fuel rails so the engine will start and when it does then the pump kicks in and starts to pump fuel. The suction of the pump will pull the rust up to the filter and the pump will starve for fuel. Let it sit for a while the junk floats off the pick up filter and you are able to start the car again. The gas that was in the car when you got it most certainly was bad from time and moisture. Believe it or not gas has a shelf life just like beer and it will go bad. As for the O2 sensor causing the car not to start after you put it back in that goes back to the fuel pump being able to run and suck the junk into the pick up filter while you had the engine running with it out.

 

[boomdriver]

600 miles in 9 years = a lot of junk in the gas tank. If the car was stored all that time with a partial tank of gas the tank became a miniature tropical forest. I would bet if you pull the fuel pump you will find a lot of rust and the fuel pump pick up screen will be clogged. Think about it when you turn the key on the pump primes the fuel rails so the engine will start and when it does then the pump kicks in and starts to pump fuel. The suction of the pump will pull the rust up to the filter and the pump will starve for fuel. Let it sit for a while the junk floats off the pick up filter and you are able to start the car again. The gas that was in the car when you got it most certainly was bad from time and moisture. Believe it or not gas has a shelf life just like beer and it will go bad. As for the O2 sensor causing the car not to start after you put it back in that goes back to the fuel pump being able to run and suck the junk into the pick up filter while you had the engine running with it out.

I'm going with a Tank full of crap for $100...........(jeopordy)


and the daily double is.....

a new fuel pump, tank screen, fuel filter and probably fuel injectors.

Gasoline turns to jelly if left sitting long enough. Its so volatile that the stuff that burns vanishes into thin air as they say...and the rest gels.
Diesel fuel grows Algae in the tank. I'm certain there is some biological equivelent for gasoline too. If its organic there is algae or some kind of growth in the nice dark tank. Probably looks like a toxic Chia Pet in there....:ugh

SeaFoam is good stuff, or any number of other fuel storage chemicals. BUT you gotto use it BEFORE storing the car.The thing is that NONE of them advise storing fuel for over a year..it just gets stale.

BTW Randy, Cats have to run LOTS of miles /Hrs to fail. Even if yours had a serious engine malfunction it would take more than 600 miles to kill the cat. If the car was driven everyday and had 150,000 miles, sure. But 600 in 9 yrs? no way. The parts guy is on crack. He must have some new generics in the back room he needs to move..