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04 Cavalier P0172 Code and Car won't Start

Engine Cranks but won’t start. Was throwing a P0172 code prior and was very slow to accelerate( gas had to be pinned to get slowly up to 30KM) Have replaced the fuel pressure regulator, tested spark and plugs were replaced a week prior. changed the fuel filter & air filter. fuel line pressure is good, so it’s not the pump. Engine still won’t start. What could be the possible cause? Have I missed anything. I haven’t checked the injectors, but I imagine I would have a misfire or attempt to catch if only one was plugged.

Maybe I flooded the engine by trying to start it numerous times?

Remove the oil dip stick and smell the oil for gas contamination.

If the oil is contaminated with gas, the engine has been running very rich.

One thing that can cause this, lack of acceleration, and a no-start condition is a plugged catalytic converter.


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Just checked the dipstick and doesn’t smell like gas, so I think it’s fine there. I am not sure about the cat though. I would think that it would have triggered the O2 sensor in the cat though if that was the case. I only had the position 1 sensor activate.

Provided you have spark during cranking, if the plug tips are wet at all, remove all of them, crank the engine to expel liquid gasoline in the cylinders (disable the ignition system to prevent sparks, have a fire extinguisher on hand), and let any gasoline in the cylinders evaporate overnight, or a day or two. I had a flooding problem with my VW Rabbit like that when testing the fuel injection system. Wouldn’t start no matter what I did. After letting the gas evaporate out the spark plug holes, it started right up.

If you have a v-style engine, this is a problem on bank one, which is the one associated with cyl number 1. There’s either too much gas or not enough oxygen in the mixture, or the o2 sensor(s) on that bank has failed. Testing the fuel rail pressure (make sure it holds when off too) and making sure the air path into the engine is open (engine air filter) are good ideas, but it sounds like you already did that. If you are certain the engine isn’t flooded, you may have to disconnect the exhaust system before the cat as a test. If it starts then you probably have a clogged cat. Sometimes you can just remove the pre-cat o2 sensor to accomplish that. Once you get it running again, measure the fuel trims and report back.

George San Jose 1 gots this pretty good. A faulty MAF sensor can make it run rich also.

A few mechanics have said it might be a O2 sensor, but I don’t think an O2 would create a no start condition.

The 04 cavaliers actually don’t have a MAF sensor, so I can rule that one out right away. I’ve pulled the spark plugs overnight, but didn’t see much come out of the cylinders when i turned it over without the plugs. Mostly just what looked like mist or smoke. I’ve got a mobile mechanic coming to take a look at it. I don’t have the tools to test compression, but the crank sounds pretty fast. So that might be the issue.

Thanks All for the replies. It turns out its the timing chain tensioner. I guess the chain is slipping when I try to turn it over. Off the the wreckers it goes. It’s more expensive to fix the car than what I had actually paid for it last year.

Thanks for the update OP. Best luck on finding a good next car.