Pontiac Repair: running badly, mass air flow sensor, mass air flow

Question
QUESTION: My check engine light came on and the code was for either an o2 sensor or my cat.  Had the cat tested it was fine, they said. Replaced #1 o2. Light came back on said #1 o2 sensor. Replaced it again. Smelled like rotten eggs, was cutting out & misfiring. Had cat replaced. Picked it up from mechanics it was still doing the same thing. Took it to another place for diagnostic. Said cat had a hole in the back of it (only had driven 75 miles on it) they replaced it. They told me there was junk in the exhaust system from the cat. Replaced it & new mufflers. Then said needed MAP sensor & plugs/wires. Replaced it. Still same prolem. Pontiac dealership diagnostic-replace fuel pump; I had already replaced the filter. Im waiting for my new pump to come in but do you think there could be something else to look at?

ANSWER: Hi Lisa:

What model car is this? engine size? I wouls tend to belive what the dealer says the issue is then any small repair shop..... I would want to look at the fule injectors on this have them tested if you have one that's leaking into the engine it can cause catalitic converter issues. I'd check the engine sensors when the engine is running to to see if any of them are giving false readings to the computer.. Depending on the engine size and model of the car it' look long and hard at a Mass Air flow sensor if it is and engie equipped with one...
good luck :)


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QUESTION: It is an '01 Grand Prix 3800 series engine. My dad took out the MAF sensor and cleaned it and also checked the vacuum hoses. We put an inline pump thinking that would fix the problem but it didn't. My brother thinks it's the computer. How do I check the engine sensors?

ANSWER: What did he clean the sensor with? if he used the wrong stuff that will DAMAGE the sensor instead of fixing it.... You need a engine scan tool to take a look at all the engine sensors to see what's going on with the way it's running... It's really a job for a qualified technician.. Even if you had a scan tool to use if you don't know what the sensors reading look like normally than you wouldn't know what you looking at if one of them was bad....


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QUESTION: He just sprayed it with compressed air. I replaced the fuel pump & it didn't change anything. My old mechanic said its either the cam or crank sensor. Needles to say, I'm tired of replacing parts & nothing happening; plus, it's expensive. Do you think that it may be one of those sensors or do you have another idea?

Answer
I suggest you take this to a shop or dealership that has a clue as to what they are looking for. I still syat I would look long and hard at the mass air flow sensor if that reading is off it throws the entire fule tril off from when the engine is at idle to cruising down the road. I doubt it's a crank shaft sensor it more than likely would have a stalling issue or just wouln't run. As for the cam sesor it's possable but it woul turn on the service engine light and store a code. My guess is still one of the sensors is reading wrong but not wrong enough that its turning on the service engine soon light. that is why you need to find someone who knows what they need to look for. It's like going to to see a Dentist for a broken ankle. You need to see the right person for the job. Good luck let me know how this turns out......