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john aka eaut
john aka eaut, The Car Guy
Category: Pontiac
Satisfied Customers: 15895
Experience:  15 years as a auto tech
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I have a Pontiac grand am GT that. While I was driving the

Customer Question

I have a Pontiac grand am GT that. While I was driving the other day I heard a loud slapping noise and the car started to slow down and the slapping continued until I could get it parked. Now it starts but will not run and still makes the slapping noise.......
Submitted: 1 year ago.
Category: Pontiac
Expert:  Lou P. replied 1 year ago.

hello, was the "slapping" noise loud like if you were to knock two rocks together? have you checked the oil level and checked for any major external leaks? so far from what you explain it very much sounds to me like the crank or rod bearing had spun or broke or even a piston, but definitely internal engine damage, it would take a few things to try to eliminate the internals of the engine.

Customer: replied 1 year ago.
Is it possible that timing belt is bad and throwing everything out of sync.serpantine belt ok. Tensioner possibly bad
Expert:  Lou P. replied 1 year ago.

you have timing chains and they are rarely a issue, a tensioner could be a issue BUT it would not hinder the engine running

Customer: replied 1 year ago.
Oil is fine. It does start but when you put it in gear it runs rough and shakes. What are the symptoms of a bad TPS?
Customer: replied 1 year ago.
Did you forget about me?
Expert:  Lou P. replied 1 year ago.

Sorry Sunday is a busy day and I didn't hear from you for 40 min. Ok so do you think it sounds and feels more like a misfire ? Does the check engine light flash? A bad today would only affect acceleration and when you accelerate quickly.

Customer: replied 1 year ago.
Dont think its misfire. During the week prior to this happening when I started it, it would squeal really really bad and sometimes would go away as I drove it. So when this was happening someone that was standing near my car said wow sounds like you have a belt thats about to break. What it sounded like to me, keep in mind im a girl and blonde at that :-). It sounded like something broke but was still attached and it sounded like everytime it went around it was slapping on the ground.
Expert:  Lou P. replied 1 year ago.

Ok I don't feel like we are on the same page you kinda keep bouncing around. Why don't you start from the beginning. What happened how did it sound , what did you do to fix it or try to fix it ? Does it happen when engine is running or does car have to drive ? As much info as possible. I'm good at helping but I need as much Info as possible.

Customer: replied 1 year ago.
Ok see if i can make any sense. For about a week I noticed upon start up that as soon as I turned it over it made a loud squealing/screeching noise at least 80% of the time. It was loud enough to be embarrassed. Most of the time as I drove it, the noise lessened and would quit the more I drove. A few times when I started it someone next to me would say, "Sounds like you have a belt thats about to break". Now, the other day I turned it over....no screach....put it in drive and went for about a mile. Now as Im driving it, moving down the road I heard what to me sounded like what everyone was saying, it sounded like a belt broke ....i could tell it wasnt going to go much farther so i had the gas pedal all the way to the floor and it was moving forward a little at a time, like putting down the road. I was able to get off the main road and get it parked. After I heard what sounded like a belt breaking and its putting along super slow with the gas pedal all the way to the ground I could hear a slapping noise. The only way I can describe it is if something under the car had broke that turned in a circle and every time it came around it sounded like something was slapping the ground. All I can picture is like if the chain falls off your bike. The car does start but idles VERY rough however it doesnt want to move much. I checked the oil, checked the serpentine belt checked for fluids thay may have leaked on the ground. Not sure where to go from here. Hope that helped.
Traci
Expert:  Lou P. replied 1 year ago.

Ok traci thanks is there a way you would be interested in a phone chat ? Let me know.

Customer: replied 1 year ago.
I'm broke or I definitely would.
Expert:  Lou P. replied 1 year ago.

Ok no problem. So it sounds to me still like engine failure. So here's what to try first. Remove the serpentine belt and then try to start it and see if it makes the same noise or if it runs. If it makes the same noise with the belt off then we know it's engine related. If it does not then we know it's a belt driven item. Does this make sense ?

Customer: replied 1 year ago.
it makes sense. I will be able to have someone try it later today and will let you know. Thanks.
Customer: replied 1 year ago.
Hi,
I had someone remove the serpentine belt and it made the same noise when we started it. We actually moved it off the street where we had it parked to the driveway so it drives also just REALLY rough. We also smelt gas as if one of the cylinders isnt firing.
Expert:  Lou P. replied 1 year ago.

Ok so now that tells me the engine is the issue. From here you will need to do a compression test. You remove all the spark plugs and screw in a compression tester. Crank the engine with full throttle until you see the gauge move 6 times and write down the reading and do the next cylinder. All cylinders should be 120psi- 140psi.

Customer: replied 1 year ago.
Hi Lou,
We changed all the spark plug and wires. It starts but idles REALLY rough. We actually drove a few miles to O'Reillys and it drives ok, not great but ok. When i had to stop at the stop signs it idles again really rough. We had them hook something up to get a reading on it and there were no codes, only a random misfire. Bad coil? My other thought is ive always had an issue with the security system and just now it wouldnt start, so i have to wait 10 minutes until the security light stops blinking and it starts right up.
Expert:  Lou P. replied 1 year ago.

Ok I'm not sure why you did not take my advice on doing a compression test. It's hard for anyone to help you if you do not follow our advice. I will have to opt out. Hopefully some one else can chime in and get you on the right path if we would have done a phone call we could have cleared this up already instead of wasting time and money on throwing parts at the car. So I will opt out. I wish you luck. Hope I'm wrong and it's not a engine and I wish you well this holiday season.

Expert:  john aka eaut replied 1 year ago.

new expert here

Customer: replied 1 year ago.
I dont have a compression thingy to check it. I had all the spark plug and wires changed because they were the originals and needed it anyways. It actually drove better once they were changed, its at the initial start up, when it idles, and if I have to stop at a stop light or stop sign that it runs really really rough, sounds loud and acts like it wants to stall. Not sure if this has anything to do with anything but Ive always had a problem with the security system as I explained previously. When I took it to the parts store for the diagnostic test it read a misfire. I suppose if I need to go buy a compression thingy I will. Whats your advice?
Expert:  john aka eaut replied 1 year ago.

I don't thins its a security issue.. Is the engine light on solid or flashing

Customer: replied 1 year ago.
Solid
Expert:  john aka eaut replied 1 year ago.

can you tell me all the codes are in the system

Customer: replied 1 year ago.
No. I don't know.
Customer: replied 1 year ago.
No codes read just the misfire.
Expert:  john aka eaut replied 1 year ago.

I would complete the tune up, I don't think a compression test in needed.. I would replace the coils and plug wires.. Spark plugs alone rarely solve a missfire

Customer: replied 1 year ago.
Thank you, ***** ***** that.
Customer: replied 1 year ago.
Hi John,
I had the one coil that was bad. Im supposed to tell you that when it hits 3800 rpm it falls. What about sensors? Map? Throttle, Crank....
Expert:  john aka eaut replied 1 year ago.

I would check fuel pressure first