2002 Pontiac Grand Am 3.4 V6 Help! - TCCoA Forums
 
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Old 08-06-2008, 04:16 PM Thread Starter
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Unhappy 2002 Pontiac Grand Am 3.4 V6 Help!

I have a 2002 Pontiac Grand Am 3.4 V6 that will not accelerate or pull an incline to save its life. When on prefectly level ground i had to baby the throttle up to a max speed of 40-45mph. If I gun the throttle the engine bogs down & sputters & carries on real bad.. I have already repalced the plugs, wires, air filter, fuel filter, and the Vehicle Speed Sensor that bolts onto the transmission. Have tested the Ignition coils & everything is fine... connected a code scanner & doesnt state that any problems were find with any of the sensors (that rules out the throttle position sensor)

Could this be a possible exhaust issue... maybe a clogged catalytic converter not allowing the gases to leave the car fast enough & its building back pressure into the engine? Maybe a fuel pressure issue?

Any help would be appreciated.

Car idles perfectly by the way...
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Old 08-06-2008, 04:22 PM
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Sounds EXACTLY what my brother in law was dealing with in his Grand Am. It was a clogged cat. He had a test pipe welded in place and the car was immediately drivable again.

I THINK the place he took it to (took it to Mexico, got the work done for next to nothing, and no one complaining about disabling an emission control) cut the exhaust in front of the cat to test it, I don't think they tried using a vacuum gauge or anything like that.

Before he couldn't go over most hills faster than 12 mph, he couldn't leave a stop light on an incline.

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Old 08-06-2008, 05:29 PM
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Well there are a couple easy ways to test if the cat is plugged. One would be to use one of those laser temperature guns, and take the car for a ride and then check the temp of the exhaust right in front of and right behind the cat. If the cat is plugged, it will be WAY hotter before the cat than after. If it is OK, the temp should be pretty close both before and after the cat, with the center of the cat being hotter.

That is the easiest way since it doesn't involve takeing anything apart or hooking anything up to the car. If you don't have access to one of those temp guns though, then another way to check is to remove the front O2 sensor. If the cat is plugged, then removing the O2 sensor will give the plugged up exhaust another place to escape. If removing the O2 sensor makes the car run better, then your exhaust is plugged up. If it doesn't, look elsewhere.

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Old 08-06-2008, 07:27 PM Thread Starter
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This is exactly what teh car is doing.. will not climb even the smallest hill more then 5-10 mph & even then I have the manually put the car in 1st (automatic) and floor it... then it just barely climbs...

I dont have access to an infared heat gun... I did however (warning for the faint of heat) let the car run for about a minute or so at an idle just to let the temperature build up..

I crawled under the car & was able to grab the pipe coming out of the converter without any pain or burning sensation... I went to grab the inlet pipe & I couldnt touch it because it was so hot.

Seems like a clogged cat is looking more & more like a culprit...

Dont think it fuel pressure because the car runs & idles fine fine as long as its under 3500 RPM, after that point the car has next to 0 power and basically worthless

Any other posibilites maybe.. something that I might be overlooking?

My father bought me a pipe cutter today (looks like a series of glass cutting wheels along a chain for $30.00) Im hoping there is an alternative without having to cut the pipe because I know exhaust work from a shop can become pretty expensive pretty fast.

By the way... Thx for the quick replys, really appreciate it.
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Old 08-06-2008, 08:27 PM
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Like I said, remove the front O2 sensor. If the cat is plugged up, that will allow more exhaust gases to escape that way, and slightly alleviate the problem. It probably won't make it run like normal, but if it runs better with the O2 sensor out, then you have just confirmed your diagnosis of the cat without cutting anything. I would say you already did that by grabbing the exhaust after the cat and it not being hot though.

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Old 08-06-2008, 09:06 PM
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I've actually had a plugged cat glowing a nice cherry red on my '82 T/A when I first got it. Visible in broad daylight, I'm surprised it didn't start a fire somewhere.

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Old 08-06-2008, 09:32 PM
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If you cut the cat off, you can put in a replacement with exhaust clamps and go to shop complaining about a leaky exhaust. The expensive part at a shop is buying the cat; if it's been tampered with already, they are not liable and will do a weld up job most of the time.

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Old 08-08-2008, 05:33 PM Thread Starter
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Okay, I got a temp gun & checked the temps once the car reached operating temps. here is what I found... Hold onto your socks im so confused:

Before Cat: 338f
Middle of Cat: 205f
After Cat: 440f

The resonator comes after the cat which are bolted together using 3 bolts in a trangle pattern... I checked the temp of the resonator in the same spots & it satayed about teh same all teh way through: about 230 or so...

Maybe a clog in the rear of the cat... any opinions?
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Old 08-08-2008, 08:13 PM
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remove the 02 sensor before the cat then start it up and see if it runs better if so you do have a clogged cat

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Old 08-08-2008, 09:56 PM Thread Starter
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Ya that was mentioned in an earlier post.. will try that in the morning. Like I said the car idles fine until its put into gear & has to actually work.
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Old 08-08-2008, 10:34 PM
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i would check the fuel pressure and it can be the maf

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Old 08-08-2008, 10:35 PM
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hook up a vacuum gauge to it. Use this website to determine the problem (flash animation towards the bottom)

http://www.secondchancegarage.com/public/186.cfm

scenario 14 is the test for a clogged cat

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Old 08-10-2008, 02:10 AM Thread Starter
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I removed the front O2 sensor & took the car down teh road instat improvement... so I cut out teh cat & the resonator levaing everything disconnected except for the manifold & about a foot & 1/2 of pipe coming out of the engine compartment.. tok down the road & ran like nothing was wrong... so was a clogged cat (Sounded like a freaking Nitro Funny Car going down teh road @ 60mph with no exhaust LOL)

Will let ya know how everything wqorks out, just gonna gut teh cat & resonator & patch back into exhaust.. cheaper & easy fix
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