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UPDATE: I bought a scan tool and downloaded the torque app. I don't get any error codes. I decided to drive it again today. I drove about a quarter mile and barely got to 20MPH. I turned around and pushed the gas pedal to the floor and car never made it above 25 MPH in about a quarter mile. The RPMs fluttered a bit, between 2000 RPM and 3200 RPM with the gas pushed down all the way. I parked the car and there were some strange smells. I am not sure how to describe them, at one point almost the burning rubber.


I own a 2001 Pontiac Grand Prix. Last week it started accelerating very slowly when pushing on the gas. Going about 20 MPH I pushed the gas to the floor and almost nothing happened. The RPMs did not go above 3000. The RPMs also got a shaky and moved back a forth a bit.

On the highway the car slowly got up to 45 MPH and 3500 RPM, then it was stuck there for about 15 seconds - it would not go any faster and RPMs would not go higher. After those 15 seconds it finally went above 3500 and got up to 60. Once at 60 everything seemed normal, normal RPMs and no weird sounds.

The next thing I tried was in neutral. I pushed the gas down all the way and it went to about 3500 RPM. Keeping the gas pushed the down the same amount, the RPMS slowly fell to about 2500 RPMs before I let off.

Could anyone give me advice on basic ways to troubleshoot this? I checked the transmission oil after letting my car warm up and it was low (just under the whole OK marker). I don't know if this would cause these symptoms, but was not sure what else to check.

The only check engine light has been on for a long time and must have a bad sensor. I have a low engine coolant light, but I have checked it a few times and even added to it and it seems to be at the correct level.

EDITS: Automatic transmission. The CEL is for "Low engine coolant".

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Do you have traction control? –  mikes Dec 19 '13 at 11:30
    
Yes I do have it. –  l3v Dec 19 '13 at 14:52
    
Is this the 3.8L or 3.1L V6? –  rrhartjr Dec 23 '13 at 19:49
    
When's the last time you checked your air filter? –  Some Guy on the Internet Dec 25 '13 at 11:30
    
Changed it about 2 years ago. –  l3v Dec 29 '13 at 17:36
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4 Answers

It sounds like the catalytic converter might be plugged. If it has self destructed, it could be causing a blockage and not allowing your engine to exhaust the gasses as it should, thus not allowing the engine to rev as high as it normally should. You can test it by tapping it with a hammer (not hard) and listening to see if there is a rattling sound. A muffler shop can diagnose this for you, as well as fix it if needed.

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Thanks Paul, I will try that tomorrow. –  l3v Dec 19 '13 at 2:34
    
Been too cold to check. Would this bring up an error code? –  l3v Dec 23 '13 at 19:08
    
@l3v ... Not unless it affects the rear O2 sensor, but more than likely not. To me, your update sounds more and more like a clogged cat. IIRC, another way to detect a clogged cat, is if you idle the engine for several minutes at night (5-10 mins), you will probably see your exhaust manifolds glowing red (dull red). It is something you normally wouldn't see at all and you won't see it during the day either way. Mind you, if you don't see this, it doesn't mean it isn't plugged, but if you do, you can pretty much bet on it. –  Paulster2 Dec 23 '13 at 23:34
    
I'll check for a glow tomorrow night. Thanks. –  l3v Dec 29 '13 at 5:31
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Your engine management is in 'limp home mode'. You need an OBD2 scan to check for any fault codes, and recification carried out.

The coolant level sensor is not OBD2, it is an info light.

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Thank you Allan. I have always thought about getting my own scan tool. Would you recommend one? Or just go to the shop? –  l3v Dec 19 '13 at 14:16
    
Try looking up Torque PRO on the net. With a budget ELM 327 it is a good insight into your engines electronics without laying out a great deal of money. I have scanners ranging in price from £60 to £2000, no one scanner does it all for all vehicles, but I use them professionally. –  Allan Osborne Dec 19 '13 at 14:46
    
Great, I see a nicely rated scanner on Amazon. Just wondering how useful it would be for me. Doubtful I could fix any problems anyway :P –  l3v Dec 19 '13 at 15:34
    
The reason I mentioned Torque Pro is because of how little it costs to set up, $20?, if you then feel the repair side is not for you then all you have to do is dodge one round at the bar and you have covered the expense. :-) –  Allan Osborne Dec 19 '13 at 16:05
    
Haha. Very true. –  l3v Dec 19 '13 at 19:10
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Sounds like a leaking head gasket or lower intake manifold gasket to me. Both are fairly common on the Grand Prix of your vintage.

CEL for Low Engine Coolant means the coolant is going somewhere. If you don't see coolant on the ground, the only other place is into the cylinders and/or the oil.

Engine sluggishness would be a symptom of incomplete combustion, since coolant is entering the cylinders. Continued sluggishness in neutral rules out most transmission issues.

Check for:

  • Milky/foamy looking oil (means coolant is mixing with the oil)
  • Oil in your coolant
  • White smoke from the exhaust

More here: http://troubleshootmyvehicle.com/gm/3.8L/how-to-test-a-blown-head-gasket-1

Symptoms for the LIM gasket are similar to the head gasket, except the coolant does not directly enter the cylinders.

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Thanks for the input. I will check these the best I can tomorrow. The only thing is that I am pretty sure the CEL is malfunctioning. I checked the coolant level multiple times and it is at a normal level. I will check that again too. –  l3v Dec 29 '13 at 5:30
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If engine rev limiter is getting active within 2-3k RPM this means that engine is in limp mode. The problem of not getting speed may be due to this. This mode is there to make you reach nearest workshop with out damaging your car. If it was catalytic converter then when you go back home after driving look below the car if it was blocked it would glow.

If you have low coolant fill it and if it further reduces you have a leak. If you see white Smoke then this means that your engine coolant is getting mixed with engine system due to bad head gas-kit.

Does not seems but this may also be due to Bad O2. Hesitation and stuff like this happens.

Is your car getting over heated?

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No it has not overheated. I will keep an eye on it when I check for the glow. –  l3v Dec 29 '13 at 5:33
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