93 SE having issues with engine speed - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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Old 08-12-2005, 09:26 PM   #1
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Default 93 SE having issues with engine speed

This happened to me today, but it is not the first time it has happened. Driving around town, my car will refuse to go above 2000-2500 rpm regardless of whether I punch it, or ease onto the throttle. If I stop and let the car sit for a few minutes, the problem will go away, but will reappear a few minutes later. All the gauges are reading nominal, and there does not seem to be any other contributing issues. Does anyone have an idea of what is going on?
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Old 08-12-2005, 09:30 PM   #2
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May be a plugged catalytic converter. I'd do a back pressure test. Is it lacking power also? I mean from idle up to 2000-2500?
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Old 08-12-2005, 09:38 PM   #3
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That'* my bet, too. Kick the cat. Hear a noise? Replace it.
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Old 08-12-2005, 09:55 PM   #4
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Agreed.... Thinking Cat here too..

If it rattles, or has too much backpressure replace it..

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Old 08-13-2005, 12:06 AM   #5
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well, at least there is a consensus here.
Fatcat, there does not seem to be any power lacking below 2k-2500 rpm,, but at 60 mph on level ground, how much do you need?
How do I do a back pressure test?
The only thing is that wouldn't a plugged cat make the car do this all the time? As mentioned earlier, I've had this happen before, then it won't do it for a week or two, then will reappear.
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Old 08-13-2005, 12:22 AM   #6
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Quote:
Originally Posted by Puddy46
well, at least there is a consensus here.
Fatcat, there does not seem to be any power lacking below 2k-2500 rpm,, but at 60 mph on level ground, how much do you need?
How do I do a back pressure test?
The only thing is that wouldn't a plugged cat make the car do this all the time? As mentioned earlier, I've had this happen before, then it won't do it for a week or two, then will reappear.
So its intermintent?

I have also seen cats that caused a lot of problems once they got hot...

I wish I could drive your car when this happens...

There are only a couple of other issues I can think of off the top of my head... Possibly the TPS is giving bad readings, or the MAF is unhappy... Maybe even fuel pressure...

Has the SES light been on at all? When you are in OD going 55mph, if you give it wot will the trans shift to second? Or is it stuch in OD with the pedal to the floor?

Pull the codes from the PCM ....


Fatcat, any thoughts?

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Old 08-13-2005, 12:51 AM   #7
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The problem is intermittant.
With regards to the SES light, no it has not come on.
The tranny will shift into second, but will then immediately start to do it'* thing.
hope this helps
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Old 08-13-2005, 06:45 PM   #8
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A busted up cat converter can plug intermittant. A big broken chunk may turn sideways in the shell and restrict flow, then turn again and allow flow. They can also be dependant on heat as far as the flow abilities....the hotter it gets the less it flows.

I'd still do a back pressure test to verify the converter condition, then a fuel pressure test to verify the fuel pump condition.

Back Pressure Tester

Basically, you unscrew the O2 sensor that is between the engine and the converter, then plug a pressure guage into the hole. Start the engine and drive the car until the problem is duplicated. If the pressure goes over 4 p.*.i. while driving, your converter is shot. Personally I don't like anything over 3 p.*.i. while driving, but if your converter is plugged it will usually register about 25-30 + p.*.i. just by snapping the throttle at idle or under a heavy load. A dead give away.

Check the fuel pressure when this is occuring also. May be a weak fuel pump.
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Old 08-13-2005, 06:54 PM   #9
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Fatcat, what kind of life would you expect out of a factory Cat Converter, taking into consideration that the car or cars are kept in tune and well maintained...

I have seen in the Owners information, that the Cat for my 95 was warranted for 80,000 miles... I am right at 142,000 pretty much... I have 122,000 on the 91 and I know the cat on it is shot( rattling )....

Any thoughts on a general life expectancy from an original cat?

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Old 08-13-2005, 07:09 PM   #10
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They last until the warranty runs out.
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