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Old 04-30-2011, 07:31 PM   #41
OldNuc
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Default Re: Mysterious Bucking at Cruising Speed, cant figure it out

OK, you replaced the filter/regulator, what brand is it?

And is your new O2 sensor a direct fit or universal type?
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Old 04-30-2011, 07:46 PM   #42
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Default Re: Mysterious Bucking at Cruising Speed, cant figure it out

The air filter? its just a motomaster, pretty basic but didnt look any different then the Fram. I havent done the regulator though, whats the technical term for it?

I actually took the O2 sensor back since everyone said its not the O2 sensor and if it was then it would be throwing up SES lights which it doesnt do at all.
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Old 04-30-2011, 09:59 PM   #43
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Default Re: Mysterious Bucking at Cruising Speed, cant figure it out

Back in post #1 you listed the following:
Quote:
We have throw about $500 at this problem so far and still nothing, we are running out of money for parts so we really need to figure this thing out, so far we have:
- Replaced Fuel Filter
- Replaced Ignition Coils and Plugs
- Cleaned ERG Valve (thought Im not sure if I did it well enough as you cant really get inside it)
- We also purchased an O2 sensor but havent installed it yet.
- Ran a couple different injector cleaners
That is a filter/regulator and any product other than the OEM or WIX 33731 or the NAPA equivalent to the WIX may cause fuel pressure problems. That is why I asked. The Canadian equivalent is a GF 1846 from G. K. Industries.

If you read back up the thread I described an EGR leak test you should try. All you need is an empty pop/beer can so it is cheap.
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Old 04-30-2011, 10:07 PM   #44
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Default Re: Mysterious Bucking at Cruising Speed, cant figure it out

Well now that saturn's gone some of the parts, especially for older saturns (before GM Gm'd them up) are getting harder to find, they had to special order the fuel filter Im not sure what brand it is but I assume its a proper part. Regardless the issue existed before the fuel filter was replaced so it cant be the fuel filter. Engine accelerates fine and if you throttle it up to higher RPM in park and hold it there it runs perfectly smooth, theres no hesitation off the line either.
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Old 04-30-2011, 11:45 PM   #45
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Default Re: Mysterious Bucking at Cruising Speed, cant figure it out

Quote:
Originally Posted by OldNuc View Post
Cut up a can and set the piece on top of the EGR gasket so that it blocks off both ports. Reinstall the EGR to hold it in place and reconnect the EGR drive car and see what happens. the exhaust gas will cut through the can in about a week so this is not a permanent fix, it is a test. This will also set a SES for the EGR. If you get any codes get the number as the "book" is incorrect.
Have you tried this yet? IIRC, there is a richpin video on how to do this.
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Old 05-01-2011, 12:49 AM   #46
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Default Re: Mysterious Bucking at Cruising Speed, cant figure it out

+1^^Do this test.

Running up an engine with no load does not actually address your issue. There are just 2 possibilities and that is either the system is going rich or lean when at a cruising condition and lean is the best guess. Have you checked for exhaust leaks between the head and the inlet to the CAT? A very small leak will do this.
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Old 05-01-2011, 01:37 PM   #47
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Default Re: Mysterious Bucking at Cruising Speed, cant figure it out

Havent tried the EGR thing yet as its been raining alot but I did clean the EGR valve fairly well, it moves freely and I installed a new gasket, but Ill try it out when the rain lets up.

But logically wouldnt it make sense that even in park if you throttled the engine at a higher rpm it should show some sign of fuel or air problems? The fact that it only does it in drive is starting to point more toward the transmission again.
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Old 05-01-2011, 01:57 PM   #48
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Default Re: Mysterious Bucking at Cruising Speed, cant figure it out

The engine will run on next to nothing fuel wise at low loads. Blasting it up in neutral proves little and nothing in this case.
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Old 05-28-2011, 07:21 AM   #49
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Default Re: Mysterious Bucking at Cruising Speed, cant figure it out

Torque converter ,Huh, My car is doing the same thing and its a manual! The only thing I havent check is the cat.
I think Ill give that a try.
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Old 05-28-2011, 11:36 AM   #50
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Default Re: Mysterious Bucking at Cruising Speed, cant figure it out

Quote:
Originally Posted by Dave3 View Post
Havent tried the EGR thing yet as its been raining alot but I did clean the EGR valve fairly well, it moves freely and I installed a new gasket, but Ill try it out when the rain lets up.

But logically wouldnt it make sense that even in park if you throttled the engine at a higher rpm it should show some sign of fuel or air problems? The fact that it only does it in drive is starting to point more toward the transmission again.
It depends on the interpretation of logic. Your logic or engine management logic. The devil is in the details.

Ignoring your logic for the moment, use engine management logic (as designed by the engine folks, not me); when the engine isn't under any load such as idling while parked, exhaust gas recirculation isn't needed. Exhaust gases are already spent combustibles and adding this into a low idling engine would do one of several things - lower idle and/or kill the engine. Since exhaust gas recirculation means recycling exhaust gases, adding this during idle wouldn't help so its not done at all. Now when a car is under load such as driving, the egr valve is (logically) used during acceleration and cruise. Never mind flooring the gas pedal while parked; its still not loading the engine down. The engine under load while accelerating can handle exhaust gases because the engine is using a richer mixture against the load (the transmission) so it can easily handle some exhaust gases being fed but carefully under metered conditions. The exhaust gases aren't just fed willy nilly but carefully against programmed parameters long ago set up from trial and error so we don't detect it. Anyone familiar with a faulty egr valve will know it as it causes; stumbling, hesitation, balking, and engine stalling. Since more power is generated during acceleration and cruise, higher combustion temperatures are created; the exhaust gases are used to lower this higher temperature to lower NOx generation.

A load is detected by the map sensor so the ecm/pcm searches it program for the map sensor and lo and behold the egr valve is now used.

Since you experience bucking during cruise, the egr valve can be contributing to it so the recommended blocking technique is tried. Until you understand EFI systems, go along with suggestions until otherwise because human logic has no place for EFI system logic as designed by the engine guys that are way smarter than we are. They've had years of engine history to borrow from as they refine engine management systems we call electronic fuel injection.

More problems are blamed on the transmissions when most issues are engine related. Even I see automatics as a mystery but can separate almost all suspected xmission issues as engine problems. The transmissions are still reliable and more so since these have also been refined to the degree that we're seeing 5,6,7 and 8 speed(?) autos? To even think of the massive mechanical engineering involved is a huge testament to brilliant mechanical engineering married to electronics - the solenoids and circuitry adapted to control more shifts than was imagined a few years ago. CVT's still can't keep up.
...
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Last edited by fdryer; 05-28-2011 at 11:44 AM.
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Old 05-30-2011, 07:02 PM   #51
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Default Re: Mysterious Bucking at Cruising Speed, cant figure it out

You should check your fuel pressure. The fuel pressure regulator and filter are one unit. It is not uncommon for the regulator to go bad, especially after 100k (if your car has more than 100k). Put a gauge on the Schrader valve on the fuel rail. Should be around 45 psi. If significantly less, suspect the filter/regulator, located back by the tank, on the driver's side. Mine was faulty, and the car was somewhat rough at freeway cruising.

Also, if the MAP sensor is inaccurate, and gives a lower than appropriate vacuum reading, this can lean out the engine somewhat.

http://www.google.com/imgres?imgurl=...w=1024&bih=649
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Old 05-30-2011, 07:08 PM   #52
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Default Re: Mysterious Bucking at Cruising Speed, cant figure it out

The correct fuel pressure is 45-51 psi no more no less, Key on engine off. Outside of that range and you will experience 'odd" behavior from the engine.

OP states the following have been replaced.
We have throw about $500 at this problem so far and still nothing, we are running out of money for parts so we really need to figure this thing out, so far we have:
- Replaced Fuel Filter
- Replaced Ignition Coils and Plugs
- Cleaned ERG Valve (thought Im not sure if I did it well enough as you cant really get inside it)
- We also purchased an O2 sensor but havent installed it yet.
- Ran a couple different injector cleaners
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