2000 Buick Surging

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  #1  
Old 03-14-08, 12:21 PM
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Cool 2000 Buick Surging

Hello,

My name is Tom and this is my first post. Problem statement:
1. Car was idling and running rough. Engine scan showed multiple cylinder misfires, possible vacuum leak or fuel pressure problem.
2. Changed plugs and wires. No help.
3. Checked coils with spare wire and plug. One coil not firing. Replaced coil. Didn't help.
4. Replaced ignition control module. That worked. Now starts and idles fine with no service engine lights. Then another problem showed up..
5. When I slowly bring the RPMs up, it runs very smoothly until 4000 RPMs and then begins to surge but no service engine light.
6. Checked fuel pressure. With key one it is 51 PSI. Running it is 44 PSI. Pressure stays constant at 4000 RPMs but still surges.
7. Checked for vacuum leaks and found none.
Any advice to what might be causing the surge at 4000 RPMs? With no code to go by, I am stumped. Thank you very much. Tom
 
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  #2  
Old 03-14-08, 01:45 PM
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At 4K the fuel pressure is constant but the engine is surging, correct? What engine do you have?

I would say worn/loose timing belt or vacuum leak at intake or throttle body. Either would do it.

Try a vacuum gauge = inexpensive diagnostic tool.

Hope this helps,

Bob
 
  #3  
Old 03-14-08, 09:51 PM
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4000 rpm in park or neutral? or 4000 rpm while driving?

4000 in park or neutral and cutting off and then back on is normal...it's the rev limiter

if it surges at 4 grand while driving, sounds more like a fuel filter or exhaust back pressure issue. just because the fuel pressure stays at 51 psi doesn't tell the whole story...you have to have fuel pressure AND fuel volume...at least a pint in 30 seconds.

back presure is normally measured by putting and adapter in the hole where the O2 sensor screws into the exhaust (ahead of the cat) and measuring pressure with a guage at idle and at 2ooo rpm. usually 0 at idle and 1 or 2 psi at 2000 rpm. there may be specs for that car...
 
  #4  
Old 03-15-08, 12:23 PM
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Originally Posted by carguyinva View Post
4000 rpm in park or neutral? or 4000 rpm while driving?

4000 in park or neutral and cutting off and then back on is normal...it's the rev limiter

if it surges at 4 grand while driving, sounds more like a fuel filter or exhaust back pressure issue. just because the fuel pressure stays at 51 psi doesn't tell the whole story...you have to have fuel pressure AND fuel volume...at least a pint in 30 seconds.

back presure is normally measured by putting and adapter in the hole where the O2 sensor screws into the exhaust (ahead of the cat) and measuring pressure with a guage at idle and at 2ooo rpm. usually 0 at idle and 1 or 2 psi at 2000 rpm. there may be specs for that car...
Thanks for the info carguyinva. Yes, it surges at 4000 in neautral and a lower RPM while driving, especially when the auto trans shifts. I think I will do the fuel filter thing first and then go from there. Tom
 
  #5  
Old 03-15-08, 03:08 PM
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yeah...probably a good call...supposed to be changed every 30k on that one, i believe. good luck...
 
  #6  
Old 03-15-08, 06:38 PM
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well, for engine to rev/surge, you have to have fuel AND air gushing in to cause it. of course, you could have electrical issues, like TP sensor, or - i had that on my taurus - bad idle control unit that will accelerate the car at will. or, as you have surges while shifting, there's a sensor that tells ECM how to adjust throttle depending on what geer you are in. but - that's electronics and probably would have coded.
i vote for leak - either vacuum leak somewhere, or intake manifold leak. something tells me that engine gasket could do same.
at 4K rpms, everything inside your motor is at fairly high pressure, that's when pores open and life happens.

i'd start with TPS and gasket around throttle body and intake manifold. next - PCV valve and any hose that is attached to valve cover. then - brake booster hose. anything that could feed more air into the intake.
 
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Old 03-15-08, 07:40 PM
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Different parts are being mentioned. I'll try EGR valve.
 
  #8  
Old 03-15-08, 09:05 PM
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fuel and air gushing...that's a new term for me...and it makes me chuckle
 
  #9  
Old 03-16-08, 07:01 PM
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Originally Posted by Really View Post
Hello,

My name is Tom and this is my first post. Problem statement:
1. Car was idling and running rough. Engine scan showed multiple cylinder misfires, possible vacuum leak or fuel pressure problem.
2. Changed plugs and wires. No help.
3. Checked coils with spare wire and plug. One coil not firing. Replaced coil. Didn't help.
4. Replaced ignition control module. That worked. Now starts and idles fine with no service engine lights. Then another problem showed up..
5. When I slowly bring the RPMs up, it runs very smoothly until 4000 RPMs and then begins to surge but no service engine light.
6. Checked fuel pressure. With key one it is 51 PSI. Running it is 44 PSI. Pressure stays constant at 4000 RPMs but still surges.
7. Checked for vacuum leaks and found none.
Any advice to what might be causing the surge at 4000 RPMs? With no code to go by, I am stumped. Thank you very much. Tom
Well folks, the Buick is running fine. Here are my conclusions:
1. Replacing the ignition control module solved the no spark at one coil.
2. The cutting out at 4000 RPM's in neutral was due to the rev limiter as suggested by carguyinva.
3. Running the car in solved all the after affects.
4. Carguyinva, I did change the fuel filter after the car started running right. It had been a couple of years since I had done it and I am sure it needed it anyway.

Thanks for everyones help. I learned a lot. Tom
 
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