bgraham
join:2001-03-15
Smithtown, NY Reviews:
 ·Verizon VoiceWing
 ·Verizon FiOS
·VOIPo
| [Help] Bad EGR Valve? My 2002 Buick Century with 95k miles has been lacking power below 3000 RPM for a while. the car runs great until the engine gets hot and goes into closed loop operation. At 3000 RPM in any gear the car just takes off, below that I can't keep up with a school bus.
There is no CEL being set and I have a Digimoto scan tool.
When I got the Digimoto a couple of years ago the car ran fine so I drove the car around the block with the scan tool connected and kept the file for comparison. Nothing has changed and the file today looks the same as the file from 2 years ago. Unfortunately, I never recorded highway driving which is where the problem was most noticeable.
Well, now it's getting worse and on small hills I the car actually downshifts to maintain 70.
If I unplug electrical connector on the EGR valve the car runs great. Is there any way to test the EGR valve other than replace it?
Anyone have any other ideas? I have already replaced the MAF sensor because it read 3 at idle instead of 0 and 100 at full throttle instead of the 160 that Alldata says it should. |
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 GemstonePremium
join:2000-12-20
Long Island | Might be a clogged catalytic converter... Symptom is car runs good cold but when the catalytic converter heats up it clogs and causes excessive backpressure...
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Go Mark Martin! |
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 The PigBazinaPremium
join:2009-09-11 | reply to bgraham
»www.wisegeek.com/how-can-i-tell-···aced.htm |
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matt5
join:2001-10-06
Lagrangeville, NY | reply to Gemstone
Incorrect, a clogged cat will cause a lose of power at higher rpms (well really it will prevent you from getting higher RPMs) this is the exact opposite. |
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GemstonePremium
join:2000-12-20
Long Island Reviews:
 ·Optimum Online
| said by matt5:Incorrect, a clogged cat will cause a lose of power at higher rpms (well really it will prevent you from getting higher RPMs) this is the exact opposite.
You are 100% correct... I read his post too quickly and thought his loss of power was at higher RPM...
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Go Mark Martin! |
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 mattmagPremium,ExMod 2000-03
join:2000-04-09
NW Illinois
kudos:3 | reply to bgraham
said by bgraham:If I unplug electrical connector on the EGR valve the car runs great. Is there any way to test the EGR valve other than replace it?
So to be clear, you disconnect the EGR valve connector and the car runs great? As in no power loss, doesn't need to downshift, everything is perfect? |
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bgraham
join:2001-03-15
Smithtown, NY Reviews:
·Verizon VoiceWing
·Verizon FiOS
·VOIPo
| Yes, and I am not nit picking either. The car is night and day.
On hills (really slopes here on Long Island) the car won't keep up with a school bus unless I press the gas pedal past half way to make the transmission downshift and get the engine going past 2500 to 3000 rpm.
As soon as I disconnect the EGR valve the car runs great / normally. (considering it's a Buick)  |
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mattmagPremium,ExMod 2000-03
join:2000-04-09
NW Illinois
kudos:3 |
Well I hate to just be a parts-changer...
Does the Service Engine Soon light come on when you unhook the EGR? If it does--good.
Can you read "EGR Position" on your scan tool or is it just a code-reader? It is not unheard of to have an EGR fail in such a way that it opens faster and farther than commanded, which could be your issue. However I would say you really need to run through the diagnostics for the valve before you just toss one on there. *Most* of the time, that type of failure will set a code for EGR Position, so I'm surprised you're not getting that.
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bgraham
join:2001-03-15
Smithtown, NY Reviews:
·Verizon VoiceWing
·Verizon FiOS
·VOIPo
| said by mattmag:Well I hate to just be a parts-changer...
That's the reason I just did not get a replacement.
There is no CEL with the EGR connected. Of course when I unplug it I get a CEL but only on the second start.
My Digimoto scan tool appears not to be able to read the EGR valve position. I am going to double check that with Digimoto.
I am a bit leery with check engine lights though. My wife's Buick had a MAF sensor die and read 0.4GPM constantly. The car was almost undriveable, but it never set the CEL. |
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mattmagPremium,ExMod 2000-03
join:2000-04-09
NW Illinois
kudos:3 |
That's the key on CEL's. You can't live by them, they are only an indicator. Diagnostics must be performed, so that's why I was asking what kind of readouts you can get. It may be tough to take the right course of action at this point, without the right data...
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Reviews:
 ·Colbanet
| reply to bgraham
Your car runs good after removing the EGR valve because you're removing the exhaust restriction.
Does your upper exhaust manifold have an O2 sensor? If so, remove it from the manifold, leave your EGR attached and functioning, and go for a drive. If it drives like a champ, you have a plugged cat.
In the unlikely event it drives the same, cut a thin gasket out of a pepsi can and block off your EGR ports, then reinstall it. Go for a drive. If that solves it, it's the EGR valve. |
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mattmagPremium,ExMod 2000-03
join:2000-04-09
NW Illinois
kudos:3 | said by dbsanfte:Your car runs good after removing the EGR valve because you're removing the exhaust restriction.
Seriously? Read his post. He disconnected the *ELECTRICAL CONNECTOR* he didn't remove the valve... 
And besides, the rest of your advice is horrible. |
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Reviews:
·Colbanet
1 edit | Nope, it's basic troubleshooting. Removal of the O2 sensor allows for exhaust to bypass a restriction in the cat and the engine will stop bogging down, if that's the issue.
I did misread his comment though.
Block off your EGR ports and drive with it connected just to be sure. It should throw a code but if it's truly the EGR mechanics that will confirm. |
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matt5
join:2001-10-06
Lagrangeville, NY | reply to dbsanfte
said by dbsanfte:Your car runs good after removing the EGR valve because you're removing the exhaust restriction. It was not removed re-read.
said by dbsanfte:Does your upper exhaust manifold have an O2 sensor? If so, remove it from the manifold, leave your EGR attached and functioning, and go for a drive. If it drives like a champ, you have a plugged cat.
Omg what, first off if you even read the thread you will it is can NOT be a clogged cat, that is 100% a waste of time, also, don't know what you guys use on the roads but here... eh, o2 sensors are a thing you really do not want to touch unless you HAVE to.
said by dbsanfte:In the unlikely event it drives the same, cut a thin gasket out of a pepsi can and block off your EGR ports, then reinstall it. Go for a drive. If that solves it, it's the EGR valve.
It is a VERY likely event, as we already determined that the cat is NOT plugged... the OP needs to see what the computer is seeing. |
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| Like I said, I misread the OP. Calm down, son. |
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bgraham
join:2001-03-15
Smithtown, NY Reviews:
·Verizon VoiceWing
·Verizon FiOS
·VOIPo
| reply to bgraham
For what it's worth, the problem was a partially blocked cat. I guess the restriction was not enough to block the exhaust completely but enough to overload the engine with exhaust gas when the EGR was opening.
The exhaust pressure according to Alldata should be 1.25 PSI at 2500 rpm and it was 3psi with the EGR valve connected and 4psi with the EGR disconnected. |
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| Glad to hear you found the problem.
I expect another bitter PM from matt5 shortly.  |
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