O2 sensors posibly bad?

itsunclebill · 10-07-2008, 09:21 AM

I have a 95 Blazer with a 4.3 CPI. The SES light is on and the code reader says the EGR is the culprit. Replacing the EGR valve didn't help at all, neither did any attempts at cleaning. The thing runs rich and surges when you try to hold a constant speed. I suspect the O2 sensors but they don't show bad in diagnostics.

Ideas?

ls1s10onair · 10-07-2008, 09:41 AM

what was the egr code exactly? if it was low flow, that can be caused by no backpressure in the exhaust (hollow cat, straight-pipe, glasspack) also, the port for the egr could be clogged up with carbon

itsunclebill · 10-11-2008, 09:52 AM

It was low flow and a new muffler fixed the problem. Thanks.

The SES stays off now but the vehicle has high readings on the measured pollution items, consistantly about 50% more than allowed.

ls1s10onair · 10-11-2008, 10:09 AM

i take it you failed inspection....? list what each reading was and the allowances, im sure i can help

itsunclebill · 10-11-2008, 10:49 AM

HC Reads 3.2356 Allowed 2.0
CO Reads 31.0024 Allowed 20.0
NOx Reads 6.03 Allowed 4.0

Yogi · 10-19-2008, 04:49 PM

Quote: Originally Posted by itsunclebill

HC Reads 3.2356 Allowed 2.0
CO Reads 31.0024 Allowed 20.0
NOx Reads 6.03 Allowed 4.0

Does it still have the cat? If so, has the cat been punched out or damaged or modified in any way?

itsunclebill · 10-20-2008, 08:45 AM

Cat still there, hasn't been touched. About 160 K on it

Yogi · 10-20-2008, 10:41 AM

I would open the intake manifold and check for leaks. The CPI is notorious for having leaky fuel pressure reg. and leaky fuel lines. Check this thread.

itsunclebill · 10-27-2008, 08:04 PM

OK.

To this point I've had the cat replaced - all the material inside had blown out - it was hollow. This got it past the emissions test.

The EGR code 0401 (insuffient flow) started coming on again. Pulled the upper part of the manifold off and found the EGR port plugged solid. Chipped it open, ran a brass brush in it and blew it out.

The regulator on the CPI was leaking so that got replaced.

EGR light stays off now but the engine (sometimes) surges pretty bad at 55 or so (it did this a bit before but I don't think it was as bad). I'm going to pull the top off again to check for fuel leaks this weekend but was wondering if there's anything else that causes this.

Yogi · 10-28-2008, 11:57 AM

Quote: Originally Posted by itsunclebill

OK.

To this point I've had the cat replaced - all the material inside had blown out - it was hollow. This got it past the emissions test.

The EGR code 0401 (insuffient flow) started coming on again. Pulled the upper part of the manifold off and found the EGR port plugged solid. Chipped it open, ran a brass brush in it and blew it out.

The regulator on the CPI was leaking so that got replaced.

EGR light stays off now but the engine (sometimes) surges pretty bad at 55 or so (it did this a bit before but I don't think it was as bad). I'm going to pull the top off again to check for fuel leaks this weekend but was wondering if there's anything else that causes this.

When you take the top of the intake off, you might also want to pull the distributor and check the gear for excessive wear. Click here for more info.

10-07-2008, 09:21 AM	#1
itsunclebill Registered User Join Date: Oct 2003 Posts: 33 Location: User is: OffLine	O2 sensors posibly bad? I have a 95 Blazer with a 4.3 CPI. The SES light is on and the code reader says the EGR is the culprit. Replacing the EGR valve didn't help at all, neither did any attempts at cleaning. The thing runs rich and surges when you try to hold a constant speed. I suspect the O2 sensors but they don't show bad in diagnostics. Ideas?
	[Reply w/Quote]

10-07-2008, 09:41 AM	#2
ls1s10onair Local Tech Age: 26 Join Date: Jan 2008 Posts: 3,242 Location: westwood, nj User is: OffLine	Re: O2 sensors posibly bad? what was the egr code exactly? if it was low flow, that can be caused by no backpressure in the exhaust (hollow cat, straight-pipe, glasspack) also, the port for the egr could be clogged up with carbon
	[Reply w/Quote]

10-11-2008, 09:52 AM	#3
itsunclebill Registered User Join Date: Oct 2003 Posts: 33 Location: User is: OffLine	Re: O2 sensors posibly bad? It was low flow and a new muffler fixed the problem. Thanks. The SES stays off now but the vehicle has high readings on the measured pollution items, consistantly about 50% more than allowed.
	[Reply w/Quote]

10-11-2008, 10:09 AM	#4
ls1s10onair Local Tech Age: 26 Join Date: Jan 2008 Posts: 3,242 Location: westwood, nj User is: OffLine	Re: O2 sensors posibly bad? i take it you failed inspection....? list what each reading was and the allowances, im sure i can help
	[Reply w/Quote]

10-11-2008, 10:49 AM	#5
itsunclebill Registered User Join Date: Oct 2003 Posts: 33 Location: User is: OffLine	Re: O2 sensors posibly bad? HC Reads 3.2356 Allowed 2.0 CO Reads 31.0024 Allowed 20.0 NOx Reads 6.03 Allowed 4.0
	[Reply w/Quote]

10-19-2008, 04:49 PM	#6
Yogi Registered (Ab) User Join Date: Feb 2008 Posts: 4,093 Location: League City, TX (Houston) User is: OffLine	Re: O2 sensors posibly bad? Quote: Originally Posted by itsunclebill HC Reads 3.2356 Allowed 2.0 CO Reads 31.0024 Allowed 20.0 NOx Reads 6.03 Allowed 4.0 Does it still have the cat? If so, has the cat been punched out or damaged or modified in any way?
	[Reply w/Quote]

10-20-2008, 08:45 AM	#7
itsunclebill Registered User Join Date: Oct 2003 Posts: 33 Location: User is: OffLine	Re: O2 sensors posibly bad? Cat still there, hasn't been touched. About 160 K on it
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10-20-2008, 10:41 AM	#8
Yogi Registered (Ab) User Join Date: Feb 2008 Posts: 4,093 Location: League City, TX (Houston) User is: OffLine	Re: O2 sensors posibly bad? I would open the intake manifold and check for leaks. The CPI is notorious for having leaky fuel pressure reg. and leaky fuel lines. Check this thread.
	[Reply w/Quote]

10-27-2008, 08:04 PM	#9
itsunclebill Registered User Join Date: Oct 2003 Posts: 33 Location: User is: OffLine	Re: O2 sensors posibly bad? OK. To this point I've had the cat replaced - all the material inside had blown out - it was hollow. This got it past the emissions test. The EGR code 0401 (insuffient flow) started coming on again. Pulled the upper part of the manifold off and found the EGR port plugged solid. Chipped it open, ran a brass brush in it and blew it out. The regulator on the CPI was leaking so that got replaced. EGR light stays off now but the engine (sometimes) surges pretty bad at 55 or so (it did this a bit before but I don't think it was as bad). I'm going to pull the top off again to check for fuel leaks this weekend but was wondering if there's anything else that causes this.
	[Reply w/Quote]

10-28-2008, 11:57 AM	#10
Yogi Registered (Ab) User Join Date: Feb 2008 Posts: 4,093 Location: League City, TX (Houston) User is: OffLine	Re: O2 sensors posibly bad? Quote: Originally Posted by itsunclebill OK. To this point I've had the cat replaced - all the material inside had blown out - it was hollow. This got it past the emissions test. The EGR code 0401 (insuffient flow) started coming on again. Pulled the upper part of the manifold off and found the EGR port plugged solid. Chipped it open, ran a brass brush in it and blew it out. The regulator on the CPI was leaking so that got replaced. EGR light stays off now but the engine (sometimes) surges pretty bad at 55 or so (it did this a bit before but I don't think it was as bad). I'm going to pull the top off again to check for fuel leaks this weekend but was wondering if there's anything else that causes this. When you take the top of the intake off, you might also want to pull the distributor and check the gear for excessive wear. Click here for more info.
	[Reply w/Quote]