96 Chevy C1500 random misfire problems - The 1947 - Present Chevrolet & GMC Truck Message Board Network

AFROBUSH · 03-18-2012, 10:42 AM

I have the 305 v8 5L engine, and it seems to be misfiring. It only begins to misfire when i am going above 50mph or right before it changes gears. After i fixed the check engine light i scanned it and the random misfire code came up, and a code for a bad O2 sensor after the cat converter did also. If anyone knows what could be causing the misfires i would like to know. I have already changed all the spark plugs, and the wires, and the problem is not fixed.

**Boog** · 03-18-2012, 11:35 AM

Welcome to the forums.
First thing you need to do is check the fuel pressure or have it done for you. Low fuel pressure can cause cruise speed missfires. Low catalyst efficiency can also be caused by low fuel pressure misfires. O2 sensor behind the cat is there only to monitor the cat activity. The ecm uses the upstream cat to make fuel adjustments.

AFROBUSH · 03-19-2012, 12:46 AM

I will get that done. Thanks for explaining what the O2 behind the cat does. Did not know that... Saved me some money for replacing them

ChevLoRay · 03-23-2012, 01:37 PM

Jim gave some good advice.

For me, I had something similar that ended up being a dirty MAF sensor. If you have a K&N filter, or other oil-impregnated one, there's always a chance that there was too much oil used at re-charge time and the oil can leave a thin film on the sensor wire. You can use alcohol and a q-tip to clean that wire.

speedygonzales · 03-23-2012, 05:22 PM

The oil thing about the cotton filters is a farce that K&N's own website debunks.

http://www.knfilters.com/maf/massair.htm

When was the last time you replaced the fuel filter??????

03-18-2012, 10:42 AM	#1
AFROBUSH Registered User Join Date: Mar 2012 Location: Brunswick, GA Posts: 2	96 Chevy C1500 random misfire problems I have the 305 v8 5L engine, and it seems to be misfiring. It only begins to misfire when i am going above 50mph or right before it changes gears. After i fixed the check engine light i scanned it and the random misfire code came up, and a code for a bad O2 sensor after the cat converter did also. If anyone knows what could be causing the misfires i would like to know. I have already changed all the spark plugs, and the wires, and the problem is not fixed.

03-18-2012, 11:35 AM	#2
Boog laying low Join Date: Mar 2001 Location: Searcy, Ark. USA Posts: 13,513	Re: 96 Chevy C1500 random misfire problems Welcome to the forums. First thing you need to do is check the fuel pressure or have it done for you. Low fuel pressure can cause cruise speed missfires. Low catalyst efficiency can also be caused by low fuel pressure misfires. O2 sensor behind the cat is there only to monitor the cat activity. The ecm uses the upstream cat to make fuel adjustments. __________________ Boog 69 Chevy stepside, 358/T350, 4.11 posi, 4.5/4 drop, rallys, poboy driver primer is finer 91 Chevy sportside, Tahoe, Yukon & GMC Crewcab All GM..'nuff said. I stand for the flag and kneel at the cross

03-19-2012, 12:46 AM	#3
AFROBUSH Registered User Join Date: Mar 2012 Location: Brunswick, GA Posts: 2	Re: 96 Chevy C1500 random misfire problems I will get that done. Thanks for explaining what the O2 behind the cat does. Did not know that... Saved me some money for replacing them

03-23-2012, 01:37 PM	#4
ChevLoRay Old Skool Club Join Date: Jun 2001 Location: Benton, AR "The Heart of Arkansas" Posts: 10,880	Re: 96 Chevy C1500 random misfire problems Jim gave some good advice. For me, I had something similar that ended up being a dirty MAF sensor. If you have a K&N filter, or other oil-impregnated one, there's always a chance that there was too much oil used at re-charge time and the oil can leave a thin film on the sensor wire. You can use alcohol and a q-tip to clean that wire. __________________ Member Nr. 2770 '96 GMC Sportside; 4.3/SLT - Daily driven....constantly needs washed. '69 C-10 SWB; 350/TH400 - in limbo The older I get, the better I was.

03-23-2012, 05:22 PM	#5
speedygonzales Registered User Join Date: Jan 2006 Location: Smithfield, VA Posts: 1,501	Re: 96 Chevy C1500 random misfire problems The oil thing about the cotton filters is a farce that K&N's own website debunks. http://www.knfilters.com/maf/massair.htm When was the last time you replaced the fuel filter?????? __________________ 99 Z71 (98 body style) Pride and joy Last edited by speedygonzales; 03-23-2012 at 05:38 PM.



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