Service engine soon light - The 1947 - Present Chevrolet & GMC Truck Message Board Network

chevymotocross · 05-26-2007, 10:14 PM

I recently bought an 87 silverado 2wd with the 305 fuel injected engine. It just recently passed emissions for me, and the previous owner had new piping, mufflers, and cats from manifolds back (dual exhaust). I took it on a pretty long trip today, on the highway the service engine soon light came on. Truck still ran great and all the gauges did not hint a problem. I opened the hood and everything was fine, including fluids. I let the truck sit for a couple hours when I reached my destination. When I started it up, the light was off. On my way home, about 30 min. into my trip, the service light came on again. What is going on here? I guess I could have someone hook up an OBD computer and see but if the light is off, will it still read the errors or does the light have to be on? Also, before my trip, I filled up with 87 octane fuel and added SNAP Fuel Injection treatment since it does run a bit rough cold.

Staceydude · 05-27-2007, 01:34 PM

I have the exact same motor/same year truck and the same issue... except mine does sumble a bit at certain RPMs. Itis a manual tranny and the engine light will come on after a while highway driving around 55 - 60 mph... but when I shut the truck off and restart later the light is gone...

or on short trips around town it is off...

Would like to hear what folks have to say about it.

Regards

Srubydo1986 · 05-27-2007, 02:44 PM

I just removed the light in mine could find anything wrong so i get feed up with the light. But after i replaced motors from 305 yo 350 light went away. Cause i put it back in to see just for sh*7 and giggles.

Just a thought

f.monroe · 05-27-2007, 09:45 PM

I have had an 87 ,88 ,and 94 truck that all did that when I bought them . The 87 even stumbled a little but they all ran OK . It turned out to be a bad EGR valve on all three trucks . I only buy the EGR valves at the dealer since there are 3 different types ( I think 3 ) and they can sell you the right one based on your vin number . Frank

Staceydude · 05-28-2007, 12:35 AM

Hey Frank,

Thanks for the info. I had thought it could be the EGR valve myself.

I also noticed it seems to effect the mileage a bit

Regards

Stacey

ratfreak8871 · 05-28-2007, 01:22 AM

Most Likely Is Egr And Yes You Can Pull Codes W/o The Ses Light On. Also For That Year Of Truck You Dont Need An Obd Scanner Just Jumper The Terminals At The Aldl.

GREASEMONKEY72 · 05-28-2007, 03:22 AM

the egr makes sense and it will affect the mpg

05-26-2007, 10:14 PM	#1
chevymotocross Registered User Join Date: May 2007 Location: East Haven, CT Posts: 882	Service engine soon light I recently bought an 87 silverado 2wd with the 305 fuel injected engine. It just recently passed emissions for me, and the previous owner had new piping, mufflers, and cats from manifolds back (dual exhaust). I took it on a pretty long trip today, on the highway the service engine soon light came on. Truck still ran great and all the gauges did not hint a problem. I opened the hood and everything was fine, including fluids. I let the truck sit for a couple hours when I reached my destination. When I started it up, the light was off. On my way home, about 30 min. into my trip, the service light came on again. What is going on here? I guess I could have someone hook up an OBD computer and see but if the light is off, will it still read the errors or does the light have to be on? Also, before my trip, I filled up with 87 octane fuel and added SNAP Fuel Injection treatment since it does run a bit rough cold. Last edited by chevymotocross; 05-26-2007 at 10:16 PM.

05-27-2007, 01:34 PM	#2
Staceydude Registered User Join Date: Jun 2004 Location: DFW Area Texas Posts: 436	Re: Service engine soon light I have the exact same motor/same year truck and the same issue... except mine does sumble a bit at certain RPMs. Itis a manual tranny and the engine light will come on after a while highway driving around 55 - 60 mph... but when I shut the truck off and restart later the light is gone... or on short trips around town it is off... Would like to hear what folks have to say about it. Regards

05-27-2007, 02:44 PM	#3
Srubydo1986 The Crazy Machanic Join Date: Jan 2007 Location: Nokesville Va Posts: 1,437	Re: Service engine soon light I just removed the light in mine could find anything wrong so i get feed up with the light. But after i replaced motors from 305 yo 350 light went away. Cause i put it back in to see just for sh7 and giggles. Just a thought __________________ 1986 Sliverado longbed 400 small block mean as hell, 700r4 trans (5 speed coming one day) * 1970 chevelle 2dr sedan Latest update June 24 2007. *1957 4 door stationwagon - pink all original needing a good restore (body great, floors bad) newest additions 1965 shortbed fleet great granddads. Been told im nuts to bring it back from the dead (still going to happen) plans-all stock with a turbo 292 inline 3 speed column shift. and thats it big block 427 and 5 speed trans and ford 9 inch theyhave no home yet thinking what to put them in and a 79 c60 trash truck um no idea i have one

05-27-2007, 09:45 PM	#4
f.monroe Senior Member Join Date: May 2004 Location: Caldwell,Tx. Posts: 3,648	Re: Service engine soon light I have had an 87 ,88 ,and 94 truck that all did that when I bought them . The 87 even stumbled a little but they all ran OK . It turned out to be a bad EGR valve on all three trucks . I only buy the EGR valves at the dealer since there are 3 different types ( I think 3 ) and they can sell you the right one based on your vin number . Frank __________________ Born and proudly residing in a Red State !

05-28-2007, 12:35 AM	#5
Staceydude Registered User Join Date: Jun 2004 Location: DFW Area Texas Posts: 436	Re: Service engine soon light Hey Frank, Thanks for the info. I had thought it could be the EGR valve myself. I also noticed it seems to effect the mileage a bit Regards Stacey

05-28-2007, 01:22 AM	#6
ratfreak8871 Registered User Join Date: May 2007 Location: ALTON, IL. Posts: 98	Re: Service engine soon light Most Likely Is Egr And Yes You Can Pull Codes W/o The Ses Light On. Also For That Year Of Truck You Dont Need An Obd Scanner Just Jumper The Terminals At The Aldl.

05-28-2007, 03:22 AM	#7
GREASEMONKEY72 Registered User Join Date: Aug 2006 Location: Bakersfield,CA Posts: 7,893	Re: Service engine soon light the egr makes sense and it will affect the mpg __________________ -steven Alte Seele S.S. "Allison" '72 C/10 LWB 350SB/TH350 - DD PITBULL IS NOT A CRIME



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