check engine light 1986 quadrajet 454

[mountaindrew]

I have an intermittent "check engine light" that comes on when cruising at highway speeds.  Sometimes I can accel or decel and it'll turn off.  It usually always goes off when slowing back down or even speeding up a bit more.  I have a factory HD emissions 454 and a quadrajet.  It's got air pumps, no cats and duals.  I have pulled the air pump hoses off the diverter valve and stopped them up because they were making my exhaust garble/pop when idling.  No other modifications.  Why the "check engine light"?  Any way to pull a code from an 86? 

[jaredts]

This should apply to your vehicle:  http://www.obd-codes.com/faq/read-gm-2-digit-obd-codes-free.php
I assume you have an E4ME carb.  They're not generally all that great.  This should help you identify your carb.:  http://forum.73-87chevytrucks.com/smforum/index.php?topic=11934.0
I have only had one E4ME and it worked o.k. other than the mixture control solenoid stop screw would not stay adjusted and I would get a check engine light and the code would be rich fuel condition.  After adjusting it a half dozen times over the course of a year I managed to get a lock washer under the screw and tightened it down.  That put it at just about the right adjustment and it would finally stay put.  Maybe this helps, maybe it doesn't.  If you do have an E4ME then a different carb. and a piece of electrical tape over the check engine light might be in order!

[mountaindrew]

This should apply to your vehicle:  http://www.obd-codes.com/faq/read-gm-2-digit-obd-codes-free.php
I assume you have an E4ME carb.  They're not generally all that great.  This should help you identify your carb.:  http://forum.73-87chevytrucks.com/smforum/index.php?topic=11934.0
I have only had one E4ME and it worked o.k. other than the mixture control solenoid stop screw would not stay adjusted and I would get a check engine light and the code would be rich fuel condition.  After adjusting it a half dozen times over the course of a year I managed to get a lock washer under the screw and tightened it down.  That put it at just about the right adjustment and it would finally stay put.  Maybe this helps, maybe it doesn't.  If you do have an E4ME then a different carb. and a piece of electrical tape over the check engine light might be in order!

I took my breather assembly off but could not find the ID numbers on the carb.  The problem you described about rich fuel condition sounds like a problem I have too.  When I'm at 45 and mash the gas, I get a kickdown to 2nd gear and a big ol cloud of black smoke behind me.  Also it idles kinda rough and black smoke comes out of the pipes. 

[mountaindrew]

What does the "check engine" light monitor on my truck?  It's an 86 with no ECM best I can tell.  I can't pull codes so what's the point?

[VileZambonie]

Sounds like someone swapped the cluster then. It should have a choke light there not ses

[mountaindrew]

It has a choke light also.  It starts fine, runs fine, and idles (although rough) but smells real gassy, soot on concrete, and black smoke on strong acceleration.  I am finding quite a bit of info about quadrajets on a chevelle and 3rd gen camaro forum so I'll keep digging too.  Thanks for your input thus far.  I would still like to hear from anyone with similar experience.

[jaredts]

Sounds like someone swapped the cluster then. It should have a choke light there not ses

Vile, do none of our trucks come with an E4ME carb?  It sounds like your saying there's no way there should be a check engine light?  I don't know...I'm new to these trucks, I've had a bunch of old chevy's though.  On my '87 Camaro I had an E4ME and it did have an ECM and an oxygen sensor and you could check diagnostic codes just like any other OBDI system.  I thought since tbi came out on these trucks in '87 that an '86 might have this.

[VileZambonie]

He said his truck is non ecm so therefore I would assume he has a non-feedback system. If he has a feedback system then he does have an ecm. He should have an M4M series carburetor (M4MC, M4ME, M4MED and M4MEF)

[mountaindrew]

I found some numbers on it after I cleaned the gunk off.  17085212  2126 hpa  Very sorry- I assumed there was no ECM since it's carbed rather than the 87 TBI.  It's the stock Rochester quadrajet for an 86 hd emissions 7.4.  Does my '86 carby have an ECM and where would the ALDL connected be?  I've looked under the dash in the usual spots.  Also I cannot find an o2 sensor anywhere.  

*edit  Also it's a "check engine" NOT "service engine soon" like I've seen posted around various places.  

[VileZambonie]

How about some pics of your set up under the hood so we can see what you're equipped with? Look behind the glove box for the ECM. You have no data link connector. If you follow the diagnostic strategy I posted you should be able to pinpoint the cause of your CEL.