kenyon

my 87 formula is running rich. i changed all the sensors, but i think the problem is i am living in Denver(mile-high), and the ECM won't adjust for altitude.

five7kid

iTrader: (14)

Welcome aboard.

That isn't your problem. I have that "altitude attitude", too; it's my daily driver, and I don't have a rich running problem.

Why do you think it's running rich? Are you fouling plugs? Black exhaust? Smelly exhaust? What sensors did you change, exactly? Are you getting an SES light?

kenyon

i just changed the coolant fan switch, and broke the connector to that sensor but could still plug it in. i think that is giving me my code #15. i changed the O2 sensor and reset my codes, now code #45 has went away, but i know it's running rich, by the smell, and the loss of hp.

five7kid

iTrader: (14)

Code 15 is "Low temperature indicated at engine coolant temp. sensor". If it isn't telling the ECM the engine is at least 110 degrees, then it'll stay in open loop, which is probably a rich condition.

The coolant fan switch and coolant temperature sensor are two different things. The CTS is on the thermostat housing, the one with two wires going to it. If you replaced that sensor in your "all the sensors" effort, you either got a bad one or there is something wrong with that circuit. The coolant fan switch is in the passenger side head, and has no interaction whatsoever with the computer.

jrr

On paper, the ECM SHOULD compensate by interpreting the voltage levels from a manifold air pressure sensor and barometric air pressure sensor. I can't help but wonder what the service life of those sensors would be and whether age would cause them to simply not respond, yet not throw any SES codes.

The GM shop manual for your car contains sample voltage readings at the ECM terminal pins for those sensors. Maybe somebody at thirdgen.org has those numbers and then, by comparison, you can tell if the ECM still believes it is at sea level by what the BAP is telling it.

War_Eagle

Very similar problem, I have an 86 T/A 305 CC carb and my radiator cooling fan was not working. I began replacing sensors. 1 on the firewall, the 2 on the thermostat housing and the one on the metal support by the fan shroud and temp switch on the head, trying to get the fan operating. Now I am having the same type of problems, fouling plugs, black exhaust, rough running and ideling, including a faster idle speed. also there is a SES light that comes on after a couple of minutes of driving. Any ideas that could help fix this? Any help would be greatly appreciated.......

five7kid

iTrader: (14)

Read the trouble code(s) first (FAQ tells how). Have to know what it thinks is wrong before going into how to fix it.

kenyon

i must of exagerated when i said "all the sensors". You were right, i confused the coolant switch, and sensor. I changed the sensor and connections on the switch and the sensor, now i running right. Thanks again, and i'm sure you all will be hearing from me some more.

five7kid

iTrader: (14)

Every once in awhile, even a blind squirrel finds an acorn.

Glad I could help finding your problem (I'm the squirrel, by the way, not you). Feel free to come here with any others that come up.

Ever go out to Bandimere? I'm hoping to do the test & tune this Saturday, run the Friday series this summer.

kenyon

I use to up to Morrison all the time with my dad, but now he's on Joe Bellam's(his boss and driver) pit crew. I'll be up in Ft. Morgan watching the late models.
You're probably asking yourself, "if his dad is on a pit crew why didn't he get him to help him." And the answer is, my dad's on a pit crew. When he looks at it, it's only for a second, and he told me to check out my cat for my latest problem. Then again, I told him that I changed the CTS also.
So thanks again for being there buddy, your fix costed a lot less, and was the right one.
Good luck this weekend.