1988 Chevy truck running rich:

[speeder]

Haven't had the time to really investigate it yet but thought I'd see if anyone had any ideas...1988 Chevy PU, 350 (5.7) TBI motor runs really well except that I can smell CO off the charts and smokes a little. Does not seem to burn any oil, just running really rich. No codes or CEL, (does it even have one)?

TIA.

[RANDY P]

There's a "service engine soon" light on the dash---- it just got smogged, right?

It squaks pretty good if you fool with it too much, if the O2 sensor, or knock sensor is out it *****es.. I'd check to see if someone stuck an aftermarket chip (EPROM) - behind the glovebox....

FYI the trick to making it responsive is to RICHEN the mixture- guys make fuel pressure regulators on the TBI adjustable to increase PSI and advance the timing to about 4 deg advanced.....(Mine is) Yours might be messed with. Normally the engines are kind of sluggish.

PS- mine coats the tailpipes, it looks rich too, and mine has a fresh GM engine and new cat...

rjp

[Zeke]

My '89 was pretty nasty to stand behind especially for the first few minutes. Yet it passed each year. I never replaced the 2 injectors, but MotorMan has them for about 30 ea. IIRC. My butterfly in the TB would get kinda crumbed up and I'd shoot it with Berryman's occasionally. A new air filter always helped.

And yes, I ran the distributor a wee bit advanced over the factory specs as well as a lower temp t-stat (by about 20º). I got over 250K out it w/o ever even removing the valve covers. Bought it new.

Going to a 16 year newer truck has been interesting.

Oh, and those years were notorious for bad valve seals in the heads, so they smoked.

[Steve Carlton]

Put a tankful of Rotten Robbie's in it. That'll teach it.

[Nostril Cheese]

O2 sensor

[speeder]

Thanks all. I think that I have more than one thing going on- really bad valve stem seals that make it smoke bad on start-up and also a rich running situation.

I have not tried to smog it, it would never pass, IMO. I'm just going by the stink of it, not actual readings. I need to get off my ass and poke around a little, do a compression test and look at plugs, etc. I did not even know that it has an O2 sensor, that's probably never been changed.

I'll report my findings here later.

[RANDY P]

O2 is ez. Driver's side downpipe just past manifold...

rjp

[Zeke]

Whenever mine didn't pass I got one of those $100 cats. They lasted about 4 years. Then CARB put a stop to the 100 bucks ones and they became 200. Only had to buy one of those a I think it was on there when I sold it after 5 years.

[thumbdoctor]

Check the CTS (coolant temperature sensor) and coolant temp running. These have the most effect on rich operation. Disconnect the 2 connections at the TBI (throttle body injection) connectors and look for gas seeping up the terminal towers. This sometimes weeps through the wires and poisons the O2 sensors and creates a gas smell inside the driver's compartment behind the glove box.

[speeder]

I'm not smellin gas inside the cabin, just stinky exhaust outside. (You can smell it also if stopped with window down from inside). I like the idea of coolant sensor, that's the kind of thing that goes bad after a couple decades. I need to find out how to test each sensor individually, do I have some form of OBD on this thing? TIA?

[thumbdoctor]

OBD I ground terminal "B" on the ALDL (assembly line diagnostic link) under the driver's side of the dash board. The check engine light will flash code 12 (ignition bypass) 1 long 2 short flashes in three sessions then immediately after that, the problem codes will flash in order of importance. Coolant sensor will be either a code 14 coolant sensor low (1 long 4 short) flashes or a code 15 coolant sensor high (1 long 5 short) flashes. For the cost of a coolant sensor, you might as well replace it as well as the thermostat (190 F).

[Zeke]

There's an OBDI port below the dash next to the steering column. You can get an iPhone adapter and app. Or drive to AutoZone.