hey all! i've got this 87 formula with the LG4 4 barrel, reman rochester. The M/C solenoid has been making this EXTREMELY loud ticking noise, car runs very very rich. here's the steps i have done so far: unplugged the TPS, the MC solenoid stopped ticking so loudly. car still ran rich, and had a hesitation when barely on the throttle, and at WOT. plugged that TPS back in. My ecu trouble codes come up once ina while for a misadjusted TPS, a MC solenoid circuit, and a rich condition. the light goes out usually, and comes on intermentanly (sp?). so today, i noticed the screw in the front top of the carb was almost all the way up (air bleed screw according to the one exploded diagram i have). when i turned the screw back down to where i'm used to seeing it at, the MC soldenoid stopped ticking real loud. took the car for a ride, the check engine light did not come on yet, but the car still runs really rich, and has some, but less, hesitation. was going to check the fuel filter in it, but the fuel line wants to twist all the way around with the fitting. i have installed a new igniton coil (OEM replacement) and rotor for the distributor. i'm goign to say it could use new wires and a cap too (plugs i replaced, bosch platinum +2's). what could be causing this very rich condition???? please help! i tried searching but could not find a direct answer to my problems. The car smokes when i start it, mostly a very black smoke, sometimes i get a little blue (which i expect from a SBC). and at WOT it smokes black smoke like crazy. so, somebody please help me fix this car, it'll prolly run really good once i get this problem knocked out. oh yea, and its only got 55,000 miles on it ;-) thanks in advance for any help!

 

I'd suggest turning the air bleed idle screw back to about where it was and replace the cap and check the wires for continuity/replace if needed. that'll complete a basic tune-up. after cap & wires are done then use a dwell meter to adjust your air bleed idle screw to ~30 on the 6 cyl scale (do this when the engine is hot and idling at the correct rpms in drive w/ your buddies foot on the brakes). Also, if you want to try adjusting the idle screws then try about 3 & 1/4 turns out for each one.

 

Scooter, that info was really helpfull. i turned the air bleed screw down some more and it seems to run alot better, trying to figure out how to slow down the amount of fuel it takes in, i know theres prolly about 2 or 3 screws on the front of the carb, and im not sure which one does which. i figure if i can slow down the fuel for now it'll even out more. but yes, cap, wires, rotor on the way :-)

 

The system is designed to trim fuel with the cycling of the MC solenoid (clicking is normal) based on O2 readings. Baseline setting is 30 degrees (or 50% duty cycling) of the MC, usually read with a dwell meter at the diagnostic terminal near the blower motor.

Your car is running rich because it is out of adjustment and/or one or another sensor is not working properly.

The O2 sensor is narrow band and unless the readings are relatively close to normal the ECM can not use the data provided by it to trim the mixture. It will essentially stay in non-feedback mode. Usually adjustment of the idle mixture screws and IAB at four turns out each will get it close enough to go into feedback mode. Once in feedback mode the dwell meter will show that the MC is responding to O2 data by wavering between readings a few degrees +/- (and leaning the mixture with a higher dwell reading when the carb is choked with a rag). Now you use the IAB to obtain roughly 50% dwell reading at idle. Out with IAB allows more air in = leaner mixture.

Unless you've got a dwell meter ('bout $30) or a scan tool you're peeing in the desert playing with your idle mixture or IAB adjustments.

Oh, and new cap/rotor/wires/plugs always help prior to adjusting the carb, along with adjusting the TPS to read 0.40 volts at idle.

There's some good stuff somewhere on this with more detail. Look for a thread started by Nate86.

 

wow thats some really good info. yea i dont have a dwell meter, so im prolly peeing into a hurricane. i turned the air bleed down just a tick more, and the idle screw near the throttle i turned in about 1-1/2 turn, and it seems to be running extremely better, plus i put my OE air cleaner back on, and took off the holley pro-flo. i think it's prolly good for now until i get the new tune up stuff here at the house. i ordered mallory ignition parts, instead of OE. its still really rich with the 4 barrels open at WOT, but i expect that with origonal equipment in my ignition from 1987 haha also, not sure how to adjust the TPS, being that its basically down in the carb with the electrical connection hanging outside the carb. i think a good fix would be to ditch the rochester and slap a edelbrock 750 or 650 on it ;-) thanks for all your help people, a wealth of knowledge here on 3rdgen. ill keep this thread updated as things change.
-chris

 

Both idle mixture screws should be set to the same number of turns out.

There's a plug in the air horn near the booster pump lever fulcrum that covers the adjustment screw for the TPS. Once the plug is removed the screw can be accessed with either the 'special' tool or the roll-pin lightly tapped over the screw head that I always use.

A lot of the adjustment stuff is covered in the sticky up top along with a few pics.

Keep the q-jet. All it takes is a little effort to learn how it works.

 

to adjust idle screws look at the front, bottom of carb (you know when looking carb w/ windshield behind carb), & there's one idle adjustment screw on each side. turn idle adjustment clockwise in until lightly stopped. then turn each one ~3 & a hair turns out.

autozone or probably another parts store near you, has carb adjustment kit >$10. includes driver w/ ~12" flex & double d adjustment socket.

 

it seems to be running alot better now, no real hesiation, and i seem to only get smoke on startup and WOT. theres what looks like a vacuum tube on the back of the carb, on top. hmm wonder what thats for?

 

nothing, five7kid said its used on older carb setups for something or other but you can cap it & forget it. that's what done on mine.

 

lol yea, i capped it off, the carb doesnt whistle anymore when i let off the throttle. i've got it adjusted by ear, seems to run pretty good, no real hesiation, except for that little bit when i first give it gas off the line, but nothing major. only smokes at WOT. still smells like its running rich, but its not rich enough to rob my horsepower anymore, plus when the new ign. parts get here thatll prolly help alot :-) thanks alot guys for all the help!