Hey, folks.

I have an 85 Elky with the 305...straight-stock/no mods...bolted to the stock 200C 3spd tranny. Roughly 180k miles. I'm the original owner.

Recently, she has developed a significant stumble when accelerating which goes away completely when cruising on dead-level pavement.

When she stumbles, I get a significant gas odor (not mine; hers...LOL). Recently the Check Engine light came on...stored a code 45 indicating a rich mixture at the O2 sensor. The light goes out on a restart.

When it first occurred, I thought she was either not getting enough air for the fuel or not enough fuel for the air. The gas odor and the code 45 tells me it more like too much fuel for the air.

This stumble is NOT present on a cold start. As the engine warms, the stumble returns gradually up to a limit once all the systems are at operating temps.

Other details: I have replaced the spark plugs, wires, distributor cap/rotor/module (included check of engine timing which was fine), PCV, gas filter, air filter, checked all vacuum lines. Does not overheat. Catalytic converter is original.

Clearly, with the mileage, the diagnostic choices are more numerous than for a newer car/truck.

Here's my guess (and please tell me if this is possible and worth doing): the carb float is either sticking or the accelerator pump is failing or has failed. And, a carb rebuild is in order.

If there are other items to check from your experiences, I'd be grateful for any and all feedback!!

Thanks.

TG

Here's my guess (and please tell me if this is possible and worth doing): the carb float is either sticking or the accelerator pump is failing or has failed. And, a carb rebuild is in order.

If there are other items to check from your experiences, I'd be grateful for any and all feedback!!

Thanks.

TG

I think you hit on the problem with the carb rebuild. Your accelerator pump is probably weak and the throttle shaft bushing is loose. I also believe you should replace that 180,000-mile catalytic converter.

Doug

+1 for the accelerator pump.

It would also be a convenient time for the cat to "fall off".

Yea that 180,000 mile cat is provably not the best flowing. I would replace that or better have it "fall off"

Thanks for tips.

Not sure in Raleigh NC I can get away with a 'missing' cat...so replacement may be in order. If any other members are in the Wake County area, tips on this would be appreciated. Smog emphasis has been on-again/off-again for some years.

As for carb rebuilding, has anyone had any personal experience with either of the following:

http://www.carburetorsdirect.com/

http://www.i-5automotive.com/page5.html

They were ref'd on another thread (by who, I forget...sorry). Although I have rebuilt this carb (original) 2x over its life, I am considering getting a rebuilt/reman and keeping my original. All this in the interest of time more than anything else. Another option is to send my original to one of these places and have them do the rebuild. There may some aspects like the throttle plate bushings that require precision tools I do not have.

I also read somewhere on this site that dipping the catb to clean has distinct advantages to aerosol spraying...I do not have the facilities for dipping.

Advice welcome...and thanks much for that already provided!! (I'm reading a lot on this site and learning a lot too...great people and site!!)

TG

Don't know where your located, (Guess that's a secret), but to your question on the carb. I have only had dealings with Carb direct on one occasion, it was customer supplied. No prob with it, been on his car now about two years. Only made an air /fuel adjustment on it at install. Reason I remember it so well is the customer is also my neighbor, and I perform all his maint. on his 5 Veh.s. Also I agree, if you rebuild yours, and don't dip it, all you would be doing is replacing parts, that's not rebuilding it, it's shortcutting it. Also ~~ get rid of the Cat, and if your worried about the Smog Police, just go with a performance Cat, you can find them as cheap as about $50.00 if you look.

I would find a local carb shop/rebuilder. There should be one in a city of your size. That way they can do the final adjustments on the vehicle, and there are a few. Also if anything is not satisfactory you have some one to correct it. Did that last summer on my '85, (Don's Carburetor) they did a good job on the carb rebuild, but took the truck back for a little better choke adjustment. The throttle rebushing was a standard part of the rebuild.

Personally I would have a new high-flow cat installed. We need the cleaner exhausts in this world and you have less worries about passing emissions tests.

Doug