Hey guys
So the last few days my truck hasn't been running right. It started last week I'd say tuesday or so an has progrressivly gotten worse. I'll sit at a light at idle and itll be fine for a few seconds then drop about 400-500rpms down. I had the curb idle set at about 850 cuz it's still cold and doesn't like the cold much. Anyways it'll drop then go back up then drop and repeat. Sometimes I rev it to 1200 and hold cuz I don't want it to die. I went up to Longview to see my biological dad yesterday. Does fine on the highway and when you give it throttle. It was even worse when I got off the freeway. We tinkered with the carb and timing. It's a little better but still not good. Can you help me out. I just need to keep driving till I can get a new carb or rebuild my old one. Thanks guys. I did do the fuel line mod last week hoping it'd help.

Any ideas and help are appreciated
Thanks
Cody.

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Old truck: 82 D150 225, 2bbl, dutra duals, 2.5" straight pipe to dual 2.5" tail pipes. Mud tires, 4spd, old forest service truck.
Current truck: 98.5 Ram 2500 ccsb, sport, 24v cummins, 5spd, 4.5" lift, 35's, 5" straight pipe.

Sounds like a carb problem to me. Try removing the idle air screw and blowing compressed air into the hole, then re-insert the screw and see if anything changed. (Make sure you either adjust the screw again or count the turns while removing it so you get back close to where it was.) I had one car that kept getting something clogged up somewhere in the carb and this was a temporary "diagnostic" fix. The carb needed a good cleaning to fix the problem, but whatever was jamming it up seemed to be stuck inside passages that I couldn't clean out. This test may let you know if you have a similar problem.

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Chuck Rivers, Webmaster

Ok thanks chuck I'll do that and see if it helps. I know it's running pretty rich again.

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Old truck: 82 D150 225, 2bbl, dutra duals, 2.5" straight pipe to dual 2.5" tail pipes. Mud tires, 4spd, old forest service truck.
Current truck: 98.5 Ram 2500 ccsb, sport, 24v cummins, 5spd, 4.5" lift, 35's, 5" straight pipe.

Are you still running a lean burn computer? What does it control? Carburetor, ignition, or both?

Yes im still running leanburn:( It controls timing, not sure if it controls carb other than bowl vent solenoid.

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Old truck: 82 D150 225, 2bbl, dutra duals, 2.5" straight pipe to dual 2.5" tail pipes. Mud tires, 4spd, old forest service truck.
Current truck: 98.5 Ram 2500 ccsb, sport, 24v cummins, 5spd, 4.5" lift, 35's, 5" straight pipe.

I don;t think the carb is the culprit here. The lean burn controlled ignition is probably your problem. The lean burn computers were notorious for causing idle and surging problems. If you are going to keep running your lean burn system, you must:

(a) eliminate all possible vacuum leaks,
(b) ensure that the vacuum transducer on the computer holds a vacuum,
(c) ensure that the vacuum transducer on the computer receives a manifold vacuum signal, not a ported signal like a distributor would get,
(d) replace the O2 sensor, if equipped,
(e) remove or replace the catalytic (I like clean air, but catalytics and carbs don't mix),
(f) make sure your base timing is set to factory specs
(g) make sure the outer ring on the vibration dampener hasn't slipped making the timing mark inaccurate
(h) make sure you don't have a worn timing set
(i) make sure all the sensors on the engine are functioning and hooked up

If you are going to keep your lean burn system, it is IMPERATIVE that you get a factory service manual and follow the diagnostic and maintenance directions for the lean burn equipment. In the long run, it will cost you less money and the motor will run better if you switch the ignition system to HEI and just get rid of the lean burn.

I want to switch to hei but my funds are running low. Plus I need brakes bad. I guess I'll have to put that as number one on my list. I'll get my factory service manual out and do some trouble shooting after school.

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Old truck: 82 D150 225, 2bbl, dutra duals, 2.5" straight pipe to dual 2.5" tail pipes. Mud tires, 4spd, old forest service truck.
Current truck: 98.5 Ram 2500 ccsb, sport, 24v cummins, 5spd, 4.5" lift, 35's, 5" straight pipe.

I'm working on getting my lean burn truck to pass smog and I was just dealing with this surging saturday. I know theres a slight vacuum leak at the throttle shaft but it's too expensive to get rebushed. I was quoted $110 and thats twice as much as I paid for my BBD to get rebushed.

So I sprayed the sides of the carb and the intake runners with soapy water and shot some compressed air up the hose that goes from the pcv valve to the carb. It took a little while but the only place it bubbled at was on one of the intake studs that hold the carb down. I took the carb off and retightened the studs. Brought my vacuum up from 15 to 17. I want it to be at least 19-20 but I don't think I'll be able to get there with the leaky throttle shaft. That pretty much stopped the surging and dropping of rpm. Either way I'll see if 17 is good enough to get past smog.