3.8 dualjet part throttle hitch

[a.graham52]

85 cutlass
3.8 w/dualjet
94k miles
no check engine light

9k miles ago:
rebuilt carb
plugs, wires, cap, rotor
intake gaskets

hey all, so i have only put about 9k miles on this gutlass turd since i have owned it. daily driver in the winter and gets occasional use in the summer. currently im doing about 500 miles a week and the car really doesnt sit any length of time.

i have had this part throttle (high load) hitch since i got the car on the road. 9/10 it happens as you pulling a hill and you dip into the throttle... almost like the point (i assume) at which the computer is telling the needles to stay up for heavy load fueling. but im not 100 percent sure. i dont have my dwell meter or most of my tools available at the moment. best way to describe it is it feels like a single smooth hitch as apposed to a rich missfire thats ragged and predictable. or an ignition missfire that happens over and over. engine sound cuts out when it happens so i dont think its the torque converter slipping... btw only does it when the TC is locked.

i turned the needle adjustment 1/2 turn rich from "base" and my hitch got a lot better, but cruising the interstates i can make a "Rich burble" as i apply throttle at say 70mph. if i go 1/2 turn lean from "Base" car lacks power and almost feels like hitch happens more frequently... but the lack of power is more prominent. i feel like its ignition related due to how "precise" this condition is but im thinking i need to start with accell pump and possibly test tps sensor. my concern is i wont find anything simply because i have had the carb apart for various reasons many times and nothing was ever found, nor was my hitch condition ever changed. im asking you guys for maybe a more narrow field at which to look. i also no longer have access to an obd1 reader.

btw, my old work commute was 7 miles long and consisted of one hill that was incredibly long that you would be doing 35-40 at the base. maybe once a week i would get a hitch, no big deal really. now my commute is 60 miles a day with various hills in which i can duplicate concern if i try.

 

[pontiacgp]

since you have hasd this problem with a fresh rebuilt carburetor I would be asking who ever rebuilt the carb about the problem you are having, that is if you know who rebuilt it.

 

[a.graham52]

since you have hasd this problem with a fresh rebuilt carburetor I would be asking who ever rebuilt the carb about the problem you are having, that is if you know who rebuilt it.

it was j&j out of cali, at this point it was over a year ago. what they will do is ask me to send the carb back to them. i do not have 3-4 weeks available to have this car down.

 

[a.graham52]

also, im catching wind that the VSS is located at the speedo, and if so is this true for my 85? my speedo bounces around 3-5mph at times. i would like to start there if that is the case.

 

[fleming442]

Your "needle adjustments" are idle only; any improvement in driveability was a placebo effect. I'm thinking it's a sticky power piston or lazy solenoids.
As far as the VSS, I thought that was only for cruise control? Speedometer is completely manual and driven by a cable.
When was the last time the O2 sensor was changed?

Mine had a buck on the highway, but only during cruise control operation. It was fine with manual throttle.

 

[a.graham52]

Your "needle adjustments" are idle only; any improvement in driveability was a placebo effect. I'm thinking it's a sticky power piston or lazy solenoids.
As far as the VSS, I thought that was only for cruise control? Speedometer is completely manual and driven by a cable.
When was the last time the O2 sensor was changed?

Mine had a buck on the highway, but only during cruise control operation. It was fine with manual throttle.

The needles I speak of are the ones the solenoid actuatates. Probably should have said rods. Vss I believe would also control tcc lock up and honestly not sure if it's smart enough to adjust timing tables. O2 sensor was done with everything else as well as a coil that I forgot to mention. I bought the car as a non runner that ended up having a Frankenstein aftermarket new carb and I did a ton on parts replacing to ruel things out.

 

[fleming442]

Sounds like you have a handle on it, then. I would lean towards the TPS myself...

 

[a.graham52]

I ruled out the Speedo tonight. Doesn't fluctuate at all over 15 mph. I'll have to pay further attention to it on my way to work in the morning.

Yeah I'm leaning towards tow or accell pump. I need to recheck my tps voltage setting first. But being at part throttle I doubt it's a base setting issue. Also only have the issue with throttle application. If you back of gently and slowly it never skips a beat. Which also makes me wounder about the pump. I know fuel injection really well, accell pumps, floats and passages not as much.

 

[jiho]

The feedback DualJet is so punishing for so little (or less). In the process of replacing the fuel filter on-car, I managed to pull out the fitting for the MAP sensor hose. So I pulled the whole thing to fix that, and while out, took the air horn off to check the internals. Turned out the M/C solenoid had a dinged wire. Once back together, somehow (I'm still not sure how, must have had hypoglycemia) the TPS adjust screw was turned in so far that once back on-car I couldn't get it backed out to adjust. So I pulled the air horn off, and wound up grinding a lot of aluminum from around the TPS screw so I could get at it to figure out how to get it backed out. It did work out in the end, and for insurance along the way I found a pristine surplus reman for just $100 shipped. But these are not things you grow fond of for a hobby. I'm trying to keep the car legal and roadworthy until I figure out what to do with it, but that duty alone has been eating up so much that anything more ambitious hasn't gotten much of a word in edgewise.

This post should feature my usual taste for a certain smilie ( ), but somehow I haven't found the mood for it.



The hex head is intact, but it's smaller than the diameter of the thread, and a bit hard to see in the reflected flash in this shot.

 

[jiho]

The idle mixture screws do affect off-idle, yes they do, very much. And they must be adjusted on-car after installing a serviced carb.