No acceleration with 4.1. Why?

[Guest]

Own a 1983 Buick Regal with a 4.1 V-6 I use as a daily driver. Great gas mileage. (have gotten over 30 mpg on the road.) But almost no power on acceleration. Fairly light car, big V-6 and should be pretty fast. (am used to blowing people away with my 318 Dodge Dart) Like the gas mileage, but the Buick is almost dangerous when really need some acceleration.

Only thing obvious is that there is a piece of linkage on the passenger side of the carb. which is not hooked up, just dangles. Assume it has something to do with the 4 barrel. Can not find any way to hook it up to what it is supposed to hook up to. Can't feel anything with my fingers. To get a better look at it would have to remove what looks to me like a choke on that side. However it is riveted in. Any suggestions? This really should be a pretty fast car, not a dangerous slow poke.

[Guest brh]

Your car is a little too new for me but off the top of my head I'd say youre on the money on the linkage. If you have a 4 barrell the linkage is supposed to kick in your secondaries. If you take the top off of the air cleaner and "goose" the engine with the throttle linkage your secondaries (back two barrels) should open. If they don't its your carb. not the car. Just 2 cents

[NTX5467]

Have you checked the exhaust for restrictions (i.e., partially clogged catalytic converter) and also checked to see if the wire to the knock sensor has possibly grounded out against something?

I'm not sure what linkage your talking about, but the choke pulloff and secondary control are on the passenger side of the carb.

I don't recall the QJets for those motors being any smaller in air flow rating that the other regular V-8 QJets so even the primary side should be adequate for your motor without the secondaries being involved. If you did open all 650cfm of carb at once, it would be vastly too much for your engine to handle unless you do some really serious modifications (which would put your mpg down to about 10 or so in the process).

The other issue is that the primary side power piston that runs the metering rods up and down could well be stuck in the economy position and is not moving upward with lower manifold vaccum events (as in when you throttle into it). You can stick a large diameter and long screwdriver through the vent tube inside the air cleaner circle to lay on top of the power piston. When you throttle into the motor, it should move upward--if not, you either didn't position the screwdriver correctly or the power piston is stuck (as I suspect it is).

If it has an ECM controlled mixture control valve in place of the power piston, it could be similarly bad and need replacement.

Between the internal carb issues and the knock sensor wire, I suspect that's where your power concerns will be located, from my experiences with QJets and knock sensors.

Enjoy!

NTX5467

[Guest]

Thanks for the good info. Probably should start out by drilling out those 2 rivets so I can see where that linkage is supposed to be hooked up. Hook it back up and go from there. Assume I can replace those rivets with sheet metal screws.

[Guest]

there should be linkage going to the secondary chokes (the dual flaps on back end of carb) Hooked across the top pass side of carb to the primary choke pull off (a little vacuum unit on the front pass side angled down with small vac hose hooked from it to carb body) this vac unit cracks open the primary choke (front top flap)on cold start and also prevents the secondary chokes from opening on full throttle until vac drops, if this is not hooked up seondary chokes go wide open right away which bogs the engine, in similar fashion if they were wired or stuck shut.

the other possible linkage problem could be the cold detent which prevents use of 4bbl until engine is fully warm, this is under the round choke housing (this is on the pass side and has black plastic cover riveted your choke may be electric or heqat stove (small pipes into manifold)) under this unit at carb base you can see the throttle shafts back is secondary, just in front is a latch which catches a pin on throttle shaft, make sure with car warm the latch is out of the way of pin.

i agree though with other post primaries should fed that engine well. check for a complete tune up, bet you have oxidation on distributor cap and rotor, check your timing is to spec, check wires and plugs, dirty air filter, EGR valve comming on when it should not.

[NTX5467]

I looked in the GM Parts database this afternoon and highly suspect you have an electronic QJet. That means it would have a Throttle Position sensor over near the accel pump (on the throttle cable side) with a 3-wire connector. Also some wires that go into the top of the carb that run the mixture control solenoid. Possibly another set of wires that go to a valve that makes the accel pump "dual stage" depending on operating conditions plus a possible set of wires for an aneroid compensator mechanism. That does not include the wire to the electric choke housing.

On the QJet, what might appear to be "chokes" on the secondary side is actually the secondary air valve itself. They are adjusted with a small set screw and tension screw on the passenger side of the carb, near the end of the shaft they are mounted on. Even though there is spring tension that the air flow must work against for them to open, the rate of opening is controlled by the choke vaccum pulloff with a drilled restriction on the vacuum hose connection. It will keep them from opening too quickly, basically.

Between the two air valves is a metering rod hanger that holds the metering rods for the secondary system. Under the hanger is a thin plastic washser-type cam that raises the rod hanger as the secondary air valves open. That plastic cam can wear and will not raise the secondary rods for the richer mixture required with the extra air. That can cause a lean condition too, somewhat common.

Only thing is that this cam and attaching hardware are not listed in all of the parts lists for QJets in the GM Parts listings. If you find one, though, they usually fit "everything". As you manually open the secondary air valve with your finger pressure on the back of the air valves, the metering rod hanger should significantly move upward--if not, the cam is worn and needs replacing.

So, several things to check for. The secondary metering rod cam. The linkage issues you have mentioned (I'm not sure why any of the stuff on the outside of the carb would be riveted together as they are all designed to be replaced and usually have screws holding them together--except for the choke coil to the carb body as there is an adjustment there that they don't desire to be changed). Might be a throttle position sensor that doesn't tell the computer you want to accelerate quickly. Might be an accelerator pump issue, but it that was an issue you'd get a backfire "pop" on sudden acceleration from a lean mixture. If you pull the top off of the carb and see little circles of red rubber-type material in the float bowl, the mixture control solenoid has failed. As previously mentioned, it will act the same as if the power valve has stuck in the full economy position, if that's where it defaulted to, but when they fail driveability typically deteriorates too.

What we found out on a Chevy pickup of the general vintage as your Buick was that when the knock sensor wire grounds out, it basically cuts the advance in the distributor to zilch. That particular truck would not pull itself up hills without downshifing few gears, but when the wire was replaced, it would light the tires.

Back then also, there was also a deal that GM Engineering and Tech Assistance came up with that was called a "vacuum trap". On many of the middle '80s light trucks with 305s, after a while they would get "doggy" and lacked power. These vehicles typically used full manifold vacuum to run the vacuum advance instead of the more common ported vacuum. So, you're sitting at a red light in gear and probably about 15" of vacuum. When the light turns green you throttle into it and the vacuum drops to about 10" or so. When the vaccum drops, the vacuum advance in the distributor went away too, leaving the engine to rely on the mechanical advance to work (which usually was set up to be very slow in advancing). Result, one big lack of power.

The Vacuum Trap was basically a deal with two vacuum delay valves (plumbed in parallel) turned around backwards so that when the manifold vacuum dropped, the vacuum advance unit stayed charged with what it had had previously. Result, the vacuum advance kept the timing advanced until the rpm came up enough for the mechanical advance to kick in. This one deal made a world of difference in how those trucks drove and acted. We put them on most everything that had a poor acceleration/no power complaint, but on others they did not work as they did on the light trucks. They have since been discontinued but could be built with some vacuum hose and plastic tees, plus some valves scrounged from the salvage yard.

I don't perceive your problem is anything really major but could just be some "maintenance" issues that you weren't expecting. If the fuel economy is still where you mentioned, there shouldn't be anything wrong with the ignition--if there was, it would be missing or cutting out under load and fuel economy would be worse than what you mentioned. All that really matters is that a spark is reliably jumping the gap in the spark plug and igniting the mixture each time. If it had failed an emissions test, having a clean set of plugs and maybe a few other ignition components might help that and might improve fuel economy some, but as long as that spark's jumping is what the main issue is. Of course, it would not hurt to change those things for good measure if it's been a while.

What about the other maintenance items like fuel filter and air filter? Just curious.

Hope this might help.

NTX5467

[Guest]

WOW Lot of good info there. Thanks a lot.

I have seen the same motor on other Buicks with 2 screws to hold on what looks to me like a choke assembly (covering up where that loose linkage is supposed to go) instead of the 2 rivets that I have. Don't know why they used rivets on mine. A little cost cutting for a while to save a few pennies maybe.

[Guest]

No,

They use rivets to deter people from playing with settings in the emission control age. You will also notice (if your carb is untouched) the idle mixture screws at front of based are capped. requires drilling to get out. Same reason as above.

[Guest]

You are right.

A 20 year old car too. Amazing anymore that you have to have at least a 30 year old car if you want to be your average shade tree mechanic.