1995 Buick Riviera Series 1 - knock and slipping feeling on accel

Hey guys - I have a 1995 Buick Riviera with a swapped 1994 Bonneville motor in it. I recently put it in, it seems to be running well although the supercharger has a bit of chatter to it.

I recently replaced the knock censor in the car and the supercharger boost solenoid. I couldn't find an exact match for the solenoid so I ordered one for a 96, which I think would make it a series 2, not sure if that matters. The solenoid does seem to work and it moves the lever to engage the supercharger so I think thats okay.

My issue is when I am under acceleration, 50% throttle or more, I feel a vibration like something is slipping. Not sure if this is due to a knock sensor being bad, I only replaced one because that is what the diagram said it had, is there a second? Similarly is this something that could be a transmission issue or is it a fuel trim issue?

Thanks for any help much appreciated!

Supercharger chatter... I would suspect the "coupler" - time consuming but not difficult.

Boost solenoid - IIRC GM uses pretty much the same solenoid on the respective superchargers, there are only a few models of the Eaton blowers that they used. The solenoid mounts differ I think, Some of them, you can swap between solenoids.

Vibration on acceleration, check the simplest stuff first. Your motor mounts among other things. Drivetrain. Plugs, wires and coils.

Thanks so much for this Albertj - I will have a look at the coils, plugs wires and mounts are all new under 5000kms on em. Could be a coil however as I didn't swap or inspect them at all. It basically never happened until I finally fixed the solenoid. Thanks for your response! I will update on what I find.

Mort wrote:

Thanks so much for this Albertj - I will have a look at the coils, plugs wires and mounts are all new under 5000kms on em. Could be a coil however as I didn't swap or inspect them at all. It basically never happened until I finally fixed the solenoid. Thanks for your response! I will update on what I find.

Check your supercharger coupler by slipping the belt off then turning the pulley with your fingers. Any play = worn coupler. The coupler is polymer and fits quite snugly. On the OE coupler over time the holes enlarge and you get a rattle.

For coils consider going to a pick and pull and getting a set from another supercharged 3800. The SC coils look the same as the NA coils but they are not. You will get a slight misfire mixing between the two. You can get hesitation on hard acceleration of you use NA coils on an SC engine.

Do a search on this site to find more about how to bench check coils (resistance, leakage)

What you want (to end up with) is a set of SC-spec coils with *matched* primaries and secondaries.

Thanks Albert - I do have another set of coils from the old engine which is nice, I can check em and then swap if needed. I think you're right about the coupler, the car has 180k kms on it and it's likely never been done.

I've also heard making sure the wires and plugs are up to spec (AcDelco) is important, which I will have a look at this xmas! Again much appreciated.

Mort wrote:

Thanks Albert - I do have another set of coils from the old engine which is nice, I can check em and then swap if needed. I think you're right about the coupler, the car has 180k kms on it and it's likely never been done.

I've also heard making sure the wires and plugs are up to spec (AcDelco) is important, which I will have a look at this xmas! Again much appreciated.

Some people like standard copper plugs.  I prefer iridium plugs because the gap does not change much over the life of the plug; I have used Delco, Autolite and Champion iridiums.  I have been happiest with the Champions, Delcos are a strong 2nd place, currently running Autolite because with rebate they were almost free of charge from rockauto.com (and will be replaced early with another set of Champion Iridiums).  

Best wires I have had for durability were Magnecors, but they (Magnecor) did not honor their warranty (after about 200 thousand miles, ahem).  ACDelco wires are adequately good.  I am currently running NAPA Belden "premium" wires I got on closeout, which are more or less copies of the Delcos. They are OK. That said, standard wires are not so good for the SC application, because the coils are about the hottest (highest voltage) of any passenger ICE car and they tend to burn out the conductors and/or ablate the terminals of standard wires.