Very Weird issues

[Reatta struggles]

Howdy everyone new to owning a buick reatta. I own a 1988 red coupe absolutely love the car but it's having some issues I can't seem to resolve. I have only had the car about a month and a half. It has 66000 miles and is in pretty decent shape for the age.

 

However I have a consistent rough idle that makes no sense. Sometimes it will idle smoother than other times. One day it's idling decently and only shakes when the rpms go up at first and other days it feels like it wants to stall on take off but it always smooths out in the higher rpms.

There are no current codes showing in the crt and just to clarify almost every sensor have been replaced on this car and vacuum lines. It also has a new fuel pump fuel filter and the timing chain was done last year. You name it and it has probably been done on this car the reason the car was given to me was because of the idle issue the original owner spent 3 months trying to figure it out and gave up.

 

Thank you for having me and any help greatly appreciated.

 

Also I have noticed my knock sensor values in the crt are 9999

 

[2seater]

A low mileage car sounds like a good find👍

 

Has the ignition coilpack, and ignition module below it, been replaced? If not, look for a sticky ooze leaking out between the two pieces. If this is observed, it is a sure sign it needs to be replaced. Plugs and wires as well of course. If they have been replaced already, double and triple check the rear spark plug cables are on the correct cylinders. This may seem rudimentary, but they happen to get mixed up more often than you might think.

 

The knock counter should reset to zero every time the ignition is turned on. There is always some start up "noise" so it is normal for the counter to show up to a couple hundred counts after starting but it should not continue to increase during normal driving. If the knock sensor was replaced recently, it will be overly sensitive if it was over tightened.

[Barney Eaton]

At least change the knock sensor.     I picked up several at the pick n pull because you don't know if a used (electrical) part is good until you try it. 

Plenty in the pick n pull on any 3800     I suspect the ECM default on a bad knock sensor is it will run rich. 

 

Some other owner have talked about a rough ride usually in the rear.   Not much you can do except try new struts if you can find them. 

You might also consider your tire pressure.    There is less weight on the rear, so you could drop the rear tire pressure maybe 4 psi and improve the ride. 

 

[DS_Porter 89 Burgandy]

 Your symptoms match the trouble I had. Relaced the ignition module under the coil pack and the trouble cleared up. It is a common problem.

 If it completely dies and then cools off and runs again it could be the crankshaft position sensor.

[2seater]

As a follow up to the knock sensor: Even though it is a pipe thread on the connection to the block, it does not seal any fluids inside the block. The passageway it threads into is a drilling for an oil passage from the oil pump further into the block. There is a pipe plug a couple inches inside the block to seal that passage so no fluids should be present when knock sensor is removed. The torque requirement is only 14 lb/ft or so.

[Barney Eaton]

Allow me to vent a little on tires........ my Reatta has stock size tire and the sidewall rates them at 1521 lb each at 41 psi. 

Do the math and those 4 tires could support  a 6084 pound vehicle when inflated to 41 psi. 

The information I have says a 1991 convertible weighs  3593 pounds or about 60% of the tire load capacity. 

If we assume the load capacity of a tire is directly proportional to the pressure,  then what psi could we safely use

on that tire?    For this exercise lets say the Reatta weight is 4000 ....  (factory weight + 2 - 200 pound passengers + gas)

Using those numbers it comes out that 26.9 psi would safely carry the 4000 pound vehicle.   My Reatta door sticker 

recommends 30 psi.      You can run whatever tire pressure you choose but 28 - 30 is a good range. 

[2seater]

7 hours ago, Barney Eaton said:

Allow me to vent a little on tires........ my Reatta has stock size tire and the sidewall rates them at 1521 lb each at 41 psi. 

Do the math and those 4 tires could support  a 6084 pound vehicle when inflated to 41 psi. 

The information I have says a 1991 convertible weighs  3593 pounds or about 60% of the tire load capacity. 

If we assume the load capacity of a tire is directly proportional to the pressure,  then what psi could we safely use

on that tire?    For this exercise lets say the Reatta weight is 4000 ....  (factory weight + 2 - 200 pound passengers + gas)

Using those numbers it comes out that 26.9 psi would safely carry the 4000 pound vehicle.   My Reatta door sticker 

recommends 30 psi.      You can run whatever tire pressure you choose but 28 - 30 is a good range. 

I have always stagger inflated my Reatta tires due to the 65%F x 35%R weight distribution in my normal daily driver mode. 34-35 psi front and 30psi rear. 225 tires on 16" wheels

[Barney Eaton]

For some reason I did not think it was that great a difference............ 

However I found in the 1988 release package information saying the distribution was 2241 on the front and 1104 on the rear. 

That is 67/33 ........... driver and passenger would put a little more on the rear ......possibly close to the 65/35 number.