Engine Performance problem
1995 Buick Riviera 6 cyl Front Wheel Drive Automatic 168000 miles

I have a 95' Riviera with a supercharger. The supercharger has been replaced, it has had all new plugs, wires and three new coils. I have had the transmission serviced and have oil changed regularly and add fuel additive every other tank. When drive I feel a vibration and with my experiece I feel it is a combustion issue. After a few minutes driving the check engine light comes on and it is to the point that I can tell when it will happen (usually once I reach 40 MPH and then let off the throttle). The testing device says the check engine light is emmission related and could be one of three things; the EGR valve, the O2 sensor or an electronic fuel sensor. This car is running better than ever and I even get 24 MPG but this rough idle vibration is driving me nuts. One other note; sometimes when I start the car back up after only sitting a few minutes, it has a toughtime staying running so I have to do a power brake take off until it straightens out in a few seconds. Do these symtoms suggest a bad EGR?

I have no idea how your post is supposed to help. You asked no question and you show some diagram as to entering diagnostic mode. First off, I have already had a mechanic do that. Second, what am I supposed to jump those two connectors with? Third, how is that going to help?

Why don't you try typing a question or give me some feedback to my detailed post.

I have no idea what you are wanting. Is this all the help a $10.00 donation gets? What a rip-off.

Use a piece of wire or paper clip to jump the two and count the flashes, this will give the code that the computer stored.So the vibration feels like a misfire? The way you describe it , it could be an EGR issue or possibly a weak injector. Those 3.8's had some issues with injectors.The stalling after restart could also be an injector issue as well, or possibly a idle speed control motor.Try removing the isc motor and cleaning it with carb cleaner.

Hello Jack and thanks for the response. This started after I had the superchager replaced and I thought it was a misfire. I replaced the three coils and it still ran rough so I took it back to the mechanic and he replaced the wires and plugs. This vibration did get less noticeable but it still did not run like it had before. I only replaced the supercharger because the bearings were shot and it was making a lot of noise. The mechanic told me he cleaned the throttle body when he reassembled but I will try and clean the injector item you mentioned.

Do oyu get the vibration at idle? If so try removing and securing the supercharger belt out of the way and starting it to see if the vibration goes away

Yea Jack we have tried that as well. In fact, I was so convinced that it was maybe a warped turbine or misaaligned pulley that I got the supercharger replaced as the company I bought it from gave me a lifetime warranty.

I did type in the instructions on my post, but sometimes when we upload the pictures, it clears the text, sorry. What I would like to know is if you already read the codes, what were they? This will be of some help, since we are diagnosing over the web! Here are the instructions to do it yourself, use the picyure above...Cross these two terminals as shown, then turn the key on. Count the flashes, a 22 will flash as 2 flashes then a short pause, then 2 flashes, if more than one code is stored, the pause will be longer. The codes will display three times and end with 12. Write them down and post here. This connector is right under the middle of the dash...

Hello Merlin,

Sorry to just be getting back but I got pretty ill fo a few days. Today I tried sticking a paper clip into the first two spots of the connector and then turned the car on. I tried the first two from both ends since the plug does not really look like your diagram. I did this several times with each but I saw nothing flashing as in lights or numbers. Can you advise?

Jim

Yep..maybe! Some 95's have the newer OBDII connector, on all 96 and new cars, if it looks like this, scan with an OBDII scanner, Autozone does it free, or you can buy one here.
http://www.2carpros.com/affiliate/uid/merlin2021_1

Hope you feel better!