1995 Buick Riviera Check engine light

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.

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.

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.

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

Do not try the paper clip trick. On OBD1.5 as it's called by some all you'll do is burn open fuses under the back seat. And by the way you can get a scan tool to read the code for free at Auto Zone. Not Orielly or Advance though as there brand does not work. You will need the Actron or similar and you must plug the scan tool into the cigar lighter as you need voltage direct from the car or the scan tool will not communicate. I used an Actron 9185 with the obd2 cable. It had the 95 buick riviera in it's software. Get the code but don't do what it says. It will tell you if its an ignition related problem. Most times it's the ignition module that's bad or has a bad contact to the plate it sits on. It must be grounded with thermal grease. If that has broken down or was never applied you will not get good ignition. This is a known issue with the 3.8 but no one will tell you. If you buy a gm oem replacement module it will come with instructions and a tube of thermal grease. The plate on the rear of the module is a cpu like you have in your computer. All ignition passes through this module. Both input from the crank and cam position sensors and the voltage from the cars computer. The like to go bad and they like to take out the coil packs too. Now check all plug wires for short. Go out at night with a spray bottle of water and a flashlight. With the engine running in the dark spray the wires and coils all the way out to the plugs and watch for arcing. Turn the flashlight on to id the location if you see sparks. These are famous for burning open wires. Chared inside of plug boot is a defiinite sign of issue and will cause severe misfire from time to time. Do not use any paper clips in your obd connector on this model. You will need a lift to get to the rear 3 plugs and wires. Access in in the back of the engine from underneath the car while on the lift. I doubt you will be able to jack it up enough to see into the area. Ignore all codes that mention cam or crank shaft position sensors or 18 crank codes etc until you replace the module, coils, wires and plugs. Those codes are often displayed when the problem is actually with one of these items. Process of elimination is key.

Excellent answer. Few people know about the module plate with the CPU located under the coil pack. Went out on mine and I played hell trying to find the problem.
Also correct on the 95 Riviera OBD. Trying to find a place to read it is in possible.( I agree NO paper clip trick!)
It is a 1.5 obd or other words a OBD2 plug in with a OBD1 operating system. Few readers have that operating system in its system. (Had to take mine to the college).