My 94 Eldorado Touring Coupe misfires and runs rough but there are no error codes. It gets worse when A/C or even heater is on. It intermittently gets worse (to the point of stuttering/chugging). No mechanic will even acknowledge it (maybe they are relying on the codes) but I can feel it and I hear it at the tailpipe.

 

Connect a scan tool, look at the data stream. Codes are useful. The data stream is often more useful than codes.

Verify fuel pressure

Verify cranking compression pressure.

How long has it been since it's had proper tune-up services?

 

I did the scan via the in the dash display and there were no codes except for the ubiquitous "service ride control" related errors. Others have done scans and found no errors.

 

Stop looking for "codes", start looking at the data stream via a REAL scan tool.

 

Any inexpensive suggestions for a scanner that does "real time" for 1994 eldorado? One that does more than the OBD.

 

Your vehicle is considered "OBD-1". The newer style is, surprisingly enough, OBD-2.

Any scan tool that is compatible with OBD-1 will work with your vehicle. Keep in mind that a "scan tool" is MORE THAN A CODE-READER. Code Readers are low-budget junk.

When it was me, I bought a used Snap-On MTG-2500 with software cartridges that go from 1980 1/2--1999, and from 1996 to 2006. The MT2500 is more common and less expensive than the MTG2500, but fully capable of accessing codes and data stream, and doing a limited amount of bi-directional control. (i.e., the scan tool commands the on-board computer to perform certain functions.)

There are probably many other scan tools that would work as well or better. The Snap-On '2500 is the only one I've got experience with. Snap-On has replaced that model with newer, better, more-expensive tools, any of the 2500 series are quite old by now. I'm not ready to upgrade to a newer scan tool, but I can see it from here. Another few years...maybe less, and I'll be looking for a replacement so that I can properly access vehicles newer than 2006.

Given a choice, I'd rather have a USED "professional-grade" tool than a brand-new "consumer-grade" tool. Others might think differently.

Be aware that there's a huge number of "OBD-2 only" code readers and scan tools. You MUST have something that works with OBD-1, and the proper connector for your vehicle.

For the record, "Scanner" is (or at least was) a trademark of Snap-On. Thus I'm very careful to use the generic term "Scan Tool".

 

What happened with these items?