Hi All.
I have an '87 MGM with a 5.0. I'm needing to pull up the trouble codes and my haynes manual tells me to run a jumper wire from the self test input plug to the #2 terminal on the harness plug. Sounds easy enough, but one small problem- my Merc does not have the STI plug. I pulled up the codes a few years back by running the jumper wires some other way, but can't remember, for the life of me, how they went. Can anyone help?

Thanks,
Paul

 

are you sure you dont have the connector? it is under the hood on driverside toward front of the car by the washer reservoir somewhat... there is a single wire plug and multi wire plug... another way to do the codes and stuff is by getting a code reader with book from ebay... the tester i am linking allows multiple testing, including cylinder balance testing and stuff too.
http://cgi.ebay.com/ebaymotors/Equus...motiveQ5fTools

 

Thanks, 87.
I looked everywhere in that vicinity for a single pigtail, but to no avail. What I did find was weird tho. There was an extra wire in the test harness connection and I traced the wire back all the way to the computer and it is the STI. Someone just took the plastic plug off and inserted it into the harness plug. I did read that some cars set up for international sale were put togather like this. I hooked up my jumper wire like the manual instructed me to, but no codes. I couldnt even get my test light or the check engine light to flash or do anything. Any ideas? The car will run, but very rough at idle and belches raw gas smoke. at highway speeds, it does great. I'm thinking the idle air bypass valve

 

when was last time the car had a tune-up or fuel filter changed? the pre 1988 panther platforms only popped check engine light when it is overheating or low oil pressure. one thing about older used cars is you never know what somebody else has done to the car...

 

uh oh, i made a typo mistake. the car is an 89 not a 87, sorry about that. after this thing started acting up, i changed the spark plugs (old ones didnt look bad at all, they have been in maybe 2 years) put new wires on and a new dist. cap. put a new fuel filter on today, and it didnt change anything. it idles very rough and will die. engine is getting way more fuel than it needs. get it going down the road though, and it runs great like it always had, very smooth and plenty of power. i checked the idle air bypass solenoid and it appears to be working. my haynes manual says it should have 10.5 volts going thru it, but my meter says 12. changed out TPS sensor and MAP sensor and it didnt help it any. the EGR valve does work when i apply a vacuum pump to it, but havent seen it actually working while on the car. I would think that if the engine is getting way too much fuel, that it would be a sensor issue and would leave a code. i've pulled up the codes before but for some reason, i cant get them to pull up or do anything. thanks for the link to the diagnostic tester. i'll check it out.
Paul