Had an 85 GT back in the day and while perusing though Craigislist, came across an 86 GT in Kansas city that had a lot of work done to it, including a 3.8 swap, that it appears they lost interest in, so got if at a good price. Drove it back from Kansas City to Oklahoma, fairly gently as it had never really taken a long trip. Been reading through the forum, tons of info here, but seem to be going in circles. Per the previous owner, they originally installed a 92 Bonneville 3.8 SC, but later toasted the engine. Appears they did not follow the coolant fill procedure and cooked it. They pulled the SC and replaced it with a "built" NA 3.8 from a 93 Bonneville from a shop in Omaha, with plans to put the SC back on, but never did. (I have the SC, but may or may not ever put it back on. If I want to go really fast, I'll drive my SuperCoupe). The car has plenty of power, but OMG, does it need a five speed, but that's for later
They did the wiring harness themselves, and from what I can tell, it appears okay, however, it is still running on the 92 SC ECM, so its burning rich and will bog under full throttle. Amongst the may parts that came with the car is a 94 NA ECM, but they said when they tried to put it in, the car would run for about 30 seconds then shut off. I'm assuming the passkey is probably shutting it down.
I'm also assuming the MAF would be different between the SC and NA, and is probably much of the problem. Car runs okay at idle and under normal load, albeit burning rich. I can't find a MAP sensor on it and I don't think those came into play until the series II.
The correct fix would probably be to get the correct ECM (assuming the 94 would work if the passkey was disabled) BUT would it be just as easy to put on a SC MAF? The second options sounds politically incorrect, and would probably require some connector plug mods, but hey.
If changing the ECM is the best course, who would be the best person to tweak the 94 ECM I have, or perhaps someone has one already that would be plug and play?
The car is very driveable as is, but would like to get this correct. Have plenty of other stuff on the car to work on in the meantime.
The maf and sensor hardware will be the same between the two, so you're ok there. You're probably thinking speed density fuel mapping which is where the different bar map sensors would come into play...of which is not used on your setup. All you need is to contact Ryan at sinister performance and he'll setup an ecm for na, no vats and that should get you running.
First it will help a lot if you have the service code off the PCM. The one that was most common was 16141470. I currently are running that PCM in an 87. With a 1995 4T60e trans, 1998 3800SC, and the PCM is from a 1993 Park avenue Ultra.
The 1994/1995 PCMs were buggy at best. I would stick with the 16141470 if it is that one. I also agree that the transmission is one of the better upgrades. Either a 5sp or auto overdrive. I had a 1993 Series 1 in the car to begin with then went to a Series II SC and will be soon be going to a 2005 Series II NA. The biggest difference that I saw in the bin file between SC and NA was the timing map. When I first edited my bin I also edited shift points. When I went to the Series II I really didn't change much and were also able to use the 1998 MAF. The MAF tables were close enough. I use Tunerpro to view the tables and the biggest difference again between NA and SC was the timing tables.
Thanks, I'll contact Ryan next week and get that taken care of. Other than some exhaust work, that will leave me good engine wise. I just want to build it for a cruiser and as long as it can get out of its own way, it will be golden. Not many of these still on the road in my neck of the woods and have encountered many who have no idea what the car even is.
Had the tires/wheels installed last week (17 x 8) and just put the new sway bars on today and new radiator support mounts. I have some wiring issues in the dash to track down, Tach is intermittent when cold and the left turn signal indicator doesn't work After it warms up a bit everything works as it should, so something with a flaky connection. The factory temp gauge is questionable but I'm going to install aftermarket gauge pod with oil pressure/temp. From what I've read on the forum, the factory gauges were of dubious reliability.
I hope to have the Eibach springs and Koni's installed and everything aligned next week if my ball joints get here in time.
