1990 SC won't pass RI state inspection

SuperCoupe

Registered User
I have a 90 SC 5 speed that has a Mac cold air, full custom dual exhaust w/a pair of Borla's and the rest is basically stock, but it runs really rich...or so my mechanic tells me. Any suggestions on where to start looking? I think I'm going to put a new air filter on it in hopes it might help. The problem is I never drive the car. It sits in my garage year round because I have a work truck, and a GMC Jimmy I use in the winter, and summer to pull my boat. I'd say I've put less than 20 miles on it in the last 5 years. I bought a new battery I need to put in, and 5 gallons of V Power to put in my tank. The last time I started it, it ran extremely rough, but I'm hoping it's because my gas was very old. I know having ethanol in our gas (no where in the state to get non-ethanol gas) is certainly not helping matters even though I use K100 ethanol treatment which is supposed to all but eliminate water. I used to have a guy who lived close by that would work on it, but I don't know any other mechanics that I trust enough who will willingly work on it. I also have stock exhaust manifolds that were bored out, plugs were changed a few years ago, but they have basically no mileage on them
 
Pull codes and see what they refer to. I would look close for vacuum leaks. If you have touched any of the intercooler tubing... thats where you're going to find them. :)
If you removed any interior stuff like the A/C panel, or the dash cluster, you may have left a line open.
Look very close at all of that set of hoses behind the throttle body. You have an EGR circuit.. There is a hose that connects it to the exhaust that gets loose or breaks. There is also a steel accordion hose section that can develop cracks.

Also, reseat all your plug wires to where they snap/click in place... no snap.. keep at it. If your hands don't ache afterwards, you probably didnt get it right ;)
And double check the coil pack and trace the wires. Its not 123,456. Its 123,465.
Lastly, if its really old gas, as in more than 2 years, you need to run it through and fill with new.
 
Last edited:
thanks for the advise...you got me thinking now. I've had my dash apart quite a few times in the past. I have an A pillar 3 gauge cluster that I put a boost, volts, and temp gauge in. I put a splitter in my boost tubing so the dash & the gauge both work....why I did that, I dunno! I was younger then, and thought it would be cool! lol I know I was very careful, and triple checked for any vac leaks, but that was years ago. I'll check again. I just ordered a new Magnum Powers cold air intake. I think it looks way better than the Mac I have on the car currently. It doesn't have the radical bends in it that the Mac has, so hopefully that will help a little, but I know it's not going to solve all my problems. I also used to have a 70 mm (I think it was a 70 anyway) TB on it, but I put the stock one back on the last time it had trouble passing inspection thinking it would help. Thanks again....much appreciated!
I have a code reader, but it's an OBD2, only good for 96+ as far as I know. Maybe I should get one that will work on my SC
 
I'd say I've put less than 20 miles on it in the last 5 years.

It's not uncommon for lightly used cars to have trouble passing emissions tests. The oil collects some fuel from cold enrichment strategies that doesn't evaporate off because the oil never gets warm enough. A dead or weak battery causes loss of fuel trim data. The cats get carboned up, and so on.ne off

As noted above, check codes, both KOEO and KOER, and correct as necessary. When that's done and you are going to return for testing get some fresh gas in it, drive the car for at least an hour prior to your appointment to ensure that is fully up to temperature, the cats have lit off and burned off any carbon, and the ECM has had some opportunity to start building fuel trim data. When you arrive don't turn the engine off if at all possible. You don't want to lose that heat you just worked to create. Remember it's not the tech's job to condition the vehicle for the test, it's yours.

edit: forgot to mention change the oil prior to the test too
 
Just get classic tags that way the insurance is cheaper car worth more

thanks Parker...good advise

NO MORE PRPBLEMS WITH EMISSIONS !!! = NO YEARLY REGISTRATION :cool: MANY COLLECTORS INSURANCE DEALERS OUT THERE :) I HAVE AMERICAN HOBBIST OR AMERICAN COLLECTORS:D:D
 
I would check the ect on the manifold, if it's bad the car will run really rich because it will always think the engine is cold. I know the Haynes manual has the resistance specs.
 
NO MORE PRPBLEMS WITH EMISSIONS !!! = NO YEARLY REGISTRATION :cool: MANY COLLECTORS INSURANCE DEALERS OUT THERE :) I HAVE AMERICAN HOBBIST OR AMERICAN COLLECTORS:D:D

I wish I could here in NH. We only have antique plates not classic plates. Mine is a 94 so that means 5 more years. :) PA has some good rules for cars. I do miss NJ. When you buy a new car there they give you 4 years until your first inspection is due. Here in NH you have to get a brand new vehicle inspected with the first ten days of purchase. It's absolutely stupid.
 
Back
Top