0 Horsepower For $0! - Jeep Wrangler YJ No-Buck TuningPosted in How To: Engine on May 1, 2010
Not working at the moment? Or maybe you are, but those bills are piling up. Or possibly you're the type who just hates to spend money on new parts when you've got stuff laying around that may get the job done. After all, why throw away good money on a better Jeep when a dark corner of your garage or shed may hold stuff almost as good as new, fancy aftermarket parts?
When the exhaust fumes got so thick driving with the rear window rolled up that it started to make our eyes water, we tore a page out of the Cheapskate Almanac and did a little no-buck tuning on our '89 YJ using only parts we had laying around. Sure, you can substitute fancy aftermarket parts, but sometimes you just can't afford (or find) hop-up parts for your hooptie ride. Here's how we added air and spark for no pennies on the dollar.
1. The formula for a healthy engine is the proper proportion of air, fuel, and spark. Our Wrangler's '89 2.5L appeared to be lacking some air and spark as indicated by the thick, toxic exhaust that routinely made its way into the cabin. To get more air into the engine, we ditched the restrictive factory air box and paper filter element. Nobody makes a complete cold-air intake for a TBI four-cylinder, so we simply cut a piece of 2.5-inch exhaust tubing from our local autoparts store and clamped an ancient K&N open air filter that came on our '68 J2000's 232 inline-six.
2. The homemade filter setup helped the Jeep pull grades slightly better in Fifth gear and the exhaust didn't make our eyes water as badly, indicating that the increased airflow had helped lean the mixture. We were still spewing a lot of unburned hydrocarbons out the tailpipe, so we turned our attention to the ignition, starting with the plugs. We had a set of Autolite 985s on the shelf from a 4.0L build, so we tossed 'em in. The 985s are a heat range D11, which is pretty hot; ideally, we would've chosen an even hotter 3926 or 3927 plug with the same 0.750-inch reach and 14mm thread. But that would have been more expensive, so the 985s got the nod.
3. With a little more air and working plugs gapped at 0.035-inch, we then addressed the plug wires since we already had a fresh cap and rotor. After busting out the multi-meter, we tested the resistance in Ohms of each wire. Most stock resistance-type wires will run in the neighborhood of 10,000-15,000 ohms/foot resistance. Any more than that and the wire is bad. To get the correct value, measure your plug wires and do the math.
4. We found a bad plug wire on the number two plug and a bad coil-to-distributor wire. Digging through a box in the shed we found one stock replacement-type resistor wire and a Performance Distributor's coil wire, which we installed. Then, we turned our attention to the factory TBI coil/ignition module assembly. Remove the two retaining bolts; the coil can then be pulled free of the ignition control module on the firewall.
5. The positive and negative posts on the factory coil simply clip into these female connectors on the ignition control module. Naturally, our connections were grimy and corroded, so we hit 'em with a wire brush, cleaned them with carb cleaner, and put some dielectric grease on them. Although it's a pain to find the right bullet terminals, you can install an aftermarket coil mounted remotely if you build a couple of jumper wires. Since we wouldn't trust the bullet connectors, we thought about using some spade-type connectors crimped onto the brass ICM terminals. Be careful not to break off the fragile brass connectors, or you'll spend real money on a new ignition module.
6. Before we tried the aftermarket coil route, we cleaned up the male connectors of our stock coil and applied some dielectric grease to see if our coil was indeed weak. We reinstalled it and the engine started more easily and revved a little smoother. Now the toxic cloud out the back isn't so bad and our clothes no longer smell of exhaust after driving down the street.
7. For now we're sorta happy, but we did find this MSD Blaster coil in the shed we ran on an old Dodge Ramcharger project vehicle. Our cheap hop-up has made the exhaust less noxious, so for now we'll stave off adding the coil and opening the plug gap out to 0.045-inches or more. Besides, if we get the 2.5L running too well, we'll keep putting off those plans for that LS3 swap.