 By Grant For the past few years I've been spouting off about the nightmarish 258 induction system. I've even suggested that the original carburetor be dumped into the trash and replaced with EFI at the first hint of trouble. Of course, that's easy for me to say - it wasn't my money after all. Well, we put our money where our mouth is, and installed a Mopar EFI system on an ‘89 YJ with 70K miles on the odometer. Like most people with the original Carter carburetor, our Jeep ran poorly, idled rough, ran rich, was hard to start, guzzled gas and was seemingly impossible to tune. Numerous carburetor rebuilds and tune-ups never had any long-lasting effect. Why keep throwing money at a bad design? Had we saved the money spent on carburetor repairs, the Mopar EFI system would have paid for itself! For those who are not familiar with the Mopar kit, it essentially includes all of the EFI components from a newer 4.0L EFI Wrangler. This makes it the most advanced, and most complete, EFI kit on the market. Other systems will simply replace the carburetor with an electronic throttle body, throw on a few wires and call it good. The only problem with that idea is that it doesn't solve the fuel distribution problem inherent in the 258. The fuel in a carburetor or throttle body setup must still travel all the way from the center of the manifold to the number 1 and 6 cylinders. The fuel has a very hard time staying suspended that long, and the majority of it is likely to get sucked into a cylinder that is closer than the outside cylinders. The result is a rough running and inefficient engine since the same fuel mixture is not reaching each cylinder. Some cylinders will be too lean and some too rich. The Mopar EFI kit solves all of these problems by replacing the carburetor with 6 fuel injectors, one located above each intake port in the cylinder head. With the Mopar EFI, the fuel has to travel only an inch or so before it hits the intake valve. This keeps the fuel suspended in air, and since each cylinder has its own injector, each cylinder gets the same amount of fuel. Feeling confident that we had purchased the best EFI system on the market for the 258, it was time to get our hands dirty:
The only complaint I have about this kit, is the need to run high octane fuel. Six months ago that was no big deal, but with today's gas prices, stopping at the pump is a little painful. The need for high octane fuel stems from the fact that the ignition timing is not adjustable on the Mopar EFI kit. Still, the fact that we nearly doubled our gas mileage and gained a significant amount of power at the same time, makes the extra cost of high-octane fuel much easier to swallow. If you are tired of the carburetor on your 258, but are otherwise happy with the engine, bite the bullet and purchase the Mopar EFI kit. It's more expensive than the other alternatives, but it works beautifully. For those of you who are concerned about modifying the engine for service reasons, the Mopar kit is serviceable at any Jeep dealer. As I said before, more power, more mileage, smooth running...what more could you ask for?
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