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98 jeep Cherokee sport runs rough

My mechanic tells me that my #1 fuel injector is always spraying and that that is why the jeep runs rough. This is after he already told me that my injectors were clogged and needed to be replaced (which he did). When the car is idling for a while, the exhaust really begins to smell like gas, so this seems to make some sense to me, unlike his previous diagnosis. But now he is telling me that I need to replace the computer to fix this problem. I can find a rebuilt computer online, and he tells me that I can do it myself, but is would sure like to get a 2nd opinion or hear from someone who has experienced a similar problem and fix. Any takers?

you could stick a lighted trouble shooting probe on the injector connector and if the light blinks it’s working properly.

And if it stays on, is that going point to a problem with the computer?


Thank you. I guess I’m buying a computer.

I d try cleaning my idle air control valve and checking for vacuum leaks. it worked wonders for my 1990 Cherokee 4.0. . also PCV valve or equivalent. if it has a slightly different set up like my jeep, then clean the orifice where it goes into the valve cover…

A couple of things to check before buying a new computer … make sure the electrical connection to the injector isn’t shorted out. That could happen for example if the wire insulation got chaffed. Injectors usually work by the computer briefly shorting the injector to ground for a few milliseconds, which produces a brief burst of gas sprayed into the engine. If the injector is shorted to ground, it will spray 100% of the time. Also, make sure the engine coolant is running at the correct temperature, 190 degrees or so. And that the engine coolant temp sensor is working. If the computer thinks the coolant is too cold, it will double pulse the injectors. A new computer won’t fix either of those problems.

I presume the fuel pressure at the rail has already been checked. If not, that’s something to do before replacing the computer too.

The light will be on all the time on one side and will pulse a ground on the other side to turn on the injector. You can test this on a good injector. If the computer side is shorted to ground it will keep the injector open.

I agree with wes

Check the basic and easy things first

Recently, I had a car that had a rough idle and wouldn’t pass the smog

A cleaning of the throttle body, iac, plus a minor idle speed adjustment . . . it was a pretty old car . . . and the car passed with a comfortable margin