This is a primer on the operation of the Jeep 258 Engine with the computer controlled Carter BBD carburetor and the Pulse Air emission system. If you are having problems passing your state smog check or just want to know what terms like: Stepper Motor, Upstream Solenoid, Downstream Solenoid, WOT, EGR, TES, O2 Sensor, 10mm HG Sensor, SolVac and others mean or even if you just need to reconnect a vacuum hose - then this article is just what you need.

These pages are intended for those like myself who live in states where an annual E-Check is required to get license tags, and for those who are just plain mystified when they look under the hood and wonder what all that stuff does.

There is some technical information here, but the mechanically challenged like myself will find easy explanations for most of the emissions freedenoids under the hood, and for the operation of the evil computer. Where possible, "Quick and Dirty" checks have been included that can be done without test equipment.

I hope someone else can benefit from what I've learned trying to keep my 258 Jeep running. This information was gathered from the Web, the original Service Manual, anyone who would talk to me, and from my own experience trying to figure out why mine was running so badly after only 13 years of neglect.

Dale Beckett

This information applies specifically to the 1985 AMC 258 six-cylinder Jeep CJ-7 with 5-speed manual transmission, and with all stock factory emission-control gear in place and operating.

With some adaptation it will apply to all 258 CID Jeeps from 1983 to 1987, and to 4.2L Wranglers from 1987 to 1990.

For 1987 to 1990 Wranglers: because of the switch to the NP231 transfer case and the left hand Dana 30 front end the exhaust now crosses under the engine from the left to the right side and the muffler and catalytic converter is located on the right side of the vehicle. This meant that some of the emissions components had to be relocated (for example: both pulse air tubes & valves are now on the right side of the engine). All of the components are still there however and with a little searching you will be able to find them. In California this system is subject to several mandatory emissions related recalls (which just may get your system fixed for free) and you should check with your local dealer to make sure that all of these have been performed.