GoinJeepin

So I failed my emissions test. Vehicle 1991 XJ 4.0 H.O. My Hydro Carbons at idle are to high. Limit is 220 I tested at 240. Went home changed the oil, spark plugs, cleaned the air filter, and replaced the cap and rotor. Retested a couple of days later all my numbers went up. Idle HC tested now at 252 . Brother-in-law said it might have been from the Supreme fuel I put in it. I guess the fuel takes longer to burn since the engine is not a high compression motor. The engine has over 300k on it and it does have oil blow by. I plan on doing an engine long block swap but need to get it passed in the mean time. Any ideas. I usually have problems with the CO not the HC. I idle at about 720-740 rpm, I'm allowed to idle at 1100 maybe adjust the idle up?

tiwvr1

Beat the snot out of it b4 u take it in, gets teh cat nice and hot to burn up impurities, other then that dont know what to tell you, we dont have emissions here like that.

94JeepCherokeeMan

1. Clean out the MAP sensor on the intake manifold. It's the only one with an electrical connector.
2. Clean the other four vacuum fittings on the intake. Use throttle body cleaner or injector cleaner and wipe them down before reinstalling.
3. Remove throttle body and clean the TB, the Idle Air Control sensor, and make sure the gasket under the TB is good. Once again, use throttle body cleaner. There's a write-up on this procedure here on CF, but I suggest just removing the throttle body first instead of trying to remove the IAC while still on the intake.
4. Clean or replace the Oxygen (O2) sensor on the exhaust pipe.
5. If you're up to it, clean your fuel injectors by actually removing them and cleaning them. There's another couple of good write ups on upgrading your injectors, but just clean them if you don't want to fork out the dough for new 703 injectors. Make sure to buy new o-rings before attempting this, and don't do it if you're not mechanically adept.
6. After performing the above steps, fill up, add the appropriate amount of Lucas Fuel Injector cleaner or Marvel Mystery Oil and run that tank up.
7. Pray to whatever God you believe in.
8. Do emissions test.

94JeepCherokeeMan

Rob

94JeepCherokeeMan

WORDS OF WARNING: Be extremely careful removing the MAP sensor. The other end you don't see is plastic. Use TB cleaner on it, too.

I don't know how much of a gearhead you are, but I have done most of the above things and I've noticed a smoother idle and better pickup. I still haven't cleaned the injectors, but I'm sure that after I have, my mpg will boost 1-2 better.

GoinJeepin

Thank you, will be doing the above tomorrow.

94JeepCherokeeMan

Just make absolutely sure that you're familiar with all the processes involved here, especially cleaning the fuel injectors. One small slip up during reassembly and your Jeep will be out of commission until you rectify the problem. Oh, and be very careful with the rubber fittings on the vaccum parts. Replace as necessary. If you're careful, you can do all of this for the price of three cans of TB cleaner and the injector cleaner, which would be like $20 max at NAPA.

94JeepCherokeeMan

Good luck, man!