gullycreeper

i have no access to a diagnostics tool and was wondering most common mass air flow and evap isues on the 98 cherokees

Bustedback

Most common codes are evap system codes, but there are hundreds of OBDII codes that could cause the light to come on. I suggest finding somebody or someplace that can scan the PCM. Just blindly throwing parts at the Jeep and guessing what the cause may be is not the way to handle the problem.

salad

Could be a zillion things. No MAF sensor on a 4.0. Throwing evap bits at it won't fix an O2 sensor or a transmission solenoid. Get the code read or purchase a reader. (the key trick was discontinued in 98 I believe)

DFlintstone

Gap your plugs to .35 lately? Lot's of places will read your codes free. Trans shops, lube shops, auto parts stores. You might look some more. (We have "MAP"s, instead of MAF's in our Jeeps Btw. )

JerrytheJeep

.035"

tjwalker

Yup, gotta start here with posting the exact code number. With OBD, the devil is definitely in the details.

You will need a code reader or a scan tool. The odometer button technique will not work on a 98.

Some parts stores like Autozone will read the codes for free.

5-90

1998 is OBD-II - code readers are plentiful and cheap. You can even go with an ELM327 adapter, and use your tablet, smartphone, or computer (a decent dedicated code reader runs $60-80 - it's no trouble finding an ELM327 for half that.)

And you don't have a "mass airflow" sensor - Chrysler (and AMC, as well as GM) used the "speed-density" system to measure engine airflow, which uses a MAP and an IAT to calculate are going into the engine.

Jesse Hallum

The "key trick" still works on my 2001; are you sure it was discontinued in 1998?

OP: Try the "key trick" and see if you get a code display on your dash: push odometer reset button while turning key to ON position, but do not start. Release button and observe diagnostic codes, if this trick works on your 98. Let us know what you discover.

tommyxj2000

if anything autozone scans for free

DFlintstone

One guy posted it only does the cluster, or is at least very limited after sometime in the 97 year. You ever get a misfire or 02 code or anything like that? TJ ^ maybe?

KD4315

The most common evap code I've seen is the gas cap, not having the gas cap on correctly, driving with the gas cap off or a bad gas cap.

DFlintstone

Do you get that off your odometer?

KD4315

I don't know. I've never tried the key trick.