XJ607

I have a 2001 jeep cherokee, I was driving the other day when my check engine light began to flash and then stayed lit, ran obd and got p0300 confirmed, p0301 confirmed, and p0305 pending, i haven't noticed anything different when driving the jeep, seems to accelerate fine, not rumbling or shaking, my idle does seem to be a little on the low side (500ish)but steady and it's always been kinda low since I swapped in a motor out of a 93 a while back, kept coil pack, the cel seems to flash when I decelerate, or brake, but it doesn't happen all the time, going to look at it today but was just looking on some input of what I could be, i have a few ideas but the deceleration part it throwing me off a bit, usually it's the opposite, thinking maybe tps? Oil pressure sending unit? Iac? Vacuum leak? Also seems to be running hot, doesn't say it on the gauge but when I pop the hood it seems pretty warm, going to try swapping out the temp sensor too, my oil pressure is around 50 when on gas and has always been around there, don't know if that would have something to do with it but just looking for some input, and I'll keep you posted if anything new arises. Thanks

XJ607

Also heard that a transmission or transfer case could possibly cause this problem, my part time light is always on but my t case is in 2wd, don't know if this could be any part of it but just trying to give all the details

autosurgeon

Those are missfire codes. Either you have an electrical missfire or more likely a fuel related lean missfire. I would guess fuel as you said it was running hot and a lean condition will cause that.

autosurgeon

Your Transfer case has nothing to do with this issue.

XJ607

Yea I was thinking fuel myself, it doesn't do it very often, the cel shut off yesterday on its own long enough for me to get my inspection but then popped right back on, it does it around 50 mph when I come off the gas, going to do a fuel pressure test and compression test today or tomorrow and go from there, my idle is also starting to hop a bit, as much as 50 rpms + or - at a time, but doesn't seem to be affecting anything

XJ607

I just did a compression test and got 120 on cyl. 1 and the rest were right around 150, so I'm thinking this might be my problem, and i did a wet compression test and it went up so thinking it's the rings, but doesn't explain cyl. 5? I'm lost and any input would help out a ton, thanks

autosurgeon

That amount of compression deviation will not cause a misfire. And since yours is specific to certain engine load requirements I would suspect ignition or fuel. How old are the plugs? Spark boots?

Fuel pressure and injector issues should show up under hard acceleration. Not decel however a fuel pressure check is not a bad idea.

pimpinr

You may need a new computer.. Tune up, or in my case it was the Fuel Pump.

autosurgeon

Computer? Really? That is the most unlikely cause I have heard yet...

Start with the fuel pressure and spark plug condition.

XJ607

I did a fuel pressure test last night and go 49-50psi, which is right where im supposed to be I'm pretty sure, and u swapped injectors 1 and 2 and the 5 and 6 just for kicks, and all spark plugs are pretty new and coil pack is new, pull off coil pack and had a buddy crank it while I watched and all had a strong spark and looked good, only thing I can think of is that my motor is from a 93 and it has the 7120 head so there is no holes to mount the coil pack so I just kinda made some mounts to go to the valve cover bolts, doesn't seem to be as secure as I would like it tho, but when I push it down when idling my idle still is the same,a little rough with a 50+/- drop at most, what is the most it can fluctuate and be okay? Also I replaced my camshaft sensor not to long ago because the magnet fell off could it be a bad camshaft sensor again? Even tho I have no codes for it this time, and what about a crankshaft sensor? Sorry for the ignorance, misfires are fairly new to me,

Cheddarnut

When you swapped the motor, what else did you change? Did you do the PCM and exhaust? 93 and 2001 are way different on emissions and O2 sensors. Just thinking that alone may be throwing the codes and causing the idle issues.

XJ607

I brought it down to just a block and head, had to use the 01 exhaust because of the 4 02 sensors and can't go back to the older 2 sensor system on a newer jeep, (for inspection purposes) and as for the computer because I used the coil pack instead of distributor I had to use the newer pcm

XJ607

I seem to be talking to myself but now I have a misfire on 1 and 4 and it's only when I'm going 50 mph and letting off gas from coming over a big hill, it barely even does it,like every 100 miles or so,