98 JeepJeep

The injectors are most likely the issue with you Missfire specially for your year.

http://djvmerchandise.com/pro1163391.html is the Site for the Popular choice for a Inline valve. This is the cause of your fuel pressure loss....Injectors wont cause that.

mchulse

UPDATE:
HOW: So on Friday night I took my fuel rail and injectors off. (BTW: Buy a fuel line removal tool at your local Auto store before starting this job as getting the fuel line off of the fuel rail is next to impossible without this little $5 tool, thank god for a shop that's open till midnight near my house). Anywho, once the fuel rail I ran some seafoam through it and all sorts of dirty looking stuff came out. I cleaned all connection points including where the injector goes into the engine and installed the new injectors using palmolive hand soap as suggested by fuelinjectioneconnection to lubricate the O-Rings prior to install. Everything popped in very nicely and the job took about 45 minutes ONCE I got the right tool to remove the line (hour and a half total time... DOH!). Then I reset the ECU by unplugging the negative side of the battery overnight.( I just wanted to post this first section incase anybody wants a half assed DIY that might be helpful.)

RESULTS: I have driven the Jeep 100 miles since the new injectors were installed and the results are profound. NO MORE LONG CRANK TIMES TO START EVER. The thing fires right up no matter if it has been driven all day or been sitting overnight. The engine light that was showing a misfire has not popped on again. But the idle is still not perfect (thinking it's probably me just being picky at this point as you can barely tell my VW is on when it idles). There are other benefits including a incredible acceleration responsivness and better gas mileage. These 4-Hole injectors really make a huge difference and I highly recommend this upgrade as for $135 I don't think you can get better results.

Copperhead, thanks for the suggestion. It seems like the new injectors have fixed the problem.

mchulse

Oh and 98JeepJeep, thanks for the link to the inline connector. I might just do this for good measure as it seems like a cheap and easy mod. Plus I can't keep from wrenching as I have way too much fun .

98 JeepJeep

glad to hear the injectors helped but you still have a FP bleeding off issue......

swnp101

Well mchulse, I'm happy to hear you got it figured out. I've gone a very simular route since I've last posted...

I went ahead and changed my fuel filter... Just cause I haven't changed it in the year that I've own it and who knows when the previous owner changed it last (didn't look too old, though).

I also (finally) tested the fuel injectors with a multimeter. I don't know why I hadn't tried this earlier. I guess it was because she ran just fine till I took her to a shop to get something else repaired... Anyway; so yeah, number five injector never would give me a constant reading. It would move all over the place and never really settle down. So I replaced it with one (of the 12 injectors) that I picked up from the junk yard. I picked up a set of EV1s and a set of EV6s from Jeeps. I've kept the EV1s in so I didn't have to splice in new injector connectors.

And lastly, I checked my fuel pressure...

Fuel filter change... no difference
New #5 injector... big change; very, very smooth... *slight* bog. But still doesn't idle perfectly smooth like it should.
Fuel pressure... 30psi while running, maybe 31 (which is what it should be)

So... I'm still lost. It'll stall sometimes going forward; but moreso in reverse.

I don't know. Any help would be appreciated.

mchulse

UPDATE:
While the injectors made a HUGE difference in the way the Jeep runs I was driving down the highway yesterday and that stupid misfire engine light popped back on! (about 130 miles after the fuel injector change).

So let's review: Fuel system is good now, Throttle Body is clean, plenty of air is getting to the chamber, ignition system is all brand new.The Jeep is still starting right up and idling better but apparently it is still missing! At this point I am thinking I did the intake water treatment and also seafoamed it to insure the exhaust valves are clean a while ago but I have read that the exhaust lifters get real sticky on these engines. I really don't want to go further without knowing what I'm getting myself into (I've never messed around with engine internals before). Also I don't really want to shell out the cash to get my cylinders compression tested (got a quote for $150 on this testing).

I haven't replaced my Crank Position Sensor yet. Is this something that could cause a misfire at highway speeds? Any other suggestions? (i.e. oxygen sensor, catalytic converter, cracked intake?).

98 JeepJeep

replace plugs....

mchulse

Plugs have been gapped and replaced twice. The Coil Rail is brand new.

swnp101

My plugs have < 500 miles on them and have been gapped twice.

I think what I'll do next is just clean off my CPS. I'm sure it works; otherwise the truck wouldn't run at all. Maybe it's a lil dirty and has a harder time reading the crank at low rpms???

IDK... that sounds like bs to me too... but I'm still gonna clean it.

kriebz

My '01 has rough idle and a permanent CEL after it had been going on and off for a while. Scan says it's a under-performing rear precat, and I've read this is common on a misfiring cylinder. If they were going to go distributorless, why doesn't it have knock sensors? Sigh.

Replaced the plugs, and the misfire got way worse. Maybe I did something wrong, but how do you goof spark plugs? My thinking is that it's the coil pack, which got worse after moving it around or something, so I ordered a new one. Says for Wrangler with 4.0, but I'm sure it's the same. I'll re-install or replace the plugs when the coil pack gets here, and hopefully it will just magically get better.

I'm also running STP through this tank, and it has made things a little smoother. Could someone tell me where the fuel filter is on an '01? My brother suspects there's an inline one outside the tank, but we're not sure.

Oh, and it's weeping a small amount of oil from the head gasket, which terrifies me. I tried a blend this oil change because the original problem was low oil pressure at idle. Going back to dino-oil I guess.

swnp101

Which brand spark plug did you use? I suggest not deviating from the recomended, stock Champion plugs. Also, spark gap seems to be pretty sensitive on Jeeps. I know the recomended gap is .035; however I like to gap it just a fraction of a hair wider. Seems to work for me. I'm not gonna tell you to gap it at .040 because you may "feel" the gauge different than I do. Try .035 to begin with and go from there. Ooh yeah, if you did use Champions, they don't come pre-gapped.

I'd guess your brother is right. But I've never owned an '01 so I can't say for certain.

Someone correct me if I'm wrong, but I thought once you go synthetic, you cannot go back to conventional? I've heard this before but I don't know for certain how true it is. You should also check your coolant for oil, and your oil for coolant because you may have a blown head gasket and it could be the cause of your missfires and hard starts.

98 JeepJeep

No fuel filter on a 01..All intank.

My head gasket leaked on the right side of the block between the head and block....once it weeps oil the only permanent fix is to replace it.

dzn,xj

I have the same problem. Did u figure it out?
00,xj

mchulse

Hey Everyone,

Sorry it took so long to get back to you on this. I let it go by the wayside till I had to get the Jeep inspected last month.

The long startups were solved with the rebuilt 4 pin fuel filters ($125 and 1 hour of work). The misfires stopped after I replaced the CPS (Crank Position Sensor) ($75 and 20 minutes of work).

I have about 1000 miles on the Jeep after I replaced the CPS and still no Engine Light. Doesn't seem to be running any better after the CPS was replaced (though it didn't run bad to begin with) but the light isn't on. Don't forget to disconnect your negative battery cable for half an hour to reset the code. Hope this helps some folks out there

apbbutt

Choppy running and stalled. Got codes p0201, p0300, p0301, p0302, p0304, and p0455. Got new plugs and coils and still running same with code p0354. Switched around coils to see if code would change and got same code along with 1 other. moved around more and then got codes for all but 2 cylinders. Changed crankshaft position sensor, and still same choppy running, but no codes coming up now. Not sure what to do next. Camshaft sensor? computer? injectors? Junkyard?