scott klandl

I got a 2000 Cherokee 4.0 stock and I am having an intermittent starting problems. 155,000 miles

the short version:

Had two rough idle COLD starts in VT when 20F after Jeep sat for 12+ hrs. Turned over then coughed, and wouldn't start repeatedly. Then after sitting for a few minutes it started and ran fine. Thought it might have been water in gas or battery, battery showed poor CCA so replaced and used dry gas, had no problems.

Drove to San Diego from VT, 3500 miles, and no problems, threw a few cans of seafoam in it along the way to clean things out

Have had several (5) outta 40(?) RE starts here in San Diego with a very similar (or same) rough idle start. Has Never not started but Im quick to pump the gas and I can nurse it till it runs smoothly (30 secs - 1 minute). A couple of small backfires later, Im off and running and it runs great.

One of these episodes was so bad it tripped P0300, P0303, P0304.

Now here is the long drawn out version:

At first I thought these might be the same problem but now Im thinking that its a vapor lock now causing my problems. All the restarts have been in 70+ degrees, full sun and on black asphalt after running the jeep for at least ten minutes and restarting after 5 minutes but before 15 minutes. Immediate restarts are fine and longer times Ive never had trouble.

I was checking for vacuum leaks and found my exhaust manifold leaks a bit everywhere so that could be adding to the dilemma. I DID do the TSB fix and wrapped the jeep insulator sleeve around the #3 cylinder last year and it fixed the vapor lock at that time.

Im thinking about replacing the intake/exhaust gasket and replacing the OEM insulation and sleeving the remaining cylinders. Or could this be something else? Does the computer controlled choke device crap out? Time for a fuel pump check?

Thanks as always for the help guys!
S

purplegrocerygogetter

Could be from Worn Out Plugs to Plug Wires. Also can be dirty injectors.
Thats what they always tell me when my jeeps start acting bad.
Just do a routine maintenance, Oil, Fuel and Air Filters, Oil change, new plugs and wires and add a bottle of Lucas on a full tank of gas. If none has been don.
Is some that has to be done anyway, so start from there. ( wow that sounded pretty good, even comingfrom me) believe it or not I have learned alot reading the forum!

DFlintstone

^^ Exactly what I was thinking. ^^. Plugs, cap, rotor & wires. Napa has quality you can trust. I'm sure there are others, I just happen to use them so I know at least I'm not canning something good and replacing it with junk!

If you find a few easy manifold bolts loose, you might want to pull the air cleaner and tighten them all, working from the middle out. I use short little bursts of starting fluid to look for vacuum leaks. If you hit one the sound of the engine will change. Myself and some others found the injector O rings leaking. (I found my bad O rings while changing the manifold gasket).

scott klandl

Plugs and filters recently done, and ran seafoam (lucas equiv)

Its a 2000 so no distributor... I hate to replace a coil pack at $100+ without know its the problem, or that it regularly fails people and should be replaced as a maintenance item at around this time. OEM claims its a lifer part. Anything about my description that tells you its a coil specifically?

Again, no problems with first start of day since new battery and in warmer weather, its only on re-starts after quick errands, in full sun and 70 + degrees

DFlintstone

Boy..I'm just learning, CPS comes up allot. Sometimes the gauges will act goofy when it's going south. If you get your codes read, (free at the auto parts), and post them exactly their are some guys here who are pretty sharp. (and gals!). And DUH! Even I know there is no dizzy 2000 and 01. Brain fart
WHOOPS! JUST SAW THE CODES. All missfire codes, I see in "info threads". For lack of a better idea I'd lean toward the CPS I guess. It's known to crap out hot. Also it's connector can be a problem. One thread said if you need to keep un-plugging and re-plugging it to get it to start,, it's time for a new one.


1984-1990 w/AMC engine are pre-OBD.

1984-1986 w/GM V6-173 are OBD-I (GM control setup.)

1991-1995 are OBD-I (Chrysler)

1996-2001 are OBD-II (Chrysler)

The "Key Tricks"
Older (OBDI) models - Start with the ignition off. Within five seconds, switch the key on, off, on, off, on. ("On" is NOT "Start" and "Off" is NOT "Lock"). The "check engine" light will flash. Count the flashes. Each code is a two digit code, so a (for example) 23 would be FLASH FLASH (pause) FLASH FLASH FLASH (long pause). It will never flash more than 9 times, so watch for those pauses!

Newer (OBDII) models - Put the key into the ignition, push down the odometer reset button, then turn the key to RUN with your finger on the button - and then release the button. The odometer will go through 1111111 through 999999, then display the car's serial number. It will then show the error codes (it might show them starting with P). If this method does not work, try the OBDI method.

tjwalker

The P0300 and backfiring in the intake can indicate a "lean" fuel air mixture.

You may be on the front end of a fuel pump problem.

First thing I would do if this were mine is to get a fuel pressure reading. Must be done with a gauge. No shortcuts. For a 2000, you should have 49 psi, plus or minus 5 psi. If the pump is marginal, you may find it on the low end of the spec or slightly out of spec. If that is the case, I recommend you replace the entire fuel pump assembly (located inside of the gas tank)

You aren't having to add coolant to the coolant reservoir are you? I almost hate to bring it up as you don't have other symptoms, but you do have a misfire on cylinders 3 and 4. Those are the cylinders that are suspect if the 0331 cylinder head has a crack. And the #1 symptom of a cracked head is "unexplained coolant loss". If you have NO coolant loss, I wouldn't worry about it. However, if you do, then it needs to be considered.

Good luck and keep us posted!

scott klandl

CPS done in april after gauges would drop out and one day it never started. Could have gone south but its fairly new.

Fuel pump/pressure/ filter was the other one I was thinking it might be. I'll check fuel pressure. and see what pops up.

No coolant loss in 2000 miles, did add a couple of cups when I started the trip but my thermostat housing was weeping.

scott klandl

Well, I must confess, I never got a fuel pressure test, or did a compression test. I went with my hunch, the leaking exhaust/ intake manifold.

PITA to get that out, should a had the head and headers machined, but hell Im cheap.
Put it all back together and Voila! the MIL light dissappears and the car hasnt had trouble again. Not sure I completely cured it yet as it still leaks a little thanks deformation of head or header.

I also wrapped insulation around the fuel rail and all injectors, and put it a new heat shield

fingers crossed.