mchulse

Hey Guys,

I was wondering if someone could help me with a misfire/rough idle/hard start issue. The Jeep is almost always hard to start unless it has been sitting for a few days (not always the case) or I disconnect the battery for a long (3+ hours) period of time (pretty consistent).

The hard start can be described as it trying to turn over but I have to hold the ignition for about 5 seconds before it actually does. When it does start up it idles pretty rough (feels like a misfire causing the rough idle). It never dies and has plenty of power but a P0303 code keeps coming up.

The engine light never came on until about 700 miles into a 1500 mile road trip. About 1000 miles in the light started blinking and luckily stopped blinking when it slowed to 70 (from 80) and got me back home. When I pulled the codes that time it gave me a cylinder 3, 4, 5 and multiple misfire codes.

I have changed the spark plugs, coil rail, cleaned the vacuum lines to the intake and cleaned the throttle body but still its doing the same thing.(sick of spending money *sigh*)

I'm guessing my next steps are to check the fuel pressure. Possibly change the Crank Position Sensor or Cam Position Sensor? Other than that I'm clueless. Thought maybe someone could shed some light as it seems strange that it starts pretty well (but still idles rough) the first start after the battery is disconnected.

Sorry for the novel!

Thanks,
Mike

Chrkee313

check your headgasket it could possibly be done

Copperhead

I've got a 2001 too...and had basically the same issues...Hard/long start...rough idle at start-up...and sometimes a #3 misfire...except if it sat for a day or two...after a few months of this... I started getting multiple misfires, and the flashing CEL..

Fuel pressure check revealed a pressure drop at shutoff..Just guessing that one or more injectors were leaking internally, I swapped in 4 hole refurbished ones(Figured even if the injectors weren't the cause of my problems..at least they were an upgrade and I could cross them off as the possible cause)...

All my issues, including the hard/long start problem immediately disappeared...I still find it hard to believe that the injectors alone were the cause of my toubles, but so far so good....

At the least I would clean and test your injectors are functioning properly...I never did bother to test my old ones...Hope this helps..

mchulse

Hey Copperhead, thanks for the insight. I will pull my injectors and see if I can get them tested (or find a way to test them myself). I went ahead and ordered a fuel pressure tester to see if it is an upstream problem too ($25). I'll reply and let you know what I find out. Thanks again.

mchulse

Hey Copperhead. You don't happen to have the Manufacturer and Part Number for the 4-Hole injectors you used do you? I have been checking injectors out and realized I know absolutely nothing about the flow rate that I need. Thanks!

swnp101

I've had the same problem with my '89 XJ (except I haven't seen any engine codes) ever since I've taken it in to a mechanic to troubleshoot a shifting problem.

I have no idea what he did, nor does he; so my XJ has being doing that for the last year or so. It's a P.I.T.A. to say the least. You say your's doesn't cut off. But mine will stall and die from time to time.

So far, I've checked my injector harness with a noid light, regapped my spark plugs, checked the distributor and wires. Everything seems fine. I haven't checked my fuel filter, pump or pressure; so I'm curious as to what your results will be.

Mine only has this problem at about idle or anything less than 1k rpms. How about yours?

Copperhead

No sorry..I don't know squat about injector flow rates either... Someone else posted this link to the place I ordered them from...

http://fuelinjectorconnection.com

Placed an order and they even emailed me to verify I was getting the right ones for my rig...found them very helpful...'Course I still don't know what kind I actually got...except they were 4 hole ones..Dunno if they give free advice if you don't place an order...but you might try shooting them an email...

98 JeepJeep

Late model Cherokees had Injector issues and Rough starts...this was Due to the Intake manifold design and heat soak. I used for Explorer 5.0 injectors and am happy.

mchulse

Hey SWNP101, I would highly recommend checking/replacing the crank position sensor as it is located near the shift cables (2'oclock on the bellhousing) and may have been accidentally damaged in your repair. It's also a VERY common part to go out on Cherokees and may be causing the issues your having. I intend on replacing mine for good measure as it might be the cause of my problems too.

Copperhead and JeepJeep, thanks for the injector advice. When I get my fuel pressure gauge in I'll let you know the results. Lets just hope Jeepers gets me to and from Mexico this week without any major issues. (fingers crossed)

swnp101

Thanks for the reply mchulse; I guess I should check this thread a little more often.

I haven't tried it yet, but I don't belive it it would be my CPS. Reason I say that is because above 1k rpms, it runs fine. I figure if the CPS was bad, it would miss all over, not just at idle. I'll check it anyway, though.

And for those asking about injectors, I believe that they are Bosch, 19lb EV1 type injectors. I'm *pretty* sure, but not absolutely certain because it's been a while since I was an injector phreak.

mchulse

Hey Guys, quick update. I got my fuel pressure reader in today, hooked it up and here are the results:
- 49 PSI when running
- 48 PSI when turned off (key in the ON position)
- 20 PSI an hour and a half later (key still in the ON position)
- 18 PSI 2 hours later (key still ON position)
I'm guessing this is the same issue Copperhead was talking about? Or is it fairly normal to see a drop in fuel pressure that long after the car has been turned off?

At any rate when I started it back up if fired up immediately (very unusual). At any rate I guess it was an exercise in futility as I just got new injectors (and fancy new heat shielding to battle that infamous heat soak issue) in so I will put those on and let you know the results. Oh BTW, the injectors I got from FuelInjectorConnection.com are 4 hole Bosch Blue Demon (FICU64) they were rebuilts that are flow matched for roughly the same price it would have been to send mine in ($138 after shipping). (Thank God for my tax return)

Thanks,
Mike

01blackcat

This occurs when the engine is hot and sat for a short time then restart. The issue they are talking about is after it sits for days. Heat would be long dissipated in two days. (my 01 has the heat soak issue as soon as it starts to get warm outside).

Willys55

Silly question Dude , but when you got that P0303 missfire code by any chance did you replace the spark plugs and check the spark plug Boots for wear or damage?

98 JeepJeep

Your issue is a weak Check valve Bleeding off pressure...this will cause Rough starts and long cranks...the Valve in in the fuel pump assembly and most people put a Inline check valve on. To avoid replacing the pump.

mchulse

Would this also cause multiple cylinder misfires? It seems like a leaky injector would probably cause the pressure drop and the misfires....well I'm gonna throw on the injectors and see what happens. If it is the Check Valve it seems like a pretty straight forward job but I figured I would ask if there is any write ups available on how to fit one up? Thanks!