Help fix my cold start problem on my 2000

I have posted this before but have never been able to fix it. 2000 with 130K. Problem became worse progressively. It isn't getting worse anymore. When I bought my XJ with 80K miles it started instantly. I have done stuff before, but just replaced my Champion truck plugs. My last plugs probably only had 20K on them. Currently running another can of BG44K through the tank. I have never replaced any sensors.

My jeep cranks a long time now before it starts. I thought it was a bad check valve in my fuel pump. However, if I turn the key and wait for the fuel pump to pressurize, it doesn't seem to help. Still cranks a while. If I crank for a while, turn the key off, then on again it starts right then. My battery was weak and I just replaced it with a Odysee 1200. Was hoping for it to get better. No dice.

Once the engine starts it sputters along. After a minute or so it will go away. If I push the gas and get past the sputtering idle, it revs just fine. It is hard to get through this spot if I try to go right away. I sputter down the street a while. I get no CEL. This is only on cold starts. If I'm running around doing errands it starts just fine. This is annoying. I have almost forgot how nice it was when my XJ turned right over. Any other time my engine runs smooth and strong. No problems. Any help is most appriciated.

Try a different plug maybe? Mine did the same thing and a change in plug styles fixed it right up.

When I first got it I put in some platinums. It developed a misfire over some time. Through a code and everything. Went to truck plugs and it fixed it. I can believe what you say, but tons of people run truck plugs in their 4.0L.:dunno:

Also, your's did the same cold start stuff? So then what plugs do you run?

sounds like some weak ingnition possibly.

have you done cap/rotor/wires/plugs recently? I'd give that a shot. Personally I've always sworn by a NGK V-Power plug. Its basically your run of the mill sparkplug with a v-cut in the electrode.

I run the regular champions, and I was using platinums previously. I had the most trouble with Bosch +4 plugs. Yes it was a hard start problem. It would pop over and then die, then once I got it started again it was a rough idle for a minute or 2, but it would rev smoothly. Most recently I have a set of NGK plugs from the stealership in and it does pretty well (my wifes does anyway, mine died this morning.)

Weird, OK. I just put new plugs in, but if I knew another $15 and 30 minutes would fix it, then I would do it. I guess of all the things I could do, $15 isn't so much. Sorry about yours.

Anyone else have any ideas?

shot in the dark but perhaps something to do with weak spark (dying coil? bad wiring to coil?)

x2 on something in the ignition being weak if plugs didnt do anything.

Jason-RJR said:

sounds like some weak ingnition possibly.

have you done cap/rotor/wires/plugs recently? I'd give that a shot. Personally I've always sworn by a NGK V-Power plug. Its basically your run of the mill sparkplug with a v-cut in the electrode.

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A 2000 will not have a cap, rotor, or wires. That is the year the 4.0 was switched to a "distributorless" ignition system.

I had a similar issue with my 2000. In addition to not idling after a cold start, mine eventually got to the point of not idling at all. I couldn't figure it out at the time, but the corroded and failing battery cables were causing the problem. Maybe someone else can describe it more thoroughly, but it seems logical to me that the distributorless ignition would be quite susceptible to poor idle if the coil strip isn't getting proper juice.

If you replaced the battery recently because it was weak, I would check the condition of your cables. The alternator trying to charge a failing battery can begin and accelerate corrosion in those wires.. If it turns out you need to replace your cables, I would recommend looking at an aftermarket, custom fabricated cable set. Not that it needs to be said out loud, but the OEM replacement at ~ $250 is hardly a bargain.

Speaking of which, check the Cam position sensor, do you happen to have an extra xj around to swap parts with? If not, I highly reccomend it. My wifes started having hard starts a while back and one day finally no start at all. Luckily I had a few spares and a code reader. It didn't throw a code till the sensor actually physically broke btw, so a quick disassembly and cleaning of the Cam Pos sensor is free, couldn't hurt, and may reveal the problem. Look for melting plastic/misaligned pickup.

Oh, and you're totally not purple.



Pinko!

I was going to replace my ccables. Needed the battery now. Going to the folks in Texas this week. I will be doing OBA thi9s winter and will be relocating the battery. So cables are something cheap and easy to do in the meantime.

I have heard of people checking their coil rail, but not sure how to do that. Didn't figure it would be intermittant but I don't know what it could be so that is worth checking into. So How would I do that?

Bourbon, you said the cam position, but do you mean the crank position sensor on the bell housing? I could check it at least for integrity. I don't have a spare sitting around. Other have guessed at that before, but then ruled it out.

And by the way, aren't we all pink on the inside?

The computer uses input from temperature sensors in computing the correct mix for a given temperature. Sounds like your sensors are giving bad values at the cold end of the range. The Engine Coolant Temperature (ECT) sensor provides info used in injector pulse-width, spark advance curves, ASD shutdown relay times, and four other things ending with Target idle speed (from the factory service manual). The Intake Air Temperature (IAT) is used by the PCM (computer) to calculate injector pulse-width and to adjust spark timing, just like the ECT. They are easy to check for resistance at various temperatures (search here for the values), and are fairly cheap to replace..I think, mine are still OK in the 1990 and the 2001. The other issue could be wiring from the PCM to the sensor and return- might be worth cleaning any connectors.

Nope, I mean the cam position sensor. Its the grey thing where a distributor should be.

Bob, the jeep is set up to run without using the input of those sensors until operating temperature is reached.

OK, I'll check the cam sensor. I have the leave for the Great Republic of Texas today, so it will have to wait. When I get back I will do my cables, and check my sensors and connectors. Couldn't hurt to clean them any way. I have a mechanic friend and I get him over to help troubleshoot. He is swaping a 4.0L into his 2.5 TJ but he wanted to keep it OBD1. Not sure I he can help with my OBDII.

I've always thought along the lines of a sensor problem because I can give it gas and push through it. I just didn't feel like replacing sensors by guessing. I suppose it could be an electrical problem such as wiring. I'll work on it when I get back cause I would love to get it rsolved.

I had a Buick once that lost compression on one cylinder. It also made a weird sound like the Jetson mobile. I had numerous mechanics look at it. I got to where mechanics would look at it as a chalenge cause nobody could figure it out. I didn't care cause I ran it into the ground. Finaly someone put their hand somewhere and changed the noise. A vacume line was hooked up wrong making the noise and causing the loss of commpression. It ran great after that. I drove that thing like that for 2 years. I would hate to have a similar story about my beloved XJ.

Change the fuel pump or turn the ignition on then off like 4 times my magic number is 3.