Normally on a cold start, my '99 Jeep Cherokee starts right up. No pumping the accelerator pedal, no fussing; just turn the key and it runs. Recently though, it started running rough on start-up. And then it began dying on start-up. If I rev the engine, and hold the RPMs for a few seconds, it usually stays running. (‘Usually’, because I’ve had to do one more iteration on a couple of occasions.) Does anyone know why it is doing this? I don’t think it even has a quarter of a million miles on it.
Kinda hard to say. Is the check engine light on? Even if it’s not on, I would hook up an OBDII reader to it and see if there are any trouble codes.
A few possible causes off the top of my head:
Clogged fuel filter
Bad fuel (e.g. water in fuel)
Dirty fuel injectors
Worn out or fouled spark plugs
Dirty air filter
Dirty MAF
Bad PCM
Vacuum leak or leak in air intake piping
Intermittent problem with fuel pump
You shouldn’t even need to touch the accelerator to start with fuel injection which yours should have.
As already mentioned, guessing water or bad gas if it just started. Dirty fuel filter or injectors if it has done it for awhile.
Long shot is if you don’t drive much and still have “summer gas” in your tank. I think it is less volatile(?) so doesn’t ignite as well in the extreme cold weather.
Yep. It wouldn’t hurt to pour a bottle of ISO-HEET into the gas tank. Best case is that it fixes the problem. Worse case is that the problem is something else.
It was warmer the last time I filled the tank, and the rough-starts started when it got colder. Still, I’ve owned this Jeep since it was new and never had this problem before; even in the 19 years I’ve lived up here where it gets cold.
Sta-Bil is a stabilizer, keeps gasoline from gumming up if it sits for a while. CM’s recommended Iso-Heet is a water remover, which is more likely what you’re looking for.
First check your air filter. Then the MAF sensor and screen, this is usually behind the air filter in your intake. Usually a screen and a couple wires. You will see where the MAF sensor plugs into the intake, look there. Might need a screwdriver to take the front of your intake off. Sometimes leaves and other things can get past your air filter and end up on the screen. Pretty easy to check and MAF cleaner comes in a spray can, do not touch the wires.
Everything there OK? You now can be reasonably confident that you have air to your engine.
Since it runs fine after starting you have spark to the engine, I wouldn’t worry about that.
The third thing your engine needs is fuel, as others have said. So then you get into plugged filter, gas contamination, water, etc.
I want to emphasize that, if you use a spray cleaner to clean the MAF sensor, do not use a “carb cleaner.” Use a cleaner that is specifically formulated for the MAF sensor.
It is important that the air intake pipes & hoses do not have any holes or openings where air can be sucked in. So the OP should also perform a close inspection of the system and look for openings, loose clamps, etc. Also inspect vacuum lines.
My dash indicators stop working, and the automatic door locks stop working, when the Jeep has been sitting a while. I have suspected the mechanic put in an insufficient battery. Since it’s currently 15ºF outside, I thought I’d start up the Jeep. Dead. I’m guessing the hard-starting problem might be due to a weak battery.
You may have more than one problem. You certainly have low voltage when you initially tried starting it, but while it was running/before it does, the voltage was reading 14, which is fine. So you may have a battery issue as well as some other issue causing cold start. Checking the air filter isn’t that hard, so I would recommend that, but the other stuff requires you to have some comfort in poking around under the hood, so a visit to the mechanic may be in order. They’ll be able to diagnose the problem in short order.
If you have any sort of power drain, like an accessory, in a vehicle that is not used every day, you might be better off with a deep cycle battery.
I put a dash camera in my car and that was enough, even though I did not leave it on all the time, to drain just a bit every day and cause problems. Most batteries are for starting the car only, and last for about 5 years. If your battery is older it probably needs to be replaced. Deep cycle batteries cost more but are well worth it.
If the deep cycle battery is the same size (physical volume) as the standard battery, then it will have less CCA compared to the standard battery. If the OP has cold winters, I would not recommend doing this.
The towing guy came and pulled out one of those hand-carry jump packs. Got the Jeep started, and took it down for the highest-amperage battery they had. We’ll see if it starts in the morning. Looks like it will get up to 20º or 21º overnight.
