Strange, intermittent startup issue

[dude1116]

Hey all,

Really need your help on this one as I'm not completely sure what's going on. This issue started happening VERY rarely a couple of months ago. Now, it's too often to ignore.

After the Jeep is heated up SLIGHTLY, I will get a no start, no crank condition; HOWEVER, I can hear a whirring noise (normal noise, I think it's the fuel pump?) AND the Jeep DOES start eventually with a little coercing. I get no CELs. Plugs DO need to be changed (they're a little over 30k now), but would that cause the startup issue? Been looking to find a weekend where I can get out there for an hour or two and do it.

Sometimes it will crank VERY weakly, then give out, or crank VERY weakly, and just barely cough to a start, where everything then on is 100% OK. I have no CELs (except for one that went away on its own about a month ago: downstream, passenger side O2 sensor).

Mashing the pedal at startup seemed to help it tonight as I tried to turn her over 5-6 times. After she's warmed up, I can turn her off, and crank her right back on with no issues/no weakness in start. For what I can tell, the worst of it comes when she's only half heated up. It DID happen ONCE when she was completely cold, but once again I was ultimately able to get her started and driver her with ZERO problems. 95% of the time, I'm able to start her up in the cold easily. Idle is good, sitting at about 1100RPM cold and 600RPM warm; normal for the Jeep the past 3 years I've been driving it. Gas mileage seems a little low (probably because of the amount of times I have to try to start it and the manner in which I sometimes have to start it).

So my guesses are the starter or the throttle body. How can I diagnose these issues? What would cause this issue to ONLY happen when the Jeep is half way warmed up? And finally, has anyone had this issue before? I don't have much in the line of tools, unfortunately, but would love to get this done myself. She's got 90k miles on her, so she's really just a baby. Most recent maintenance done besides an oil change was a transmission replacement before all of this started happening (used transmission with 39k miles on it in May or so).

Thank you all for any and all help that you can provide me!!

 

[Billwill]

How good is your battery....90% of these type of problems are caused by:

Bad battery...Optima Red tops have a bad reputation.
Bad battery terminal connections...need to clean them up and clamp them tight.
Bad earth connection connecting engine to chassis....likewise clean and tighten.
Bad earth connection of negative battery lead going to chassis....likewise..

If you are satisfied that all of the above are good then maybe you need a new starter solenoid but first swap out the Starter Relay with an identical one.

With ignition on....jumper out pins 87 and 30 of the starter relay....if it starts cleanly every time then suspect your Starter Relay or the power coming from the ignition key to the Starter relay although I do not see how this final point could be heat related.

 

[dude1116]

How good is your battery....90% of these type of problems are caused by:

Bad battery...Optima Red tops have a bad reputation.
Bad battery terminal connections...need to clean them up and clamp them tight.
Bad earth connection connecting engine to chassis....likewise clean and tighten.
Bad earth connection of negative battery lead going to chassis....likewise..

If you are satisfied that all of the above are good then maybe you need a new starter solenoid but first swap out the Starter Relay with an identical one.

With ignition on....jumper out pins 87 and 30 of the starter relay....if it starts cleanly every time then suspect your Starter Relay or the power coming from the ignition key to the Starter relay although I do not see how this final point could be heat related.

My sentiments exactly on that last part. Wish I had the equipment to test all of the electrical components as far as the starter goes. Tested the battery at Autozone a couple of weeks ago and everything checked out. Terminal connections are good with only slight corrosion on the positive terminal (will get a wire brush and clean up). Will need to check the other battery connections. Battery is about a year and a half or so old with maybe 20k miles on it? My only problem with a battery diagnosis is that I'm getting good power everywhere else. Is it still a possibility? Absolutely.

Maybe I'll take it to my mechanic over the weekend to see if he can test the electrical components of the starter.

Thanks for the start. Any other suggestions always greatly appreciated!

 

[rockymountain]

The battery might check out ok, but it sounds like it can't sustain it's CCAs very well. You say it acts up half warmed up. Well, the battery could be drained from starting it and won't get charged up again for a while. Starts cold; once again you shut it off (last night or whatever) with the battery charged up so it has enough to start it next time. Basically it sounds like starting the engine is depleting the battery.

 

[dude1116]

The battery might check out ok, but it sounds like it can't sustain it's CCAs very well. You say it acts up half warmed up. Well, the battery could be drained from starting it and won't get charged up again for a while. Starts cold; once again you shut it off (last night or whatever) with the battery charged up so it has enough to start it next time. Basically it sounds like starting the engine is depleting the battery.

What would allow it to eventually start though? And I can sit there almost all day and just start her up, shut her down, and start her up again when it's warm. I can also drive it for a few hours, then let it sit until it's about half way cooled down, and try to start it up and it would be a similar situation to the problem. That's what's got me COMPLETELY thrown off. Not to say I won't check everything there is to do with the battery. Cause I will. Gotta start somewhere!!! :icon_arrow:

 

[rockymountain]

What would allow it to eventually start though? And I can sit there almost all day and just start her up, shut her down, and start her up again when it's warm. I can also drive it for a few hours, then let it sit until it's about half way cooled down, and try to start it up and it would be a similar situation. That's what's got me COMPLETELY thrown off. Not to say I won't check everything there is to do with the battery. Cause I will. Gotta start somewhere!!! :icon_arrow:

Yeah, weird, but I think you have an intermittent situation sitting on top of an intermittent situation. Usually with these it is the battery. Start there, get a good one. May I ask what type you have now?

 

[dude1116]

Yeah, weird, but I think you have an intermittent situation sitting on top of an intermittent situation. Usually with these it is the battery. Start there, get a good one. May I ask what type you have now?

Yeah I'm running a Diehard. I forget the exact model, but it wasn't the cheapest nor was it the Platinum. Middle of the line type of thing with a decent warranty.

 

[Luke]

Mine does something similar ... It happened on Monday (just once) but hasn't happened for over a year prior to that.

Normally it takes the lightest twist of the key to start, so I get used to that... I have had it stumble and die ... but then with a solid turn it will start. On rare occasions it has needed two or three attempts to get it to start.
It reminds me of "vapor lock" .. but I don't even know if that is possible on this engine. :shrug:

No cels .. moderately clean intake and throttle body, IAC etc etc, clean terminals, all at the time of the first occurrences. Then it just stopped happening all together until Monday.

The warm state is exactly as you describe ... and it has never happened at any other time.
My battery was about 2.5 -3 years old when it happened (for a few weeks in a row).. it is now 4 yrs old.

I will keep you posted...

 

[dude1116]

Mine does something similar ... It happened on Monday (just once) but hasn't happened for over a year prior to that.

Normally it takes the lightest twist of the key to start, so I get used to that... I have had it stumble and die ... but then with a solid turn it will start. On rare occasions it has needed two or three attempts to get it to start.
It reminds me of "vapor lock" .. but I don't even know if that is possible on this engine. :shrug:

No cels .. moderately clean intake and throttle body, IAC etc etc, clean terminals, all at the time of the first occurrences. Then it just stopped happening all together until Monday.

The warm state is exactly as you describe ... and it has never happened at any other time.
My battery was about 2.5 -3 years old when it happened (for a few weeks in a row).. it is now 4 yrs old.

I will keep you posted...

Glad to know (loosely glad to know; I don't like others having problems with their Jeeps) that I'm not alone!

The only thing that started to concern me was the fact that it took 5-6 times to start it last time this happened.

 

[HoosierJeeper]

Mine does something similar ... It happened on Monday (just once) but hasn't happened for over a year prior to that.

Normally it takes the lightest twist of the key to start, so I get used to that... I have had it stumble and die ... but then with a solid turn it will start. On rare occasions it has needed two or three attempts to get it to start.
It reminds me of "vapor lock" .. but I don't even know if that is possible on this engine. :shrug:

No cels .. moderately clean intake and throttle body, IAC etc etc, clean terminals, all at the time of the first occurrences. Then it just stopped happening all together until Monday.

The warm state is exactly as you describe ... and it has never happened at any other time.
My battery was about 2.5 -3 years old when it happened (for a few weeks in a row).. it is now 4 yrs old.

I will keep you posted...

I get the same thing maybe 3 times a year. New plugs helped quite a bit, along with some fuel treatment once or twice a year seemed to help.

 

[MadDog]

I'm not certain that my experience is related to the OP's issue, but thought I would post in case it would help.

I once had my KJ stumble and die on start-up. I had gotten gas from a RaceTrac (second or third tier gas station). The only reason I could trace it back to the gas was because I had fueled my 92 Camry there a day earlier and it also stumbled and died. I didn't think of the gas at first, since I was having IAC issues with that car at the time, but then the KJ doing the same thing a day later after fueling confirmed it. It hasn't done that since, and I did a seafoam carbon cleanout, cleaned IAC and TPS ports and did a plug change shortly thereafter for good measure. I also only go to first tier gas stations, even if there is a price difference of a few cents since I just don't trust those other stations anymore.

So maybe this is a path worth pursuing for some of you...

 

[dude1116]

I get the same thing maybe 3 times a year. New plugs helped quite a bit, along with some fuel treatment once or twice a year seemed to help.

Oh yes. She's DEFINITELY getting new plugs. Maybe that's why it's happening more often than it should??? I've also been treating my fuel lately as well to see if that will help. I have one more bottle to go and I'm out. Then I'll just stick with straight up gas and see how it affects it.

I'm not certain that my experience is related to the OP's issue, but thought I would post in case it would help.

I once had my KJ stumble and die on start-up. I had gotten gas from a RaceTrac (second or third tier gas station). The only reason I could trace it back to the gas was because I had fueled my 92 Camry there a day earlier and it also stumbled and died. I didn't think of the gas at first, since I was having IAC issues with that car at the time, but then the KJ doing the same thing a day later after fueling confirmed it. It hasn't done that since, and I did a seafoam carbon cleanout, cleaned IAC and TPS ports and did a plug change shortly thereafter for good measure. I also only go to first tier gas stations, even if there is a price difference of a few cents since I just don't trust those other stations anymore.

So maybe this is a path worth pursuing for some of you...

That's probably some good advice. The only problem is that I've gotten the issue using stations such as Exxon, BP, and Citgo (those are the only 3 around here). 3 different "brand name" stations.

I DO however have a plan to Seafoam the gas tank and clean anything related to air. (I JUST changed the engine air filter about 3 weeks ago, so that should be fine.)

Basically going to start performing a little extra maintenance to see if I can minimize the problem.

 

[dude1116]

Sorry to resurrect this, but got a new CEL. P0522 - Oil Pressure Sensor Low Voltage. Could that be related at all...?

 

[yankee4rb]

same intermittent starting problem

My 2004 Liberty 3.7 runs great, not timing issues, no acceleration issues only fault codes are 440 and 441 with are o2 sensor crap codes. Every once in a while it will turn over but will not start, not very often but it is annoying. After turning the ignition off for about 2 minutes it will start just fine. I am thinking fuel pump? maybe going out? It has 104K miles on it. Or could it be the filter?

 

[dude1116]

Mine ended up being the starter. The engine wasn't spinning. You could hear the starter spinning but the splined piece wasn't coming out far enough to catch the flywheel. Replaced it and I was good to go.

 

[yankee4rb]

Thanks for the reply! I wish it was that scenario, so I knew for certain, but the starter turns the flywheel just fine, and after it sits for a while, it does start. Thanks anyway !

 

[johnnygrace]

Hey guys im getting what seems to be this exact problem. I didnt think about the heated up start problem but yesterday after leaving a store it took 4 cranks to get started. It would turn over and cough itself out then finally i was able to get some gas into it while it was barely idling and that got it started. This was the first time it didnt start on the first crank. It was parked on a weird sideways slope. The usual problem for me is that everytime i crank it, it sounds like its slowly gonna not crank one day. Super low idle at startup but then after giving it some gas and driving its fine. I guess it might feel a little low on power on hills. My battery is less than a year old and i cleaned terminals when it was installed. Im thinking i will have the battery checked then replace spark plugs and clean IAC maybe as those seem to be first steps. Anyone have any other advice?

Also two weeks ago it threw p0300 and another code for a bad o2 sensor but both went away after a few hrs and nothing since....i replaced one o2 last year, the downstream passenger side one which was a huge PITA not to mention the store clerk gave me the wrong sensor so you can imagine my frustration with my hand shoved up in there cursing why it wouldn't plug in....

 

[dude1116]

Like mentioned above...mine ended up being the starter!

 

[ltd02]

I didnt think about the heated up start problem but yesterday after leaving a store it took 4 cranks to get started. It would turn over and cough itself out then finally i was able to get some gas into it while it was barely idling and that got it started. This was the first time it didnt start on the first crank. It was parked on a weird sideways slope. The usual problem for me is that everytime i crank it, it sounds like its slowly gonna not crank one day. Super low idle at startup but then after giving it some gas and driving its fine. I guess it might feel a little low on power on hills. My battery is less than a year old and i cleaned terminals when it was installed. Im thinking i will have the battery checked then replace spark plugs and clean IAC maybe as those seem to be first steps. Anyone have any other advice?

From your description, I think mine does sort of the same thing, but only when it is warmed up. Say if I stop for gas and try to fire it back up I get what seems like a relatively slow crank and it fires with a brief/slight "weak" idle. I have let off the crank early and it has not started (coughed a bit but not sure I'd call it a stall). If you hold it a little longer and let it crank it will start every time. Let it sit for maybe an hour or so (depending on outside temp) and it fires up strong. Now the bummer. It's done that as long as I've had it which is almost 7 years. Got it with 80k and now have 165k. Always a bit annoying but it always does start. This is with some spark plug changes and a new battery. If it didn't start I'd be way more concerned.

Now with your more persistent problems: Slow crank and I'd lean toward electrical like mentioned above (battery or starter). But persistent slow or low idle after it did fire and I'd lean toward fuel delivery. Never checked my fuel pressure since it is so intermittent, I'd be more likely to blame fuel pressure. Maybe injectors gummed up, pump is failing or the filter is getting plugged. So don't know if this helps but at least may make you feel a bit more at ease not being alone in this. Start with the easiest like fuel pressure and maybe run some Techron through it for the injectors first.

New plugs and an IAC cleaning will never hurt too!

 

[johnnygrace]

thanks Itd02, I did the spark plugs yesterday and so far that's made a huge difference. I might tackle IAC cleaning as well. I'll see how it drives this week but my problem might have only been due to bad spark plugs and they were old....here's a post I made about them.....http://www.jeepkj.com/forum/f196/spark-plugs-possible-age-57139/ I'm gonna try running the techron thru as well. Seems like a good idea.