the annoying hard start issue

Nathanael Rusciolelli

Nathanael Rusciolelli

TJ Enthusiast
Joined
Dec 4, 2016
Messages
118
Location
North Carolina, United States
So I've posted on this forum several times concerning my hard starting issue. I've gotten lots of helpful advice but I still can't figure out what's causing this. My Jeep is a 99 2.5l. Here is the run down. It only does it when the engine is hot. It starts right up in the morning especially if it's cooler. I've tried the insulation around the injectors to prevent heat soak and that didn't help. I'm getting the correct amount of fuel pressure and pressure does not bleed off after i shut off the engine (otherwise it wouldn't start so well in the morning). I've replaced the crankshaft position sensor and that did nothing. The starter works fine, the battery is new and holds charge well. For some reason it starts quicker if I hold the gas pedal down while cranking the engine. My thought is it is some sort of air flow issue. The air filter is not clogged. I've been inspecting all of the vacuum lines and there seem to be no leaks. If it starts faster while I'm holding the gas pedal wouldn't that mean it's because more air is being allowed into the intake?

Another opinion i had was I've heard something about the coolant temperature sensor causing similar issues. I'm loss at this point. The jeep never fails to start but this is annoying as hell. Any help would be much appreciated. Especially from you guys with 4 bangers who may have experienced something similar.
 
Gosh, I seem to remember @Jerry Bransford mentioning to another member with a similar issue that it may actually be the fuel pump. I don't think it was the fuel pump as a whole, but a part of the fuel pump that unfortuntely could only be purchased as a whole, with a new fuel pump.

Hopefully Jerry will chime in, because I may be remembering wrong.
 
Nathanael Rusciolelli said:
The fuel pump is actually a brand new bosch unit. Probably should have mentioned that. I sort of installed it just for the hell of it and because I think the original was still on there and it was bound to go sooner or later.
Click to expand...

My suggestion would be to pull the spark plugs when it is hot after it is hard to start, and see what they look like? Are they dry and white or soaked and dark? While they are out do a quick compression test. This is an easy test that can rule out something or give you a clue of something more to search.
 
That it starts faster when you step on the gas pedal a little means (to me) it's not getting enough air when you're not stepping on the gas. Which to me makes me immediately think that the IAC (idle air control) is either too dirty to let air in as it's supposed to when you're not stepping on the gas, or (far less likely) the IAC has gone bad.

There's a thread here in the forum on how to clean the IAC. Basically start the engine then spray throttle body cleaner into the throttle body at idle rpms. The IAC will only draw the cleaner in through itself when the engine is at idle. The cleaner will flood the IAC so the engine will die. That's ok, just restart the engine. Plus the extra time the cleaner sits inside the IAC after the engine dies and before you restart it helps it work.

No guarantees of course but thoroughly cleaning the IAC usually fixes this kind of problem. My goal is to get 1/3 of the can of TB cleaner through the IAC.
 
  • Like
Reactions: StG58
  • Like
Reactions: Chris and StG58
Jerry Bransford said:
Good writeup of course but to me, actually removing the IAC to clean it is seldom required. When cleaned as suggested above, the IAC usually pulls in enough cleaner through itself to restore it back to good operating condition.
Click to expand...
For what it's worth. A tech at the dealership said that it is better to remove the IAC as there are plastic gears that can get gunked up with carbon deposits that are blown off when not taking it off. I have no firsthand knowledge though. Just what he said.
 
Gerund said:
For what it's worth. A tech at the dealership said that it is better to remove the IAC as there are plastic gears that can get gunked up with carbon deposits that are blown off when not taking it off.
Click to expand...
There are no plastic gears inside an IAC, it is solenoid operated.
 
Gerund said:
It seemed odd to me too that there would be plastic anything beyond it. I just kinda nodded when he said it.
Click to expand...
I used to have a half-dozen new Jeep dealers as clients and I used to shoot the shit once in a while with their service techs. (Imagine that. ;)) Anyway, they used to surprise/shock me once in a while with what the didn't know or misconceptions on many common things. They pick up hearsay and often believe what they hear without question, especially the younger ones. More than a couple swore to me that the correct fix for Death Wobble was a new steering stabilizer. :eek:
 
Last edited:
  • Like
Reactions: JMT
I cleaned out the IAC as prescribed above. No noticeable changes. This is kind of just a random guess but I've heard of the coolant temperature sensor causing issues similar to this. My jeep doesn't run hot but I don't know if there is a possibility that this issue has to do with the cooling system.
 
Sit rep. I noticed today when I had the air intake off that after sitting for a couple of hours, there was a small puddle of gas in my intake manifold just below the throttle valve. I started the jeep up and cut it off after about 30 seconds. The puddle was gone of course but during those 30 seconds the jeep ran very poorly (i'm assuming because of a rich mixture). I'm going to keep checking periodically to see how quickly the puddle forms after I cut the jeep off but what do you think may be causing this? Leaking injector? I've heard on this forum that the fuel injectors very rarely go bad but hell, I'd believe anything at this point. Any help is appreciated.
 
Jerry Bransford said:
More than a couple swore to me that the correct fix for Death Wobble was a new steering stabilizer. :eek:
Click to expand...
I've only been messing with TJs for six months and I've already heard that from at least 5 different mechanics
 
Nathanael Rusciolelli said:
Sit rep. I noticed today when I had the air intake off that after sitting for a couple of hours, there was a small puddle of gas in my intake manifold just below the throttle valve. I started the jeep up and cut it off after about 30 seconds. The puddle was gone of course but during those 30 seconds the jeep ran very poorly (i'm assuming because of a rich mixture). I'm going to keep checking periodically to see how quickly the puddle forms after I cut the jeep off but what do you think may be causing this? Leaking injector? I've heard on this forum that the fuel injectors very rarely go bad but hell, I'd believe anything at this point. Any help is appreciated.
Click to expand...
A leaking injector or a bad/leaky injector o-ring is all that comes to mind. You can always move the injectors around and look at their o-rings while they're out, they're only held in by their o-rings once you have removed the fuel rail.
 
just pulled off the fuel rail and primed the fuel pump a few times. Definitely noticed fuel leaking out of at least the two outside injectors (4-banger). I thought I did an injector leak down test before but I must have done it wrong. What should be my source for new injectors? I've heard you can swap in some junkyard injectors but what's everyone's opinion?
 
Hi all, my first thread and I'm bringing this back from the dead.

Did this issue ever get resolved? I'm experiencing similar problems with my 99 2.5L.
Has 46-48PSI fuel pressure, has spark (I pulled a plug and visually saw the spark with it laying it on the engine block). I am having the same fuel pooling in the intake? its been running rough the last few months? when it was running I sometimes had to feather the throttle from a dead stop to avoid stalling? some days it would start and others it wouldn't? when it didn't I'd just let it sit a few hours and then it would start right up...but then one day it didn't. I haven't been able to get it started in a week.
I've had this Jeep since it was new and it still has a ton of original parts. I did replace the original IAC last July with a cheap O'Riellys unit.

Thanks in advance for the help.

PS, this is the first I've heard of trying the part throttle to open the IAC while starting. I will try that this evening when I get home from work.
 
So I got it resolved.
Initially I tried the part throttle opening of the IAC, still no start. Knowing that it was getting air and knowing it was getting fuel I thought more about the spark. Turns out you need more than just a spark. You need a good spark! It had the original Ignition coil still in there and after 200,000 miles it was time for a new one. I threw that in and it roared to life.
Its running better than it has in a year. No more hesistation off a stop, no more poor idle, and lots more power!

So yeah, heres my follow up in case anyone else has a similar issue.
 
  • Like
Reactions: hyperdub808, Equilibrium31, Boinked and 1 other person
Top Bottom
Back