Really really need some help!!!

[Rednek1280]

I've posted a couple of times about this situation and still no help. I have a '99 TJ 2.5L. When I start it up after sitting for a little bit, I have to give it a lot of gas and it runs rough at idle for a little bit. I've replaced my plugs, wires, fuel injectors, vacuum hose from throttle to brake booster, and brake booster check valve. If I pull that vacuum hose off from the booster while starting it, it cranks right up and runs fine. I'm at a lost for what else to check. By the way, I replaced all of those parts after it started happening.

 

[54cj3b]

whens the last time fuel filter was replaced

 

[Rednek1280]

6 months ago

 

[ga jeep family]

What about O2 sensor or catalytic converter being stopped up

 

[Rednek1280]

Wouldn't that cause an engine code?

 

[ga jeep family]

I think the O2 sensor will but I don't know if the catalytic will.

 

[mud4feet]

Wouldn't that cause an engine code?

The O2 sensor should definitely cause an engine code......plus I don't think it would be a problem with starting, but you would definitely notice a performance/gas mileage drop-off with a bad O2 sensor. Have you checked the MAP sensor? Relatively inexpensive replacement and it can cause starting/idling/running problems. I'm no expert at all, but I saw similar things happening with my brother's 2.5 (YJ). Hopefully those more knowledgeable with reply. Good luck!

 

[ga jeep family]

Have you cleaned inside the distributor good it could have water in it that will make it idle bad

 

[69jeepcj]

What about your fuel pump, It may be going out. you may have to look into it but they run at a certain PSI and if its not putting out the right psi it would run like crap if at all.

 

[Saddle Tramp]

What about your fuel pump, It may be going out. you may have to look into it but they run at a certain PSI and if its not putting out the right psi it would run like crap if at all.

I’m with 69JeepCJ. Check the pump. When the pumps start to fail they won’t give the pressure needed to properly supply and atomize fuel to the cylinder. As things warm up and expand the motor runs better. Once left to stand for a while the cool down make the symptoms return.

 

[Rednek1280]

Something else new to add. I was reving it while under the hood and there's this weird noise. The best way to describe it, it sounds like when blowing through a straw into water. You know that bubbling noise. Never heard that before on any vehicle.

 

[808CJ7]

Did it overheat?

 

[Rednek1280]

Never over heated

 

[808CJ7]

Never over heated

I know you said you changed the plugs. Did you try and pull them to see what they looked like after running the engine?

 

[Saddle Tramp]

Something else new to add. I was reving it while under the hood and there's this weird noise. The best way to describe it, it sounds like when blowing through a straw into water. You know that bubbling noise. Never heard that before on any vehicle.

Could just be the thermostat opening.

 

[JPNinPA]

So correct me if I have the details wrong.
On a cold start. You could start with no issue but it will not idle on it's own. You need to step on the pedal to keep it running. It runs rough until warmed up.

On a warm or hot start you have no issues.


Possibilities:
Intake leak that seals once warmed.
Slow upstream O2 sensor. And a Slow O2 will not throw a code but a failed one will.
CPS gone bad.
Distributor/timing is off.

Someone within the last month posted about a timming chain issue with similar effects.

 

[Rednek1280]

On a cold start, I have to hold the gas pedal down. If I take off the vacuum hose at the brake booster, it will idle fine. If I don't unhook it, it runs rough at idle until it warms up.

 

[RudeDog]

Vacuum hose off and it gets better? That seems to me like a vacuum related problem? Pull the hose off and put your finger over the hole in the end of the hose... Get worse? Is their possibly a crack or issue with the vacuum @/in the booster: Check fittings, all other hoses?

 

[superj]

do you have an idle control valve, like a 4.0? the one in the side of the throttle body? i would pull that and clean it, if you have one. it makes for idle issues on the 6 cylinder motors because it gets carbon all over it and then won;t seal right and has a hard time moving in and out properly. clean it and hte throttle body

 

[Rednek1280]

I'm going to check all the sensors and valves. I'll check the fuel pump and filter when the tank is almost empty.