94 Grand 5.2L idles rough when cold.

smoulding · 11-07-2009, 08:28 AM

When you first start it, it takes several cranks, when it used to fire right up. It starts, then it idles rough, revs up and down, then after about 30 seconds the idle smooths out and is fine.

When you shut it off and start it up right away, it fires right up. It only happens when it's been sitting for at least a couple of hours.

It used to not start at all, so I replaced the fuel pump and filter. Now, I have this problem.

jeeponthebeach · 11-19-2009, 07:21 PM

Quote:

Originally Posted by smoulding

When you first start it, it takes several cranks, when it used to fire right up. It starts, then it idles rough, revs up and down, then after about 30 seconds the idle smooths out and is fine.

When you shut it off and start it up right away, it fires right up. It only happens when it's been sitting for at least a couple of hours.

It used to not start at all, so I replaced the fuel pump and filter. Now, I have this problem.

Sound like you have a very similar problem as me. Mine take more than several cranks to start and runs rough, revs up and down for 5 to 10 mins. Then is fine. Starts up fine when warm. Does your blow black smoke that smells very rich?
I noticed that if I leave the key in the on position for a minute it starts up wayyyy quicker but still runs like crap.

BlackbeastZJ · 11-19-2009, 08:22 PM

Quote:

Originally Posted by jeeponthebeach

I noticed that if I leave the key in the on position for a minute it starts up wayyyy quicker but still runs like crap.

I've heard that some vehicles have it so that when you turn the key to on position, it activates the fuel pump, kinda sounds like what you've got going. My uncles Dakota has it....

I have the same rough running in cold wheather thing on my 4.0, I'm thinking about changing the plugs and cleaning the IAC to see if that helps.

jeeponthebeach · 11-19-2009, 10:25 PM

Quote:

Originally Posted by BlackBeast95

I've heard that some vehicles have it so that when you turn the key to on position, it activates the fuel pump, kinda sounds like what you've got going. My uncles Dakota has it....

I have the same rough running in cold wheather thing on my 4.0, I'm thinking about changing the plugs and cleaning the IAC to see if that helps.

Yeah I actually leave it till I hear the fuel pump clicking which I think means it fighting a fully pressurized system. Around 10 rapid clicks. I was thinking my problem could be with the fuel system but I sprayed starting fluid down the throttle body and tried a cold start and it didnt fire up at all so im guessing its not a fuel problem.