I have replaced the map, idle air control, crank position, and the tps sensors. I have also replaced fuel pump and the distributor and I put a new computer in it. The Jeep will start if I floor the gas but as soon as I take my foot of the gas it does. Any idea what it could be. Has good compression and fuel pressure
Spark and fuel are good, but it won’t stay running
- Thread starter Michaela
- Start date
That is a lot of parts thrown at it. I am assuming when you say you replaced the map that means that you replaced the computer? If indeed you have a programmable map, I would look at that. What is your fuel pressure? Are you getting any codes? Is the distributor put in correctly? Is the firing order set? Is it backfiring in the carb or exhaust? Is the timing set close?
If your fuel pressure is good, then I would go back over all of your ignition parts. What happened prior to you doing all of this work? Is the check engine light on when you do have it running? If so are there any codes and what are they? Set it to TDC and make sure you are right on the number one wire that goes to the number on cyl.
If your fuel pressure is good, then I would go back over all of your ignition parts. What happened prior to you doing all of this work? Is the check engine light on when you do have it running? If so are there any codes and what are they? Set it to TDC and make sure you are right on the number one wire that goes to the number on cyl.
I’ve replaced both the map sensor and the computer. The computer was
Programmed to my vin number. Fuel pressure is I believe 60 psi. And I’m getting a p0505 which is idle control valve. I’ve replaced the idle control valve twice but the code keeps coming back. Timing is set right and no it’s not back firing
Is the orifice in the throttle body the IAC plunger fits into and moves in/out of clean and able to pass lots of air?
Kiwi TJ
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The old adage of needing fuel, spark and air to get a car running looks the first have been taken care of.
ToddL
TJ Enthusiast
Did you measure fuel pressure while running? Sounds like a clogged fuel filter. It will show good pressure not running, but not while running.
Clogged fuel filters are pretty much unheard of on modern vehicles, especially the TJ. So rare the main fuel filter is not even accessible without dropping the fuel tank. Due to the main fuel filter's enormous surface area Jeep considers it to be a lifetime part.
Physically the main fuel filter sits inside the fuel pressure regulator that sits on top of the fuel tank.
I'm holding the fuel pressure regulator the fuel filter is inside of in this photo...
Yes cleaned everything in the throttle body good. Cleaned it with break clean.
Kind of sounds like a major vacuum leak to me. But even though you cleaned the throttle body, did you actually inspect and clean the inlet for the IAC? Could be plugged with something. Not just squirting the cleaner in the port inside the round part of the throttle body, but the smaller port on the side of it where the IAC would be inserted.
A major vacuum leak is essentially what happens when you open the throttle. A major vacuum leak causes sky-high rpms, not the inability for the engine to run unless the gas pedal is stepped down on which opens the throttle valve plate.
Which is why I asked about the IAC's orifice being able to pass air since the IAC had been replaced. The IAC is what provides all of the engine's air at idle. A bad IAC system can cause the exact same symptom as the OP reported above... the engine won't idle unless the gas pedal is stepped down on to give the engine air via that action opening the valve plate to give the engine air when the IAC isn't giving it enough air.
I was under the understanding that if the vacuum leak was POST throttle body, that the IAC would not be able to cope and therefore would kill the engine (and throw the IAC CEL). Don't remember now where I pulled the little nugget of information (or misinformation) from...
Nope, post IAC vacuum leaks are notorious for causing either higher or sky-high rpms..
Hayduke
New Member
Plus if it was a vacuum leak that massive that you can't keep the vehicle running you would hear it. It would be pretty obvious.Nope, post IAC vacuum leaks are notorious for causing either higher or sky-high rpms..
Plugged cats start showing up more the higher the engine rpms are. My main cat plugged so suddenly it reduced my top highway speed to 5-10 mph within a quarter mile. It idled fine and I drove it about 20 miles at 5-10 mph on the side of the highway to get it replaced.
@Michaela, if the new fuel pump was installed, they dropped the gas tank.
When you drop the gas tank you need to be careful not to break the plastic "y" vacuum connection, like I did on my 97 last week. :-/
Here's a pic..
Its in a hard to reach spot, near the top of the tank, I didn't know it was there hence the above.
If this breaks, it's a major vac leak.
Also if your TJ is old like mine, the rubber hose can somewhat conform to the large ends, giving intermittent engine miscues with no codes thrown. I fixed mine and the engine runs better now and I thought it was great before, check that if you can.
When you drop the gas tank you need to be careful not to break the plastic "y" vacuum connection, like I did on my 97 last week. :-/
Here's a pic..
If this breaks, it's a major vac leak.
Also if your TJ is old like mine, the rubber hose can somewhat conform to the large ends, giving intermittent engine miscues with no codes thrown. I fixed mine and the engine runs better now and I thought it was great before, check that if you can.
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Already checked to make sure that the y connector wasn’t broken which it’s not. I’ve checked for vacuum leaks and a plugged catalytic converter. Everything is good. I’ve cleaned the throttle body cleans where the sensor goes in at cleaned the sensor still won’t idle. It idled fine after about 10 minuets of keeping foot on the gas. I don’t even have to have gas pedal clear to the floor just as long as it is pressed a little bit it will run for as long as I want it to. Like I said before I’ve replaced idle control sensor twice just find t hard to believe that two brand new sensors could be bad.