Weird Low Idle Issue
- Thread starter 4x4 AG
- Start date
The throttle body shaft seal is located above the MAP sensor so that leak won’t affect trims like one downstream from the MAP. A base gasket leak certainly will.
To narrow it down, disconnect the HVAC vacuum line, EGR solenoid line, and brake booster line at the manifold and plug them. You get an evap code which you can clear but you’ll be able to focus on the engine itself. You’ll have no power brakes so don’t pack the family in the jeep for church. If it still exhibits the condition, look at the intake bolts particularly around the #6 cylinder. Intake leaks are difficult to smoke unless they are significant and in which case you’d probably have a high idle.
To narrow it down, disconnect the HVAC vacuum line, EGR solenoid line, and brake booster line at the manifold and plug them. You get an evap code which you can clear but you’ll be able to focus on the engine itself. You’ll have no power brakes so don’t pack the family in the jeep for church. If it still exhibits the condition, look at the intake bolts particularly around the #6 cylinder. Intake leaks are difficult to smoke unless they are significant and in which case you’d probably have a high idle.
So the throttle body base gasket was a new fel-pro gasket. then i RTV'd both sides, i know, trying to make sure no leak. but it still looks to leak from there.
Honestly it is hard to tell as it is coming from all around the throttle body. The return spring, out of the relief at the bottom of the TPS sensor, and also looks like back next to the IAC.
Could i use the test you are taking about and smoke it again? I guess the main thing i am looking for is where is the leak coming from that is making the jeep throw more fuel at the idle?
Ok. so before i put the jeep back together, so i could move it, i smoked it again.
It pours out of both sides of the butterfly shaft on the throttle body. comes out a little of the breather tube in the valve cover vent, so will likely get that as well.
But looking at my fuel trims from before and thinking it was a vacuum leak, do we think the leak at the butterfly shaft on the throttle body could be the issue? I watched the video posted on one of these threads of how to replace the o-rings. thought about trying that.
What are yalls thoughts?
It pours out of both sides of the butterfly shaft on the throttle body. comes out a little of the breather tube in the valve cover vent, so will likely get that as well.
But looking at my fuel trims from before and thinking it was a vacuum leak, do we think the leak at the butterfly shaft on the throttle body could be the issue? I watched the video posted on one of these threads of how to replace the o-rings. thought about trying that.
What are yalls thoughts?
Ok, I am resurrecting this thread again.
UPDATES:
1. Smoke entire EVAP, found nothing.
2. Smoked entire engine, after O-ring rebuild of stock throttle body. find smoke coming from:
a. throttle body shaft on return spring side and TPS side.
b. small amount at PCCV hose that comes into intake.
3. Started up and sprayed starting fluid at the throttle body leak areas, alot, and at the PCCV area, and no change in Idle. So I am assuming the leak is not enough to really change anything.
4. ran a fuel rail pressure test. Prime is at 40 psi. running, idle and rev is at 45-46 psi. and it holds 40 psi pressure after cutting off for the 5 mins.
5. I adjusted the set screw under the return on the throttle cable. Doing so did bump the idle up, but also threw a code, P1294. which interwebs said could be IAC, so we replaced that and adjusted set screw back.
6. have replaced spark plugs with stock ones, have cleaned fuel injectors, and have tested the coil packs.
a. cylinder 6 injector was terrible, looks like oil may be seeping at the rear of valve cover, not excessive, but may be over the 100k miles it caked it. but cleaned up and all sprayed nice and uniform.
SO, what other things do yall think? The Jeep runs and drives decent. The idle dropping at stop lights just gives a shimmy and some plastics rattle to the jeep. So my untrained ear says something is a miss.
Motor mounts? Why are the Fuel Trims high? That seems to lead to it is trying to dump more fuel to compensate for something. and maybe that compensation is causing the shimmy?
Or should i just put a louder radio system in it, and call the problems you can no longer hear fixed?
UPDATES:
1. Smoke entire EVAP, found nothing.
2. Smoked entire engine, after O-ring rebuild of stock throttle body. find smoke coming from:
a. throttle body shaft on return spring side and TPS side.
b. small amount at PCCV hose that comes into intake.
3. Started up and sprayed starting fluid at the throttle body leak areas, alot, and at the PCCV area, and no change in Idle. So I am assuming the leak is not enough to really change anything.
4. ran a fuel rail pressure test. Prime is at 40 psi. running, idle and rev is at 45-46 psi. and it holds 40 psi pressure after cutting off for the 5 mins.
5. I adjusted the set screw under the return on the throttle cable. Doing so did bump the idle up, but also threw a code, P1294. which interwebs said could be IAC, so we replaced that and adjusted set screw back.
6. have replaced spark plugs with stock ones, have cleaned fuel injectors, and have tested the coil packs.
a. cylinder 6 injector was terrible, looks like oil may be seeping at the rear of valve cover, not excessive, but may be over the 100k miles it caked it. but cleaned up and all sprayed nice and uniform.
SO, what other things do yall think? The Jeep runs and drives decent. The idle dropping at stop lights just gives a shimmy and some plastics rattle to the jeep. So my untrained ear says something is a miss.
Motor mounts? Why are the Fuel Trims high? That seems to lead to it is trying to dump more fuel to compensate for something. and maybe that compensation is causing the shimmy?
Or should i just put a louder radio system in it, and call the problems you can no longer hear fixed?
When I had the battery go dead in our 04 , after recharging the battery and starting it , the engine would idle very low and die . I clean the IAC no help .
After driving it and keeping the idle up with my foot , normal idling returned . All that to say you've looked at the air leak side of things , but what about the electrical .
well that is a good question. The only diagnosis i have done on that would be:
1: it starts fine, plenty of cranking power
2: volt meter check vehicle off, volts good. vehicle on, alternating charging at 13.9.
3: volt gauge shows 14 when running.
Part of me thought PCM issue, as i know they have some years with issues. But i called and talked to the @Wranglerfix guy i believe that works on the failing PCMs and he stated my 04 was not in the bad ones. Could be an issue, but likely not since no other issues.
Voltage drop or weak connection through the IAC wirings or sensor connection wiring might be a place to look. You have addressed the other possibilities pretty well . Another thought , have you taken any live data stream info. from a scan tool , Some of the guys on here might have a good insight if there are issues.
how would i check this.
note i am a youtube certified mechanic only, not a real mechanic.
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