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.
Ok, I got more updates:
texas had winter weather this weekend, so like good texans, we holed up and never went any where. so i worked in the garage.
1. inspected all motor and trans mounts - GOOD.
2. pulled spark plugs, only 6 and 3. Mainly wanted to see if 6 had any oily residue, i suspect my valve cover leaks at the back. Both pulled, OE spark plugs, but new, were a nice toasty marshmellow color. So GOOD.
3. pulled the injectors again. I had previously taken them off to clean. They were good. Mainly wanted to see them free and clear and see if #6, the worst when i cleaned was clean and not oily - GOOD.
4. when we had the skid plate down to check trans mount, I pulled the dust shield and looked at the torque converter bolts. They were smoked on there. I gave them all 3 grunts and an elbow pop, so i called that torqued to spec.
5. also looked at torque converter area and figure i must not have a leave rear main, as there was no oily residue inside there. mainly at the back of the pan, so maybe valve cover?
Next steps:
1. going to run some MMO in the oil and fuel to see if i can quiet what i think to be a noisy lifter. It is time for an oil change, been 3k miles since last, and will run it for a bit and drop the oil. Going to run Valvoline VR1 10w30 this time, see if it likes that dinosaur juice.
2. going to changes the trans fluid as well just to make sure it has fresh stuff in there. it was done at 80k miles. but that was 10 years ago.
3. still chasing that idle issue, so plan is to drive it till it is hot and them some home and try to spray starter fluid at the areas of the throttle body that leak smoke in smoke test and see if anything changes. It doesnt on cold start, but maybe when the metals are warm? Dont know.
texas had winter weather this weekend, so like good texans, we holed up and never went any where. so i worked in the garage.
1. inspected all motor and trans mounts - GOOD.
2. pulled spark plugs, only 6 and 3. Mainly wanted to see if 6 had any oily residue, i suspect my valve cover leaks at the back. Both pulled, OE spark plugs, but new, were a nice toasty marshmellow color. So GOOD.
3. pulled the injectors again. I had previously taken them off to clean. They were good. Mainly wanted to see them free and clear and see if #6, the worst when i cleaned was clean and not oily - GOOD.
4. when we had the skid plate down to check trans mount, I pulled the dust shield and looked at the torque converter bolts. They were smoked on there. I gave them all 3 grunts and an elbow pop, so i called that torqued to spec.
5. also looked at torque converter area and figure i must not have a leave rear main, as there was no oily residue inside there. mainly at the back of the pan, so maybe valve cover?
Next steps:
1. going to run some MMO in the oil and fuel to see if i can quiet what i think to be a noisy lifter. It is time for an oil change, been 3k miles since last, and will run it for a bit and drop the oil. Going to run Valvoline VR1 10w30 this time, see if it likes that dinosaur juice.
2. going to changes the trans fluid as well just to make sure it has fresh stuff in there. it was done at 80k miles. but that was 10 years ago.
3. still chasing that idle issue, so plan is to drive it till it is hot and them some home and try to spray starter fluid at the areas of the throttle body that leak smoke in smoke test and see if anything changes. It doesnt on cold start, but maybe when the metals are warm? Dont know.
Ok, I THINK I have made it somewhere. Looking for the knowledge on here to help me verify that.
Yesterday after the Jeep had been driven to town and back, about an hour, I left it running and sprayed starting fluid at the places on the Throttle Body that leaked smoke in my smoke test. This time I got a change in idle. So I take it that means as it warms up, it is leaking more at those spots.
When I did this test before, when it was cold started, there was no change in idle when spraying the starting fluid there. Which kind of tracks because the Low Idle issue is worse the warmer the motor gets.
SO...... do you think it is likely this is my idle issue vacuum leak? I did the O-ring repair to this TB as it was really loose in the throttle shaft originally. It leaked smoke worse before that o-ring rebuild.
Should I just replace the Throttle body? I know Mopar ones are not available, so I would likely put the BBK on there. I know it won't make it a hot rod, but would figure it is the best aftermarket one out there.
Helpful insight appreciated.
Yesterday after the Jeep had been driven to town and back, about an hour, I left it running and sprayed starting fluid at the places on the Throttle Body that leaked smoke in my smoke test. This time I got a change in idle. So I take it that means as it warms up, it is leaking more at those spots.
When I did this test before, when it was cold started, there was no change in idle when spraying the starting fluid there. Which kind of tracks because the Low Idle issue is worse the warmer the motor gets.
SO...... do you think it is likely this is my idle issue vacuum leak? I did the O-ring repair to this TB as it was really loose in the throttle shaft originally. It leaked smoke worse before that o-ring rebuild.
Should I just replace the Throttle body? I know Mopar ones are not available, so I would likely put the BBK on there. I know it won't make it a hot rod, but would figure it is the best aftermarket one out there.
Helpful insight appreciated.