After hours reading the forms and troubleshooting it is time for a post...
I have a 2004 4.0 Auto 111k miles - The start of the problem is there is a slight rough idle, almost like a faint misfire, cold or warm. The jeep starts cold at 1000 rpms and drops down to 650-680 when warm, runs and drives fine. Here's the kicker, when you click on the ac, in park or neutral, it gets worse and there's a bad resonance, id say it's worse warm but it is still bad cold. When you shift into gear with the ac on at idle the vibes get worse and the resonance rattles your brain. This is the problem im trying to solve. Ac works fine, pressures have been checked. No codes. Vibes and resonance go away once you start driving. RPM only increases about 20 with the AC on.
I have an Autel MK808 Pro but I am still learning how to use it and not really sure what to be looking for.
A quick background on the jeep, a year ago I completed a full frame swap, the only non-stock items (its a daily) are reman bosch injectors (the originals were cracked), an MRD coil pack, a tmr custom trans mount, and MORE engine mounts. I dont feel the poly mounts are the cause of the vibes, its only under the conditions i said above. It has been running great until this problem recently presented itself. Another note is the jeep sat for almost 2 years during the rebuild, before starting it up for the first time I removed the cam synchronizer to manually prime the oil pump. I followed the FSM to reinstall at TDC, thought I should mention that because I have read a few posts about them and the magnets going bad in the CPS if they sit.
So far ive tried cleaning the IAC with Jerrys method, then ended up taking the throttle body off and removing the IAC housing to completely clean the orifice and throttle body. Bought an aftermarket IAC to test, no change.
I had autolite plugs but swapped them to ZFR5N, checked the gap. No change. I have an MRD coil pack and checked the ohms, seems to be good. I did a smoke test through the manifold (brake booster hose) and fixed 3 vacuum leaks on the evap lines. I still have a small leak at the throttle body shaft and im going to try the oring work around from Rusty 411. My vacuum gauge is reading 16 inhg at the manifold with engine running. I read a post from @Chris about a broken clock spring interfering with the TPS, i thought this may be an issue from the frame swap, disconnected the clock spring, no change. Checked grounds, they seem to be good. Im getting ready to test the fuel pressure. A friend of mine mentioned it could be heat soak at the injectors, I have the heat shield in place but never wrapped the rail or injectors. Another note, i tried running an active test to set the RPM to 1500, 2000, etc on my Autel and the jeep wouldnt do it? Not sure if that one was user error.
Ive only seen 2 posts on here with this issue:
https://wranglertjforum.com/threads/rough-idle.77189/ this one went nowhere
https://wranglertjforum.com/threads/really-low-idle-and-vibration.31685/#post-1620247 and this one from @MikeE024 which led to a new PCM from @Wranglerfix
I have a 2004 4.0 Auto 111k miles - The start of the problem is there is a slight rough idle, almost like a faint misfire, cold or warm. The jeep starts cold at 1000 rpms and drops down to 650-680 when warm, runs and drives fine. Here's the kicker, when you click on the ac, in park or neutral, it gets worse and there's a bad resonance, id say it's worse warm but it is still bad cold. When you shift into gear with the ac on at idle the vibes get worse and the resonance rattles your brain. This is the problem im trying to solve. Ac works fine, pressures have been checked. No codes. Vibes and resonance go away once you start driving. RPM only increases about 20 with the AC on.
I have an Autel MK808 Pro but I am still learning how to use it and not really sure what to be looking for.
A quick background on the jeep, a year ago I completed a full frame swap, the only non-stock items (its a daily) are reman bosch injectors (the originals were cracked), an MRD coil pack, a tmr custom trans mount, and MORE engine mounts. I dont feel the poly mounts are the cause of the vibes, its only under the conditions i said above. It has been running great until this problem recently presented itself. Another note is the jeep sat for almost 2 years during the rebuild, before starting it up for the first time I removed the cam synchronizer to manually prime the oil pump. I followed the FSM to reinstall at TDC, thought I should mention that because I have read a few posts about them and the magnets going bad in the CPS if they sit.
So far ive tried cleaning the IAC with Jerrys method, then ended up taking the throttle body off and removing the IAC housing to completely clean the orifice and throttle body. Bought an aftermarket IAC to test, no change.
I had autolite plugs but swapped them to ZFR5N, checked the gap. No change. I have an MRD coil pack and checked the ohms, seems to be good. I did a smoke test through the manifold (brake booster hose) and fixed 3 vacuum leaks on the evap lines. I still have a small leak at the throttle body shaft and im going to try the oring work around from Rusty 411. My vacuum gauge is reading 16 inhg at the manifold with engine running. I read a post from @Chris about a broken clock spring interfering with the TPS, i thought this may be an issue from the frame swap, disconnected the clock spring, no change. Checked grounds, they seem to be good. Im getting ready to test the fuel pressure. A friend of mine mentioned it could be heat soak at the injectors, I have the heat shield in place but never wrapped the rail or injectors. Another note, i tried running an active test to set the RPM to 1500, 2000, etc on my Autel and the jeep wouldnt do it? Not sure if that one was user error.
Ive only seen 2 posts on here with this issue:
https://wranglertjforum.com/threads/rough-idle.77189/ this one went nowhere
https://wranglertjforum.com/threads/really-low-idle-and-vibration.31685/#post-1620247 and this one from @MikeE024 which led to a new PCM from @Wranglerfix
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