Timing issue

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Krischick33

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Joined
May 10, 2020
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67
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2001 2.5 5sp 108k miles

I've been working working through a surging idle issue. Almost all sensors have been changed except Intake Air Temp sensor.
Last sensor change, camshaft sensor in the distributor made the most improvement. Idles better and no more hiccup during accelerating.
The question now is why does my timing advance jump from 7-19? Idle stumbles more when closer to 7 and seem to smooth out when in thr 13 range. I've attached a short video. What else can I look into? What controls timing advance. I know all the info says the PCM. Could i have a bad PCM? The other bit of info is that if I'm rolling with engine running and clutch in (like) coming to a stop the timing advance is constant at 16. During this time there is no idle surge.
Any help is appreciated as always.
Thanks
 

Attachments

  • IMG-0004.MOV
    14.9 MB
NTK 02
Mopar CPS
Other are a mix of Duralast and BWM?
I know the consensus is mopar sensors but do sensor control timing?
 
Your timing has to advance as the RPMs go up. It's why older distributors had either a vacuum advance or a mechanical advance. So the fact that it goes up as your rpms increase is the way it's suppose to work.

Some of your sensors give input to the computer which then controls the timing. You don't set the timing like you did on older distributors by turning it.
 
Wildman. Understood that timing increases with rpm and we can't adjust on our TJ's. My issue is at idle. Timing goes from 7 to 19. It just all around. My idle is relatively stable until timing hits 7 or close then idle stumbles until advance increases.
 
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Reactions: Wildman
Krischick33 said:
Wildman. Understood that timing increases with rpm and we can't adjust on our TJ's. My issue is at idle. Timing goes from 7 to 19. It just all around. My idle is relatively stable until timing hits 7 or close then idle stumbles until advance increases.
Click to expand...
Sorry I misread your other post.

My guess is it feels the stumble/misfire so then enriches the fuel to try and keep it from dying. That just a SWAG on my part.
I would get out a multimeter and test all your sensors and make sure they are working within their specified ranges. Just because you replaced them doesn't always mean that they are good.

Have you checked for vacuum leaks on your intake manifold and all vacuum hoses? Any exhaust leaks? Wiring to your O2 sensors are all good and not contacting hot exhaust anywhere?

Do you have a code reader that can do live viewing/recording?
 
I hear you on checking the sensors with a multimeter. I went the route of replacing because I didn't know how to test them. I guess I could spend some time on YouTube and learn. Since the timing jumps up and down regardless of whe its hot or cold do u recommend a sensor to start with?
I'm pretty sure I've identified all vacuum leaks. I've also replaced the intake/exhaust manifold gasket.
I'm using Touque Lite (free version). Not sure if that has live viewing/recording. Did you happen to view the short video I posted?
 
Wildman said:
Sorry I misread your other post.

My guess is it feels the stumble/misfire so then enriches the fuel to try and keep it from dying. That just a SWAG on my part.
I would get out a multimeter and test all your sensors and make sure they are working within their specified ranges. Just because you replaced them doesn't always mean that they are good.

Have you checked for vacuum leaks on your intake manifold and all vacuum hoses? Any exhaust leaks? Wiring to your O2 sensors are all good and not contacting hot exhaust anywhere?

Do you have a code reader that can do live viewing/recording?
Click to expand...
Did you ever get this problem fixed? Mine is doing the exact same thing.
 
LONGJP2 said:
For a surging idle, I would start with cleaning or replacing the IAC.
Click to expand...

Thank you getting back so fast! The idle is actually stable.

What seems wrong is that the ignition timing advance jumps around between ~5 to ~15, changing with nearly every reading (using an Autoxray EZ-SCAN 6000). I thought it should be more stable, and that jumping around might indicate the PCM trying to compensate for some other problem.

I wondered if the advance should be more stable at a stable idle, or if jumping around is normal?
 
Sorry, the original poster had a surging idle.
Can't help you with the fluctuating timing.

Google says it's normal. ;)
There's a constant influx of sensor information.
So it seems logical that it would be constantly changing to compensate.
 
LONGJP2 said:
Sorry, the original poster had a surging idle.
Can't help you with the fluctuating timing.

Google says it's normal. ;)
There's a constant influx of sensor information.
So it seems logical that it would be constantly changing to compensate.
Click to expand...

Thanks. I should have been more clear, but got fixated on the part of the discussion about the timing jumping up and down.
 
The timing will move up and down at idle to help control the idle speed. It is a part of the idle stability strategy. More timing if the idle is low and less if the idle is high.
 
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