The occasional hesitation/dip in rpm’s when idling.
12-11-2023, 05:46 PM
#16
Rennlist Member
Thread Starter
I really want to post a thread with my experience on the Crank Position Sensor but there are so many. Most people will tell you that it causes a stall when warmed up/hot.
In my case, I started out with idle dips exactly like yours and would stabilize after a second or 2. It progressed to stalling only when hot when the AC was off, to stalling on cold start as soon as you’d turn the AC on (or if it was already on), to stalling when cold, to stalling ALL THE TIME. After replacing it today, the car runs perfect.
All this is to say, I suspected the wrong items based on just the idle problems such as yours.
In my case, I started out with idle dips exactly like yours and would stabilize after a second or 2. It progressed to stalling only when hot when the AC was off, to stalling on cold start as soon as you’d turn the AC on (or if it was already on), to stalling when cold, to stalling ALL THE TIME. After replacing it today, the car runs perfect.
All this is to say, I suspected the wrong items based on just the idle problems such as yours.
12-11-2023, 06:18 PM
#17
Advanced
Actually, about a week out from the CPS sensor and while I’m not in the same boat as before with the random stalling, I am actually in the same boat as you. I only had CEL for O2 sensors below
limit values.
The idle still dips, doesn’t stall, will drop to about 500 and only when completely warmed up. It doesn’t do it nearly as often so I am not THAT worried but I do want to shoot for a perfect
idle if possible. So, at least I resolved the stalling.
To date, I’ve done this:
- Replaced MAF
- Replaced fuel filter
- Cleaned TB and ICV
- Fixed vacuum leaks and passed the smoke test (when the engine was cold)
- Replaced CPS (biggest change so far was from this)
Get a durametric, and start checking your fuel trims. I am not sure what “good” fuel trims look like though.
Here’s what I’m doing next:
- Read everything I can with Durametric and confirm it’s normal
- Do a smoke test when the engine is hot and hopefully see that maybe there’s a vacuum leak when warmed up
- Replace ICV, and maybe the throttle position sensor if all of the above checks out.
I am not too worried about this though - I’ve seen idles drop on old cars, and never thought of it as being anything until this car came into my life. Phew.
limit values.
The idle still dips, doesn’t stall, will drop to about 500 and only when completely warmed up. It doesn’t do it nearly as often so I am not THAT worried but I do want to shoot for a perfect
idle if possible. So, at least I resolved the stalling.
To date, I’ve done this:
- Replaced MAF
- Replaced fuel filter
- Cleaned TB and ICV
- Fixed vacuum leaks and passed the smoke test (when the engine was cold)
- Replaced CPS (biggest change so far was from this)
Get a durametric, and start checking your fuel trims. I am not sure what “good” fuel trims look like though.
Here’s what I’m doing next:
- Read everything I can with Durametric and confirm it’s normal
- Do a smoke test when the engine is hot and hopefully see that maybe there’s a vacuum leak when warmed up
- Replace ICV, and maybe the throttle position sensor if all of the above checks out.
I am not too worried about this though - I’ve seen idles drop on old cars, and never thought of it as being anything until this car came into my life. Phew.
12-14-2023, 04:21 PM
#18
Rennlist Member
Thread Starter
Actually, about a week out from the CPS sensor and while I’m not in the same boat as before with the random stalling, I am actually in the same boat as you. I only had CEL for O2 sensors below
limit values.
The idle still dips, doesn’t stall, will drop to about 500 and only when completely warmed up. It doesn’t do it nearly as often so I am not THAT worried but I do want to shoot for a perfect
idle if possible. So, at least I resolved the stalling.
To date, I’ve done this:
- Replaced MAF
- Replaced fuel filter
- Cleaned TB and ICV
- Fixed vacuum leaks and passed the smoke test (when the engine was cold)
- Replaced CPS (biggest change so far was from this)
Get a durametric, and start checking your fuel trims. I am not sure what “good” fuel trims look like though.
Here’s what I’m doing next:
- Read everything I can with Durametric and confirm it’s normal
- Do a smoke test when the engine is hot and hopefully see that maybe there’s a vacuum leak when warmed up
- Replace ICV, and maybe the throttle position sensor if all of the above checks out.
I am not too worried about this though - I’ve seen idles drop on old cars, and never thought of it as being anything until this car came into my life. Phew.
limit values.
The idle still dips, doesn’t stall, will drop to about 500 and only when completely warmed up. It doesn’t do it nearly as often so I am not THAT worried but I do want to shoot for a perfect
idle if possible. So, at least I resolved the stalling.
To date, I’ve done this:
- Replaced MAF
- Replaced fuel filter
- Cleaned TB and ICV
- Fixed vacuum leaks and passed the smoke test (when the engine was cold)
- Replaced CPS (biggest change so far was from this)
Get a durametric, and start checking your fuel trims. I am not sure what “good” fuel trims look like though.
Here’s what I’m doing next:
- Read everything I can with Durametric and confirm it’s normal
- Do a smoke test when the engine is hot and hopefully see that maybe there’s a vacuum leak when warmed up
- Replace ICV, and maybe the throttle position sensor if all of the above checks out.
I am not too worried about this though - I’ve seen idles drop on old cars, and never thought of it as being anything until this car came into my life. Phew.
I cleared the P0491 and P0492 codes that were present.
After it sitting for about 45 minutes, I disconnected the SAI pump then started the car…no dip in RPMs after 2-3 seconds of it idling like it normally does…
Interestingly, no CEL popped up either about the SAI pump being disconnected/no reading. Hooked up a a PORII and there are still no codes.
I’m at school in the parking lot and it’s currently 52* outside….I get done at 830 (5 hours from now) so the motor will be completely cooled by then and will definitely try to activate the SAI pump…we’ll see if the dip in RPMs was from the massive pull of voltage from the alternator when turning on the SAI pump or something else. I think the last time I had it unplugged it wasn’t completely disconnected and I pretty much just pulled it out of the being seated, but didn’t COMPLETELY set aside the plug, I just kind of left it there and it may have still be JUST ENOUGH connected to still work…. We’ll see in a few hours when the engine is completely cold.
Last edited by Nate.Evans; 12-14-2023 at 04:24 PM.
12-14-2023, 09:46 PM
#19
Rennlist Member
Thread Starter
Well, no dip during cold start. However, after driving for 20 minutes, I pulled into Chick Fil A, and it did dip one time when I pulled into the drive thru…otherwise, all other idles and stops lights it was fine.
After reading a bit, I think the variocam solenoid seems like it may be an issue worth investigating. It gives the issues we’re both having, and given you’ve replaced all the other usual suspect, it makes me think it’s that…
After reading a bit, I think the variocam solenoid seems like it may be an issue worth investigating. It gives the issues we’re both having, and given you’ve replaced all the other usual suspect, it makes me think it’s that…
12-14-2023, 09:51 PM
#20
Nordschleife Master
U can graph the rpms and actual crank angle. This might tell u if the variocam is hanging up
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Nate.Evans (12-16-2023)
12-14-2023, 11:24 PM
#21
When it dipped after 20 minutes drive after cold start, was SAI pump still disconnected?
Did you get any codes set for no SAI function?
Lastly, on a .2 (is yours .1 or .2?) I know the SAI pump runs more than at startup. For example, mine was accidentally left disconnected after some work I did. The next morning I drove to work, and after 30 minutes of driving, finally hit a stoplight. So that was the first time at idle post startup. At that time, the DME called for the SAI pump to run, instant code set. I pulled over, pulled codes, got SAI code. Looked at pump, noticed I left disconnected, reconnected it, cleared codes, no more issue.
So, moral, SAI pump can run at different times.
-Tom
2003 C2
Did you get any codes set for no SAI function?
Lastly, on a .2 (is yours .1 or .2?) I know the SAI pump runs more than at startup. For example, mine was accidentally left disconnected after some work I did. The next morning I drove to work, and after 30 minutes of driving, finally hit a stoplight. So that was the first time at idle post startup. At that time, the DME called for the SAI pump to run, instant code set. I pulled over, pulled codes, got SAI code. Looked at pump, noticed I left disconnected, reconnected it, cleared codes, no more issue.
So, moral, SAI pump can run at different times.
-Tom
2003 C2
12-16-2023, 11:56 AM
#22
Rennlist Member
Thread Starter
When it dipped after 20 minutes drive after cold start, was SAI pump still disconnected?
Did you get any codes set for no SAI function?
Lastly, on a .2 (is yours .1 or .2?) I know the SAI pump runs more than at startup. For example, mine was accidentally left disconnected after some work I did. The next morning I drove to work, and after 30 minutes of driving, finally hit a stoplight. So that was the first time at idle post startup. At that time, the DME called for the SAI pump to run, instant code set. I pulled over, pulled codes, got SAI code. Looked at pump, noticed I left disconnected, reconnected it, cleared codes, no more issue.
So, moral, SAI pump can run at different times.
-Tom
2003 C2
Did you get any codes set for no SAI function?
Lastly, on a .2 (is yours .1 or .2?) I know the SAI pump runs more than at startup. For example, mine was accidentally left disconnected after some work I did. The next morning I drove to work, and after 30 minutes of driving, finally hit a stoplight. So that was the first time at idle post startup. At that time, the DME called for the SAI pump to run, instant code set. I pulled over, pulled codes, got SAI code. Looked at pump, noticed I left disconnected, reconnected it, cleared codes, no more issue.
So, moral, SAI pump can run at different times.
-Tom
2003 C2
Last edited by Nate.Evans; 12-16-2023 at 12:11 PM.
12-16-2023, 12:30 PM
#23
Nordschleife Master
Not exactly sure how it reads in ml2 telemetry. On my scanner for the mk1 i could see "actual" crank angle. Its a value that would change around 3200rpm as opposed to the cam deviation number thats more of an average and doesnt change. Not sure what scanner u have but a durametric and my autel will see and graph the value as well as most shop scanners.
12-16-2023, 07:14 PM
#24
Rennlist Member
Thread Starter
Not exactly sure how it reads in ml2 telemetry. On my scanner for the mk1 i could see "actual" crank angle. Its a value that would change around 3200rpm as opposed to the cam deviation number thats more of an average and doesnt change. Not sure what scanner u have but a durametric and my autel will see and graph the value as well as most shop scanners.
12-18-2023, 11:48 AM
#25
Rennlist Member
Thread Starter
When it dipped after 20 minutes drive after cold start, was SAI pump still disconnected?
Did you get any codes set for no SAI function?
Lastly, on a .2 (is yours .1 or .2?) I know the SAI pump runs more than at startup. For example, mine was accidentally left disconnected after some work I did. The next morning I drove to work, and after 30 minutes of driving, finally hit a stoplight. So that was the first time at idle post startup. At that time, the DME called for the SAI pump to run, instant code set. I pulled over, pulled codes, got SAI code. Looked at pump, noticed I left disconnected, reconnected it, cleared codes, no more issue.
So, moral, SAI pump can run at different times.
-Tom
2003 C2
Did you get any codes set for no SAI function?
Lastly, on a .2 (is yours .1 or .2?) I know the SAI pump runs more than at startup. For example, mine was accidentally left disconnected after some work I did. The next morning I drove to work, and after 30 minutes of driving, finally hit a stoplight. So that was the first time at idle post startup. At that time, the DME called for the SAI pump to run, instant code set. I pulled over, pulled codes, got SAI code. Looked at pump, noticed I left disconnected, reconnected it, cleared codes, no more issue.
So, moral, SAI pump can run at different times.
-Tom
2003 C2
About 15 minutes into my drive, CEL popped up. Code was from it being disconnected, and the below value in bank 1 and bank 2….no other codes.
12-18-2023, 12:21 PM
#26
-Tom
12-18-2023, 06:43 PM
#27
Rennlist Member
Thread Starter
Reset the codes, started right up…no issues. Then this afternoon, same thing, except when I checked the codes, there was only 1 code: “Low bank 1”…no code about there being no SAI pump connected, and apparently bank 2 was fine lol. This is beyond frustrating lol.
Last edited by Nate.Evans; 12-18-2023 at 07:12 PM.
12-18-2023, 09:58 PM
#28
Race Car
Try unplugging the sai relay. It's in the relay rack behind the back seat. Might be a problem with the wiring?
12-20-2023, 11:42 AM
#29
Rennlist Member
Thread Starter
SAI pump hasn’t been plugged in for a few days, no codes since the last time I cleared them. It was 28* out yesterday and no hesitation/dip or codes…