Idle inconsistency

[Arthur Digby Sellers]

Upon having both T-belts swapped after the driver's side slipped, I got my 92 manual Loyale back from the shop to find it would not idle properly.  Occasionally, it will stay at about 1000 RPM. In other cases, the RPM will drop, in tiny increments, until it dies. There does not seem to be any correlation between this happening and any other factors; occurring at random, from what I have observed. Lightly applying the throttle will keep it from dying.

 

My research has led me to lean towards a leaky vacuum line or an issue with either TPS or IAC sensor. Additionally, a member of the forum suggested the cam sprockets could be one tooth off and I will be starting there, unless someone advises that is likely to not be the cause of the issue. 

TIA for all of the help. This forum is a lifesaver. 

[DaveT]

The CTS can cause weird idle problems.    Normally, makes it go high though.   I had the wire to the IAC valve break once, intermittent - It ran fine, but no idle.  If I kept a little gas pedal, it would stay running.

[Arthur Digby Sellers]

4 hours ago, DaveT said:

The CTS can cause weird idle problems.    Normally, makes it go high though.   I had the wire to the IAC valve break once, intermittent - It ran fine, but no idle.  If I kept a little gas pedal, it would stay running.

Thanks. I'll take a peek at the IAC valve, seems it winds up being the cause of a lot of idle related issues. 

Edited August 8, 2020 by Arthur Digby Sellers

[Ionstorm66]

Make sure all the hoses are connected and not cracked. Especially the PVC hoses.

[Subarule]

Mine would do that when the alternator started going bad.