High Idle when car has been running for a while Topic is solved

lcc014 · Post by **lcc014** » 17 Jun 2020, 18:43

This problem happened in around late April when we had the stay home advisory. When car is "cold" idle is fine, in park or waiting for traffic light. Once the car is driven for a while - "hot", idle speed goes up above 1300 rpm in Park position and a bit over 1000 rpm while waiting for traffic light.

Initially, I cleaned the IAC and the valve inside was moving freely when I shake the IAC. I also cleaned the throttle body too, not too much black deposit around the front and back side of the throttle body valve. Test drove the car after cleaning, same issue.

Then I got a new IAC from Volvo dealer and installed it. Still the same idle issue when car is "hot".

My car is 1995 NA wagon, what could be the problem here to cause the high idle in Park or waiting for traffic light ?

Thanks,

Ching-Ho Cheng

Post by **RickHaleParker** » 17 Jun 2020, 22:01

Check for DTCs, Air leaks intake and exhaust, stuck/leaking EGR.

lcc014 · Post by **lcc014** » 18 Jun 2020, 05:00

There is no CEL. I will check the DTC anyway. Exhaust manifold was replaced a while ago due to the flex elbow leak. EGR was replaced years ago when I did the PCV replacement. How to check air leaks in intake, exhaust and EGR valve ?

Thanks,

Ching-Ho Cheng

lcc014 · Post by **lcc014** » 18 Jun 2020, 15:23

I checked DTC code and found one in A2: 233 (Idle Air Trim Exceeds Control Limits); A1 had no code (111). So any more suggestion to troubleshoot the issue ?

Thanks,

Ching-Ho Cheng

Post by **misha** » 18 Jun 2020, 16:17

A6?
Being a '95 it should have Jetronic LH 3.2 management will can have 2 separate ecu(s),one for engine and the other for ignition.

lcc014 · Post by **lcc014** » 18 Jun 2020, 16:56

I have not tried A6. I only know A1 and A2 are for engine and transmission. I will try A6 to see any DTC.

Thanks,

Ching-Ho Cheng

lcc014 · Post by **lcc014** » 18 Jun 2020, 17:45

Just went out to check for A6 DTC. There was no code, meaning, no LED lighted up in A6 socket. I had tried 4 times, no LED light up. I could see the female connector inside A6 hole, but just no LED light up when compared with A1, A2, etc...

Thanks,

Ching-Ho Cheng

Post by **RickHaleParker** » 18 Jun 2020, 19:57

Volvo 850 modules and Flash codes. Smoke injection is the best leak detector. You can use starting fluid on the intake side of a running engine for leak detection. When a leak sucks in starting fluid you will hear the engine surge.

Post by **misha** » 19 Jun 2020, 01:16

Open up ecu box.
If it's Jetronic...it will have 2 ecu(s) in ecu box....for a car with manual transmission and 3 ecu(s)...for a car with automatic transmission.
That said...
-2 ecu for engine and ignition for a car with manual transmission
-3 ecu for engine,ignition and TCM(transmission control module) for car with automatic transmission.

lcc014 · Post by **lcc014** » 19 Jun 2020, 04:56

misha wrote: ↑19 Jun 2020, 01:16 Open up ecu box.
If it's Jetronic...it will have 2 ecu(s) in ecu box....for a car with manual transmission and 3 ecu(s)...for a car with automatic transmission.
That said...
-2 ecu for engine and ignition for a car with manual transmission
-3 ecu for engine,ignition and TCM(transmission control module) for car with automatic transmission.

Thank you for the information. If it is not Jetronic then it will have 2 modules (Engine & TCM); is that correct ?

Thanks,

Ching-Ho Cheng