Erratic idle -99 V70 2.5T

Eliotlm · Post by **Eliotlm** » 30 Apr 2025, 01:10

Hi! My v70 has an issue where the idle revs up and down and I am having trouble resolving it and knowing where to start. The problems got worse after not using the car for a while during winter. The car seems to be staying at a higher rev for longer after letting go of the gas. This might also be the reason for the engine stumbling when braking and coming to a stop. In those cases it "recovers" (most of the time) after dropping to only a few hundred rpm. When idling the car often goes from normal idle to about 1500 which makes it move as the car is equipped with an auto. I have a hard time pin pointing the cause of this as it seems like the dreaded ETS failure. But what makes me doubt that is that I have never gotten an ETS light. That makes me suspect either MAF sensor or vacuum leak. Do you guys have any suggestions on what might be the problem and how I would go about pin pointing the issue? Thanks in advance!

Post by **scot850** » 30 Apr 2025, 08:27

With the MAF, disconnecting the MAF will help identify if it is an issue or not. No change then not the MAF. If the car settles then it is the MAF.

Vacuum leaks are often the issue with turbo cars of this era. Easiest way to find is to smoke the intake system looking for leaks in the intercooler hoses and intercooler. Vacuum lines in the engine bay are also worth checking for.

The ETM may be dirty (Electronic Throttle Module). Careful cleaning with the correct cleaner and not soaking it with cleaner is the way to go.

Neil.

Eliotlm · Post by **Eliotlm** » 30 Apr 2025, 08:37

scot850 wrote: ↑30 Apr 2025, 08:27 With the MAF, disconnecting the MAF will help identify if it is an issue or not. No change then not the MAF. If the car settles then it is the MAF.

Vacuum leaks are often the issue with turbo cars of this era. Easiest way to find is to smoke the intake system looking for leaks in the intercooler hoses and intercooler. Vacuum lines in the engine bay are also worth checking for.

The ETM may be dirty (Electronic Throttle Module). Careful cleaning with the correct cleaner and not soaking it with cleaner is the way to go.

Neil.

Thank you! I will try that. I presume that ETM and ETS are the same system?

Post by **scot850** » 30 Apr 2025, 12:44

No. ETS is the Electronic Temp sensor or coolant temp sensor. It is part of the thermostat housing. The wiring and connector for it which are mounted near the power steering pump should be checked for corrosion of the joints and connectors as well as the wires breaking/corroding. There are specifications for resistance values to check the ETS versus ambient temperatures on MVS somewhere. I think Abscate has added this a few times. For your issue, I'd expect it not to start if it fails or have difficulty starting. Once the engine is up to temperature the needle on the gauge should be horizontal. If it is low then it is failing and the car could run rich. The other issue would be the thermostat was stuck, but again I don't think this is an issue for this problem.

Neil.

Post by **abscate** » 30 Apr 2025, 14:22

ETS ETM and ETB are all used to talk about the electronic throttle body - its a bit confusing.

You might not see the ETS light on the dash for quite some time if it is malfunctioning , the error process is complex and requires many conditons to be met.

Eliotlm · Post by **Eliotlm** » 30 Apr 2025, 16:03

scot850 wrote: ↑30 Apr 2025, 12:44 No. ETS is the Electronic Temp sensor or coolant temp sensor. It is part of the thermostat housing. The wiring and connector for it which are mounted near the power steering pump should be checked for corrosion of the joints and connectors as well as the wires breaking/corroding. There are specifications for resistance values to check the ETS versus ambient temperatures on MVS somewhere. I think Abscate has added this a few times. For your issue, I'd expect it not to start if it fails or have difficulty starting. Once the engine is up to temperature the needle on the gauge should be horizontal. If it is low then it is failing and the car could run rich. The other issue would be the thermostat was stuck, but again I don't think this is an issue for this problem.

Neil.

Alright, thanks. Not easy to keep track of all the abbreviations. The temp gauge always stays vertical or 80°C when warmed up and seems to move in a reasonable manner. But I will check the wiring and voltage just in case. I think my game plan will be to check vacuum lines, clean MAF, check wiring and then, if I don't find anything, take a look and the ETS (hope i used the right one? The electronic throttle body)

Eliotlm · Post by **Eliotlm** » 30 Apr 2025, 16:04

abscate wrote: ↑30 Apr 2025, 14:22 ETS ETM and ETB are all used to talk about the electronic throttle body - its a bit confusing.

You might not see the ETS light on the dash for quite some time if it is malfunctioning , the error process is complex and requires many conditons to be met.

Thank you for the clarification, I will keep in mind that it might be a problem despite not lighting up in the dash!