In the past couple of weeks my car has randomly had trouble starting. It would take more than five seconds and then it will either stumble and then fire up or you try again and it fires right up. Once the car is started it sometimes fluctuates the idle between maybe 700-1200 RPMs instead of holding steady around 800 RPM, the A/C is off and not on defrost. It will do the fluctuating for 10-20 seconds and then idle steady for 10-20 seconds and then repeat. It does the weird fluctuation and vibrates moderately when engaging a gear and not yet accelerating, but the vibration feels different than at idle while at a stoplight with the poly upper mount. Earlier this week the Check Engine light came on and the ECU shows the code for the ECT sensor being faulty. Would a bad ECT sensor/thermostat stuck open cause these problems or is there something not showing an error code that could be failing? I am thankful for any help as this is my first car and I am starting to rely on it. I am already planning on replacing the ECT and thermostat very soon. I have searched around and not found anything similar...

 

Does the car run smooth once it warms up? Does it restart fine when it's warm?

 

It never really warms up past 1/3 of the gauge (wish it was actually scaled) unless stopped for a while, but it runs great after I start driving. It's just the period before I start going down the block that this happens. The car starts right up 100% of the time that it is warm, but it only does the odd stuff during about half of the cold starts. It has gotten worse since the check light came on. The car has never stalled after it starts or idles. I ordered the thermostat, ECT sensor, air filter, and spark plugs today.

 

https://volvoforums.com/forum/volvo-...al-pain-59278/

My guess would be that your fuel pressure regulator is bad and it's not holding fuel pressure when you start it. You should also replace your fuel filter while you're at it if it's older than 10 years/100,000 miles. Also, how old are your plug wires? They have a date on them. If they are 7+ years old, replace them along with your distributor cap and rotor.

Another issue could be the TCS which a lot of people change when they do their thermostat. I do not but you are having cold start issues which means that your temp sensor may be telling your computer that your car is already warm and causing your car to run lein or rich.

 

I had the same issue on our 95 Turbo (especially the 1/3 gauge) Replaced both the thermostat and the ECT. Problem solved. Sounds like you are on the right track. BIG TIP. When you remove the torx head bolts that hold the thermostat cover on (If you are lucky enough to get them off without wanting to throw a brick at the car) PLEASE replace them with hex head bolts. Makes the job a piece of cake in the future.

 

Thanks for all the advice. I'll check the plug wires tomorrow and plan on replacing the fuel filter soon as I doubt it has been changed in ages. And when you say TCS do you mean the engine coolant temperature sensor or a completely different sensor?

 

Thermostat and Engine coolant temperature sensor should fix the issue

 

+1 on this: Engine coolant temperature sensor