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I have had nothing but problems since getting a tune up. I had to replace the spark plug wiring and got a tune up. Then my check engine light came on 3 weeks later and I had to get a new gas cap and a new valve canister. I also had an oil leak which I never had until I got the tune up. Now my car sputters hard when I turn it on and has a strong exhaust odour. It misses when I accelerate on the highway. And now yesterday my car started to overheat when I'm in idle! UGH! Help! 2006 Chevy Equinox. Nothing but issues! Well maintained but has 170k miles.

  • How did it run before the tune-up? After the tune-up? If it was good, then three weeks later started running bad doesn't necessarily mean the tune-up was at fault. There are SO many things that could be causing issues. There just isn't enough specific information here for us to be able to tell you what it is. We need codes to start with. That would be a great place to start. – CharlieRB Jun 6 '17 at 20:20
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There's a few things going on here:

  • What's a tune-up? Most cars built in the past 25 or 30 years don't need a tune-up anymore, as most of the engine management is now taken over by computers and sensors instead of spring tensions and adjustment screws. So when you said you got a tune-up, what did you really get?
  • Vehicle ageing I own 4 vehicles, the youngest one is 3 years older than yours and the 2 oldest ones have way more mileage than your, so I can speak with confidence and expertise about vehicle ageing. Vehicles, even when properly maintained, invariably reach a point where a lot of little things start wearing out, seemingly one after the other. When vehicles reach this point, owners often feel like "the car is dying" and get rid of it, others just bite the bullet and replace all these little things, as long as "the cost doesn't get stupid." This is probably what happened to your gas cap (fuel systems need to be pressurized).
  • Overheating at idle Idling is actually the hardest thing a vehicle needs to do. It's not getting enough air to maintain idle so it needs to open some kind of auxiliary air valve just to stay alive, and since the vehicle isn't moving, the radiator doesn't have the airflow to keep the engine cool and is entirely dependant on the cooling fans.
    • Fans Pop your hood, start the car, wait until it gets to temperature and just stand there looking at your radiator fans (keep your hands and fingers away from it while the engine is on, the fan can start unexpectedly). If the engine overheats and the fans never came on, you have a fan problem (check the fuse, the relay and electrically test the fan itself).
    • Radiator cap Make sure your cooling system pressurizes and that your cap is holding the pressure, otherwise your coolant will boil and flow out of your overflow/deaeration tank. There's a pressure tester for this, just don't open the radiator cap if the engine is still warm, you can get seriously burned by coolant fizzing out of there.
    • Coolant Make sure you have enough coolant. You may want to drain the coolant and flush the system. GM vehicles running DEX-COOL are prone to getting lots of deposits in the cooling system after a number of years. I would suggest, after draining it, to fill the system with a household cleaner that dissolves calcium, lime and rust deposits, run the engine to temperature (so the cleaner circulates everywhere), then drain it and fill it with new coolant.
  • Missing on the highway An engine missing and sputtering is an engine that is missing one of 4 things: air, fuel, spark or compression.
    • Air Check the air filter (they do need to be replaced every couple of years), clean your mass airflow sensor (if you have one) and inspect the ducting from the airbox to the throttle body for tiny little cracks.
    • Fuel Check your fuel pressure, electrically test your fuel injectors, get your fuel lines cleaned.
    • Spark Inspect your spark plugs, change them if needed. Also test each spark plug for spark (using a timing light), this will make sure your plug wires are conducting properly and that your igniter chip is firing.
    • Compression Perform a compression test. All cylinders should be pretty even, if not, your pistons rings or valve seats may be worn out.

Many of these tests can be done at home if you have the correct tools.

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If you have or can rent one from a parts store, connect an ODBII meter and run the entire test set . But look at the computers on board data first, make note of any excessive values, clear the memory and run the tests. 9 out of ten issues can be resolved using the ODBII meter.

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