Hi Scotty,
I have a 2015 Chevy Cruze 1.4L Turbo, automatic, that I bought 2 years ago with 67,000 miles. It now has 108,000 miles. Most of my driving is back and forth to work, 32 miles each way highway driving, 70-80 MPH. I'm very light on the accelerator, I get about 32 MPG on premium gas(it doesn't like regular). It has been running great, until a few months ago. Since then it seems to be holding back/hesitating/surging, at all speeds and loads, sometimes much worse than others, it sometimes looses power and downshifts where it never did before. Sometimes it looses power and doesn't downshift when it should, I downshift manually and it will pick up. If I mash on the accelerator it gets up and goes fine. The other day I was Cruzing down a long grade on the interstate at 74 mph, light steady pressure on the accelerator, and it downshifted into 5th! I manually shifted up to 6th, and drove on. No DTC's. Whats going on?
Thanks, Dave
it could be quite a few things. First step in diagnosing this should be to hook up a diagnostic scanner.
Its been scanned, hence "No DTC's" What kind of scanner are you referring to?
The battery and alternator check OK.
I have also cleaned the MAF sensor, and throttle valve.
Yes. Have it scanned.
Also, have the battery and alternator tested. Free at Autozone, etc.
Find out if there is any software update for the transmission.
See here for diagnosis -
https://carkiller.com/scottykilmer/qa/misfire-4/
Normally I’d say 6yrs is too soon for a fuel pump to go out, but then this is a GM..
Fuel pressure runs between about 43 - 58 psi while driving.
What’s it at idle? Although it seems normal -
Fuel pressure at idle: 43.5 PSI
I don't detect anything like a misfire. It idles fine, and runs fine on hard acceleration. It happens on cruising and light load, could it be the TPS?
Last week we had several days of cool (low 70's F) cloudy, rainy weather. The car ran pretty OK thru this. Now the hot weather is back, in the 90's, and the car is running crappy again. The coolant temperature stays around 210 degrees no matter what.
I’m with @doc on this one. Sounds like it’s your MAP sensor acting up when warm. Or find a good independent mechanic who’s good at diagnostics. A new OEM AC Delco MAP sensor is $22 - https://www.rockauto.com/en/catalog/chevrolet,2015,cruze,1.4l+l4+turbocharged,3308749,exhaust+&+emission,manifold+pressure+(map)+sensor,11207
Check your MAP sensor in the intake manifold. They get crudded up over time. They can usually be carefully removed (they have an o-ring), cleaned and replaced after lubricating the o-ring. Check all your wiring connections too.
I checked the boost pressure sensor when I cleaned the throttle valve, it was clean.
Today I checked the MAP sensor, it is clean.
The wires and connectors all appear good.