2005 Saturn Vue 2.2 ecotec, 5 speed std. 124,000 miles. Shows misfire code only if full throttle applied. Starts right up, idles fine, will rev up without missfire if done slowly up to 3400 rpm, w any additional pedal, starts to misfire, rpms drop, if given full throttle will drop to 1400-1600 rpm, stumbling.
Let go to idle, normal. Try to rev back up slowly, will now only go to 2400, any more throttle, stumbles back to 1400 rpm. Holds 55 psi fuel pressure the whole time. I checked the pedal output, it is smooth, 1 volt to 4 volts. Replaced the throttle body ( I know, makes me a parts changer) it was good.
For entertainment; Background; I am new to computer/electrical diagnostics, grew up with points and mechanical diesel, and really prefer them . I've had this Saturn since almost new was a great car, developed an odd all stop, ignition no spark, turn completely off, would restart, drive 1 minute, stall, if restart attempted without full key off, would not restart. Because it would re-set on full key off -on, it was thought to be the ECM at the shop. Could not get a new one so they installed a re-furb "plug and play" ECM from flagship one, but could not get it to run at all after that. I was told it would not accept programming.They sent it out to a specialist, where the car stayed for another 2 months. Technician #2 gave up as well, it had the wrong VIN and thought the security system was preventing ignition, said if I could find a new ECM he would try again. The final advice included schooling on the vehicle trade in value verses junkyard. Brought it home, decided to try and learn something new. Found SD on youtube, got the courage to start checking 5 volt reference circuits, injectors, coil pack. Guess what? An injector pulse, a trigger signal, that means the computer is fine. wow with new coil pack, IT RUNS!!, aww, but not to full power (see symptoms above ). I tried the original computer, it also works, but runs the same. It appears that parts were changed, but not new, the coil pack, the throttle body, the MAF has been brutalized, The crank position sensor has also had wrenches on it. IT Was gone 4 months got sicker in hospital, but still alive. I bought a cheap code reader and an OBDLink SX (to change the VIN in the ECM) I'm stuck now.
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