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Engine hesitation/misfire 97 chevy 1500 suburban. started with slight hesitation about 10 months ago. From then until now has gotten considerably worse. It also now has a definate manifold leak and sounds horrible when accelerating. that mixed with the hesitation, and it sometimes sounds like it is shooting a cap gun at you when pulling away. At the same time, i can remember times when all the problems would disappear briefly and run like it was brand new with full power. The one piece of information i have learned is that the previous owner ran the driver side into a concrete pillar at Wal Mart and hit hard enough to replace the front quarter panel. as well as i now have to change out the outer tie rod on that side tomorrow. Then ofcourse from what i gathered the hesitation issue happened after this guy ran it into the pillar. And of course he just returned it the the dealer/financer and said he couldnt justifiably pay them for it since it had a hesitation problem. Anyways just trying to figure out where to start. it does have the check light on and it is #7 misfire or random misfire.
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http://engine-codes.com/p1125_chevrolet.html
According to that website above, its your Accelerator Position Pedal Sensor. If you have already replaced it check your wiring harness.
Here is a website that for your wiring diagram for your 2005 Chevy Suburban.
P0300 random misfire, slight rough idle good , by the way your repair is good you dont want a identified misfire, Lets start by what it is not. Not a misposition sparkplug wire you would of gotten that cylinder code, as misfire, Oh try this got carburator cleaner? spray safely along the intake gasket, How about inspecting the vacuum hoses especailly at the map sensor. Here the thing you got. a vacuun leak. on a 5.7 a vacuum leak causes random misfire, by definition P0300 means 2 cylinders or more. By experience its a vacuum leak
get u a heat gun and check ur temp on the exhaust manifold while truck is running bellow each plug the one misfiring will be considerably cooler then others,theres ur misfire
Unplug the connector at the rear wiper motor, turn the switch on and probe the wires with a test lamp, if you have power back there you more than likely have a bad motor. If there is no power start checking fuses they are all labeled easily on the back side of the fuseblock covers both on the dash and underhood. Good Luck!!!
The cylinder 7 misfire is likely a symptom of the problem, not the problem itself.
Typically, the catalytic converter has an oxygen sensor in front and behind it. When the vehicle is warm and running in closed loop mode, the upstream oxygen sensor waveform reading should fluctuate. The downstream 02 sensor reading should be fairly steady. Typically the P0420 code triggers the check engine light if the readings of the two sensors are similar. This is indicative of (among other things - such as faulty sensors in the "emissions loop") a converter that is not working as efficiently as it should be.
I do not believe that it is a problem with a valve/head gasket or cam.
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