2004 Aveo Rough Idle + Full history of this thing over the past 30K miles

Loooong time lurker here and I've searched a lot.

2 years ago fell victim of the 64K mile timing belt break.

Well the car is immaculate, (still is inside and out) so I decided to have the 1600 head job done + timing belt + everything else.

Fast forward to a month ago (now i have 94K miles). Car overheated. Leaks in heating hoses. Had all replaced and a stuck thermostat. Also Shocks and struts! Compression test was done to diagnose any outstanding head issues.

Was running like a champ for the past 3 weeks, now I have extremely rough idle and low end just ugliness. Engine light is on.

p1781, p0700, p0300 all lit up in my OBDII reader. So reading on here I replaced: Upper O2 sensor on manifold, plugs, plug wires and coil pack.

Cleared codes but same symptoms remain...and codes lit up again.

Wondering what on earth to try next... Would hate to find out I have another Head issue. Just noticed there looks to be another O2 sensor below the Cat. Should I replace that too? Would a bad Cat cause crappy idle too?

Before I dump more money into this aveo, just wondering what you guys think and what I should try next...

Thanks in advance :)

may sound silly but check any cable that is a gound (earth) can cause major rough idle only take one cable to earthing right to cause a multitude of problems. possibly the cat is cloged with crap? the rocker cover gasket isn't leaking oil into the spark plug wells by any chance is it as this will cause a bad spark putting soot onto the o2 sensors? try checking those things all free to do if you have a half decent knoledge of cars which it sounds like you have

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Originally Posted by marmite369

may sound silly but check any cable that is a gound (earth) can cause major rough idle only take one cable to earthing right to cause a multitude of problems. possibly the cat is cloged with crap? the rocker cover gasket isn't leaking oil into the spark plug wells by any chance is it as this will cause a bad spark putting soot onto the o2 sensors? try checking those things all free to do if you have a half decent knoledge of cars which it sounds like you have

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-Valve covers are pretty clean for as many miles this has. Normal dirty...
-When i pulled spark plugs they really looked bad... ceramic was looking horrible, etc. Could have been from the overheating 2k miles ago though...
-Checked grounds that I could find.. Maybe worth a grounding kit? (I could make my own w/ 8 guage wire) but I'm not sure if that would be good or not.

I'm leaning towards a cat...but don't want to spend 300+ dollars and find out that wasn't it. I suppose I could pull it out to see what it looks like.

start by swopping the spark plugs however when was the last time that they were changed if it was within the past 6-8k there may be a more underlying issue here with the combustion mix for whatever reason. maybe some oil has gotten onto your MAF sensor in the air pipe perhaps filthy filter? ust throwing idea out there really.

Spark plugs and wires were changed along w/ the coil pack after I discovered the rough idle...

I'm wondering about other things like crankshaft position sensor, etc...

OBD-II Trouble Code: P0300 Random/Multiple Cylinder Misfire Detected

worth reading the symptoms describes the issues that you are having which link nicely into the p1781 code information below.

P0700 Transmission Control System TCS Malfunction

doing a little reserch into this i take it that your car is auto? if so the reserch that i am coming up with is saying your throtal body positioning sensor is the issue perhaps


http://www-odi.nhtsa.dot.gov/owners/SearchVehicles fill in the details for our car and this is the information that comes up that i found relating to the error code. may be esiest after entering the details to run a find on page search going through the pages one at a time.

Quote:

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Service Bulletin No.: 050601030
Component(s): ENGINE AND ENGINE COOLING

NHTSA ID Number: 10017820

All Products Associated with this Service Bulletin http://www-odi.nhtsa.dot.gov/owners/...range-down.png

Details http://www-odi.nhtsa.dot.gov/owners/.../orange-up.png

0 Associated Documents

Manufacturer: General Motors LLC
SUMMARY:

1.6L L91 INTERMITTENT MISFIRE COLD DURING DECELERATION OR STEADY STATE HIGHWAY DRIVING AFTER COLD START WITH DTC'S P0300, P0700, P1781 AND/OR U0401 SET (REPLACE VALVES AND VALVE STEM SEALS) *TT UPDATED 11/02/07 *NJ

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so in conclusion possibly one of two or both things.
1: bent exhaust valves (if my reserch is correct these will be the damaged valves) could have been damaged when the car over heated.

2: throtal body positioning sesnsor is not reading corectly would cause rough idle and transmision issues as the engine doesn't know exactly whats going on at this point confusing it.

i personaly would lean towards the bent valves maybe have a compresion test done just in case it is this.

Talked to my mechanic who does the head work and compression tested it a few weeks ago after the overheat. Compression test was good then and he was almost leaning towards the catalytic converter heating up w/ the engine light blinking on/off. He's gonna take a look and run it through a better diagnostic tool that will show him the manufacture codes.

whilehe's got it in for what it's worth may be quick double check as it only takes a microscopic bend to cause all sorts of issues. but yeah once you get the actualy manufacture codes it will give a much clearer picture of what is going on.

OBD-II Trouble Code: P0138 Oxygen Sensor Circuit High Voltage (Bank1, Sensor2)

explains the code

it is the rear o2 sensor i personaly got my pre cat one off ebay was a risk however it's had no isses since replacement about 18 months ago. was only about a third of the price.

i know i skimmed the thread for the most part, but i missed where he said the p0138 code is set with the light?

What are the current codes? I would suggest a throttle body cleaning with the what i am reading, but it seems to point more directly to the coilpack. But you already replaced that.