Troubleshooting rough running - got a ScanXL graph!

Still having the problem where the car runs HORRIBLY for about 1 or 2 minutes after starting, then something "clicks" and it smooths out and runs fine.

Finally got a graph to prove it!
http://lh4.ggpht.com/_s5dIzKL6pT8/TG...14%2012.31.jpg

I started recording about 10 seconds after starting the engine. Right on the vertical white line is where the car suddenly starts running fine. It's about 60 seconds in. The green line is Ignition Timing Advance (Cylinder #1). Look how badly the RPMs are jumping around. No, that's not me doing that... :)

This time just happened to be REALLY bad - bad enough that the car almost died a couple times. It's not usually QUITE that bad, but it is pretty random from day to day. I'm glad I got a recording of this one.

So what are possible causes of the "timing advance"?

maybe the timing is off?

just did the timing belt and the marks were dead on.

If the timing was off, why would it run perfectly 99% of the time?

i cant remember if it was brought up in another thread, but did any codes pop up?


I would say check the plugs and the gaps again to double check if you have not, and maybe run some fuel injector cleaner, could also be the fuel pump

looked like it almost stalled out twice, but after the white line, why was there a spike?

my car for example sits at about 1500rpm when i turn it on for about 10 secs then drops down to 1000 rpm until it warms up, then it will stay at about 780 when im stopped at a light, warmed up

do a cold start and run the program again until the car warms up to operating temp, if it runs smooth after it warms up then the problem could be related

ahh i read the other thread again, the car is doing this to warm up, but doing it in a poor fashion, disconnect your battery for an hour or so and reset the ECU if you have not already, thats my first guess

also, are you running your A/C when the car is turned on and running? How many miles does it have?

It's done this with and without the AC on. Sometimes it's so rough it feels like it'll die if you turn the AC on while this is happening.

The battery has been disconnected for a few hours a number of times. When we did the timing belt it was probably disconnected for 4 hours or so.

I'm in denial that it might be the ignition coil... just because I decided to spend almost $200 on diagnostic equipment instead of rolling the dice and guessing that it was the $80 ignition coil. :)

Is it possible a lack of ignition is what's causing the timing advance to be so high? (take this with a grain of salt) Maybe the timing has to move further into the "cycle" to ignite the gas because the ignition is weak or missing on one or a few of the cylinders.

The other question is: is this just a SYMPTOM of something else that is wrong? I was hoping to find that a sensor was completely out of whack, but so far everything looks good.

i want to say something else is going wrong somewhere, how many miles is on it at the moment?

if the ECU has been reset, then i would also take a look at the throttle body and see if it needs to be cleaned, if it has a good amount of miles on it that is

if it only does this while its warming up, then a sensor may be reading wrong like you said, but take a look at maybe the thottle body like i said, there are several sensors and plenty of known problems related to the thottlebody

myself, i have drove some cars that have a rough idle when they are warming up and then go back to noraml when its up to operating tempature, my 98 escort had a similar problem

but there are no codes?

Sorry, I'm doing a half-assed job of conveying all the info since I already posted the other thread... should have linked to it or copied it or something.

Yeah, it gives a random cylinder misfire, but not every time. It definitely did this time. Also get a flashing HOLD light, but only when this happens and only ever at the same time when it throws the misfire code. I heard from someone that the flashing hold light was fixed when they replaced plugs, wires, and ignition coil. I'm not sure if that is related and I haven't found anything about a flashing hold light.

It's got 83k miles on it. We cleaned the throttle body when we replaced the timing belt (and water pump, timing idler, timing tensioner, and drive belt)

Any idea what sensors I should be looking at? I was thinking it might be IAT but that is reporting correctly.

i knew about the hole button but i didnt know it was mis-firing, might as well change out the coil and see what happens, but if there was an issure with it then it would be mis-firting even after the car has warmed up

i dont remember which sensors are on the TB, there are some threads on here that talk about it, but that is the only thing i can think of, anything else would be giving you trouble even after the car is warmed up, so i wonder if there is a problem with a TB , hence the rough warm up cycle

is the car in park while it warms up to normal? I think you might have missed it but why did the rpm numbers peak after the white line?

besides a sensor or the TB itself, i have seen first hand people having trouble with an auto tranny, sometimes it just not shift at all lol, there are vacuum/some kind of hose/s that lead from the engine to tranny to "tell" it when ti shift, but i think that is an unrelated problem itself

Yeah, the car is in park while it's warming up. You can drive the car while it's doing this and it will still click over and suddenly run fine just the same as if you left it sitting in Park.

The spike after the white line was me hitting the gas. I should record again with the throttle position on the graph.

Cool program! Probably total overkill for what I'm doing, but that's half the fun.

looks like a good program, im sure it has many more applications that can help you in the future

getting that new reading will help

i wonder, if all else fails, perhaps look at all of your fuses in the hood and inside of the car to see if any have gone bad, and maybe if all that does not work then take it to the dealer to see what it could be, or maybe replace the ECU (they are on ebay sometimes for cheap)

but in the end my gut says the TB is at fault

sound like your primary o2 sensor is taking too long to heat up, skimmed the rest, any codes ? i missed that answer.

seems like its just a mis-firing code, which is very helpful, would that sensor cause such a rough idle?

Quote:

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Originally Posted by thehunterooo

ahh i read the other thread again, the car is doing this to warm up, but doing it in a poor fashion, disconnect your battery for an hour or so and reset the ECU if you have not already, thats my first guess

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You could also pull the ECU fuses in the fuse panel in the driver's door jam area. Should do the same thing if you have them out for a little while. No need to wait for half hour.

Quote:

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Originally Posted by petrified.rabbit

sound like your primary o2 sensor is taking too long to heat up, skimmed the rest, any codes ? i missed that answer.

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p300 - random misfire. It's like searching the internet for "causes for a headache" LOL

If the O2 sensor is bad, any idea what I should be looking for? I can pull voltages from it (i think) in ScanXL but not sure what I'm looking for. Maybe i'll just set it to monitor that and try another recording today. I'm really just looking for whatever changes at that 1 minute mark when it smooths out.


Appreciate all the responses.

the o2 sensor wont accurately set the fuel trims until its warmed up. the primary o2 in the aveo is heated. so it comes up to temp really fast (not sure how fast) definitely under a minute i would think.

if its not coming up to temperature as soon as it should for whatever reason, that would prolong the high idle the car has, until the o2 heats up to send a proper signal. but when the signal is in and out of range until its fully heated, the ecu could jump between o2 signal and warm up, creating a rough idle.

check the o2 signal and engine load comparatively on a scan tool and see how the coincide?

older cars used to not have heated o2 sensors, so it would be in warm up, or open loop, or preset fuel trim, longer, but as part or stricter emissions we now have heated o2 sensors to get the fuel trims matched asap.