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Discussion Starter · #1 · (Edited)
so this seems to be a common problem, but i am not finding my exact problem. we have the 3.8l v6

when we first test drove the car. it has bad shaking in idle, or traffic, stop sign. buddy switched a sensor, not mass flow, but one beside it.
turned out it was mainly the auto start. the seller/dealer figured it out it was that after doing tones of tests. it was kind of the last thing to test/rule out. they cut the "purple wire" and it got 95% better. the auto start isn't removed. (which i think should still come out)

so we decided to buy it. assuming maybe it was the sitting. OH!!the other thing is it was sitting 4-6 months. maybe closer to 4.

so the next week,a little bit of the roughness returned, a bit. if i but it in neutral its ok. park, OK.

my buddy is a mechanic at a GM dealer, and he is helping me on the side. he computer says cylinder 3 misfire, in idle, but as soon as you give it gas, it disappears. so as the flow goes up, its gone.
(over different days)

tried fuel injector cleaner. ran line new for 1.5 days

next, we found cylinder 4 plug was loose, fixed that.

he did the fuel pressure test, all is good, injectors aren't perfect, but should be the problem.

spark plug wire 3 broke as we took it off one of the last time so we changed them all. still there

found out on another test the spark wasn't constant. made sense, change the coil. tested spark was great.

after changing the cables and coil it actually felt pretty good again. little roughness in traffic. but it has returned today.

its got my friend at GM scratching his head also.

so what the hell can it be??? i seen someone mention seafoam. i heard mixed things about this. but maybe it woudl help if the valves are gunked up??
any other idea.
seen people mention catalytic converter, it's new but not factor. i don't see the connection with that and the exhaust

any help would be appreciated



code show the misfire on 3.
 

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Sounds like there are a few things that are wrong.... I can almost tell you that the Remote Start isn't at fault lol... I love how so many people put fault on after market items as a way to stress of not knowing what the problem is... I am going to take that your talking about removing the Wire from the OBDII port purple wire? If that is the case there is 0% chance that has anything to do with your car and a missfire...

Not sure what Auto Start your car has in it but if you were in my area I would be willing to Remove it for you at no cost other then to Keep the unit...

I am going to say from what I have read and seeing I am not in front of the car it is really hard to say. But I think your problem is a short somewhere in your car. This is not related to the aftermarket RS unless it was installed by a Fly by night that don't care...

If you were telling me that the car wouldn't start, and that it won't crank. Then and only then maybe I might think it was related to the RS or an aftermarket Alarm system... Not in the area of the Purple Wire again if your talking about the one for your OBDII There are so many computers that run our cars today and one talks to another one over data lines, and there is test that are being run over sensors and switches all the time the car is running...

If this was my CAR and I wanted to know what was wrong with it, I would (in your case) use your friends OBD II scanner and set up some live data testing and take the car on a test drive. Look over your MAF, your trims, your RPM, your speeds, 02 and a few other things that may need to be looked over related to spark and what not... This is after making sure the Battery is fully charged, The car isn't so out of timing from bad plugs and wires if they are old or fouled. I would replace them... Then after all that I would make sure before I go anywhere that was no leaks, or shorts, Could be done in many different ways... Once I am sure there isn;t anything that I can see or touch wrong with it. Then take for the Drive look over the data and find out what the right data should be. Find something wrong then do more testing with that item to make sure it is at fault and not just a short or bad connector...

Buying cars today isn't like cars from the 70's or before loads of computers and things that can go wrong.... Don't always fault the RS systems lol Most times they were put in by people with many hours of training. Some are MECP certified kind of like a Mechanic can be ASE kind of thing.

Keep us informed on what the resolution ends up being. (Won't buy it personally being RS as there is no connection for timing or spark)

James
 

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Oh and Forgot about the Rough in traffic.. That could be related to bad Motor mounts, struts, and even a bad Sub Frame from a accident that may or may not have been known. Trust me, Sub frame damage that isn't seen, is hard to find at times... Drive the car a few hundred miles in a car with a bad sub frame you will know it later lol... IT don't always shake and dance but does enough to make your body remember when the drive is over lol...

Easiest way to look at bad motor mounts by your self is to have Hood OPen, car off in park semi flat ground slight angle facing the front of car. Put your knee on the bumper and psh back the car as far as it moves, Then let it go when it goes back to the locked park area the motor would JOLT rather well.. If little to no movement in the motor then your mounts are most likely ok. This is again needing some movement to back and letting it free move back to locked park. IF your around someone... You can do it another way but is hard because I don't ever put my life in another persons hands.. LOL.. But Parking brake on. Left Foot on brake, HOOD open, car running, person (Your Self) looking at motor (Would be off to the side) have the person put the transmission in to drive. Then with the RIGHT FOOT as the left one is still holding the brake.. Have them give it some gas and see if the motor tries to move out of the car lol... We don't want them to punch the gas. Just giving it a little gas will do... Might be smart to not be around anywhere something can get damaged from a car that rockets from someone not doing it right... Just saying..

James
 

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Discussion Starter · #4 ·
thanks James.

maybe i see if i can get his computer and him and do the test drive thing. plus i will look around for some exposed wires that could be shorrting it. but if that is the case why would it go away with more gas?
 

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Thought! If there was a short say to ground, It could be that with more gas flow the motor moves just enough to take what ever the short is off so it is no longer a short but in working order! This going on the idea of maybe having bad motor mounts as well. But really even without bad mounts there could be enough movement in the wiring to make things short or clear a short

Same idea with bad wiring in the connectors. Maybe moves enough to make a sensor not like the data that it is getting because it is failing at the plug! Sadly I don't make the reasons only things that I have seen in the past...

I am not saying you have a short, I am just saying that for what I would do is test all areas of thought before parts so only install Parts needed.
 

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Discussion Starter · #6 ·
but the rough in traffic. I think is from the misfire in cylinder 3. so i am not seeing the connection to the motor mounts.

Plus i forgot, sometimes it starts one turn, other times its a bitch to get going without holding the gas. this i assumed is to were the car shut off and cylinder 3 being in a up or low position and it misfire, and the lack of flow.
 

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Sorry I guess it is hard to understand all that is going on. Hard to convey what has or may have happen to another person so they try and give ideas of what things may or may not be as a way to help...

Sadly I am not there to be able to hook up scanner and set some pids and do some Real World testing. I understand you were talking about a Mis Fire, That was in with my whole bunch of things that could be wrong. Mis fire still there after repair? Not sure I am not there!!! SO I was also offering that the rough in traffic could be related to another issue all together... Could be like it has been for other and or my self where there was motor mount damage or even Sub frame Damage. This makes the car or can make the car rough, Not normally at idle but more when taking off, or around mild driving times. Some times up to as high as 60 MPH and let off gas smooths out, But want to pick up speed even at that speed it may or may not act rough..

Back to my last answer, I don't know seeing I wasn't there, Then you asked how could it be related to bad mount and or short... So I answered in what could happen with a Short also on a car with bad mounts to even one without bad mounts.. and a short could cause the car to get false reading from the computer and may or may not be related to your mis fire.

I guess in the end. This car had problems from what it sounds like at the car lot where you bought it! I would assume that it wasn't a GM car lot and that you got the car for a cheap enough price because they wanted to dump it... With mind telling someone that it has to be Related to an Aftermarket RS (Again No Relation) as someone looking for a car has accepted the car in like condition with mind that it may need some work. Sadly I am not there, I can't put my Scanner on it, Check it with my scope or do any testing for shorts or any other things other then give some general ideas of what the problem maybe and a place to look over to try and help someone with like for cars and help with ideas to try and save the person money by not buying un needed parts.

I guess one of the things. I read the post and all these parts or sounds like parts were used. Coil tested then good spark? So i took that you replaced part tested and now good spark over the bad you had before! Again I am not there it is hard to know what is what. Mis fire most times can be related to Spark, fuel, and air intake. Maybe need some more testing with scanner, looking over your MAF, Trims, RPM, speed, 02 data, and other items that may be related to advancement of spark that your scanner is able to test. With some scanners they can pull data off the computer of history and maybe able to find what the issue is looking over data when the last code was set... Sorry I couldn't be more helpful. Wish you luck and hope your car gives you many years of happiness. Love my Impala's, My youngest son. (Not really young just under 30) but always says you wouldn't trade any of your cars for (This car) some in high price I was always like no. Until the last time he asked if I would for a VET we were Sitting next to at a light. I was Sure. HE looked at me in Shock... lol As light changed I told him I wouldn't drive it to anywhere but home and then Sell it for 10k under book so I could buy a few more Impala's lol

James
 

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Discussion Starter · #8 ·
no problem. thanks for your thoughts on the problem.
i am going to try and look for shorts to be save.

i bought it off a mechanic. but i think he was more just the guy that did breaks & tires. cutting the wire for the RS really helped. i know. casue they just cut it. a few days after we had it. it got rougher, again. i looked and the 2 ends of the wire where basically touching/overlapping. i moved them and tapped them the car was 95% better again.

i am still going to go get it ripped out. 50$ for piece of mind.
 

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I would be interested in what the RS is your talking about and the the Purple wire your talking about as well... In fact if you have the Model # and both remotes for the unit maybe take a picture of one of the Remotes and upload it here... I know there is a Purple Wire for our ODBII port (Hope that wasn't the wire they cut) However, Another thing I can think of that has a Purple wire is only from one of the units I know where that wire goes to the Brake Peddle to de-activate the RS and act as a safe kill if someone tries to jump in while it is running without key in. When press brake the RS shuts off.. There are other units with a Purple Wire as well. Another that comes to mind is Avtistart 4103 and some others by DEI. The Heavy Gauge Purple wire from Brain would be to the Starter wire Only function is to start car... Or a smaller gauge wire purple/black or white I can't remember to many darn wire colors to remember lol... But that one is Input to the AlarmRS only for Tach. Reads tach info of car for Alarm brain to know it is not over revving the motor if to high motor is shut off, Again only for alarm and only shut off if ALARM RS was actively running the car. None of them would effect the ability of a car to run.

Let me know what it is when you have it removed. Tell them you want to keep it, and maybe if good enough Brand I will pay the 50 you had to pay for your Peace of mind and toss in 20 for shipping seeing it wouldn't cost no where close to ship to me... And I will take it off your hands.. Hope for the 50$ your going to pay for its removal they will do a better job then just Ripping it out... I charged 40, Didn't leave trace anything was ever installed, Taped all areas back with Good Scotch Super 33+ Black tape. I have been in some cars where it was cut out and all the wires were just hanging there inch or more from connector or even unplugged but connectors still in place... When i work on a car like that I let the customer know before any work is preformed, offer to repair or they sign a release before work starts..

Sorry your having problems with your car. I do hope you can find out what it is soon.

James
 
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