im about to take my car to gm and see if they can find out
what could be the cause of a miss the first 15-45 seconds after starting my car in the morning when its dead cold?
i believe this is also my cause of a miss while running after warm!
no hesitation to start. but starts and misses its butt off
its not the opti, i have a brand new one. i also have ngk tr55 gapped to .50, and new wires
it did this before the opti wire and plug change and after

 

man i was just about to post the same question. my car has done that a few times lately as well.. when i start it. it kind of sounds like its cammin..

anyone have any ideas?

 

Well if you have headers and it misses as bad as you say it does, it is easy to find the missing cylinder. From dead cold, start it up and quickly check the temp of all the primaries with an IR thermometer. The primarie(s) that stay much colder than the rest are not firing at the time. You could wait until it starts to run smoother to see if the suspect primary then begins to shoot up in temp.

Now you could do one of a couple things at that point. You could shut er down and let it cool off again and then put an inductive timing light on the plug wire that is suspect and see if it shows the pattern of miss firing. Of course since you did the ignition system work you could skip this part for now and go to the injectors.

Or you could swap the injector with one from a good cylinder and see if the problem follows the injector. My thinking here is maybe the injector is sticking until it heats up. The GM Motec suffers this problem however I have not heard of the problem occuring in the Bosch style injectors. But who knows

Last if you are sure there is good spark to the suspect cylinder and swapping injectors doesn't cure the problem, do a leakdown test both at dead cold and then again when it's warm.

If you do take it to GM, don't mention anything about what you replaced. I guarantee you they will say it needs a new opti. HOWEVER, make it clear that you only wish to have a diagnosis, no work will be done until you approve it. Ask what the minimum charge is and if diagnosis is one of the minimum charges or if it carries it's own charge. Ask if they have an hourly shop labor rate and if so, what is it. Before you give any approval for repair, make it clear that you will not pay for any repair if you do not receive the defective part. Write it on the WO when you sign it if you feel comfortable doing so. Be leary if you receive a part that is physically broken that doesn't appear to have to been broken to remove it.

Also, be very suspect of any repair that is done to some part and then there is another part and another corresponding charge on the bill. This is usually caused by a mechanic taking a guess at the problem that doesn't repair the problem and then the second part actually repairs the problem. That's not to say there isn't the possibility of two bad components but if they are wrong in the first case, you should not have to pay for it. Thus the reason for receiving the defect part and of course a little forethought and being allowed to think about the repair before giving approval.

Sorry for ranting just trying to help protect fellow board members from being taken to the cleaners.

 

why cant i tell them that i have a brand new opti and plugs and wires along with o2 and maf ect???

and ive done the temperature test and with only running about 20 seconds the rear 2 headers are 20-30 degres colder than the rest, which are all within 10 degrees of eachother
thanks