Cold Start Rough Idle
 

So, my 7mgte just randomly started to cold start rough and after warming almost seems to miss fire every once in a great while, though after it warms up the roughness go away. I checked the ISCV and it was pretty clogged so I cleaned that out and it did not improve the rough idle, I did a compression test and it came out good, also did a chemical leak down test which came back negative. So I ruled out a bad head gasket and clogged ISCV, I also checked as best I could for vacuum and intake leaks, I found none that were visible. So what I'm hoping for is basically just some ideas.

Oh yeah pulled the plugs and they looked in good condition and the wires only have 20k on em.

Bump... No ideas?

Just throwing out ideas here i'm no expert but...

As for the cold starting, have you checked the cold start injector?

Also, the miss every great while... Is that a full miss or just a lil bump, my celica and supra both always kinda bump a lil bit while idling not really a miss tho.

Feels like a complete miss every once in awhile, it has no real rhythm but I can definitely feel a miss in the exhaust pipe pressure, I have not checked the cold start injector. Any idea on the average life of this part? I pretty much have been slowling replacing everything in an effort to do a complete restore when it hit 100k miles last month.

Also another thing that I did read about is the HAC sensor, anyone know if that component failed would it cause my issues?

If you're doing a full restore piece by piece anyway. You may want to go ahead and do the fuel filter next... And if you can do it all at once, go ahead and do the fuel pump while your at it. I've seen a clogged fuel filter cause that kind of thing before... not on a supra, but, same principle. I'm going to do that on mine as soon as I get it turning over again =p

Yeah for 25 bucks I can go get an upgraded TRD fuel filter from the corner, might as well do it now.

Saving for a better fuel pump... so for now I can definitely throw the 25 at the filter.

Cool, let us know if that works out I'll cross my fingers for ya.

Ordered filter will put it on thursday when I have a little bit of extra time, but before that, my god damn hatch stopped working today... I of course can't get to the fuel filter without access to the metal plate in the back of the car, anyone know how to release the latch without being able to use the pulley cable or key? Also the trim on the back hatch seems to be on the other side of the latch making it impossible to remove without cutting a slit... I'd like to avoid this... help meeeee...

I think I found an old post that might have had pictures of underneath the center plastic panel in the rear hatch, they have been deleted or moved... anyone might know where those pics went? Or could possibly take some so im not so blindly trying to stuff my fat ass underneath the hatch while its closed ;;

Fixed the hatch, had to make a small cut on the lip that went around the hatch latch to get the center interior cover off and the wire had simply come off the lever, Used a small knife with a lighter to make an unnoticeable cut so if I ever have the same problem I can fix it in seconds.

Ok so im getting the fuel filter tomorrow, so I decided hell maybe the 91 octane I had wasnt helping, went to the local shell and put 96 octane in. With the 91 octane it was constantly running rough on every cold start, with the 96 octane it only runs rough on the first cold start of the day but after a much shorter amount of time the rpms will kick up about 300 rpm and it smooths out instantly, as before the rough idle would just slowly go away after it got completely warm, with the good gas it will run rough for about a minute then rpms will just up slightly and smooth, I'm still going to replace the fuel filter seems like it needs it regaurdless, but is there anything else that could be wrong? How can I check the cold start injector and does anyone have good pics?

I've never had so much trouble ordering a common part before, I have been waiting for pepboys to get me this fuel filter since monday or tuesday damn. Let you know how it runs when I get it.

Ok, So I put in the fuel filter and it helped, but did not fix the rough idle on start up. So I pulled out all the spark plug wires again took them up to wyotech and tested them, all came back good, tested all my spark plugs also came back good at both places I tested them. So I said fuck it, since I had one extra spark plug, started with replacing cylinder #1 spark plug, still rough idled, then moved the good plug to cylinder #6, rough idle went away but now I can really feel the miss fire, I almost want to say its inconsistently missing 2 cylinders... Coil pack? If I remember correctly the coil packs are 1 per 2 cylinders, get back to me please, the problems almost fixed!

Yes, the gte uses a wasted spark ignition. The ge uses one coil connected to a distributor cap. I know 1 and 6 share a coil but dont remember the order of the rest. Its posted in numerous places. There are tests to determine a bad coil in the tsrm. You can sometimes spot tiny cracks in the plastic and epoxy on them if you just take them off and look closely at them. I've even seen the plastic surrounding the connector terminal crack and corrode inside causing intermittent misfires.
Have you checked the timing? I've noticed on many cars that prior owners/mechanics will adjust the timing to mask other problems (vacuum leaks, tune up, bad sensors,etc.), so when you start fixing those problems the timing sometimes winds up needing adjustment. My opinion is, it's always a good idea (though not always necessary) to check timing after repairing things relevant to drivability issues. Try checking it, it's free and who knows, you might get lucky.

I was able to check the main coil on the coil packs but after reading there is a secondary coil inside that is... uncheckable, or atleast I can't figure out how to check the secondary, after checking the mains they tested good.

Doesn't feel like a timing issue but im no pro, its next on the check list.

The secondary winding can only be checked using an oscilloscope as far as I know. There is also a device that measures Kilo volts using an inductive clamp somewhat like a timing gun. Though i'm not really sure if it will tell you if the coil is bad, only that there is increased or decreased resistance to current inside the cylinder. I'm sure someone here knows more about it than myself. Hopefully they will comment. Definitely one of those cases where having a known good part to swap or compare would be useful.
You shouldn't use the "feel" method especially with a computer controlled car. The computer can change the "feel" by adjusting fuel and timing to compensate for discrepancies (issues, driving habits) even while you drive. They are surprisingly active little boxes for the technology. The only way to know for sure that the timing is correct is to actually check it which is very easy. It may not be the cause of your problem, but it would be free to eliminate it as a suspect. Also make sure the crank pulley is in good condition, a worn and shifted pulley will throw off the timing mark.

Check the cold start time switch can cause this. Mine is doing the same thing now and I already replace every vacuum line on mine so on to the next thing now.

same happened to me,
i replaced the bvsv (becuz mine was cracked, maybe this is happening to you?{its located right above the radiator, to the left if your facing the engine)
its part number 23262
http://www.cygnusx1.net/Supra/Librar...spx?F=1708&P=3
you can get this from driftmotion.com or rock auto.

i did that and it still didnt work...
i noticed my valve covers were leaking...BAM.. did a valve repair job and im on my way...

hope this helps..
also if this is an automatic car then your syncros? may be bad...people rule that out but honestly even with the valve cover repair and the bvsv it still did it abit...i did an auto to manual and i dont have that problem anymore.