Cold Start Rough Idle

916MKIIIx2 · 05-23-2011, 12:07 AM

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.

916MKIIIx2 · 05-23-2011, 05:55 PM

Bump... No ideas?

chezpo0f · 05-23-2011, 07:42 PM

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.

916MKIIIx2 · 05-23-2011, 08:24 PM

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?

chezpo0f · 05-23-2011, 08:37 PM

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

916MKIIIx2 · 05-23-2011, 08:40 PM

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.

chezpo0f · 05-23-2011, 08:42 PM

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

916MKIIIx2 · 05-25-2011, 12:48 AM

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 ;;

916MKIIIx2 · 05-25-2011, 07:06 PM

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.

916MKIIIx2 · 05-25-2011, 07:13 PM

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?

05-23-2011, 12:07 AM	#1
916MKIIIx2 3" Exhaust Join Date: Nov 2008 Location: California Posts: 152	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.

05-23-2011, 07:42 PM	#3
chezpo0f Stock Join Date: May 2011 Location: Mississippi Posts: 8	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. __________________ 1990 Mk3 Supra completely stock 1985 Celica GT stock minus .20 over-sized pistons

05-23-2011, 08:24 PM	#4
916MKIIIx2 3" Exhaust Join Date: Nov 2008 Location: California Posts: 152	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? Last edited by 916MKIIIx2; 05-23-2011 at 08:38 PM.

05-23-2011, 08:37 PM	#5
chezpo0f Stock Join Date: May 2011 Location: Mississippi Posts: 8	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 __________________ 1990 Mk3 Supra completely stock 1985 Celica GT stock minus .20 over-sized pistons

05-23-2011, 08:42 PM	#7
chezpo0f Stock Join Date: May 2011 Location: Mississippi Posts: 8	Cool, let us know if that works out I'll cross my fingers for ya. __________________ 1990 Mk3 Supra completely stock 1985 Celica GT stock minus .20 over-sized pistons

05-23-2011, 05:55 PM	#2
916MKIIIx2 3" Exhaust Join Date: Nov 2008 Location: California Posts: 152	Bump... No ideas?

05-23-2011, 08:40 PM	#6
916MKIIIx2 3" Exhaust Join Date: Nov 2008 Location: California Posts: 152	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.

05-25-2011, 12:48 AM	#8
916MKIIIx2 3" Exhaust Join Date: Nov 2008 Location: California Posts: 152	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 ;; Last edited by 916MKIIIx2; 05-25-2011 at 01:18 AM.

05-25-2011, 07:06 PM	#9
916MKIIIx2 3" Exhaust Join Date: Nov 2008 Location: California Posts: 152	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.

05-25-2011, 07:13 PM	#10
916MKIIIx2 3" Exhaust Join Date: Nov 2008 Location: California Posts: 152	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?

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