DIY: Rough idle in cold start/cold temps LGT 07-09

And ready to push the car into a lake. So a chunk of the gasket came off when trying to wrangle it back out...I assume it went down past the TVG's. Soooo now what? Deal with fuel rails and take off the manifold? Guess so. ARGH And any write ups on that? Can't seem to find anything complete

 

EDIT: Since it's small and rubber it will prob burn up, worst case stuck in a valve for a few sec until it melt :/

 

Also looks like it was both gaskets leaking on the driver side. Ordering 2 more, since I know I'll destroy them getting them out.

 

Any way to test for leaks before putting everything back together?

Edited March 21, 2015 by gimpydingo

I'll be giving this a try on saturday, hoping it solves my issues. Found sets of 4 on ebay for $17 shipped if anyones interested

 

http://tinyurl.com/mafyuhf

I'll be giving this a try on saturday, hoping it solves my issues. Found sets of 4 on ebay for $17 shipped if anyones interested

 

http://tinyurl.com/mafyuhf

 

Good luck.

Just replaced the intake gaskets to try and fix a warm/hot idle p0171 problem that otherwise matched all the cold idle problems.

 

Yes, that was it!

 

Also - no more weird pulsing sound. I figure one of them was leaking, causing that - and that seems to have been true. Tip when assembling - use high-tack gasket spray to hold them in place while you line up the manifold with the ports.

 

Bryan

Edited September 7, 2015 by hallkbrdz

I just replaced these gaskets on my '07. Not cold enough yet to see a change, but by looking at the difference between the old and new rings, I am sure this will be it.

 

By the way, this job was a major PITA. It's certainly doable (with a lot of patience), but the gasket on the driver's side closest to the firewall is near impossible to reach. Once all the gaskets are out, it's a cakewalk, but until then, have something to punch in your garage.

but until then, have something to punch in your garage.

 

ahhah! Good to know!

well, just completed this and the trottle body oring. Wasn't to bad of a job but I have a massive vacuum leak, it reads 0 vacuum. I torqued the mani down tot he proper 71 inch lbs but no go. PUll it back up and reinspected, all are seated into the receese and intact. Not sure what to do at this point.

well, just completed this and the trottle body oring. Wasn't to bad of a job but I have a massive vacuum leak, it reads 0 vacuum. I torqued the mani down tot he proper 71 inch lbs but no go. PUll it back up and reinspected, all are seated into the receese and intact. Not sure what to do at this point.

How much vacuum do you see when the motor is running? Hahah jk

If you're getting zero vacuum it must be a huge leak.

Stupid question... Is your throttle body to IC hose attached?

How much vacuum do you see when the motor is running? Hahah jk

If you're getting zero vacuum it must be a huge leak.

Stupid question... Is your throttle body to IC hose attached?

 

And not a stupid question, but hoping it is just something stupid

 

Yea, all is connected and tightened. I have done it 2 times now, removing checing gasket and reinstalling and nothing. I still need to give it one more try and make sure the throttle body is sitting flush. If that doesn't work, I am not sure if I should try and tighten down on the gasket till I see it get vacuum.

 

Also the throttle body only has the oring correct?

Just did this on my 2005 LGT since I got my first CEL last week when the weather dipped into the low 50s. Took about 4 hours, really not bad at all, could probably do it in 2.5 or so next time. The only pain in the ass access point was the rear inside bolt on the passenger side manifold; to get it you need to unbolt the wiring harness plastic cover behind the manifold and wedge something in there to hold it away, then nudge aside a little hose that sits directly over the bolt.

 

Dental pick isn't expressly required but it really is the perfect tool for the job - get one with a single oblique angle, not with a 90° bend. The gasket access point is the little tab that sticks out, all of which I managed to shear off during removal but jamming a fine square-headed screwdriver into the slot let me get it started and then sliding the pick around got the rest out. New gaskets were about twice as thick as the old ones. I used my cheap hand vacuum pump to remove the coolant from the reservoir before disconnecting but still got coolant everywhere.

 

We'll see if it solves the winter CELs or makes it idle smoother. It was a good thing to do regardless as it didn't look like the old gaskets were forming much of a seal anymore.

About to tackle this this afternoon.

How did it go? Did it cure your rough idle?

Haven't done a cold start yet since doing it. I'll know tomorrow morning for sure. I didn't really have a rough idle I had a bit of a stumble between 2k-3k RPM when cold.

Has anyone used these IM gaskets?

 

 

http://www.rallysportdirect.com/shop/product/sub-14075aa161-subaru-intake-manifold-to-tumbler-gasket

Are the new updated orings still orange? and does anyone have the new part numbers?

 

Just placed the order but i did not order orings for the throttle body. ill need to get part number for that unless someone has part number for that.

Has anyone used these IM gaskets?

 

http://www.rallysportdirect.com/shop/product/sub-14075aa161-subaru-intake-manifold-to-tumbler-gasket

I've always wondered what those are for... are they instead of, or in addition to the orange o-rings?

 

Are the new updated orings still orange? and does anyone have the new part numbers?

When I installed new ones about a year ago they were orange. The old ones were also orange, but noticeably smaller.

From the original post "The part number for the new o-rings is #14035AA492"

 

Just placed the order but i did not order orings for the throttle body. ill need to get part number for that unless someone has part number for that.

Per RockAuto.com the p/n for the TB o-ring is 16175AA331 (or 16175AA330 ?).

The updated IM gaskets I installed recently were orange as well and the part number StkmltS listed is correct. I still have a bit of a stumble between 2-3k on cold starts but not near as bad as it was before. Thinking it might be the fuel pump? And I have one to install in January.

I think this is the "water hammer" effect of the fuel line setup. Adding an inline filter and/or extending the fuel line in the engine bay is supposed to help I think.

It looks like there are several people who've gone through some pretty extensive (expensive) trial-and-error stuff trying to banish the stumble, and from what I've read on here and on NASIOC it seems like replacing the OEM fuel pressure regulator from an '07 or older STI fixes the stumble.

Here's one of the easy-to-read threads.

 

Adding an inline filter or extending the lines sounds like it would be a cheaper solution to accomplish the same thing, it's just not as "correct" as replacing the FPR because it doesn't address the root cause of the stumble. I'm not correcting what you said, I'm just mentioning it for the good of the generic internet population. The stumble isn't doing any damage to the motor, so it really just comes down to how much #BecauseRacecar dedication you have... and how much extra cash you have to spend on replacing something that isn't actually broken.

Edited December 1, 2015 by StkmltS

And not a stupid question, but hoping it is just something stupid

 

Yea, all is connected and tightened. I have done it 2 times now, removing checing gasket and reinstalling and nothing. I still need to give it one more try and make sure the throttle body is sitting flush. If that doesn't work, I am not sure if I should try and tighten down on the gasket till I see it get vacuum.

 

Also the throttle body only has the oring correct?

 

So it ended up being the main vacuum line ont he backside of the mainfold directly in the middle that caused the 0 idle condition. Pushed it back on, zip tied and all good to go.

i placed an order for some grimmspead gaskets....i want to do this 1 time and be done.

Did this today and it didn't solve my misfires on cylinder #4 and #1. Noticed that the new gaskets were thicker than the old ones. Already replaced plugs and swapped coil packs, also checked the coil pack wiring. Considered swapping the injectors around to see what would happen, but couldn't figure out a way to get to them, so I took my chances with the gaskets and here I am again at the beginning, it seems. When I had the banjo bolt filters removed last year, they smoke checked everything and I remembered them telling me that there was no vacuum leak, but I will double check that. Now I guess the only thing I can do is a compression test...unless someone has another idea...

Did this today and it didn't solve my misfires on cylinder #4 and #1. Noticed that the new gaskets were thicker than the old ones. Already replaced plugs and swapped coil packs, also checked the coil pack wiring. Considered swapping the injectors around to see what would happen, but couldn't figure out a way to get to them, so I took my chances with the gaskets and here I am again at the beginning, it seems. When I had the banjo bolt filters removed last year, they smoke checked everything and I remembered them telling me that there was no vacuum leak, but I will double check that. Now I guess the only thing I can do is a compression test...unless someone has another idea...

 

A compression test and/or a leakdown test should give you more info on how to fix the root problem. If it checks out OK read the first post in my misfire thread (link below) for a ton of cheap and/or easy things to try. Nothing I tried could fix my problem because I ended up finding a cracked piston. Hopefully your story turns out better.

Did the compression test, here are the results (cold engine btw):

 

Cylinder #1 dry 130, wet 110

Cylinder #2 dry 110, wet 113

Cylinder #3 dry 130, wet 126

Cylinder #4 dry 107, wet 103

 

I'm wondering why the driver's side is lower than the passenger's one.

 

Also checked for vacuum leaks with carb cleaner, found none. Test drove the car, no CEL and it drove great. This morning I let the cold car idle in the garage and monitored the misfires with Rom Raider. For a minute there were none at all and I was getting hopeful, but then the count on #4 just shot up and the CEL came on eventually. See attached image for graph on the misfire count over time and engine speed.

 

Also, there are some misfires on all of the other cylinders from time to time, but no more than one or two before the counter resets.

 

So, I'm wondering the following:

 

- Why did the misfires show up only after a minute or so and not right away? What changed within that one minute that could trigger them?

- If everything were normal in the other cylinders, the misfire count there should be zero, right?

- Can one or two misfires be dismissed?

- Can it still be the fuel injectors if I'm seeing misfires in pretty much all cylinders? Maybe we need to look at the bigger picture?

 

Thanks for the advice, StkmltS, I will check your post. For now my suspicions lie with fuel delivery since I already excluded ignition and combustion air.

Edited January 28, 2016 by Rob van Halen
Added graph, clarifications