2003 996TT. 71k miles. Manual. EPL tune, EVO intake, 5 bar FPR, lots of other mods.

Hard to say when this may have started, I bought the car about a year ago. I'd say it only just started recently.

When I am in second gear, say driving thru a parking lot - I take my foot off the throttle and coast.
I should continue to slow to an eventual stop (assuming I am on a flat surface or an incline). However, my car continues to go as if it is still being fed gas - not accelerating but continuing at a steady pace. RPMs remain constant as if I were at a stop and idleing (@1k).
Maintenance in the past year = rebuilt diverter valves, replaced all boost hoses, replaced N75...I'd say I am in very good shape regarding hoses and connections. I replaced sparks and coilpacks @4 months ago - coilpacks were toast (likely stock), sparks were in good shape. New fuel filter.

Not sure if any codes are preset (no reader - I know)

I have not yet tried coasting in 1st or 3rd gear to see if I get the same results.

I'm thinking dirty throttle body?
Any thoughts?

 

If you pull it out of gear, does the engine rev?
-V

 

From my memory...no, but I'll try it tomorrow.

 

(!) you said "idle @ 1k"? that doesn't sound right. did you mean that? you should idle at 750/800 max. (2) does your idle "hunt" up/down btw 750 and 1000 rpm? if so.. could be a leak.. or a dirty/failing maf..

then i would work my way toward the TB. but not on my own.

 

More info.
At idle, upon cold start - it will hunt a bit between 1k and the first hashmark below 1k. Will settle to here, just below 1k =




I tried coasting in gear in 1st, 2nd, 3rd - all exhibited the same problem where I would not coast to a stop / stall - I kept going. In second gear, the tach settled here as I continued forward - just below 1k, speed was maintained - registering 10mph


When I took it out of gear, there was a small blip to just over 1k, then back down.

Also, which may be of note - I do have a 964RS LWFW and Clutchmasters clutch. The previous owner had a custom tune done at EPL after this work, assume with the LWFW, the tune needs to play with the Rev settings so you don't stall. My idle RPM number has always been here since I got the car - assumed this was normal. However I had never noticed the continuing to move when in gear and off the throttle.

 

vacuum leak

 

... and there you have it. get whoever did the work to check all their hoses again.
idle should be solid 750 when warm. no hunting. though i suppose its possible two issues.. maybe the tb IS dirty but first sort the leak.

 

Thanks for the leads.
The last set of work done (most recently) was replacing all boost hoses with silicone hoses. Sorry for my ignorance, but would those be considered part of the vac system? If so, then it is a good bet that this issue was related to that install.

I had other work done @8 months ago for the DV rebuild and the N75 replacement - that was too long ago..but turbos are turbos and this is how it goes.

 

that's your second clue. the only pro in the thread also said it sounds like a leak also.. so.. hoses are the first place to look.. esp since you know there was work done involving same.

relatively simple to check the install. have you told the shop of the issues? they should know instantly that a leak could be present with those symptoms and they recently replaced hoses. but it will really suck if the folks you use left stuff "un" done as it were. doesn't sound major though. GL w it.

 

Bingo. Reason I asked.
-V

 

Wrap up after having a shop do full diags -

Yes, it was a significant vacuum leak, traced to the intake manifold sleeves. They will replace all 6 of them and possibly something else once they get in there. It must be buried as labor cost is $1,500, parts are @$250.

They will have the plenum fully exposed so I could upgrade that as well for +$1k for the part - but I think I'll pass.

 

glad you got it sorted. wow that's a lotta labor $. i'd wanna know what that "somthin else " might be at those rates. but doesn't matter. cars running again and thats what matters.

 

Yea - I am pretty frustrated with all of this labor cost. Welcome to 911 ownership...I guess