• Hello Guest, welcome to the initial stages of our new platform!
    You can find some additional information about where we are in the process of migrating the board and setting up our new software here

    Thank you for being a part of our community!

Stall & RPM Dips - Mystery

J

JulezSteele

New member
Joined
Aug 10, 2003
Location
Houston, TX
Basically my car will stall out or almost stall if I let of the throttle quick. Its really notiable with bumper to bumper stop and go - My idle will dip wicked low, engine shaking everytime i let off the gas. With the hood opened hand on throttle, I can almost stall the engine out if I rev quickly at idle(to a point of hearing the intake with the ricey bog sucking sound) (Cone Intake) , after letting off when the rpm's go back to down they dip way too low but a second later catch back up to normal. You can hear a rush of air flow back to the filter. Is air being flowed backwards tripping the AMM? I'm guessing the bypass is working, I replaced it with a brand new porshe valve. My mechanic said there is no vacume leaks at all, and my brake check valve is fine.

Ive had this problem for so long and I really dont know what to think of anymore. I just want to drive it normally. Ive replaced the IAC, tank-pump, FPR. Ive posted it up before but maybe I'll get some new ideas.

I put this in peformance related because I have +T, and it didnt happen before the conversion

-Julian
 
Gonna move it - I think you will get better response in M + P.

JB
 
I have the same issue, and I believe it is related to the CBV and/or idle stepper motor. I will post my symptoms to avoid starting another thread:

B230FT LH2.4, Turbo has integral CBV which has a small tear in it. The problem started when i put a blockoff plate on the CBV to remove the holey diaphragm from my list of "why isnt my car fast" variables. I also get a stall/low idle when suddenly letting off the gas after sharp acceleration. Problem is more pronounced with load on the engine, i.e. car in gear. Here is the big symptom that might help someone identify the problem - I am curious if you or anyone else experiences this:

When the problem occurs, my idle/decel vacuum level is noticably stronger (more vacuum) than I normally experience. Since I have a calibrated boost/vac gauge, i can read that the engine pulls approx 4.in/hg more vacuum on decel while the problem is occurring. While my engine normally pulls about 20in of mercury on deceleration, i read 24-25in/hg when the fault ocurrs. This typically only happens at cruising speeds, when I sharply release the throttle while in boost. During this time, the engine runs fine, but there is more vacuum during deceleration. If I let the motor come to idle, it will die. I can alleviate this sometimes by feathering the throttle. There is no change in running performance, only idling. Use of the brakes does not seem to affect the problem.

My theory is that, for whatever reason, the Idle Air Control motor is not opening, and the increased airflow resistance causes the higher vacuum readings. So basically the engine doesnt have enough air to breathe during deceleration. But I'm not sure if this really matches the symptoms.. So can someone answer this - If the Idle motor was not opening during idle, would the manifold vacuum increase due to the lack of available air?

Jules - Do you have a calibrated boost gauge? And also, does this happen at speed or only at idle? I am curious if you notice similar vacuum readings since we have a similar setup. For what it's worth, I had a similar problem once before when I had my stock 13c, and it turned out to be a hole in the CBV causing it, or at least the problem disappeared when I replaced the CBV diaphragm.. I have a new diaphragm for my TD05 in the mail, so I will let you know if that fixes the problem

thanks everyone,
justin
 
I have a VDO 15psi gauge but only boosting up to 4-5PSI right now
Garret T3 w/ turbonetics housing
I cant completely stall it on idle, but I can stall it while driving
Those are almost identical problems, I can prevent stalling from feathering too, I know its not my IAC cause I put a brand new one in it. I'm thinking maybe its not getting enough of a signal to open up? Theres more of a chance of stalling when the turbo is spooling up or let off under boost. You can easily stall if off the bat if you boost up a steep hill and let it roll. Glad im not the only one here :)
 
Ok, well I am glad you are having similar symptoms (you know what i mean) - Hopefully one of us will figure it out soon. I have a list of items I will be replacing in the next week or so, and I hope that one of them turns out to be the fix... Perhaps someone will chime in with some ideas. P.S. I am running an upgraded turbo as well, volvo TD05 with a 16g compressor. Similar specs to the 60trim T3 but with internal bypass..

p.p.s I like your avatar picture ;)
 
hey, i have the same problem, and am also still looking for a solution. i was thinking it might be an intermittant problem with the tps or something, but i havent checked. also, do you know where the screw on the cbv is supposed to be at?
 
i know how to fix it ......

megasquirt.

+T on lh suxors the b!g ONE !!!!111!!!!!1!!!!!!!!!1!1!111121
 
You must log in or register to reply here.
Back
Top