Car idles low/dies when quickly let off throttle

[D.J.T.]

Yup...I have an auto, with an HKS recirc valve...give it any gas and let off fast it stalls. Give it wot, let off and if the car shifts after you let off it dies. On idle, floor it, let off, it dies? If this sounds familiar, it's your BOV. It won't go away until you get a piggyback/standalone, or put the stock bov back on. Its especially annoying with an auto. Just get used to throwing it into neutral when it stalls on the road and give it a quick start while rolling haha. Or, you can also manual shift the tranny so it always has a little bit of load and that keeps it from stalling. Goodluck.

It's not suppose to stall if the BOV (recirculated)/BPV is doing its job. Unless your valve is on too tight & not allowing all the air that the stock BPV would let through when the throttle is released. I have a vacuum leak & my Stock BPV is failing... the Vac leak is the culprit so check for vac leak as well.

 

[suprajim54]

So I tested the alternator and got about 12-13volts with the car off. Started it up, turrned on everything electric and it was at 14-15v at first. Once it warmed up, it dropped to about 13. I raised the throttle to 2000 RPM and voltmeter went back up to 15v. My voltmeter is a cheap analog, so readings aren't completely precise. The battery light doesn't ever come on until the car dies or idle drops to around 500. When I've had alternators go bad in the past, the light would always come on and stay on and the car wouldn't start once the battery drained and engine died.

I do experience some of the same issues that Supra0089 mentions but I wouldn't think that these issues would be caused by the BOV if it was recirculated. I, too, have had to do the restart while rolling. It's one thing to stall in a manual, but takes a special kind of idiot to stall an auto. I'm always embarassed. Haha.

 

[D.J.T.]

So I tested the alternator and got about 12-13volts with the car off. Started it up, turrned on everything electric and it was at 14-15v at first. Once it warmed up, it dropped to about 13. I raised the throttle to 2000 RPM and voltmeter went back up to 15v. My voltmeter is a cheap analog, so readings aren't completely precise. The battery light doesn't ever come on until the car dies or idle drops to around 500. When I've had alternators go bad in the past, the light would always come on and stay on and the car wouldn't start once the battery drained and engine died.

I do experience some of the same issues that Supra0089 mentions but I wouldn't think that these issues would be caused by the BOV if it was recirculated. I, too, have had to do the restart while rolling. It's one thing to stall in a manual, but takes a special kind of idiot to stall an auto. I'm always embarassed. Haha.

Get a good meter... my old man has a Blue-Point (Snap on) Extremely useful in many ways. :icon_bigg

 

[supradjza80]

My HKS valve would still cause stalling when recirculating. It also had Surge issues with the recirc fitting and hose on it (it definitely impedes the flow a lot compared to just open vent), but this only started once I ran my 57 Trim CT. I am also on Lex/550, and even vented to atmosphere the car never stalled with the stock components but does stall sometimes this way. If you know what you are doing its 100% preventable through your driving style though.

I also do not think it has anything to do with your alternator (just my $.02)

 

[boostinsupra]

im betting you have a vented blow off valve. This is normal if you do. Recirculate your BOV and it will go away. I run my car vented though and do have stalling issues but very rarely.

are you saying to have two blow off valves? one recirculating and one atmospheric or something this used to happen to me alot how do you fix this issue?

 

[MKIIISupraGuy]

interesting test results, based on what you have posted on how your car is set up. How about a good pic under the hood showing your bov area ? Pic might help us see what is up and get this figured out...

 

[suprajim54]

Here is a pic of my BOV setup:

 

[supradjza80]

are you saying to have two blow off valves? one recirculating and one atmospheric or something this used to happen to me alot how do you fix this issue?

No, I only have one blow off valve. But I have ran my car with recirculated, and vented just to see how the car reacted. Once I went to Lex/550/CT2657/afpr it didn't matter what I did (recirc or vented) the car would sometime stall if you are in boost and let off the gas (happens pretty rarely). Back on the stock turbo/fueling/metering it almost never stalled.

engine bay shot (old) but still the same BOV position - it is vented in this pic

 

[Supra0089]

My HKS valve would still cause stalling when recirculating. It also had Surge issues with the recirc fitting and hose on it (it definitely impedes the flow a lot compared to just open vent), but this only started once I ran my 57 Trim CT. I am also on Lex/550, and even vented to atmosphere the car never stalled with the stock components but does stall sometimes this way. If you know what you are doing its 100% preventable through your driving style though.

I also do not think it has anything to do with your alternator (just my $.02)

No, I only have one blow off valve. But I have ran my car with recirculated, and vented just to see how the car reacted. Once I went to Lex/550/CT2657/afpr it didn't matter what I did (recirc or vented) the car would sometime stall if you are in boost and let off the gas (happens pretty rarely). Back on the stock turbo/fueling/metering it almost never stalled.

engine bay shot (old) but still the same BOV position - it is vented in this pic

It's your bov...even recirculated...the afm (stock or lex) hates it

Because you have an auto, it will die when it shifts w/o enough load as well....as I said before...keep a load on the motor by manually shifting until you get a piggyback or reinstall your stock bov and keep the boost at a reasonable amount...goodluck

 

[MKIIISupraGuy]

Ok I have to agree with Supra0089 after reviewing the pics in recirc and vented mode. Get some sort of piggyback. If you get a emanage, you can vent the bov because it will compensate for it.

 

[supradjza80]

It's your bov...even recirculated...the afm (stock or lex) hates it

Because you have an auto, it will die when it shifts w/o enough load as well....as I said before...keep a load on the motor by manually shifting until you get a piggyback or reinstall your stock bov and keep the boost at a reasonable amount...goodluck

I do not have an auto... and Im not complaining about how the car acts. I know exactly what is going on. However when the stock fueling/turbo was in the car, it was able to prevent stalling much better even with the same BOV and configuration.

---------- Post added at 11:29 PM ---------- Previous post was at 11:27 PM ----------

Ok I have to agree with Supra0089 after reviewing the pics in recirc and vented mode. Get some sort of piggyback. If you get a emanage, you can vent the bov because it will compensate for it.

You do realize the two engine bay pictures are of different cars right? You guys can continue to help the OP but I don't need any help regarding the stalling. Just giving the OP my experience so he can draw his own conclusions about his car.

 

[B shaw]

I have a similar issue. I also have lex/550/walbro with safcII. No matter how much I attempt to tune it it still stalls if I don't let the engine brake it's self a little before going to neutral or stopping. I have a 5 spd by the way. I reverted back to stock air bypass for break in period but problem is still there. It's more if a bother unless I need to stop quick, which happens a lot living around a military base due to the over confident drivers around. I'm becoming used to it. As far as trying to prevent the stalling I'm thinking its more if an upgrade issue since my buddy has stock fuel on his 91 and runs a vented ssqv with no issues.

 

[suprarossa]

Same here with Lex/550/Mk IV pumps/Aeromotive FPR/SAFC II, except I am NOT running an aftermarket BOV. Not only does it die coming to a stop unless I let the engine brake a little like you described, but it also 'bucks' on deceleration/light throttle input - like going slow through my neighborhood or using the cruise out on the highway and coming to a downgrade. Interestingly, and not mentioned here before, is the smell that accompanies my issues. Each stall or deceleration buck is followed by that sick smell of a BHG, but I have no other BHG symptoms and the HKS metallic gasket is less than 10k old

 

[Sside]

Funny I have this same problem after getting my turboxs bov...... They gave me some washers to adjust the rpm's and kep it from stalling but I have yet to use up all my wahsers.... Ima try it tomorrow and see if it makes a difference..... ...... If not then ima jus put my old bov on again....... Prob use both since the stoker jus goes straight from the 3000 pipe to the accordian hose.... Why? Racecar...