SR Veterans, Lend me your ears

[Sil80315]

Ok, semi common problem but not.

Heres the deal. Just rebuilt the motor, went to a top mount t3/t4 set up and all the good stuff, Im using all my sensors, coilpacks, injectors, maf and ecu Ive used before the rebuild when I had a big t28.

heres my issue. Car is dumping full on deceleration, Example is if I was comming to a stop sign and even if i was slowing down in second gear and pushed in the clutch around 1k rpm it stalls but before it stalls I see it hit 9-10 on my wideband and takes forever to try and start it cause now the plugs are nice and fouled out and when it finaly does start its miss firing till the afr's level out.

My afr's at crusing are around 13.9-14.2 and when im wot or over 80% throttle its around 11.5

Before you ask. This is what Ive done

Boost leak tested, cars vac is around 15 (im running HKS step 2 cams, Heard bigger cams lower vac)Changed coilpacksChecked MafRecirculated bovPeplaced IACVReadjusted TPSChecked ecu for codes ( Shows 11 for the cas but only when it stalls)Adjusted Timinginstalled new O2 sensor

The latest thing Ive noticed is when I did a boost leak test the wastegate started leaking so im pretty sure thats not good so ill be taking that out and seeing what the heck is wrong with that cause it has to be my main reason for my boosting problem (only made 2lb of boost till around 4500 then went to 7lb)

Then after that all i could think of is new plugs.

Let me know what you guys think, like I said. drives fine..can idle all day long but once you go to drive it to a stop sign its a totally different motor and stalls.

My setupDenso 555cc injectorsZ32maft3/t4 50 trimTurbosmart wastegateGreddy intake manifoldHKS bovEmance ROM tunewalbro 250HKS step 2 cams 264 degree

Thanks
Modified by Sil80315 at 9:52 PM 6/28/2009

[Blown240sx]

so it leaked boost from the wastegate or bov? If the BOV is leaking the car will stall out.

[Sil80315]

from the wastegate. I guess it has a bad seal? cause when i do a boost leak test it opens the the valve ( which i can understand cause its positive pressure) but even before it opens it, it starts hissing and gets louder when the valve is fully opened.

[Sil80315]

Ok installed new spark plugs. changed out the wastegate. tightened a few clamps, runs better and have good air fuel. when driving.. The stalling has come down to it wants to stall..goes down to about 4-500rpm and trys to catch itself but i noticed when its doing that its dumping a s*** load of fuel to try and catch it.

heres what im getting while driving

cruisen 14.5WOT or 80% bottom 12's high 11'sat idle 13.5 to 14

could a bad FPR cause it to dump more fuel cause its hooked up to vac?

[jr_ss]

What engine management are you on?

[Sil80315]

Im running emance rom tune...

Keep in mind..this set up worked perfectly fine till it threw a rod bearing..

[Sil80315]

*Update!!!* On side note.. f*** you flex-a-lite fans. yeah over time you were nice till you decided to run into my radiator over time and slicing it open. so now I have to buy another $300+ radiator

Back on topic

Heres my issue. Something is making the ecu dump fuel at low RPMs like comming up to a stop. cause if i let off the gas it starts to bog out and you can see my afr's jumping from super rich to rich trying to catch the motors rpm's. SO if the motor doesnt stall it catches itself and levels out like normal and goes back to 1100rpm woth 13+ afr's

WTF can this be?

Bad FPR?Not enough air to IACV?

[racemydatsun]

ive noticed you said you went to a top mount setup after rebuild. how far is the maf from the turbo? you need a good amount of distance to not screw with the readings going into the ecu (recirc'd bov or not). I had the same exact problem when i went to a top mount setup, and couldnt figure why the hell it kept stalling. try to add an additional small section of pipe between the mafs and turbo to see if that helps. GOOD LUCK!

[Sil80315]

The maf is about 4 inches away from the radiator..just enough room to squeez in those small HKS filters. and the pipe is about 8 inches long, not including the inch or 2 you get from the couplers

[DrifterProdigy85]

your getting turbulance which messes up the MAF reading. I get it with mine too. I temporarily fixed mine by placing a mesh screen right behind the MAF. If you dont wanna do that then it has to be tuned out of it.

[Sil80315]

so your saying if i put in a screen some after the maf it will help? the z32 maf already has a screen on both sides though? or do I still need to add another one?

[FAST-DATSUN]

one of two problems. 1 BOV vented to atmosphere and can not get closed fast or leaking. 2 Maf not at least 12" and at least 1 90 deg from turbo.

[0wn3r]

i'm mostly stock but having an issue with stalling when putting the clutch in, or it comes REAL close to stalling and then catches itself. It's only when it's hot/humid out but happens totally random. It could do it a few times in a day and then not again for a couple weeks. i don't have misfiring issues, but when I had backfiring it was under light throttle around 5k rpms. Cleaning the MAF worked to fix the backfiring and idle hunting, but not for the stalling w/ the braking/clutch-in issue.

I swear it's a giant mystery what it is in the SR world. I have yet to see a thread where someone has had this problem and fixed it. So if you figure it out, post it up.

[DrifterProdigy85]

so your saying if i put in a screen some after the maf it will help? the z32 maf already has a screen on both sides though? or do I still need to add another one?

Try adding another screen. I had to do this with my top mount setup. Im using a 4" diameter intake pipe with a 45* bend going to the Z32 MAF. Be sure to use a Aluminum Mesh so it doesnt break and get sucked in the turbo. Dont use this as a solution, use it as a temporary fix and plan on getting it tuned properly.

[Sil80315]

Ok so I went to a blow through set up tonight. It deffently stopped the stalling and my afr's didnt change all that much.

Is anyone else running a t3/t4 50 trim? Im not seeing full boost till 3800 is that normal or am i just used to the t25's?

[DrifterProdigy85]

Thats pretty good spool. I dont think my 2871R i used to have spooled that fast. Did you do anything special on going blow through? A while ago i heard people blowing the MAF apart under high pressure.

[Kouki KAT]

Ok so I went to a blow through set up tonight. It deffently stopped the stalling and my afr's didnt change all that much.

I have the same problems, so maybe i'll try out a blow-through set up. Where in the piping did you mount the MAF? What did you use to connect the MAF inlet to the I/C piping? Any pics?

Thanks for (probably) solving my problem.

[DrifterProdigy85]

http://htperformance.net/compo...1.jpgI bought one of these. Ill be switching mine over in the next week or 2. Im doing a Q45 TB with 3" cold piping with the MAF in there. Should be able to really optimize flow and get the most power with that setup.

[Sil80315]

Yup I mounted the maf like halfway in the engine bay and half way in the fender. I had to cut about 4 inches of both the cold pipe and the pipe that goes to the intercooler.

I have to say it made a big difference. After the car is warmed it idles awesome and never stalls. Didnt notice much is throttle responce as some would think but my air fuel ratios are right on

The only problem I had was the maf itself.. it has a smooth side where the coupler goes on so for awhile it kept slipping off under boost..untill i replaced the hose clamp with a t-bolt clamp. Ive seen someone on here that changes all that.. by basicaly taking your maf and all its guts and puts it in piece of pipe that has beveled edges so the couplers wont slide off.

[DrifterProdigy85]

How much boost are you running with your setup? Im gonna be doing 20+psi. Im really hoping i dont blow the MAF apart.

[Sil80315]

Im making around 15psi. I read on here that someone did a pressure test on these mafs and they got close to 60psi

[DrifterProdigy85]

Cool. Ive got my adapter ordered and will be doing this. I had someone tell me it started to leak around the top piece of the MAF so ill probably place glue or epoxy around that area just to be safe.