New AZ guy, some questions on VG30ET

[madmax_087]

Hello all,

I lurked here for a few days but didn't see what I was looking for.

My dad and I just got ourselves a sand car that happens to have a sweet VG30ET in it. It runs pretty good, boost is set around 10-12psi from what the gauge is telling me and it pulls like a freight train through all 4 of the VW transaxle's gears. The whole car weighs roughly 900Lbs, so you guys can imagine what a rocket this thing could potentially be, IF it was running right.

The problems we're having: It has a high idle on initial start from cold, around 2k. After you shut it down, restart it and its warmed up, the idle lowers to around 1,200 RPM. After this, the engine will run decent until you get into the throttle and then let off- it dies. Seems like a fuel starvation issue, maybe, because you can keep blipping the throttle to keep it firing until eventually settles back down.

Really, I need a good Nissan guy to check this thing out. I know plenty of Subaru people, but no Nissan specialists. Can anyone in AZ recommend a good mechanic in Valley I can take this thing too? Or are there any good private tuners in AZ I could ask?

Thanks for your help in advance, guys!

Just for SnG's, here is the car:




And a link to a short video that shows the problem:

[Ace2cool]

I have a sneaking suspicion you may have bought this guy's sand rail.

vg30det-wont-pull-rpm-after-warm-up-t595210.html

[madmax_087]

The issue sounds similar, but my rail will pull rpms, it just dies abruptly. Plus, I got the rail before this guy made his last post, so I don't think it is the same. But, I'm reading the posts you've made in there to help solve problems with my own! Thanks Ace

[Ace2cool]

Haha, no problem! Just thought it sounded a bit too similar to me. If it dies while coming down from rev, I would think it's somewhere in the idle control devices (not too familiar with the Z31, though it's still a VG, has a completely different everything past the block, haha.

[Ace2cool]

If you're still running the factory ECU, this would be a good place to start: http://www.xenonz31.com/ECUcodes.html

[madmax_087]

Very cool, thank you again Ace. Let me check through the link you posted, and do a bit of clockwise turning. I'll post up what I find.

Also, I haven't been able to get a solid answer on how to accurately identify my block. Where are the factory stampings? I've read behind the valve cover, on the top right rear, and I also found a short string of numbers on the head I think, about six digits long with no letters.

Any pointers on block identification?

[Ace2cool]

Nissan didn't serialize engines to the VIN, if that's what you're going after. They only made a casting serial number for the block itself. What are you trying to figure out from it?

[madmax_087]

I need to know the year of manufacturer and everything. I don't really care what car it came from, it's probably dead anyway. Just the year it was made so I know what parts I need and what not.

[evildky]

Assuming you have the stock ECU step 1 would be to check the ecu for codes. Next step is to look for vacuum leaks. No air should be able to get in past the maf. Next is to look at the ide air and fast idle circuits. remove, clean and, lube and adjust as needed the ficv and iacv. If you are running 12 psi with no intercooler you are asking to blow the motor. I recommend you cap it off at 9 psi.

[madmax_087]

Ok, well I definitely don't want to blow the engine. How does one turn the boost up or down on these setups? Is there a pill or something in one of the airlines that may have been taken out or needs to be inserted? Would it just be a change of waste gate spring?

Also, I want to check the possible error codes, but It looks like I need to know what year the engine/ECU is first before I can accurately check. Still looking for the block stampings so I can find out what year this engine is. Is there a way I can tell what year the ECU is from by looking at the ECU itself?

Thanks for your input and help so far guys!!

[madmax_087]

Ok so after looking at my ECU yesterday, I realize it says the codes right on the top, thus giving me a date range from which my engine and ECU are from... Heh... Sorry guys, I'm new. I'm sure you were all just rolling your eyes like "what an effing newb". I would be!

For right now I'm not messing with tuning the engine (I've removed the battery). Since the radiator developed a leak on our shakedown run Saturday, we've pretty much stripped the entire interior of the car, including the radiator. This frees up space in front of the engine and, with the new location that is planned, will put the radiator in the actual flow of air. I'm cutting out all the hack welding on this car and putting some decent work into it. I wish I could show you all a picture of the battery mount before I cut it off... Just heinous!

You can see how close that battery was to the exhaust manifold here:



Also, look at the upper cross tube welded in here, compared to the lower tube.



The weld points are more than two inches off from each other.

[Ace2cool]

Oh my. Good thing it's an offroad vehicle. That thing would be unpredictable on street with measurements like that.

[evildky]

The stock wastegate actuator should be around 5 psi, if you are running more than that it's because someone changed or added something to raise the boost, They could have a manual or electronic boost controller, they could have changed out the wastegate actuator, they could have added a restrictor in the reference line going to the actuator, they could have been the bracket or rod or any combination thereof. I cant tell you how to fix it as I don't know what has been done to raise your boost.

[madmax_087]

Oh my. Good thing it's an offroad vehicle. That thing would be unpredictable on street with measurements like that.

Definitely. I'm upset that they would take such a well-built frame and just hack weld things onto it. It seems like someone got into a huge hurry to get it going.

The stock wastegate actuator should be around 5 psi, if you are running more than that it's because someone changed or added something to raise the boost, They could have a manual or electronic boost controller, they could have changed out the wastegate actuator, they could have added a restrictor in the reference line going to the actuator, they could have been the bracket or rod or any combination thereof. I cant tell you how to fix it as I don't know what has been done to raise your boost.

Great, I'll have to look at the boost system a lot more in-depth now... Just more poking around I need to do. That actually doesn't bother me, because I want to know what makes this lil' guy tick. I really just want to drive it already!

[evildky]

Clean and check the iacv and ficv and adjust as needed, also make sure someone didn't crack the tb adjuster to compensate for a sticking or non functional aicv or ficv. Also make sure no unmetered air is getting in beyond the MAF

[madmax_087]

Sounds like I need to get myself a repair manual. Can I get an effective book that won't break the bank? I know an FSM can be extremely pricey, would a Haynes or Chilton manual provide me enough overview to perform checks and fixes like you guys have mentioned?

Also, just wanted to post up a picture of some of the hack work that is on here...



This single piece of steel strap is the only thing holding up the air-filter/MAF assembly and the intake elbow.

[Ace2cool]

http://www.nicoclub.com/fsm

[evildky]

it's pretty simple just follow the air, there should be a small tube that bypasses the TB thats leads to the iacv and or the ficv. Check all the tubes and hoses between the maf and the TB for cracks or leaks.

[AZ-ZBum]

FSM is very technical if you're capable. Otherwise, the Haynes is the preferred manual. Chiltons is a door stop.

[madmax_087]

Thanks for the contributions fellas.

Haven't gotten over to mess with it again since I cut out the hack work I posted, but I plan to check out the FSM for some help tracing airlines and making sure all my necessary electronics are plugged in. I'll post up any progress I make!