Anything wrong with this vac setup?

[redsn95gt]

Long story short- i've been battling vac issues far too long. I had the car working and driving a few months ago but I had to take it apart to fix some stuff. I've put it back together this week and it idles great with the spout out and I can lock in the timing at 10 degrees but with the spout in, it surges and dies. I took EXTRA EXTRA EXTRA care to set the lower manifold with a giant ton of sealer (around ends and coolant ports) so it is tight as a vault. A vac gauge (plugged into the canister line shown below) is showing low vac so somethings wrong. However- when I depress the brake pedal on idle, it seems to flatten out and surging goes away, but still very low vac, like 10lbs of pressure.

Troubleshooting steps done:
1) Compression test on all cylinders (newly rebuilt engine, all pass)
2) Reset throttle body - set arm 0.010" + 1 turn preload from body, set bypass to be 2 turns out from closed.
3) Pulled MAF and cleaned it with MAF cleaner
4) Cleaned ISC/IAC and verfied connections solid
5) Fuel pressure at 38-39psi, AFR 14.2-14.8 on wideband
6) Set timing at 13* at balancer, advanced dizzy to who knows and it idles but its still surging
7) Reset KAMs between steps above.

To Do:
Measure TPS voltage

This is my vac setup, am I doing something stupid here? Why would depressing the brake pedal stop the surging?
View attachment 158831
These are the mods:
Holley Systemax II intake
BBK 70mm TB
BBK cold air
stock MAF
stock injectors
AFR 165 heads
EGR delete
Anderson AF-N41 cam
Moates Quarterhorse tuner with Binary Editor - running base CABZA strategy with only EGR disabled and idle upped to 800rpm. I've driven the car near perfectly on this same tune before.

 

[toyman]

Is the breather port an open breather? If it is, you are drawing unmetered air into the system. This would be the same as having a vacuum leak. Normally, air is drawn from the intake tube into the engine at the valve cover which is then pulled through the engine via the PCV and back into the intake.

 

[redsn95gt]

Breather is not open, its just a port the hose connects to. I had a breather on the car before but I removed it and replaced it with this hose port instead.

 

[BlackVert]

IIRC, a stock setup also has a breather in the valve cover to the air intake after the MAF. It has been so long though that I may be not remembering correctly.

You could clamp the hose off to see if it changes anything, but I doubt it will.

Comments/Questions:

- Surging is pretty common with our modded SN95s.
- Do you have a tune for it?
- Is that vacuum reading typical for the cam? The Anderson folks might have some thoughts on that.
- Did you change the injectors and/or MAF?
- If "yes" to the above Q, and you have no tune, then are the injectors and MAF "calibrated" for each other?

 

[toyman]

6) Set timing at 13* at balancer, advanced dizzy to who knows and it idles but its still surging

As I read this it appears that you physically set the timing at 13* but when you advanced the dizzy you didn't have a timing light to see where you actually are. If that's not the case what is the timing, engine running, with the SPOUT disconnected? Also wondering if the HB has spun such that timing readings are bogus.

 

[redsn95gt]

Thanks for the input guys. This stuff helps me think.

IIRC, a stock setup also has a breather in the valve cover to the air intake after the MAF. It has been so long though that I may be not remembering correctly.

The stock engine did not have a breather, just a small hose port off the oil fill neck that went to the intake tube.

You could clamp the hose off to see if it changes anything, but I doubt it will.

I think thats what I'm going to try next. I'm going to try some blocking. Clamping in certain spots should kill the engine. If its not, then I have some sort of leak.

- Surging is pretty common with our modded SN95s.

Yes, i've been reading quite a bit about surging on all sorts of levels from tunes, timing to cams. ISC seems to be a popular culprit too. Funny thing is i already had the car running and working with zero surging before, so I'm not sure what has changed on my setup besides the new pcv routing. That and i went back to stock maf and injectors.

- Do you have a tune for it?

Yes I am doing the tuning. I have a very mild tune at the moment, mostly stock with egr/smog delete, a few changes to raise idle by 200rpm to keep it from stalling so fast.

- Is that vacuum reading typical for the cam? The Anderson folks might have some thoughts on that.

Good idea, i'll see if they have that documented. The vac reading now is too low for any cam but it would be nice to have a ballpark to target.

- Did you change the injectors and/or MAF?

Originally yes, they were 30# and MAF was 80mm ProM for 30# but I have since put back stock injectors and MAF to eliminate those as the problem. Fuel, spark and maf curve all set back to stock on the tune.

As I read this it appears that you physically set the timing at 13* but when you advanced the dizzy you didn't have a timing light to see where you actually are. If that's not the case what is the timing, engine running, with the SPOUT disconnected? Also wondering if the HB has spun such that timing readings are bogus.

Yes, I've tried 10* and 13* with spout out. Locked in timing on both with timing light. Surge is worse on 10*, tiny bit better on 13* and if i advance the dizzy out of time at 13*, it gets even better but doesn't go away. HB is brand new and has only about 10 miles on it.

 

[BlackVert]

The stock engine did not have a breather, just a small hose port off the oil fill neck that went to the intake tube.

Sounds sort of like a breather to me ...

 

[toyman]

There isn't anything that can be really cleaned on the IAC. It's a solenoid valve which is either open or closed. There is nothing in between. If it's the original I would be inclined to replace it. Another thing to consider is the fact that all electrical sensors over time deteriorate and while they may function they become "lazy" to the extent that their response time to changing events are much slower than when new. Also, all engine sensors are dependent upon a solid battery to engine ground and engine to chassis ground. I don't see where you have pulled the DTC's but noticed that you stated the KAM was reset. Pull codes and confirm the TPS sensor voltage readings from closed to WOT.

 

[revhead347]

There isn't anything that can be really cleaned on the IAC. It's a solenoid valve which is either open or closed. There is nothing in between. If it's the original I would be inclined to replace it. Another thing to consider is the fact that all electrical sensors over time deteriorate and while they may function they become "lazy" to the extent that their response time to changing events are much slower than when new. Also, all engine sensors are dependent upon a solid battery to engine ground and engine to chassis ground. I don't see where you have pulled the DTC's but noticed that you stated the KAM was reset. Pull codes and confirm the TPS sensor voltage readings from closed to WOT.

You can clean out the crap in the IAC, but it will get you like another day out of it.

The vacuum setup looks good to me. It's very close to what I have, except I have a breather in the fender instead of running it back to the CAI. It's so little unmetered air, it doesn't make a difference.

Kurt

 

[Bullitt347]

. However- when I depress the brake pedal on idle, it seems to flatten out and surging goes away, but still very low vac, like 10lbs of pressure.



This is my vac setup, am I doing something stupid here? Why would depressing the brake pedal stop the surging?

.

Because the vacuum booster is the source of the vacuum leak and low vacuum reading.

 

[redsn95gt]

Because the vacuum booster is the source of the vacuum leak and low vacuum reading.

Very interesting. I did replace the vac booster while I had the engine bay stripped down because all the seals and crap on the inside of the original one literally fell out when I pulled it. The new booster was a re-issue from pep boys and its about a year old now. I'm going out now to take a closer look at it. I'm going to try capping it off to see if thats where the leaks coming from.

 

[redsn95gt]

Ok i took a look during lunch, tried a few things-

First, with spout out- i ended up disconnecting the vac booster and plugging the vac tree with my finger. The surging leveled out. Although vac was low, it was now idling without stalling in under a minute. I let go, surging returned. I put the hose back on really tight, surging just about gone (need a better hose for sure). Vac is still low, car still dies eventually. I started disconnecting stuff to see if i could kill the car immediately. First, i disconnected at the breather port. Car stayed on and was fine, no change really. Put that back and I disconnected the PCV hose at the intake, idling actually improved. Hmm ok. Tried to set timing again. Damn sun was out and I couldn't see jack. HB is a total blur right now. Then my battery died because i was starting the car so much and I can never actually drive it to recharge so that ended my short troubleshooting.

At least I know I have a vac leak still for sure. I have no idea where its coming from. I would love to eliminate as much of these vac hoses as possible to eliminate leaks. What can I cut out. Someone told me I can cap the PCV valve hole and just run a breather? Would that be a better approach? I have a breather to fit, just not sure what to cap the PCV hole with, maybe just a hose and something plugged into it.

 

[Bullitt347]

There are vacuum hoses down at the brake pedal as well if you have cruise control. Be sure to check for a vacuum leak there as well

 

[redsn95gt]

There are vacuum hoses down at the brake pedal as well if you have cruise control. Be sure to check for a vacuum leak there as well

Yea, I deleted the cruise control entirely but I kept the vac reservoir in the fender which hooks to the tree and the brake hose. The brake hose is still present and makes a hiss when you push the pedal which I learned is normal but its a bit louder than I remember before taking the car apart. Brake press feels right, pedal is firm but not completely stiff. Brakes work good as well when driving. Maybe by deleting the cruise control stuff that threw off some of the vac? Also deleted all the vac solenoids for the smog stuff on the passenger fender as well.

 

[Bullitt347]

Do you hear any Hiss from the brake pedal area when the engine is just idling and your foot is not on the brakes? This area should be quiet/no noise when not on the brakes and really should not hiss continually when foot is on the brakes. Should only get vacuum noise as the pedal is being pushed down if at all.

 

[redsn95gt]

Do you hear any Hiss from the brake pedal area when the engine is just idling and your foot is not on the brakes? This area should be quiet/no noise when not on the brakes and really should not hiss continually when foot is on the brakes. Should only get vacuum noise as the pedal is being pushed down if at all.

No hiss when my foot isn't on the pedal but yea, hiss is pretty loud and stays that way while its on the brakes. I think I know why- I have been doing some reading on cruise control delete. Looks like I should have eliminated the vac reservoir (the ball assembly on the fender) as well. The hose to from there to the brake switch isn't used without CC enabled apparently so it can go. I would imagine this is making a leak any time i push the brakes, reason for the hiss continuously. I'm going to get a plug and try eliminating it off the vac tree to see if it helps.

 

[redsn95gt]

Ok- bought a plug to cap off the vac tree fitting going to the vac reservoir. Seems to have fixed the problem! Vac pressure is still really low, like less than 10, but the car is idling and running. Not perfect, still a little surging here and there but it actually works much better than before. I need to lock in the timing later when its not so bright out and see if that helps. Took the car for a few spins, once on the main road, ran awesome, brakes were great, definitely funky once I hit 3rd gear, engine drops rpm big time seems like its being starved. I may be topping out the MAF. I'll bring the laptop next trip to data log but thats a whole other dog to deal with.