Boost Spike / Codes 21 & 52 Too Many Possibilities! Help!

[Shytheed Dumas]

Wednesday, I ran my car hard for the first time since my hg job about 1,000 miles ago on the way home from work. Later on I punched it pulling out of my driveway. My boost gauge shot right past the normal ~6psi and pegged, and the whooshing sound from under the hood made it sound like a major boost leak. There was no loss of power or stuttering, just way too much boost.

My BOV checks out okay and I haven't found any obvious leaks. Ran codes this morning and there's 21 & 52. Don't beat me up over this, but I threw a CEL as soon as I finished the hg and didn't bother checking it until I had this new problem and I've just had a feeling that power has been lacking since I did the hg. Car is a completely stock, '90 turbo with recent JDM swap. Forum searches have pointed fingers in a lot of directions, and I'm not sure where to start, so...

1. In order, what step should I take to diagnose from here?
2. Some of the confusion is a lack of correlation b/w these codes and boost spike. Are they even related?
3. Is it worth my time to do a positive pressure test? SF has a method using a soup can to plug the intake and a tire valve stem to pressurize the system up to ~12 psi.

Sorry for the long post, just wanted to cover everything I know. Thx, Kurt

 

[Bishop92t]

Your code 52 will definitely sap your power. Start by diagnosing your knock sensors. Make sure you didn't accidently unplug or break them during your HG swap. If they're still plugged in then you probably have to rewire your knock sensors to make that code go away and restore your power.

Code 21 could possibly sap power, but more then likely it will just make the car run too rich. You need to make sure the O2 sensor is still plugged in, if so the sensor itself could have gone bad.

Neither of those codes will cause a boost spike, but the two codes could make a boost spike feel like it added no power. Chances are you have a 3rd problem with the boost spike. Boost leaks will not cause boost spikes, but it's always a good idea to check the system periodically for boost leaks. The problem probably lies in your wastegate system. Check your compressor housing to wastegate hose to make sure it's securely attached and intact. Also if you've got access to compressed air with a regulator, try to apply a couple psi (1-2) to the wastegate itself and make sure it starts to open. It should open more with a few more psi.

 

[Shytheed Dumas]

Thanks Bishop. I'm on my way outside now. Just to keep things moving along, I have a couple of quick questions: There is a KS on the drivers side of the cylinder head, below the valve cover, right? And is that the only one? Also, I do have regulated air, but where exactly do you pressurize the wastegate? I assume if there's airflow < 2psi then there's a problem just as much as if it doesn't open at higher pressures. Thanks!

Update: Okay, I found a KS sensor with no wire attached - just some frayed, broken crap sticking out of the plug. I have no idea where the other end of the wire is. Am I going to have to remove the intake to find it????? Is that the only KS? Anybody know where this is in the TSRM?

 

[Shytheed Dumas]

Boost problem solved! The hose to the WG actuator had blown near one of the nipples. It's a pretty tight and twisted in there and I think the sharp turn just past the nipple put some extra pressure on the hose. O2 sensor is cheap, so I'm going to get rid of Code 21 next.

Still need to figure out the broken KS plug/wire issue. If anybody has any input on where the wire starts from and what I will need to remove to find it so I can reconnect it to the plug, I would really appreciate it.

 

[NDBoost]

to fix your knock sensor issue follow this:

http://supras.com/06/techcenter/display.php?QID=69

 

[supramike7m]

there are two knock sensor on our cars. both on the block on the drivers side right under neath the intake manifold. one is at the back by the firewall and one is closer to the front of the engine. check the wires right off the sensor, mine were just broken off at the sensor. you should feel a difference once you get these fixed.
Mike