user 72239

iTrader: (4)

The past few weeks I've been having an issue with the car not boosting correctly or just feeling sluggish. Sent a log to term and he told me it might be a stuck WG or leaking BPV.

Couple of weeks ago, I went WOT, interceptor immediately jumps to 5.9 degrees of knock and I let off immediately. No matter what I did, it would jump to 4+ degrees of knock at WOT.

I go WOT last week, no knock and boost spikes 26 psi, falls to 24 psi and holds. Car runs great

Tried it again on Saturday, 2.9 degrees of knock at WOT but holding boost.

Now, from what I read on ZZPs website knock that jumps to a high degree instantly and doesn't get higher is false knock. I am getting a bit frustrated. I did a boost leak test and it came back fine. Will a faulty MAP sensor cause this?

I ask because, when I was putting on my Treadstone lower CP I ripped my old map Sensor O-ring and tried to seal the leak with RTV (probably not a good idea but I had to get my car working). Well i got a bit of the RTV on the Map sensor but cleaned it up.

Any thoughts would be great.

oh and btw my LTFT shift between 0 and +5ish

user 72239

iTrader: (4)

bump

ECaulk

iTrader: (6)

Sub'd

tomj77

iTrader: (2)

I sealed my map sensor Oring with silicon, just be carful and let it dry for night, it works great, and what's the weather like where u r and what gas u using, I got knock using 91 from certain stations, but stick to 94 now which my car loves

user 72239

iTrader: (4)

We only have 91 here unfortunetly.

Its been cold to hot. we got snow on Wednesday last week, but it was 59 on Friday and all the snow melted.

I tried sealing it with a RTV and it did NOT Hold.

ECaulk

iTrader: (6)

91 here is like 93, gotta love altitude...

Omiotek

iTrader: (2)

this might sound retarded to some but have you ever had the intake manifold off? if so did you put the fuel rail foam piece of crap back in?

raver0789

Need more info. Does the car constantly boost 26psi and falls to 24. Or does it change? Is boost not consistent? Are you familiar with what a wastegate does? Pretty dangerous **** for your motor. I would look into and fix all issues before you pound it. Then dump in the highest octane fuel yoi can get and get your tune re-logged.

I would assume all knock is real...

ECaulk

iTrader: (6)

When was the last time you changed/checked the gap on your plugs?

user 72239

iTrader: (4)

Yeah thats what I do. I dont go WOT if i see knock.

The wastegate controls boost right? It reads the ECU commanded boost and adjusts to let excess exhaust gas out.

Omio, no. I have not taken it off.

user 72239

iTrader: (4)

Also, it would seem boost is inconsistant. Term said "Might be leaking there but it looks more like the BPV or WG is leaking internally not leaking air outside the system because the fuel trims are not going negative at WOT the car just is not boosting properly or moving as much air as it used to. Car looks like it is down 30-40 wrtq and over 25 whp just looking at the logs. Peak boost was only 225 kpa vs 254 kpa begfore so it is seeing 3 psi less than before."

user 72239

iTrader: (4)

Bump

raver0789

The first thing I would do is flash back to either the stock tune or gms1. I would assume this is a wastegate issue. Take the car in and see what they say.

user 72239

iTrader: (4)

I was thinking about putting my stock PCM back in but I did a boost leak test yesterday and it sounds like my lower map sensor is leaking just a tiny bit. I could see bubbles. When i first put it all back together it was good so I wonder if the O-ring deteriorated more. I had ripped it when I tried to put it in the Treadstone CP that wasn't drilled correctly. I ordered the O-ring and am going to replace it on Friday when it comes in.

Psykostevo

Does your car still have a CAT and cat overtemp protection/fueling?

If so it might be over richening and knocking.

When it knocks do you recall the operating conditions of the motor? Anything consistent between each time it knocks? There are a lot of possibilities.

Timing adders for IAT for example. Did you floor it from a lower rpm than what you do when it didn't knock?

user 72239

iTrader: (4)

No I have a catless downpipe and Terminator disabled the warmup.

I only go WOT when the car is fully warmed up. so between 185ish to 190 temp. When I do go WOT, my interceptor hits a arbitrary number. One time is was 5.9 degrees of knock. The next week I got 0 knock when WOT, then last week it went to 2.9. I haven't done any WOT pulls since

and no. I only floor it above 3000 RPMs and never in 5th.

Psykostevo

Yeah, that rules out user error and cat over temp, I think.

Since the number doesn't change it's most likely false knock. As you probably know, real knock generally fluctuates and also disappears in the absence of knock. Are you able to modify you knock decay rate? I don't really think it would help in the case of false knock, but would in real knock as long as the real knock goes away.

Are there any unusual vibrations that you are aware of?

user 72239

iTrader: (4)

Yes. I have some bad vibration in my shifter and in my steering wheel. I think my CV joints are hosed. I am going to check this weekend

Psykostevo

Yeah. Driveline vibrations are a big culprit for false knock.

Some other cars have their knock sensors so close to the transmission that high rpm gear shifts can cause it too. But haven't seen that issue on the cobalt.

user 72239

iTrader: (4)

yeah it just started happening after I put my intercooler on. before then I had no knock what so ever.

Psykostevo

The driveline vibrations started after you installed the intercooler, or the knock started afterwards?

When you installed the intercooler did you disconnect the battery?

user 72239

iTrader: (4)

negative.

Area47

burst knock.

Powell Race Parts

iTrader: (3)

knock,knock , who's there?

the usual suspects.
the usual suspects who?

ECaulk

iTrader: (6)