boost spike or surging

[mbagge01]

I am hoping that the collective knowledge of this forum could help answer the problem I am having. It involves a 63000 mile 2004 CTT with evom tune, evom intake, upgraded intercoolers, ipd plenum, new fuel pumps, fuel filter, and FPR and new boost solenoid. I have no CEL on durametric. My car pegs the boost gauge which is what should happen with the evom tune so I am assuming that I do not have a boost leak. My issue is that the car feels more powerful at half throttle than at WOT. It is a very rare occasion that I can hit WOT and the car pulls like a freight train but this usual only happens right after the car is started. I have tried 4 different types of spark plugs and currently using denso pk20tt which evom suggested. It came with a gap of .033 inches and I know that this is smaller than the porsche recommended gap but my understanding is that creating a smaller gap is good when a vehicle is tuned for more boost. Regular driving is fine but if I ever give it hard throttle, the boost gauge goes up but the acceleration feels very slow, and even as if the timing is being pulled for some reason. Could my boost solenoid not be reacting fast enough, could my changeover solenoid be acting funny, should I reduce the gap of my spark plugs even more. I am probably going to log some runs with durametric to see if I can get anymore insight into what it could be. Appreciate any advice on what else I should try or look for.

[mbagge01]

I just wanted to add that I decided to regap the plugs to .025 inch and the first run with the car was perfect but after it warms up, that is when the problems start up. I am now starting to wonder if it could be something like the O2 sensors going bad and giving bad signals when they heat up. Has anyone had any problems with the O2 sensors doing funny things, even though a code has not popped up yet. What are the O2 signal values that are normal in durametric.

[bigbuzuki]

Regarding O2 sensors, I have heard that they have a service life of around 100,000 miles.

They will still output after this mileage and won't throw a CEL, but they won't be giving an optimum signal.

[mbagge01]

On inspecting on how to car drives some more, I think it has something to do with the way the boost comes on. If I am around 2-3k and give it WOT, the boost gauge shoots up and it does the weird surging issue. If I give it part throttle to get the boost to around 0.4 first and then give it WOT, I don't seem to get the problem as much when the boost pressure raises. If I hit WOT at around 4500-5000k, I don't seem to have the problems either. I already have a new boost solenoid valve and MAP valve and I am wondering if I should change out my changeover valve. Could it be possible that I am having boost spikes or my boost is raising to fast due to the changeover valve not opening properly causing the diverters to open erratically, affecting boost control?

[lewisweller]

On 12/08/2013 at 3:04 AM, mbagge01 said:

On inspecting on how to car drives some more, I think it has something to do with the way the boost comes on. If I am around 2-3k and give it WOT, the boost gauge shoots up and it does the weird surging issue. If I give it part throttle to get the boost to around 0.4 first and then give it WOT, I don't seem to get the problem as much when the boost pressure raises. If I hit WOT at around 4500-5000k, I don't seem to have the problems either. I already have a new boost solenoid valve and MAP valve and I am wondering if I should change out my changeover valve. Could it be possible that I am having boost spikes or my boost is raising to fast due to the changeover valve not opening properly causing the diverters to open erratically, affecting boost control?

Did you ever resolve this? The descriptions you give about cold and warm running seem to mimic exactly what I have and my ctt is standard except for the e81 power kit from factory. 

 

If run from cold it is great absolutely perfect. As soon as the temp reaches 70oC ish it will miss on acceleration between 1-3k rpm then clear to redline OK. 

Pulling timing sounds correct or a lean misfire as the temp has risen and now it's no longer on warm up enrichment. 

Edited December 30, 2016 by lewisweller

[mbagge01]

It ended up being that I had a leak in the vacuum line going to the wastegates as if would not hold pressure when tested and also a leak in the boost control lines to the turbo. They were not massive leaks but when tested under prolonged pressure, they would not maintain pressure.

[lewisweller]

13 minutes ago, mbagge01 said:

It ended up being that I had a leak in the vacuum line going to the wastegates as if would not hold pressure when tested and also a leak in the boost control lines to the turbo. They were not massive leaks but when tested under prolonged pressure, they would not maintain pressure.

Glad you got it fixed, Shame, I have changed those pipes already. 

How did you get on with spark plug gaps? I'm running beru oem plugs at 0.8mm as standard spec. I thought about reducing the gap to 0.7 to see if the warm running misfire would reduce or disappear. I know on high boost the spark can be "blown out" or struggle to spark under lean high load conditions of combustion. 

Any advice on gapping? Any alternative ngk plugs better. Ive always used ngk or iridium plugs without any problems. 

[mbagge01]

I reduced my spark plug gap to .026mm which was recommended by EVOM who I got my tune from. They recommend Denso Platinum TT plugs

[lewisweller]

3 hours ago, mbagge01 said:

I reduced my spark plug gap to .026mm which was recommended by EVOM who I got my tune from. They recommend Denso Platinum TT plugs

.026 inch you mean? Which is 6.6mm 

Any reductions in power or mpg by running a tighter gap? 

I may go ahead and pull all plugs and regap to 0.7mm just for the hell of it. 

I'm running out of idea to fix this car with no codes and nothing to follow. 

 

[mbagge01]

I did also find a tear in my divertor valve line to the solenoid which was not showing up on a boost pressure test but was occurring under vacuum. Also check the lines on the back of the intake which are hard to see.

Sent from my VS987 using Tapatalk

[lewisweller]

Re-gapped all beru oem platinum plugs to 0.7mm from the spec gap of 0.8mm. 

 

Plugs look OK to me, possibly a bit on the hot lean side?

 

What I did find was plug from cylinder 1 had three cracks in the ceramic insulator running from top to bottom! The cracked track was dirty so must have been tracking for a while. 

(Some people say dropping the plug, over tightening or wrong angle with socket could cause this, but as the crack is blackened I don't think so). 

I put in a used plug from before for now until I can go buy a new one. 

 

Short drive home pretty much the same, felt fine at higher rpm and wanted to hesitate at lower rpm as the boost and load comes in. 

 

I'm considering getting ngk plugs as I don't rate beru much. Maybe a heat range cooler as well as its OK when cold and only starts bucking when warm. No codes as usual. 

 

Any thoughts guys? 

[lewisweller]

Results after some days and few hundred km's is no change. In fact I would think the Butt dyno is saying at top end I've lost a few horses and the weather is cool and dense air foggy here now so the turbo should be howling. The Audi does or was going like a train until some moron T boned it when my wife was driving my son to school yesterday. Lucky no one was hurt and two new doors and some body work in the B pillar will fix it good as new. 

 

Sorry back to the plugs.......

Growing impatient and not liking the look of the cracked plug insulator on cylinder 1 I'm going to replace these Beru plugs with NGK's iridium BKR6EIX or maybe the BKR7 instead one step cooler plug as I'm in middle east and lowest ambient temperature is 16oC and hits 50oC in summer easy. 

Pre-Gap spec is 0.8mm (.032") but some tuned turbo's have reduced this to 6.6mm (.026"). 

 

As this ctt has the E81 power pack is there any other plug better recommended? 

[ekstroemtj]

Audi looks not good. Strong hit. Be happy nothing serious happend.

[lewisweller]

Bought ngk iridium BRK7EIX fitting tonight!

[lewisweller]

Bought ngk iridium BRK7EIX fitting tonight!

[lewisweller]

Fitted new ngk BRK7EIX plugs with standard pre-gap 0.75mm. 

The ngk just look so much better and more design specific I think, a fine tip and a tampered elctrode strap all designed for max spark and burn pattern, the beru look caveman in contrast. 

 

The results of driving is smoother and more responsiveness. It hasn't magically made the stutter and bucking under boost disappear but wasn't expecting it to, only throttle body resets seems to be able to get the sluggish back after a while of deteriorating driving performance. 

Idle is smoother and quieter. 

 

For a bit of fun using a smart phone app called Vibrometer I measured the vibration of the engine (by placing the phone on the intake manifold just behind the throttle body) at cold start just after the "choke" kicks off, it was 4.4 with the 8000km old oem Beru plugs, with the ngk plugs it was 3.8! Make of that what you will. 

 

[mbagge01]

Lewisweller, I would get looking around for a vacuum leak somewhere. I must have changed my spark plugs with different models 10 times and the car always feels great at first and then the problems resurface. Have you tried disconnecting the battery and resetting everything because that can help when new parts are installed

[lewisweller]

2 hours ago, mbagge01 said:

Lewisweller, I would get looking around for a vacuum leak somewhere. I must have changed my spark plugs with different models 10 times and the car always feels great at first and then the problems resurface. Have you tried disconnecting the battery and resetting everything because that can help when new parts are installed

I've smoke tested it 4 times over the last 6 months after doing works like removing pipes and manifold etc. The idle is fine except now it Dips coming to a stop unless I really baby it down. 

I'm really confident (famous last words) that there is no more leaks or vac pipes or check valve leaking by, purge valve faulty or aos or divertor valve split, coils plugs two sets and fuel filter and regulator and new maf sensors (I'm listing all the stuff found faulty or replaced maintenence/service stuff). 

I'm really focusing on the fuel pumps now. 

I've just read a post from 2012, Thomas had the idle Dip and the garage replaced both pumps and fixed the issue. 

At 122,000km and the symptoms of a warm engine lean misfire hesitation and idle Dip I'm really leaning towards the pumps getting hot and showing themselves to be less than effective at delivery. It must be borderline as I don't get any codes but the effects are consistently felt whilst driving.

At this stage of pulling my hair out and eliminating so many other variables it's the only one of a few remaining possibilities that make sense logically.  

 

[bigbuzuki]

I had both fuel pumps, fuel regulator and filter replaced as part of my preventative maintenance schedule at 170,000 km.

 

The idle dip is still there.

 

Replaced the engine mounts and transmission mount which removed the chassis shudder that was felt when the idle dipped.

 

 

 

 

Edited January 9, 2017 by bigbuzuki

[lewisweller]

3 hours ago, bigbuzuki said:

I had both fuel pumps, fuel regulator and filter replaced as part of my preventative maintenance schedule at 170,000 km.

 

The idle dip is still there.

 

Replaced the engine mounts and transmission mount which removed the chassis shudder that was felt when the idle dipped.

 

 

 

 

Yes it seems aside from fuel problems the list of possibles for idle problems and dips is a few:

Dirty maf's

Dirty throttle body or adaption required or complete replacement

Coils and or worn/contaminated plugs 

Leaky or blocked injectors

Stretched timing chain or camshaft deviation 

Vacuum/gaskets leaks is the most likely. 

 

As I said I'm 95% sure I cover all the above. 

 

The worn  mounts just allow you to feel the Dip more pronounced through the chassis despite some other posts swearing the new mount will fix the Dip, it won't. 

 

Thanks for the feedback guys, I won't give up on this. 

[mbagge01]

Lewisweller, make sure you check the vacuum line with the T connector which is hidden behind the intake manifold and connects exhaust lines from the turbos to the crankcase. Mine was cracked and fixing it did help.

[lewisweller]

36 minutes ago, mbagge01 said:

Lewisweller, make sure you check the vacuum line with the T connector which is hidden behind the intake manifold and connects exhaust lines from the turbos to the crankcase. Mine was cracked and fixing it did help.

Yep found that epoxy glued back together when they did the head gaskets. Replaced the black piping for new Porsche one. That pipe itself doesn't leak but Im sure those metal pipes which run to each turbo oil collector block are leaking on those crimp type floating adaptors (from metal to hose piping). I can see the oil and dirt build up there but despite this which yes would be a vacuum leak of a relatively small amount I think, if I blow or sick the pipe I could get any air in or out. Im not sure house that oil collector block and vac metallic and hose line really work. The pipe goes the valve covers left and right so it sacking the oil vapors from the lubrication oil of the turbo's so as not to build up  pressurised vapors around the turbo oil supply and return lines. That's my best guest. So worst case is I've got small amount of extra air going in the system. 

 

If I pull the oil cap the engine vacuum is very good, the idle will burble and hunt a bit as the throttle tries to stabling the rpm. The aos at the time can also be heard to quietly whistle some air inside because the oil cap is off and extra air is entering. 

To summarise I do have some small leak at the back there, it is not enough to cause the running issues I have at the moment. 

Edited January 11, 2017 by lewisweller

[lewisweller]

New left side fuel pump has fixed this stutter 85-90%.

Thanks to all who posted with support and advice. 

[mbagge01]

glad to here lewisweller. At full throttle, both fuel pumps kick in so at some point you might consider replacing the right side also if you car has a lots of miles on it.

[jbwhiton]

I wanted to chime in and echo the similar results. I have a tune as well, and all new Denso IK20 plugs, which helped the low RPM stutter from 1-2K rpm. All new vacuum lines to the DV's. Had surging under full throttle and the idle dip as well, and a rumbling rough idle when warming up. Pulled the right fuel pump fuse and ran on the left and all symptoms were gone. Almost no idle dip, no surging, and almost no perceivable( very slight) stutter down low.