Sonic'

Got a bit of a weird one

Scoob lately when going on boost, tends to hesitate, slight judder then kick in

MY00, with PPP Ecu, full decat, ported headers

Ive tried to watch the boost guage when this happens, and it seems to spike quite excessive and the knock link lights up to red very very briefly

Now it doesnt do it all the time, but does it more in 3rd, 4th & sometimes 5th

I have a HKS VTA dump valve on, and thought it was that, so have put the recirc adapter back on, and it is still doing it

1st and 2nd on boost doesnt really do it either

I checked the boost pipe and restrictor and gave these a quick clean, and checked hoses etc and they all look ok too

doesnt matter how much fuel I have in so it isnt fuel surge

Any ideas ?

Oh, and idle is perfect, so cant see it being the MAF, plus AFR is fine when on WOT too, so the lambda should be ok (although could it be that?)

EddScott

Mines got a hesitation between 2750 and 3250 - driving me bonkers.

List of possibles:-

MAF
Lambda
Coil Pack
Leaky hose

When I bought the car IIRC it had Esso SUL in it and it was a PITA on the motorway at 3K. Its now got a full tank of V Power which I think has made it a bit better but its still there. Haven't used the car much as its been raining and I'm being a bit of a fanny with it

vulnax999

iTrader: (7)

Evenin' Steve!

Have you changed anything before this started?

Plugs, fuel type, or headers etc.??


Do the usual MAF test - remove plug on idle and see if it dies or not ...dies it's MAF if not its erm not.

Do you have central coil or individual coil packs? At high boost the coil packs when old and brittle can "blow out " and get a misfire... but not usual in mid range. Central coil pack could have breaking down leads.

If the boost is spiking is it hitting fuel cut - 17.5 psi ish... but why has it started spiking at all?
If it's hesitation then maybe loosing boost from TMIC to throttle body and solenid is trying to make it up so allows more boost, until larger volume of air at higher boost overwhelms the lost volume / pressure from the leak, and solenoid goes back to normal? Check into / out of TMIC pipework or holes in tubes, and TMIC to throttle hose loose or pinholed.
Possably a leak on the boost to control solenoid pipes to wastegate so control not good enough? If you still have a restrictor in the pipe it's the OEM pipework, try fresh silicone hose ( or fuel pipe! ) to/from turbo, wolenoid and wastegate and see.

Doing it in 3rd, 4th, 5th indicates it is occurring when the engine sees load, fast boost increase and higher boost production, ties in with the knock ( overboost ?? ) too much ingition advance, oil in cylinder, poor fuel, etc.


Seems a few symptoms but with many causes, if you have a delta dash ( or Apexi PFC and hand commander ) you could eliminate some of these possible problems.
Else pop it into somewherelike Prosport for diagnostic dyno run??

Dunno if that helped


N

Sonic'

Cheers yes it has a bit

Think I might have to take the intercooler off and check all the pipes properly

I do have Delta Dash, so was going to give that a go, but it means I have to rebuild a laptop first LOL

Nothing has changed on the car, it started happening a few days ago

I do have another set of boost pipework that I can try too

I think the knock link lights up because of the noise, it sounds like the turbo might not be spinning up either though (not sure though, it could be dump valve too)

I dont have the OE dump valve anymore, otherwise I would put that back on and try it (at least I dont think I have anymore )

It is due a big service, plugs etc

I have a fuel guage in the car, and this is normal, loads of fuel pressure on WOT, so its getting plenty of fuel, it only seems to do it more under load too

Rally fan 555

iTrader: (7)

My WRX 02 NB-R is doing much the same - feels sometimes like I'm running low on fuel - hesitates then shoots off as normal until I try going through the gears again (4 spd Auto/Tip), got the car booked in next week for diagnosis (fingers crossed) checked for oil overfill/blocked pipe to soleniod all OK, 1 plug checked looks fine, I know should look at the others - I too wondered about the BOV messing thing s up - though has been on car before I got it (Turbosmart Dual Port) also noticed faltering while just cruising along at 70 odd.............

Sonic'

Anymore ideas?

unplugged the MAF and the idle started to hunt, plug it back in and idles even again, unplug it a 2nd time, and the engine cuts out

So not sure it is the MAF, plus its onyly done between 5-10k miles

Still doesnt do it every time, but now seems to be worse at 2.5-3k revs in 5th gear

vulnax999

iTrader: (7)

Ok Sonic old bean,


From the MAF test looks like it is more or less OK, may need a clean with carb cleaner but otherwise seems sound. Worth doing all the pipework in case of oil carry over / contamination.

Did you check all boost solenoid and turbo to TMIC and to throttle pipework? If no splits or leaks then I am a bit stuck, may be turbo wearing, bearing sticking, passing boost into exhaust? Turbo mounting gaskets and header gaskets, to heads and up-pipe to turbo? May be a blow by leak??

Actually, just thought, can you adjust the wastegate, tighten it up if you have the lock nut & threads by the clevis bracket ( held on by a circlip ) at the back/top of the turbo where the waste gate is ... help seal the wastegate in case it is passing boost.

What boost are you getting at hesitation points, less than usual, or just different?

Did the Delta Dash identify any issues?


Still just throwing ideas at you, simple free/cheap fixes.


Otherwise need a trip to the Scooby garage for diagnostics, I believe Prosport at Stockport ( 30 mins from here! ) do a diagnostic rolling road run for around £70 so Pete there may be able to help?


See ya around,


V

Sonic'

Hi Neil

I still havent found my Delta Dash connector LOL, it is around somewhere I spent half the weekend looking for it but no joy

The boost seems to be about 1 bar at the moment

I noticed today when accelerating from about 70mph in 5th gear that it was just like the engine had been switched off momentarily then came back on

However do the same thing but prior to accelerating drop to 4th and it isnt as bad, more like a little blip

sometimes when it should be hitting boost it feels like the car is dragging before it kicks in, seems to be fine over 4k revs though

I wonder if its the turbo struggling to spool up, but something else being the cause of it

Fuel Pressure is fine, and AFR's are fine on WOT too, however without my Delta Dash OBD2 plug I cant get the accurate readings

I will have another look for it tomorrow night LOL

Sonic'

Finally found my Delta Dash plug

Did a few runs and tbh not sure it was showing anything up, certainly the MAF and Lambda sensor readings seemed fine

However I did notice that the pipe on the MAP sensor had come off, so I reconnected this, did an ECU reset and still no different

Anyway here is a snapshot of one of the runs, not sure if anyone can help, as I have had little response, even had no response over on the ecutek forums

vulnax999

iTrader: (7)

Quick reply so I can see the table at same time.

Hmm let me ask how you drove that run as there is something funny in my view 3 seconds in ...

You only ran it up for 4 seconds to 4600 rpm ish? Did you lift off at 4500rpm / time 3500 m/seconds, as the throttle is closed there, and that makes the other readings go funny/drop too, looks like cruising at 43/44 mph...! Then foot down again at 4500 msecs.... If you didn't "confidence lift" then there is the problem range. ( Might suggest the throttle position sensor is on way out or the windings on the scale of TPS are dirty / worn in that position so loses signal ).
You are making just over 13 PSi boost @ 3800 rpm
It seems pretty det free as little correction applied.
Looks a bit rich 3500 - 4000 rpm, but not too much, but in normal working range for Lambda,
MAF volts look normal for your state of tune,

But as you know I am not a doctor ... or ECU man!


Can you do a run on the test track from say 2500 - 7000 rpm in 3rd or 4th and send me / post if OK to do so! to check from any sudden dips in values at the point you feel the hesitation?


I don't think the MAP sensor hose will matter much as I don't really know what it does apart from fuel cut at max boost pressure allowed by ECU!!! But will be a slight loss of boost but not enough to cause hesitation or delayed spool up...


Neil

vulnax999

iTrader: (7)

To rule out ... MAF seems OK on values and the hunt / stall on pulling the plug.
Coil packs would be failing at higher boost levels; central coil pack / plug leads possibly failing at higher revs unless arching badly?

Lambda values look OK but a bit rich around 3000 rpm, but that is about the point where the ECU changes from lambda control of fuelling to MAP in ECU control, so may be something there?

Do you have your OEM ECU to swap back and try, may be intereting to see if problem clears up?

Sonic'

Hi Neil

Cheers again for the replies

I may have lifted off slightly on that particular run, I did do a few runs and logs, but I will do another one from 2500 to 7000 (or close to it ) will have to be in 3rd, but I can try it in 4th, but a good chance of approaching a tight 1st corner on the test track

At around the boost point, its almost like someone shoves a potato in the tailpipe during the boost stage, then its like the potato gets forced out (if that makes any sense)

Being a bit rich will almost certainly be the HKS VTA Dump Valve, but I have put the recirc pipe back on for the time being

What I did notice with the MAP pipe off is that the boost pressure just read 14.4 instead of the normal boost reading

vulnax999

iTrader: (7)

OK.

Whatever gear gives the problem and the rev range it occurs in will suffice.

May well be different numbers on AFR with the recirc dump valve, ( although was rich at 3000 - 4000 area, not when boost being dumped, from the other readings showing around 13 psi boost in that area ) and I expect the boost control by the ECU would be based on the manifold air pressure read by the MAP sensor ... that's what the ECU sees as it tries to control the boost solenoid duty to achieve target boost. If MAP pipe off ECU may just see atmospheric pressure of 14.4 psi ... ?
that could affect boost response. But your plot above does show changes in MAP readings so you must have put hose back on before that run?


I think it seems like a boost control issue ( whether ecu control, turbo, pipework/hose or sensor problem ) where the boost solenoid is not opening enough as you put foot down / increase engine load / demand boost.

I am more used to external boost controllers, and still have my hybrid controller and solenoid here ( think I have a wiring diagram for 2000 cars ) if you wanna try independant boost controlling?

Sonic'

Hmm, I may need to clean the boost solenoid

Over on ECUTEK they cant see a problem with the table I posted above, and suggested possible MAF, but also to do a log file from 1000rpm to 6000rpm

I will do one shortly and post it up

Rally fan 555

iTrader: (7)

I had hesitation and as if the car didn't want to boost(3k-4k revs) then all of sudden the boost would come in and it would hesitate again during the next gear change, it also would "jerk" when cruising, almost like a fuel problem, i'ts done now, went to local garage and replaced MAF, also the base of the BOV was not sitting right, replaced this also, now all OK.......just thoughts mate, good luck hope you get it sorted soon.

Sonic'

Just done 3 runs

one in 2nd gear, one in 3rd gear, and one in 4th gear

Here are the graphs

2nd Gear run







3rd Gear run







Finally 4th gear run, which seemed to hesitate the most

dynamix

iTrader: (3)

Remap.

It is overboosting because of the decat. Detting like hell and taking lots of timing out, reducing the advance multiplier down to 10 rather than 16, reducing the power even further to protect itself.

TonyBurns

iTrader: (3)

PPP'd cars dont like being decatted, either you need to drill out the restrictor screw or have the car remapped

Tony

PS, mine did exactly the same thing when i decatted her.

vulnax999

iTrader: (7)

This car has just a PPP ecu with home done other mods listed. Never remapped as is AFAIK.

Sonic'

Yes, never been remapped and done some 60,000 miles since the mods where done, never missed a beat until now

It has, PPP ECU (and correct restrictor) STI Intercooler, Magnex Twin Dump downpipe, Magnex non resonated centre section, TSL Backbox, Ported and lagged headers, ported up-pipe on header side

The rest of the mods are cosmetic, bar Defi guages, Knock Link and AFR guage

Rob_f

I have had a similar problem for over a year now but think i've cracked it.
There is a pipe off the manifold near the throttle valve which goes to some condensor or other near the drivers side headlight (goes to the fuel tank I think, please correct me if i'm wrong). Check the one way valve is working near the condensor. Mine was blowing both ways and the unusual fluctuations in MAF confuses the hell out of the ECU wrt boost solenoid duty cycle, ultimately resulting in apparent det, fuelling and timing issues.

Obviously could be many things but thought i'd throw this in.

Sonic'

I did check earlier one of the one way valves that goes to the boost solenoid, and that appeared to be working ok (ie I could only blow down it one way)

Not sure if what you are talking about it is the carbon cannister one, I havent checked that one yet LOL

I have another problem that has appeared the last day or so

When I am driving the door open light has started to come on and flicker on and off, it seems to do it more if I go on boost, or lift off sometimes one or the other

Ive checked all the door switches and they are fine, and this door open light only tends to come on and off when im driving, or at least when the engine is running

vulnax999

iTrader: (7)

The valve mentioned is ;ikely the one under the throttle body - the PCV, looks after breathing into/from crankcase... and may well be involved with the petrol tank breather that goes to the carbon canister.

See here -
AndyForrestPerformance


As for the door open light, check the wiring at the door hinge side as these wires can / are crushed and earth out!

Rob_f

Check the valve next the the carbon canister. If this is not working your manifold pressure under boost will leak into the fuel tank. Your MAP sensor will tell the ECU to adjust the boost solenoid to compensate, and basically everything gets messed up.

TURBO187

I have exactly the same issue.
Car judders under boost like you describe and also the door open light goes on and off intermittently. I have check wiring and door light sensor. ALL OK
Could this be linked with the car juddering?

Sc0oby

had the same problem with my V8 jdm sti motor. under part throttle it feels like hessitating but when you boot it under full throttle its fine. really curious how to solve the part throttle judder

GH80

I had something similar on an old Clio I had a few years ago. When I went round a left hand bend the car gave a slight judder. Got worse quickly and caused it to break 2 engine mounts! LOL french piece of crap. It turned out to be a dodgy electrical connection, have you tried letting the engine idle and giving all the wires a wiggle?

The door open light would make me think bad connection or earth somewhere.

joz8968

iTrader: (13)

LOL I had an engine mount break on my old ph.1 Clio 16V too!

The resultant vibrating noise sounded just like a massive big end failure! Scary.