Punk3rs

Can any one help with an issue I have with my classic? I'm suffering from engine hesitation when the car is not on boost, once boost kicks in the hesitation stops and the car runs fine. It happens every time I accelerate medium to hard. The car is completely standard with no modifications at all, I've owned the car for 8 weeks ish i bought it as a non runner and this is the last issue to fix. So far I have I have fixed/replaced:
MAF
IACV
TPS
Plugs
Leads
Coil pack
Boost control solenoid

I'm out of ideas now. it feels like an ignition problem but I've been over it a few times I took the plugs out yesterday and they were spotless no carbon build up at all. I'm at a loss now any help would appreciated if you need any additional info let me know thanks.

It spent the day at my local garage today where they got it on a proper diagnostics machine but no faults were found, not even an intermittent misfire which is what it feels like. This problem is really annoying :-(

Punk3rs

Noone?

albob

given what u have replaced -- its a difficult one !!

How bad is the hesitation ??

I have a hesitation on mine (my00), but it disappears after the engine warms up properly

Punk3rs

When its cold its pretty bad (kangaroo fuel) but probably more apparent cos I don't boost it till its warm, when it's warm it ls like having a dead zone between 2k-3k with very little and uneven power once past that point it has full and smooth power, it's not just acceleration though if I'm cruising up the motorway and the engine is within that range the hesitation is still felt.

TonyBurns

iTrader: (3)

What year car and what model?

Tony

Punk3rs

96 awd 2000 wagon, 2.0l Turbo

TonyBurns

iTrader: (3)

Stupid question, but turbo lag?
Have you ever owned a turbocharged car before as you get the lag before the turbo kicks in, especially on a bigger turbo'd car like a 96 which runs a TD05 16G.

Tony

Punk3rs

It's not Turbo lag the problem is only happens within the lag but it defiantly isn't turbo lag my last car was a rb26 skyline. Everyone who has driven can feel there is a problem including the mechanic today. I thought it was a misfire in this rpm range but the diagnostics unit didn't register any misfires .

underground.scoobys

check for any vacuum leaks/splits around the turbo. all so if its a 2 port boost solenoid check if the restrictor pill is in the small vacuum pipe after the T going to the turbo if there's no restrictor pill you just ruining wast gate presser.

if its not that it could really be a number of things normally maf / lambda sensor as both needed to keep the car running smooth. all so might me worth cleaning your temperature sensor.

is the CEL on? and did you reset the ECU if it was on.?



BASH FROM UNDERGROUND SCOOBYS.

Punk3rs

Just checked there is no restrictor pill so I will add one and see if that improves the situation, I've pressurized the system so I know it's not a vac/boost leak cos that was my 1st thought, I don't have the CEL on and connecting the black/green plugs under the dash show no error, neither did the diagnostic machine in the garage.

I will add a pill and update, thanks for the advice Bash. I have one more question about the plumbing and the pill now :-)

My layout is:
A small pipe from the Turbo to a T-joint (pill in this pipe?).
1 side of the T-joint goes to waste gate.
Other side of T-joint goes to the back of the boost control solenoid (side that points towards the inner wing))
Then one long pipe from the base of the BCS to the inlet pipe before the Turbo, by the start of the plumbing for the IACV if memory serves me right :-)

underground.scoobys

The 2 port boost solenoid has 2 pipes one on the side one at the bottom. And the restrictor is as you mentioned in the post on the pipe from turbo nipple to the T. It’s about an inch from the turbo nipple in the pipe.

The 2 port and the 3 port boost solenoid are a different lay out.

And it sounds like you got the 3 port boost solenoid it has three pipes one on top one in the middle one at the bottom.

If am not wrong the top pipe is to the turbo nipple

The middle pipe is to the waste gate actuator

The bottom pipe is to the air intake resonator box

The restrictor is in the bottom solenoid pipe just after the first little bent its about an inch from the solenoid to the pipe.

On the 2 port solenoid its better to reduce the restrictor pill holes size for greater safe maximum boost.

On the 3 port solenoid it’s totally the other way around you should increase the restrictor pill hole size for greater maximum boost.

The restrictor in the bottom pipe determines the rate of bleed a large restrictor hole has a high bleed rate making it easier for the solenoid to keep the system pressure below the actuator spring rate pressure which will result in a higher boost output.

The feed from the turbo outlet duct has to pass through the solenoid to get to the waste gate actuator if the solenoid is dirty with oil vapours it might have all so blocked the restrictor i would recommend cleaning the solenoid if its second hand and make sure the hole is not blocked on the restrictor.

A small restrictor hole on the 3 port solenoid has a low bleed rate making it harder for the solenoid to keep the system pressure below the actuator spring rate pressure which will result in a lower boost output.

Check your exhaust and manifold for any leaks as well.

Hop it helps good luck



BASH FROM UNDERGROUND SCOOBYS.

Tidgy

was the garage a subaru specialist or a general garage?

Punk3rs

Thanks Bash! it was the 2 port one on mine, I replaced all the hoses from one that was being broken for spares and it made a huge improvement to the boost. I did try making the hole a little smaller but it just felt like I was crashing into a wall at about 5k rpm I'm guessing fuel cut or somthing from over boost maybe, so went back too stock pill till I get the hesitation issue fixed.

So the pill did sort out my ow boost issue but I'm still getting hesitation so I've replace a few more bits as they we're going cheap and the car being broken was running right. I've now done boost solenoid and MAF as old ones we just cleaned and checked. Also now done MAP sensor and the ignitor? (The flat unit on the same strut as the BCS which is on some coil packs). Still no change just before boost I'm getting a lot of hesitation. Also whenever swap out parts a do a ecu reset.

Tidgy, it was a standard garage but the diagnostics guy deals with jap cars, it was only computer diagnostics to check for things that wouldn't throw up a CEL I.e. occasional misfire. but it came back with no faults found.

DonNedly

iTrader: (10)

sounds like it needs a go on a dyno with a specialist/tuner.

Tidgy

yeah my thinking exactly, afriad he's fallen into the chasing an issue round the engine bay trap

underground.scoobys

what kind of dump valve are you using stock or after market recalculating or atmosphere one?



BASH FROM UNDERGROUNG SCOOBYS.

daza1974

iTrader: (1)

i have this on my 99 turbo 2000
it is quite a common problem i was told by a few people on here .
its something to do with the standard map so i guess a mapping session will sort it

Punk3rs

Its the stock recirulating valve.

Punk3rs

Fixed this issue it was the O² sensor that was giving the ecu incorrect information so the ecu was over/under fueling, replaced that now everything is working well.

astraab

heya mate i had the exact issue . turned out to be my fueling .. has your filler neck pipe been replaced as mine was the fillerneck being rusty and getting aload of **** in the tank , when i ran down to nothing or close to it pulled all the crap in the bottom of the tank into the ful filer . i replaced my fuel filter and there you go it was fixed . but my fuel pump is noisy now so il replace that too . just try changing the filter if it hasnt been done in a while