larry

Impreza classic juddering on high revs..Help pls!!

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Hello people

I took my car impreza classic out today and was giving it a fair bit of acceleration. However upon doing this the car hesitated to accelerate and appeared to have

more of a lag/juddering feeling not a major judder no sounds of grinding from under or back or the front of the car just abit of lag then acceleration then

lag again and i stress it was hesitant.

 

Has this happened to anyone before and does anyone know what it can potentially be?

Cheers

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1 hour ago, larry said:

Hello people

I took my car impreza classic out today and was giving it a fair bit of acceleration. However upon doing this the car hesitated to accelerate and appeared to have

more of a lag/juddering feeling not a major judder no sounds of grinding from under or back or the front of the car just abit of lag then acceleration then

lag again and i stress it was hesitant.

 

Has this happened to anyone before and does anyone know what it can potentially be?

Cheers

I’d try cleaning the MAF and the boost solenoid. Failing that have a look at the HT leads and the spark plugs. Start with the easiest and least expensive first. Is it used daily and when did you last have it serviced? 

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I have cleaned the MAF sensors a little over 3 weeks now. I'd say this happened some time shortly after cleaning the MAF. It is used as a main car.

Last service was done around 2-3k ago. 

How do you check HT Leads do you mean for cracks or slits?

This might sound dum but where is the boost solenoid?..

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Best way is with a multi meter to see if there’s resistance in the electrical flow. 

 

Ive put a pic on. The boost valve is behind the air box. There’s a video on YouTube showing you how to do it. Instead of me writing it out. Ha. 

22C86841-E075-4F74-B33C-89E066ABA1E4.jpeg

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I’d clean the MAF sensors again, sounds like it might be cause.. if it doesn’t come right after another clean just replace it. 

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Did you reset the ecu after you've cleaned the maf ?

Maf clearing is a quick temporary fix so it may be that it's goosed,
What colour label is on it ?


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Thanks Mattb i'l take a look at that video and try it. Aswell as cleaning the maff again.

Stants I did remove the battery terminals for a very short period few minutes and reconnected them back. 

Do you guys have an opinion on this. The car has got a sti turbo (vf 28) decat, sti top mount engine rebuild 2k ago but i have not yet got it 

mapped.. do you think this could be a potential cause? if so why would it happen now... just a thought...

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Could very well be the problem,

If the fuelings all over the place it won't be able to compensate enough for all the changes you've made, what turbo was on before ? & have you changed the air filter for an induction kit or cone?
Personally I wouldn't drive it on boost till it's been mapped,

Worse case it will start to lean off too much and could kill the engine again



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It had a TD04 L Turbo. I have changed the air filter for another stock 1 (service) so no after market induction or cone.

If it is that it needs a map why now after a year. Ill check the above things first and see if it makes a difference then shall contact mappers

how ever £550 for a map is alot.

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If you increase the air flow or/and the exhaust flow you need a re map. It might be that it was ok with just a de cat and a different turbo. I’d get a new MAF sorted and have it checked out to see how it’s running. 

If it’s in need of a re map I’d get an induction kit put on or at least a high flow panel filter. 

 

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I suspect you'll get overboost/ boost creep too if the turbo's trying to push more air.

A map is deffo the 1st thing i'd have done,

You'll gain more power better mpg and you'll know that the car is running safe

Have you uprated the fuel pump yet ? & if the cars not got one a 3port boost solenoid would be a worthwhile investment too

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Thanks Mattb il see now the maf is clean if it happens again then might be worth getting it changed.

Stants I have not yet uprated the fuel pump would you say a wahlbro  255 is a good one for 300-340bhp?

Also a map God willing shall be next just a few things i need to do such as service and reseal a couple of plates.

This might seem like a dum question but What is a 3 port soleniod what does it do?

 

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Hi mate depending on what year or version you have the cars came with either a 2 port boost solenoid or a 3 port solenoid,

The 2 port one is good at controlling regular levels of boost, but if your going over the 300bhp then a 3port one will control the boost alot better, and avoid any unwanted problems, with overboost or spiking or bleeding of and leaving you with none,

If you look at the engine bay from the front of the car you'll see it attached to the suspension turret on your left, there's alot of pipes and vac lines running around it.


2port 1st pic

3 port 2nd pic
34f038ab00fc1dfcad605f380e5116b4.jpg976e106b7f8fb78085f3552fbee5e1df.jpg

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Cleaning the maf again wont fix it. Just had the same issue on my hawkeye. Reading the maf with a proper tester not just a scanner will most probably show an irregular reading. Test dont guess!

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