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Engine Surge ???


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Hi guys Can anyone shed some light on my problem please whilst I still have some hair left ?

Ive got a w reg turbo 2000 thats surging ? holding back ? almost methodically whilst accelerating gently, more noticeable uphills or under load !, its like someone switching something on then off at the same speed repeatedly wether engine hot or cold.

So far I have fitted a boost gauge to see if its losing pressure and all seems to be fine, ive changed the plugs  for NGK 6s. and the plug leads. coil pack, fuel filter, most of the induction pipes pre and post turbo including the t piece (and the restrictor pill is in place) ive changed the boost solenoid pack and cleaned the idle control solenoid, and I only run it on Shell v power.

Ive tried an ecu reset and ive had a diagnostics chap plug his box of trix in and its not throwing any codes nor has any history of. Its also had another tmc and dump valve chucked at it, but still its the same.

If anything since the weathers turned colder it feels worse, can it be oil related ? ive only owned the car a couple of months so as yet not done an oil change.

Any ideas anyone pleasssssssse ????? 

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Hmm with the list of stuff you've tried I'm stumped, it sounds like the map as the are prone to these faults, is the other man new or used? Could be a dodgy used one, or even a bad batch of new ones, also was it genuine or repro, is the label the same as the one you removed? Are the wires for the man in tact at the 3 pin plug?

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Hi mate welcome to S.O.C 

I'd have a look at fuel pump make sure it's working ok and not struggling to push the fuel through under load. Again sounds like same problem another chaps having with his Fozzer, he's just testing is lambda sensor this week well changing it see how that goes I guess, and if it works worth a try . 

I've found with MAF it happens when slowing like at light's or a roundabouts it would cut the car out but underload was fine so don't think it will be that. I would also check for any air leaks split pipes or not pushed on tight enough. :D

 

I've not heard bad oil doing that either so unlikely but if you aren't sure when it was last changed I'd give it a change with new filter :) maybe worth doing the fuel filter to. try the cheaper option's 1st :D

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Hi thanks for the welcome and reply.

Ive changed just about all the pipes in search of an air leak and cant find anything out of order. Its fine on de-acceleration and tickover (although a little lumpy maybe, like a very slight misfire) but it starts and runs fine, boost still comes in when supposed to although when it does it exaggerates the surging pull, literally every second, its like boost brakes boost brakes.........etc etc, but it still achives full boost and holds it, and your speed still climbs quickly. but I get the distinct impression that it wants to clear its throat and really start pulling without the holding back, and ive changed the fuel filter with no difference.

Im thinking maybe I could check the flow rate of the fuel pump but is it forced to give me a correct reaing when not under load ie going uphill ???

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My maf was faulty when I got the car, the guy explained it just like papa has and as soon as I relayed that info to a mate he knew it was the maf, he then told me to do the diagnosis thing for classics and that confirmed what he had said, mine was fine coming down the revs but would have a break in the pull under load, it idled sometimes lumpy and sometimes died altogether, weird thing was with mine you could have a 2 mile drive with it doing it non stop and other times you could drive 20 miles without a hiccup

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Has it done it since you've owned it ?

Has it got any mods or been remapped?

Maybe do a compression test (check the plug gaps / condition while there out)

Check the map sensor , vacuum pipes and for loose loom plugs /earths

Hope you suss it soon fella

Keep us updated ;-)

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Yes bud i noticed it straight away, wish i hadnt bought it now, but it didnt seem that bad at first.

Ive no idea about a remap as ive not had it long, no mods that i can tell of. The plugs are new last week and ive replaced the leads and checked for air leaks.

As for earths ??? No, which ones ? And yes think a compression test is in the menu, although the plugs that came out looked all in pretty good nick and a reasonable colour, nothing that would ring alarm bells and shes not smoking either. Confused.com !!

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have you got a boost gauge fitted ? as if its unmapped it should read 0.8 bar

I run ngk 7's (not the ngk6's)but I think their the same fitment just a different heat rating . if you pop the plugs out (to do a compression test)check the gaps and look for cracks in the porcelain.as if over gapped the spark can be blown out by the boost and being awkward to fit ive heard of them cracking during install ,both of which give a misfire symptom .

earth sometimes the earth cable under the tmic can either be forgot to be refitted or corrode .The loom plugs are 2 grey plugs that undo to allow you to remove the engine without unplugging every sensor . There located at either side one behind the windscreen washer bottle and one near the boost solenoid ,id check those and look for any break in the insulation on all the sensor plugs (cam,crank ,maff,map lambada ect...)

ideally I guess you need to find someone local with the same version scoob that's willing to swap items over ie maff map ect as there the usual culprits for your symptoms. or find a local (or mobile)scooby mapper as they might be able to fault find a bit better than someone with a generic code reader.

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Hi bud, thanks for the input, The plugs are new last week so should be ok, the ones that came out didnt look to old either. I will pull them and double check though, what gap do you recommend, 25 ? As for the boost gauge yes its reading about 0.8 ive changed the plug leads,coil pack, fuel filter, boost pack cleaned and changed, maf replaced with new non gen ( but worse so took it back off ), inlet pipes before and after turbo. Tmic replaced for one off a bugeye ( bit newer and bigger) and dump valve changed from recirc to bov. Problem never changed.

Il also take a look at this earth strap, dont remember seeing one when i had the intercooler off !

Cheers bud, will let you know how it goes.

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On the classics the earth is from the gear box to the chassis leg/battery, most cars have one from the gearbox to the Battery or somewhere near the Battery as an earth point, the wife's first car a pug 306 had issues one day on the way to uni, she said the clocks were bouncing the needles all over the place and the engine was acting like she was out of fuel despite filling the tank before she left, I told her to get to uni as she was half a mile away and I'd go and look at it, she didn't get there, it died just round the corner, I went to go look at it and straight away spotted the earth had snapped off the box end, in was expecting a fried ecu so was quite shocked when I re connected it and it fired up, I've had a bad earth on a v6 conversion I've done for someone too, they were all connected but as they'd been removed and refitted they were not making full contact and we only had 2 out of 6 injectors firing, I got some 8awg cable from my audio system and ran it from the neg on the Battery to the fuel rail and got all 6 injectors, I then removed all earth's and sanded all the connecting faces and refitted and it was fixed, even though they weren't dirty they still didn't contact properly

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Well just to update on the surging issues, ive now checked and cleaned all the earths and loom connections and.......... It made no difference.

Them i discovered theres a local garage who specialize in subarus, so i took a drive to see them and explained the problem, yep they said, its the knock sensor, common as muck on them to be faulty, apparently. So £40 later i had the sensor changed, and guess what guys ??????........... Its still doing it !

returning to the garage tomorrow.

To be continued....

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Ok well £295 later and i just got my car back from the scooby guys, they had her plugged in checked everything and decided that the ecu was to blame ! So fitted another.

They said everything was 100%, car pulls like a train they said, one of the

Tidiest UK scoobies theyve seen ! Theyve been up and down the rd and cant feel it anymore. Yippee !!! Bril i said. They insisted i took it for a drive with one of them in with me to prove it was fixed..................The cars booked back in for thurs, its still doing it :-(

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