My zed well this is the problem driving along boot it gets to 4000rpm boost kicks in heavy hesitation/missfire goes past this all the to 7000rpm change gear rapid ,foot down no power revs dropping foot off the accelerator fires back up tap the throttle fine as soon as you boot it the same thing happens again when you change gear it dies again with your foot down take foot of fires up accelerate gently no probs only occurs when you load up the engine .

 

here is the spec 93 tt import

apex afc

hks evc 3

hks fmic

running 385 bhp at flywheel at 0.95 bar rolling roaded to weeks ago at sanspeed in bexleyheath evc and afc set up correctly .

 

here are the other problems possible slight leak at egr possible manifold leak only slight though .

 

Here is what i have done so far cleaned up ptu connections, changed coilpacks cleaned up injector connections and cleaned up temparture sensor connections stiil got the same problem .

 

Sorry for the long thread but i thought id give you as much history as possible so you know what im dealing with suggestions on this would be much appreciated jim

Boost leak or possible damp maf causing massive overfuel.

ok mate ill check those possibilities out anything anyone can suggest i should look at ???

Have you checked the obvious, the plugs? A few other things that can cause it are....

TPS or dirty connector

Throttle bodies dirty and sticking

Dirty fuel filter

Injectors or Harness

fuel pressure regulator or Damper

fuel temp sensor

Air regulator

Cas or connector

 

cant think of anything else at the moment

And also

O2 sensers

EGR

AAC valve stuck

there is a hidden message here, imho "dont put your car on a Dyno" This is the third car I ve heard of over last few weeks that have probs after being put on a dyno!!

Boost leak or possible damp maf causing massive overfuel.

Sounds like a major boost leak to me as well.Check your intercoolers and pipes.With the hot weather its possible a hose has softened and come off under boost.

I havnt had a butchers at the car yet because its at my yard at work but the plugs are rulled out and fuel filter are both good and have been checked and also if i had a boost leak would i not be able to hear it last time a pipe come off the intercooler there was f++k all power and when you booted it ,it sounded like a little get engine (heavy whistling)

also the egr or manifold is slightly leaking a slight exhaust tap noise could this exhaust leak be causing the problem ???

seen many a boost leak that couldnt be heard.if you nurse the car up to speed and it drives fine your only using the vacuum side of the cars piping circuit but if you bring the car on boost and it splutters it usually indicates a boost leak.

Jim, mine does this exact same thing!!!! It is not, on my car anyway, a boost leak. It feels like something electrical being knocked out, either by boost or by sheer amount of load.

It is not over fueling, if it was, the exhaust would fill with fuel and you would either get smoke from the exhaust, as it burns in the exhaust, or flames as it runs properly.

My theory, and it is only a theory at the moment, is that its a lack of fuel. I'm wondering if the fuel pump is not providing enough fuel pressure at the time when the engine is demanding max fuel.

Don't know if anyone else has had this symptom and discovered fuel pump problems, I've done a search and don't come up with much although there is lots on hessitation/lack of power etc. The fixes range from temp sensor connector to PTU etc but not much on pump trouble, they either seem to work or don't work but I have known weak pumps before, that continue to provide pressure but run out of umph at the top end.

PS I'm gonna change my pump so will let you know.

Also forgot ask Jim, mines worse if engine is loaded IE A/C on, what about yours??

i dont know about with the air con on mate because ive taken all that out to save weight i see what your saying about lack of fuel pressure when i had i dynoed the bloke said he thought the fuel pump might be a bit lazy because he had to turn the last 2 knobs on the afc right up to run 0.95 bar he said it was leaning off towards the top end but was safe .But although saying that the pump would have to be proper shot to cause it to do this if that is the reason ,surely you would get detting or something if the pressure was a bit low ??? I think what i might do is get an uprated fuel pump i mean if mine aint knackered its getting lazy so it wont do know harm and go from there i think its a bloody pain in the arse though !!!!

i dont know about with the air con on mate because ive taken all that out to save weight i see what your saying about lack of fuel pressure when i had i dynoed the bloke said he thought the fuel pump might be a bit lazy because he had to turn the last 2 knobs on the afc right up to run 0.95 bar he said it was leaning off towards the top end but was safe .But although saying that the pump would have to be proper shot to cause it to do this if that is the reason ,surely you would get detting or something if the pressure was a bit low ??? I think what i might do is get an uprated fuel pump i mean if mine aint knackered its getting lazy so it wont do know harm and go from there i think its a bloody pain in the arse though !!!!

 

before you spend out on a new pump try the fuel pressure regulater and damper as i suggested in the list i put up of possible causes

Carl, correct me if I'm wrong but if the regulator and damper were shot this problem would be there all the time? I've mentioned this problem before and tested both the regulator and damper with a vac gauge and both were fine. My hessitation isn't always present, it comes and goes, but does exactly what Jim's does.

Carl, correct me if I'm wrong but if the regulator and damper were shot this problem would be there all the time? I've mentioned this problem before and tested both the regulator and damper with a vac gauge and both were fine. My hessitation isn't always present, it comes and goes, but does exactly what Jim's does.

 

Fuel pressure regulator has a valve in it, the valve can intermitantly stick so juice gets pumped back to the tank and shutting off fuel supply to injectors, cheaper option to try first

ooow yes worth a try, is there anything that could be added to fuel that might stop it sticking?

carl im going to try your damper theory before changing the pump see what happens the car is at a garage at the moment i thought id let a specialist look at it as im getting very impatient and they are adament its the spark breaking down at some point but im not so sure now your talking about this fuel shortage matter i think maybe thats the avenue to go down now i mean the ptu is fine sparkers are new coil packs have been changed injector connections cleaned i think it must be something to do with the fuel ill phone them tommorow and get them to have a look

Let us know jim if they come up with anything, cheers,

jase

carl im going to try your damper theory before changing the pump see what happens the car is at a garage at the moment i thought id let a specialist look at it as im getting very impatient and they are adament its the spark breaking down at some point but im not so sure now your talking about this fuel shortage matter i think maybe thats the avenue to go down now i mean the ptu is fine sparkers are new coil packs have been changed injector connections cleaned i think it must be something to do with the fuel ill phone them tommorow and get them to have a look

 

Well look at it this way, I'm not saying this is the problem but it def worth looking into. Your loosing power when you have throttle wide open.

 

The Fuel pressure regulator's job is to maintain a constant fuel pressure in the fuel rail and across the injectors.

 

The Fuel Damper smooths out fluctuations in pressure in the fuel rail caused by the injectors pulsating so ensures accurate fuel metering.

 

If either of these isnt working correctly you wont get the correct fuel delivery.

This may well explain why its intermitant, sometimes stuck, sometimes not. Do you know if they are availble after market or Nissan only. Second hand it will probably be!!!

This may well explain why its intermitant, sometimes stuck, sometimes not. Do you know if they are availble after market or Nissan only. Second hand it will probably be!!!

 

give mike at mjp a call,he is listed in the traders section on this forum.

 

he does all nissan oem parts and is a top bloke ;) .

 

 

 

 

 

cheers garry

Let us know jim if they come up with anything, cheers,

jase

 

no worries mate as soon as they sort the problem i let you know what it was im going on holiday next week and im leaving the car with them i so they should have solved it by the time i get back ill put a post up f.a.o of jase m so keep your eyes open in about three weeks if you aint solved the problem by then and vice versa if you solve it before i post you could you leave a post for me mate ??

No probs Jim, just to let you know went out last night in the Zed. Journey there problem there, journey back no prob at all!!! Its weird. If I find it I'll let you know, gonna have a proper look on Tues or Wed next week when I've got some time.

Have a nice holiday mate, make sure you save some serious wonga for your garage upon return. he he. :rofl: :rofl:

No probs Jim, just to let you know went out last night in the Zed. Journey there problem there, journey back no prob at all!!! Its weird. If I find it I'll let you know, gonna have a proper look on Tues or Wed next week when I've got some time.

Have a nice holiday mate, make sure you save some serious wonga for your garage upon return. he he. :rofl: :rofl:

jase i see you live in margate what garage you using to do your then mate ???