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[maracus]

hi peeps bit of a puzzler for ya...

I recently changed from a td saloon GLS to a CDX estate, both on a manual. i used to get a calculated 36 mpg on a regular basis and occasionally nearer 40 for driving like Gramps. The car didn't exactly feel slow after being used to a 1.8 astra sport. Now i'm in my estate i'm barely getting more than about 30/32 mpg and it feels flat below 2,300 rpm. I had the car 3 up the other week and to accelerate from 50 i had to find 4th, then 3rd to make any sort of effort to overtake. The old saloon could pull a bus behind it like it was empty (not literally but the point is there).

One night i was heading home with my foot to the floor in 5th, could barely muster 115 then when i backed off, a load of red hot embers flew out from the exhaust. For the next day or2 it had its low down pull and was great on fuel, but progressively got worse again.

I assumed it was the cat blocked so changed that. No difference. Then i changed the rest of the exhaust. No difference. I noticed the thermostat seemed to be stuck open as the engine wasn't getting hot properly. Changed that, temp now spot on, all else, no change. I've poured a tub of redex derv into  20 ltrs of fuel and thrashed it, no change. and again by the reccomended dilution, still nothing. Also swapped the egr valve, little solenoid things attached to the vacum pipe from it, and the MAP sensor off the other car, also no difference.

The turbo sounds like it boosts fine and it doesn't smoke more than i can expect. i cant see any obvious hose splits or damage to the intercooler, but, that said, i haven't removed the hoses to thoroughly inspect. Also, it seems spot on as it should when its hot and sunny, but as soon as it starts to think about getting cooler it all goes out the window. 30ish MPG cant be normal even for the heavier estate, surely???

Sorry about the waffle i hope someone can shed light on this, much thanks in anticipation. I desperately want to chip the car  but want it running right first lol so kinda wanna get it sorted; 450 miles to a tank is starting to get to me

[aaronjb]

450 to a tank? I should be so lucky - I get 350 around town out of mine (granted it is an automatic).

Anyway, moving on..

I'd check if the MAF is hooked up to the correct manifold reference line; if it isn't you'll get a general lack of power but no fault codes (been there, done that)

Also that the EGR isn't stuck open and/or the EGR solenoid isn't continually open - then you'll get a lack of power off boost (plus plume of black smoke) and power on-boost albeit less than you should have as you blow boost out of the exhaust.  In my case that was solved by disconnecting the vac line to the EGR valve on the manifold, otherwise you'll have a slightly more complicated test (or blank off the connection to the exhaust manifold with a bit of tin can - it'll last long enough to test it, at least!).

[Welung666]

Where are you Maracus?

[maracus]

i'm in the Huntingdon area, Cambs.

disconnecting the vac line- do i need to blank it off or doesn't it matter? i'll give that a go tomorrow see what that does. not got an airflow meter on this one so doubt its that..
in fact, thinking abut it, i bet it is that solenoid because i didn't swap that one  (couldnt figure if it just pulls out or what so just left it) Does it undo or just slide off or anything like that?
will blank off the EGR valve anyway i gather this gains a bit more power anyway but want it running right first lol

Will post on here again tomorro to inform of progress...

[Evo]

Suggest you check the small diameter tube which goes from the underside of the inlet manifold to a pressure sensor (a 1" cube) mounted on the bulkhead .... it's above the dipstick. This get blocked by oil & prevents the turbo from operating effectively thus causing poor acceleration.

Once you have the engine cover off it's a 5 minute job to check. Not sure it will effect your fuel economy though.

[Omegatoy]

Interesting one!! I would have said exhaust blocked too, did you only change the cat or the whole system?
should be almost full boost at around 2000rpm not as late as you say at 2300, wondering if you have a boost leak in the intercooler or something? if its been driven like mrs daisy for a few years it could be the ecu has to learn, when i swap ecu around as im want to do occasionally it always goes very well for the first few days then gradually the performance settles down as up here on the mountasin roads you cannot boot it,
if the boost sensor is not blocked with crap or its pipe split, and your positive the leak off pipes including the one back to the pump are ok, then try removing the ecu for a few hours, let us know how you get on!!

[hoofing it]

have you tried the paper clip test.

[Agemo]

Not sure if you are due for a fuel filter, but try the Diesel Magic trick.    It will make sure your injectors are clean (Better than just Redex in then tank). 

[aaronjb]

disconnecting the vac line- do i need to blank it off or doesn't it matter? i'll give that a go tomorrow see what that does. not got an airflow meter on this one so doubt its that..

It doesn't matter - the vac feed on a diesel is from a vac pump rather than the engine, so unlike a petrol you're not introducing an unmetered air leak when you unplug it.

And .. you do have an airflow meter Early TDs (like mine) have a MAP sensor only, later models have a MAF sensor just after the airbox.

Here's some pictures from an earlier thread of mine:

Here's the EGR valve - I've unhooked the vac feed from mine since this photo was taken (everything was plumbed in wrong after the previous owners engine swap!):



This is the EGR solenoid - yours should be attached to the bracket on the inner wing, not dangling down here like mine was:


(Depending on year you may have three hoses on the solenoid with one running to a little filter cartridge)

This is the MAP sensor - it should be attached to the hose going directly to the underside of the inlet manifold:


Like this one:


HTH!

Oh and yes, I forgot to say - obviously do a new air filter/fuel filter/diesel magic in the fuel filter if it's not all been done recently

[maracus]

cool cool... just a quick point to add (gotta dash- mrs's house for dinner by 5, oven is on!!!) while i got chance...

Based on what my tired mind could take in during the early hours this morning, today i unplugged the two little black boxes, one in turn. The first one i unplugged, the car performance was completely shot, so plugged back in and removed the other plug.
Its abit hit and miss i know but on the way from work, the instant cons gauge seemed to be giving a much better reading than it did. I will not know for sure til i've driven it abit more but will update soon..

..and yes it has had new filters oil and redex in the fuel filter too but i'll try that D magic stuff it seems highly rated on here

I'll reply abit better later when i got time to think abit easier and will check the further points suggested.
Not paperclipped it yet, surely nothing will be flagged if the management light aint coming on?

Changed whole exhaust eventually, and as for the turbo, you can hear it spooling up it just seems slow doing so, but the car doesn't open up and pull until the 2300 mark

I'll let ya know a bit more shortly... ta

[hoofing it]

cool cool... just a quick point to add (gotta dash- mrs's house for dinner by 5, oven is on!!!) while i got chance...

Based on what my tired mind could take in during the early hours this morning, today i unplugged the two little black boxes, one in turn. The first one i unplugged, the car performance was completely shot, so plugged back in and removed the other plug.
Its abit hit and miss i know but on the way from work, the instant cons gauge seemed to be giving a much better reading than it did. I will not know for sure til i've driven it abit more but will update soon..

..and yes it has had new filters oil and redex in the fuel filter too but i'll try that D magic stuff it seems highly rated on here

I'll reply abit better later when i got time to think abit easier and will check the further points suggested.
Not paperclipped it yet, surely nothing will be flagged if the management light aint coming on?

Changed whole exhaust eventually, and as for the turbo, you can hear it spooling up it just seems slow doing so, but the car doesn't open up and pull until the 2300 mark

I'll let ya know a bit more shortly... ta

this shows codes stored and won't always display the eml light.
try pulling he vac pipe off the egr valve and see how it runs

[aaronjb]

Changed whole exhaust eventually, and as for the turbo, you can hear it spooling up it just seems slow doing so, but the car doesn't open up and pull until the 2300 mark

That sounds exactly like mine was when the EGR was stuck open - what I presumed (but haven't proven yet) is that my EGR solenoid is stuck in the 'open' position, always supplying vacuum to the EGR valve rather than only supply vacuum during steady cruise states.

Incidentally you don't really gain power by disabling the EGR as the valve should only be open when you are cruising at a steady speed and/or very low throttle angles (er.. not that there's a throttle plate on a diesel, but you know what I mean!) - what it does is pass a certain amount of inert (exhaust) gas into the intake to be re-burnt, thus reducing the effective cylinder capacity and increasing steady-state economy and decreasing NOx emissions.

[maracus]

Changed whole exhaust eventually, and as for the turbo, you can hear it spooling up it just seems slow doing so, but the car doesn't open up and pull until the 2300 mark

That sounds exactly like mine was when the EGR was stuck open - what I presumed (but haven't proven yet) is that my EGR solenoid is stuck in the 'open' position, always supplying vacuum to the EGR valve rather than only supply vacuum during steady cruise states.

Incidentally you don't really gain power by disabling the EGR as the valve should only be open when you are cruising at a steady speed and/or very low throttle angles (er.. not that there's a throttle plate on a diesel, but you know what I mean!) - what it does is pass a certain amount of inert (exhaust) gas into the intake to be re-burnt, thus reducing the effective cylinder capacity and increasing steady-state economy and decreasing NOx emissions.

often wondered the ins and outs of the whole EGR thing 
also, 'steady cruise states' is when fuel consumption really suffered, why stuck open?? maybe not opening at all?? Which makes me wonder, would blanking off the EGR not cause such symptoms?

Any hows, yeah... i unplugged the wiring to the EGR solenoid and it goes loads better now, it has throttle response and a desire to accelerate again too. Also, for the first time ever, i managed to maintain an average consumption reading of 37mpg heading into cambridge 
 also, the turbo spools by the time its around the 2k mark 

I would think that this 'cure' would indicate that there is a problem, as you suguest, with the EGR. Altough i did change the valve for one i can assume was good, I would think maybe there is a problem along where the other vac pipe goes from the solenoid off under the manifold, or maybe the wiring/some sort of eleccy control unit hidden somewhere in the dash/etc. - any ideas???

will be getting some diesel magic, tried to earlier but the local halfrauds only had petrol magic 

I did try previously disconnecting the EGR vac pipe from the valve but it seemed to make no difference.


  a MASSIVE thank you to all involved so far... you have saved me some serious annoyance!!

[maracus]

Suggest you check the small diameter tube which goes from the underside of the inlet manifold to a pressure sensor (a 1" cube) mounted on the bulkhead .... it's above the dipstick. This get blocked by oil & prevents the turbo from operating effectively thus causing poor acceleration.

Sorry i should of followed this up  will look tomorrow i think thats what im getting at (???the solenoid??)

[Omegatoy]

glad you found it, first thing now is to thoroughly clean the egr, (unbolt the whole throtle plate housing)you should be able to suck the tube and see the egr moving in and out when its clean,
if this dont cure it then it must be the solenoid