boost problem in lower gears

[stronzen]

hi guys,

we recently discovered a problem on a friends fd

its a 98 model, that has sat in the garage for the past months (since august/september 2010)

anyway, we took it for a spin yesterday and everthing seemed fine, while just cruising around

once we got the temps up, we starting to give it a go

3.,4. and 5. gear were pulling really well. you could feel both turbos kicking in (first at 3500rpms and secound around 5500rpms)

however 1st and 2nd gear we just felt something must be wrong. unfortunately the boost gauge is not working at the mo, but you deffo feel there is just pretty much no boost. it drives like a N/A car. you could slightly feel the first turbo spooling up, but not much more

every now and then tho, we surprisingly did get boost in second gear too (tried it a couple of times)
say out of 10 atempts from 30/40kph to 90/100kph we had two with boost!

i couldnt figure a pattern to it tho

mods:
complete 3" exhaust incl high flow cat
hks filters
hks intercooler

suppoused to have a tuned ecu from hks. but we never saw a seal or sticker (does hks do that ??)
strangely the car is still limited at 180kph and i dont think any tuner will leave that out

no boost controller as for yet

any ideas what the problem here might be ?

[JohnP]

sounds like one-way check valve classics.. did the car feel like it pulled on the first turbo and not the second? i\'ve had all kind of trouble with check valves on mine, made the mistake of replacing a couple with used ones once which went again a year later.. going viton now.

[stronzen]

heard about that before, but never thought it could be them...how many are there about and which is the one to be faulty one ?

is there a way to check them ?

and where do i buy them new ?

and yes, it very ofter felt like its pulling on the first and not on second. you couldnt feel another turbo kicking in

[JohnP]

it could be any of them, but for me, it was the check valve between the pressure chamber (pink, on the right of the diagram) and the turbo Y-pipe.

when looking in your engine bay, the pressure chamber looks like a small black box, and sits right next to the strut brace, on the top of the engine. it has 2 hoses coming off the side of it, that double back under itself. the check valve is under there.

as for new valves, i\'m tryin to get some called "viton" valves from this guy on ebay.

http://myworld.ebay.co.uk/rx-7guru?ssPageName=ADME:X:CEM:GB:1181

hes in the USA, but its cheaper than buying mazda parts, and numerous users on here have done the same.

[stronzen]

is this the one you are talking about ?





how do i check if a valve is faulty or not ?

and how do these viton ones work ? are they a direct replacement ?
how much is he asking :-) ?

[JohnP]

yes, thats the valve i had issues with. these should be non-return valves. so if air travels both ways through it, you have a problem

its quite common that these valves split, or that the hose simply comes off.

i think he was asking around £25 for 4 viton valves, but i\'ll know more when he has them back in stock. i\'m expecting a msg

[stronzen]

alright, i will have a look into them later today :-)

let me know when you have heard back from him buddy

and thanks for your help so far

[stronzen]

just checked the valve, and air is only going one way. so guess that one is ok then !?

[JohnP]

yup.. most of the other ones are hiding under the throttle body/uim. probably wise to check them next?

[stronzen]

will do. will  i need a new gasket or so ?

[stronzen]

i could another thing that i just noticed... when starting the car from cold and keeping it idle i can smell quite a bit of fuel !

now i know from a friends car that rx7s tend to smell a bit, especially when cold, but with this car it doesnt seem to be within the normal range anymore

could it be that there is something wrong with the fuel pump, related to the fuel pump relay issue i had ? or maybe some fuel lines !? but then again i should be able to see some sort of a leak ?

let me know what you think guys

[stronzen]

edit: also i noticed that there is something wrong with the idle control or  so. meaning if the car has warmed up and i give it a few revs (say up to  2000rpms) and let go off the throttle it would almost stall (going  below 500rpms) stays there for a bit and goes up to normal again (around  750rpms) ... that would suggest a vaccum leak, wouldnt it !?

[rust]

i think you should check the Map sensor aswell.. i had that problem and my friend changed it and its idle great now.

[stronzen]

i have already replaced the map sensor with one from a mate´s car (which is running fine)
 
could it be the gas filter in front of it !? how would i check that one ?

[JohnP]

you should check the same sensor i did on mine this week then.. right up on the bulkhead mounted high up, near the oil filter, is a small sensor on a bracket marked *boost sensor* or something similar. my revs were all over the place this week because a hose had slipped off enough to cause a leak.

i\'m 90% your issue is going to be a vac line/check valve issue.... which probably covers half of the car, but check there next.