ive just rebuilt my head on my 1992 escort cosworth, new valves ect.. put it back together 2 days ago when it started from cold it runs perfect and drives fine but as soon as it warms up slightly idle goes up and down and its hard to drive it holds back when accelerating and slightly misses lack of power!!! its running stage 3 by the way!!! from stone cold its mint but after 5 to 10 mins it does this any one help please?? all sensors are new and timming is spot on the fault is obviousely temp related????

 

have you set the base idle?

 

hello yes its set up ok!!! just found that if i clamp off the return fuel hose it runs perfect?? fuel pump or pressure reg ?? what do you think?? thanks adam.

 

increasing the fuel pressure is masking the fault unless your base pressure is to low

 

ok then any ideas?? cos im lost now!!! i thought it could be a lazy pump or pressure reg fault?? is there anything else any1 can think of ?? obviousely increasing fuel pressure sorts it out??????

 

air leak

 

realy??? i put new gaskets where i could!! how would increasing fuel pressure overcome an air leak?? just cant get my head round it!! im a bmw mechanic by trade but this one has stumped me!!

 

air leak will cause all sorts of idle issues,

increasing fuel pressure will mask the fault as it will run rich, just like it does on cold start when you say it is ok.

pressure test the inlet from the turbo up.

set the base idle when hot with the iscv unplugged via the base screw under the throttle body.

check fuel presure is 3.5 bar with the reference pipe off and blocked,

is it on p8?

 

ok thanks, i will test it asap, it was fine b4 i rebuilt the head so its got to be something i touched!!! also it does hold back and wont accellerate properly when it plays up?? almost a missfire!! but not if you know what i mean??

 

added a few more checks in the last post

its worth running a fuel pressure gauge into the car aswell and checking the rate raises 1:1 with boost pressure,

 

its got a stage 3 pts tunning chip??

 

hi have you remembered to plug the map sensor pipes and wires back in. mine ran the same and it turned out to be the map sensor pipe i forgot to connect.
good luck
chunky3

 

hello mate yes ive checked everything its doing my head in!!!!!!!! must be air leak or fuel pump thatas all i can think of, its just weird that its ok when its cold!!!and it runs perfect with the return fuel hose clamped off!!!