I seem to be experiencing a few issues, randomly when I start the car it holds itself at about 2500rpm and then will sudenly return to a proper idle, this does not happen everyy time I start it, then yesterday it did it just driving along, I was in traffic in 4th gear and felt the car just pulling away without throttle, put the clutch down and it was the same again 2500rpm stayed like that for about 5 min, did it again today one on startup and for a few seconds driving along, also but possibly unrelated, when i turn the ign on, but dont crank the engine it sparks and fires whatever fuel is left in the cylinders, its running msd closed loop and coil pack conversion. Any suggestions as to what the hell is going on? as a side note the secs nonitor does not show any sensor problems or funny readings when any of this happens

 

I would say you have a problem with the closed loop not falling, ie not cancelling out and leaving a lean cruise mix when it should not.
Closed does not work all the time, like accelerating, high speed/load etc.
If these go too lean the ECM will detect a stall about to occur and raise revs, check your CO at idle, which will NOT BE IN CLOSED LOPP AT IDLE anyway, at least it should not be.
STU is a very very clever chap and knows what he is doing without a doubt, so it might also be wise to seek his help, but I would check baseline CO, set at around 2- 2.5%
tabetha

 

ok I will give stu a bell and see if he can help.

 

I disagree but see where your coming from.

No matter what you set teh fuelling to, if your throttle is closed it simply will never reach 2500rpm. If you go back to basics you will realise that to run a 2litre engine at 2500 rpm, you need an abundance of 1 item... AIR.

Look for:
1) Sticky throttle cable/butterfly.

2) ISCV sticking. (Unplug it when teh idle problem is there, so what happens... If it stays high, give it a clump with a spanner, see if it drops.)

If unplugging it fixed it, its possible your ecu thinks the TPS angle is actually open when its not, as the ecu opens the ISCV once the throttles open. (contrary to popular opinion. It does NOT stay closed... it stays open. )

Also, your ecu SHOULD be closed loop at idle of course, unsure why you think it shouldnt? Expect CO emissions with one of my chips to be <1% (with HC's of sub 500 normally) no matter what injectors your conversion runs.

 

Hi stu

if I unplug it it drops back to base idle straight away so it sounds like the ecu thinks the throttle is open when it isnt! however it doesnt show this on the secs monitor?

last time fueling was checked it was .75%co at idle and hc much less than 500