engine goes to stall when revved from cold. help?

[DAVES_GT3]

evening!

i have a small problem, well i hope so anyway.
when my 1997 gt3 is revved from cold it goes to stall rather that pick up. if i keep the revs above 2500 rpm it seems ok. its also ok when warm.
i was suspecting the IAC.
I did a log file but unfortunately never started saving the file unlil it got to 47 deg c. at this point the IAC was at 105.
i have since reset the IAC via freescan so i cant really get a true reading at the moment.
it does currently read 175 from first starting (ambient temp) and 131 at 47 deg c. this sounds about right i think..
still obviously have the fault.
it doesnt seem as bad at the moment because of the warmer weather but when it was colder i couldnt move it off the drive for 5 mins because if i did it would stall. it was embarassing having to keep the revvs so high to stop it stalling when the clutch was engaged. very spluttery.
TPS is all ok.
as i say cold fault only.
any ideas anyone?
dave

[medic327]

Is the throttle body clean? If not the iac will give you high counts when you first start the motor, as it will open up to try and keep the revs up. If there is too much carbon build-up in the throttle body the IAC may not be able to compensate enough by opening up maximally, requiring you to depress the accelerator in order to keep the revs up and prevent a stall. Might be worth a quick look inside the throttle body behind the butterfly valves for any carbon build-up. NOTE: I don't know if the butterfly valve in the lotus throttle body has a protective chemical coating, so if you do find any carbon build-up you may not want to use any chemical cleansers. Take a look at the inlet for the iac as well for any carbon build up. Had a similar sounding problem on my car once (non-lotus), cleaning the throttle body corrected it for me. Hope this helps. Disclaimer: I am not a mechanic, so please take my advice at your own risk. Best of luck!





>> Edited by medic327 on Sunday 3rd July 23:32

[lotusse89]

IAC should be 30-40 when water temp is up to 82dec C.

Travis
Vulcan Grey 89SE
www.lotuscolorado.com/vulcangrey/

[daves_gt3]

cleaning the throttle boddies then. does this involve taking the turbo inlet box off?
unsure how do do it really.
thanks
dave

[medic327]

****BUMP**** That's a good question Dave, I don't know the procedure for opening up your throttle body. I was just answering your question from the perspective of any car with high IAC counts and an unstable idle. Like I said I am no lotus expert (not even a lotus owner....YET) and not a mechanic, just good with my hands. Can anyone else here help out Dave with a throttlebody check? Best of Luck!

[daves_gt3]

if anything the IAC counts are low.
they should start at 170-175 when cold and go down to 30-40 when warm. it does seem to be doing this now after resetting the IAC via freescan but i still have the fault.
before resetting the counts wernt the same.

thanks anyway
dave

[lotusse89]

daves_gt3 said:

if anything the IAC counts are low. they should start at 170-175 when cold and go down to 30-40 when warm. it does seem to be doing this now after resetting the IAC via freescan but i still have the fault. before resetting the counts wernt the same. thanks anyway dave

Well, if the IAC is staying at 30-40 when warm then that ruins my theory that you have a manifold leak...

I recently worked on an 89 that wouldn't start well, or rev without dying, and the IAC was almost impossible to adjust correctly because it had a leak in the hose between intake manifold and the crancase breather, same hose goes to the fuel pressure regulator.

A crack or hole in this hose can usually be heard as a soft clicking sound. Once I replaced the hose, it was possible to get the IAC to stay still at 35 when the engine was warm. Now the engine will start easily, idle steadily, and rev without dying.

Look for a manifold leak, and then redo the IAC adjustment using freescan and the minimum air rate bleed screw adjustment.

If that doesn't work, then look at dirty butterflies, just take off the plenum cover.

Lastly look at ignition or timing issues.

Travis
Vulcan Grey 89SE
www.lotuscolorado.com/vulcangrey/

[DAVES_GT3]

thanks travis

i did have an exhaust manifold leak a few months ago but now that is sorted. that may have been why the iac was offset then.

what is the minimum air rate bleed screw adjustment?

just found out the iac is at 45 - 60 when running warm. a bit eratic. it does show in the freescan manual that it should be between 40-70 when running

i also had a perished rubber elbow that came iff the end if the fuel rail. the pipe the elbow fits onto is very thin, 2-3mm, and goes into a box by the engine wall but im unsure what they do. ill maybe have a look see if there is a problem around there too.

is there anyway of cleaning the throttle bodies without taking them off? i.e: like a fuel injector cleaner does.

cheers dave

>> Edited by DAVES_GT3 on Tuesday 5th July 20:09

>> Edited by DAVES_GT3 on Tuesday 5th July 20:12

>> Edited by DAVES_GT3 on Tuesday 5th July 20:18

[lotusse89]

DAVES_GT3 said:

thanks travis i did have an exhaust manifold leak a few months ago but now that is sorted. that may have been why the iac was offset then. what is the minimum air rate bleed screw adjustment? just found out the iac is at 45 - 60 when running warm. a bit eratic. it does show in the freescan manual that it should be between 40-70 when running i also had a perished rubber elbow that came iff the end if the fuel rail. the pipe the elbow fits onto is very thin, 2-3mm, and goes into a box by the engine wall but im unsure what they do. ill maybe have a look see if there is a problem around there too. is there anyway of cleaning the throttle bodies without taking them off? i.e: like a fuel injector cleaner does. cheers dave >> Edited by DAVES_GT3 on Tuesday 5th July 20:09 >> Edited by DAVES_GT3 on Tuesday 5th July 20:12 >> Edited by DAVES_GT3 on Tuesday 5th July 20:18

The minimum air rate bleed screw is a little slot5 headed screw at the butterflies. it is protected by a cylinder that is around it. If you have a bendable screw driver attachment with a flat blade, you can reach it by snaking under the fuel rail, to the left of the throttle (left being towards the front of car, leaning over the passenger side UK).

You warm up the car, and then adjust this screw by very tiny ammounts while watching the IAC counts in freescan. Let the IAC counts settle between each adjustment.

Look for intake manifold leaks, not exhaust.

Look at the charcoal cannister vent line to the front of the engine (intake manifold) near the thermostat housing. Also trace the hose from the fuel pressure regulator, under the intercooler to the intake manifold, and then follow that to a one way valve and then to the crankcase breather ontop of the engine near the flywheel. Any leak in the intake manifold will screw with the IAC, and the idle. Also trace the MAP sensore hose (you can see all the hoses on the diagram under the hatch).

Travis
Vulcan Grey 89SE
www.lotuscolorado.com/vulcangrey/

[DAVES_GT3]

good info.
just been having a look.
ive cleaned all the throttle bodies because they were gunged up with fuel/oil/carbon depasits.
took the charge cooler off and the black plastic t-piece that suplies the fuel regulator was loose. tightened that up. also found another couple of joints that needed doing.
checked the two one way valves. there ok.
going to give it a good check over again when its daylight to check some more pipes.
ill also check that minimum air rate bleed screw.

at least it gives me something to check for.
thanks for your help

dave
ill report back soon

[medic327]

so what happened??

[daves_gt3]

sorry for late reply been busy staring at the engine bay
still not got any further. definately found a couple of dodgy air pipes that would cause a problem but no joy.
since reset the ecu and no difference.
noticed when i blip the throttle though from tick over it hesitates there too. its strange. maybe its supposed to be like it. could do with another GT3 sitting next to it to compare really.
i think all in all ive run out of things to check.
pepole have said to me about the 3k stumble but its at lower revs than that. not saying i drive like a grandad but there comes a time when your at 2000 rpm approx in 2nd 3rd or 4th.
any suggestions?
dave

[DAVES_GT3]

IAC replaced and set up correctly along with fuel filter.
Seems to have cleared the problem and runs a lot smoother.
still got the stumble at very low revs but im not too bothered abou that.

Just got to try and sort the low boost now.
suspecting the EPROM chip. Every reading ok and no leaks or blockages were ther shouldnt be.
might try a chip upgrade to prove a point.
im presuming if there is something limiting my boost to 0.85 it will still do the same with a higher boost chip.
if it runs up to 1.2 bar on a puk 11 chip then all is ok.

will keep posted

dave