Cold Start / IACV Question

[c7trp]

My car won't start from cold without applying a little bit a throttle. It used to start with "no feet" at all, but now it won't....

 

When it catches, it doesn't really want to tick over for the first few seconds, and then the cold start seems to kick in and lift the revs to 1500rpm until it warms up a bit.

 

IACV was changed last year as full of grot, and its never really be spot on since. Tried resetting the ECU.

 

I can hear the IACV 'home' itself when the engine is turned off. It also makes a high pitch whine for a few minutes too (the old IACV did this also).

 

Un plugging the IACV seems to make no difference to the starting procedure, so I figure it's getting a duff signal from another sensor?

 

Where do I look next? Coolant temperature sensor, I assume the ECU uses this to figure out if the engine is cold and wind out the IACV accordingly...?

 

Cheers

 

2003 K-Series EU3 1.8 Standard alloy plenum

[CB]

BTTT

 

Anyone have any ideas? I have the same problem with a 1.6 K (though the IACV has not been changed)...

 

[Markiebabes]

Have you tried the ECU reset ? clean the IACV ,then reset ECU

have a look on Angus's site here half way down page may help

 

 

Mark

---

_{R400 MW 203 bhp of pure fun ( more so with Aero fitted )}

[kart]

Did you manage to find a resolution to this?

My car's been exhibiting the same behaviour.

Used to start fine, then began to catch and die unless you applied some throttle.

Over time required more and more throttle to nurse it through the first 10 seconds of running then all was fine. Now still turns over but barely catches at all.

Have ruled out IACV and battery, now thinking it could be the coolant temperature sensor.

Any ideas? I've found a few similar threads but none with a resolution.

(EU3 K-series 1.6)

 

Edited by - kart on 3 Jan 2009 21:34:58

[Carlos Prangdango]

Had the same problem back in October with my 04, 1.6K. Began to not want to start from cold without increasing amounts of throttle, and would not idle without it. The problem lies with the iacv not opening enough. I removed the plug in the inlet manifold and the car started, sugguesting a lack of air.

Went the long way round and changed coolant temp sensor, iacv, crank sensor, cam sensor and even had the loom apart and traced associated cores looking for damage, but to no avail. I was sure that the problem was not with the iacv but the electronic system that positions it.

Battery then discharged and failed to hold a charge after attempting to start the car one morning. Changed battery for powervamp pcr25 and fitted a new throttle pot at the same time and the problem disapeared permanently. The car now starts like never before.

So I cannot single out any one componant but would recomend checking that the resistance of the throttle pot changes as the throttle is opened and closed, and the volt drop across your battery whilst cranking the engine. Mine fell instantly to 5volts.

It is also worth pumping the throttle several times (10-15) before starting the car with the ignition off to try and clean the track of the throttle pot. If the car starts better after this then I would sugguest that the pot requires changing.

 

I hope this helps.

[c7trp]

Yes - Fixed it yesterday

 

Fitted a new battery.

 

Cranking speed seems to be the same, but it now fires instantly with no 'help'....

 

FWIW the conditioner reported the battery as healthy, but it couldn't crank the engine for long before it started to slow, so I expect it's caput.

 

I found a site with information how to test the various sensors - its on my work PC - Blat mail me if you want a link and I'll look it up on Monday.

 

 

[kart]

Thanks for the suggestions - it's looking like the common fix is to replace the battery (which I suppose would explain the degradation over time).

I had managed to convince myself that the battery was fine though: electrolyte topped up and charged overnight, 12.55V with no load, lowest voltage witnessed on cranking 9.75V, hydrometer reading 1.250 for all cells (all readings taken at about 5 degrees celsius).

 

Tim that site with the tips for testing sensors would be handy if you can find it YHBM.

 

P.S. checked TPS resistance varies as it deflects, WD40'd it and pumped the pedal but to no avail ☹️

Ta.

 

Edited by - kart on 4 Jan 2009 18:07:07

 

Edited by - kart on 4 Jan 2009 18:08:49

[Carlos Prangdango]

Try the following site.

Full of helpfull advice on testing of sensors and what to expect.

 

http://homepage.swissonline.ch/TomsSeven/Navigation2/Map.htm#

 

Drive it like you stole it!!

[kart]

Cheers for the link CH - good site.

Seems to be EU2 based but most of it still applies.

 

[c7trp]

Yep - thats the site I used!

[kart]

New battery sourced - no joy ☹️

I'm going to have to admit defeat and find a grown-up to fix it.

[c7trp]

☹️

[kart]

Thanks for the sympathy.

Having got my trusty multimeter out it seems as though with the car mobilised and the ignition on I'm not seeing any voltage on any of the output pins of the MFRU (aside from the momentary one that primes the fuel pump when the ignition first goes live).

Why's that then?

[Johnty Lyons]

Suspect faulty MFRU it's a common problem.... You can open them and clean up the points if you are really keen.. Or replace it with Ordinary Relays. We don't use MFRUs on any of our builds any longer but fit a supplementary relay bank beside the Caterham Fuse/relay block 😬

 

---

jj

N.I. L7C AR 🙆🏻

Membership No.3927.

240BHP 1900cc K Series 40th Anniversary

 

[kart]

Thanks for the response - any tests I can do to verify that the MFRU is at fault?

I've already taken it apart and had a look inside, unfortunately the relays in mine are enclosed so there's no way to check the contacts (unlike the pictures of earlier versions that I've seen).