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Idling issue - '89 SE


Hammer59

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Hi all.

Loving my SE which I imported from UK to NZ earlier this year.  It has an issue whereby it either idles too high (around 1400rpm) and the revs drop very slowly when taking my foot off the accelerator, or it idles a little too low (800rpm) but the revs drop normally.  It sometimes stalls in this mode.  A probably unrelated issue is to do with hot starts.  Cold starts are fine, as are starts when hot and the engine has been off for less than about 4 minutes.  Any longer than that and it takes about 6-8 seconds cranking to fire up again.  I suspect leaking injector(s) but any input would be appreciated.

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Also sounds like an IACV reset could be in order?

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88 Esprit NA, 89 Esprit Turbo SE, Evora, Evora S, Evora IPS, Evora S IPS, Evora S IPS SR, Evora 400, Elise S1, Elise S1 111s, Evora GT410 Sport

Evora NA

For forum issues, please contact the Moderators. I will aim to respond to emails/PM's Mon-Fri 9-6 GMT. 

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14 hours ago, jonwat said:

Have you read the ECM codes? Always worth doing first. :thumbup:

No, I haven't.  I take it I need to read using freescan or the like?  I've downloaded freescan but haven't yet got the right cables.

 

14 hours ago, Bibs said:

Also sounds like an IACV reset could be in order?

Would this be done manually, just by disconnecting the battery or using freescan?  Gotta get those cables organised!

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You really need to buy a cable. The IAC valves are cheap as chips on rock auto and a service item. These were from the GM days any were awful on the cavaliers in the day.

Only here once

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@internets is your man for the cables and it's a button in freescan to reset the IACV 👍

88 Esprit NA, 89 Esprit Turbo SE, Evora, Evora S, Evora IPS, Evora S IPS, Evora S IPS SR, Evora 400, Elise S1, Elise S1 111s, Evora GT410 Sport

Evora NA

For forum issues, please contact the Moderators. I will aim to respond to emails/PM's Mon-Fri 9-6 GMT. 

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Thanks for the tip re cabling.  I've messaged @internets and hope he can sort me out.

Re Rockauto:  I've been to their site but there doesn't seem any listing for the iac valve under '89 lotus esprit. Would it be a generic iac valve that I can find elsewhere on the site?  Thanks.

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  • 4 months later...

I now have the cable and freescan's up and running.  What should I be checking to identify the idle issue?  I'm tempted to get a new IAC valve (assuming 217-427?) as a first port of call, but if freescan can narrow it down, that would obviously be better.

I installed new RC injectors a few weeks ago but that didn't help the hot start issue.

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Check the tps is set correctly and when you press the pedal to the floor you see 100% WOT.

reset the iac - start the car and do a relearn cycle. If you haven’t changed the iac - they really are a service item.

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https://www.rockauto.com/es/moreinfo.php?pk=942744&cc=1355857
 

427 works fine - some folks find 421 better. Cheap as chips from rock auto. You could buy one of each and it’s still cheaper than SJ.

Only here once

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  • 1 month later...

Installed the new IAC.  No difference unfortunately.  Still hard to start when hot or even slightly warm.  It really needs an overnight rest before it starts first pop.

Which values should I be checking in freescan to hunt down this problem?

Thanks in advance.

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Mine was a combination of AICV and and a bad O2 sensor. Also check your throttle cable is either a) not adjusted too tight

b) Not binding on anything.

On the Freescan check your IAC count once the car is up to operating temp. I recall from a conversation with Sailorbob this should be reading around 45. Im sure he will give the correct figures here. This can be set with the screw underneath the secondary injectors.

Also I have RC injectors and not a fan. If you still have the Rochesters try swapping back. Did you use new o rings and happy they are seated as an air leak can cause high/uneven idle.

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2 hours ago, Clarky5150 said:

Mine was a combination of AICV and and a bad O2 sensor. Also check your throttle cable is either a) not adjusted too tight

b) Not binding on anything.

On the Freescan check your IAC count once the car is up to operating temp. I recall from a conversation with Sailorbob this should be reading around 45. Im sure he will give the correct figures here. This can be set with the screw underneath the secondary injectors.

Also I have RC injectors and not a fan. If you still have the Rochesters try swapping back. Did you use new o rings and happy they are seated as an air leak can cause high/uneven idle.

 

The IAC is controlled by the ECM not the screw you mention, so turning it won't make any difference, the ECM will simply readjust the IAC to suit. The count should be around 70 when it's all settled.

Margate Exotics.

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Not if the tickover is too high. The ecm will drop the IACV to zero counts and has no further adjustment to lower the tickover. It then has to be lowered with the screw to allow the ecm to control the IACV again. This shouldn’t need to be tampered with as is set at factory however bigger injectors have been introduced and always a possibility of previous fiddling with said screw.

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2 hours ago, Clarky5150 said:

Not if the tickover is too high. The ecm will drop the IACV to zero counts and has no further adjustment to lower the tickover. It then has to be lowered with the screw to allow the ecm to control the IACV again. This shouldn’t need to be tampered with as is set at factory however bigger injectors have been introduced and always a possibility of previous fiddling with said screw.

 

If the tickover is too high and cannot be corrected by the IAC then either the valve is knackered, or someone has been fiddling with a screwdriver. Just be be clear, which screw are you referring to? I was referring to the throttle cable stop screw.

Margate Exotics.

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No the factory set air mixture screw (adjusts the air gap around the throttle body butterflys when off throttle)I agree, 99% of the time it’s previous owners (or current in my case 😳) who have fiddled with it but this will be apparent with the AICV count (ie it will be low at full operating temp)

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14 minutes ago, Clarky5150 said:

No the factory set air mixture screw (adjusts the air gap around the throttle body butterflys when off throttle)I agree, 99% of the time it’s previous owners (or current in my case 😳) who have fiddled with it but this will be apparent with the AICV count (ie it will be low at full operating temp)

 

If you adjust the balance screw, all it will do is open or close the butterflies on the front pair of throttle bodies. That in itself won't give you the best idle, as it assumes the air bleed screws are all identically set, which they almost certainly won't be. You should balance one pair of throttle bodies at a time with a synchoniser, then adjust the balance screw to get equal airflow through all four throttle bodies. Once set, the IAC should be well within it's operating parameters, and the ECM can control the desired idle as it should. Yes, it's a pain to do, but worth it.

I'm sure @CHANGES posted on this subject, and no doubt his explanation will be streets ahead of mine.

Margate Exotics.

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It was the throttle plate stop screw that needed adjusting on Shaun's engine a few weeks ago to fix the idle problem. The butterflies were open too far at closed throttle resulting in the IAC valve being fully closed (IAC counts = 0) and thus preventing the desired idle RPM being reached. 

When the engine is at operating temperature, the ECU is in closed loop fuelling and all electrical accessories are off the IAC counts should be about 30 - 35 to give the desired idle RPM at closed throttle.

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Thanks Derek, i knew you would have the correct name for the thing. I knew it wasn't the balance adjustment but struggled to put it into context. Put a couple of hundred miles on her since your lifesaving surgery and the engine is now running night and day better for them. Thanks again for the help. 

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  • 3 weeks later...

Was watching an American car restorer on youtube rescue an Esprit from water damage and/or been left out in the elements for years.  He referred to a fuel accumulator that apparently holds fuel pressure for about 24 hrs to thwart vapour locking.  Would a faulty accumulator give me my symptoms?  i.e. fine on cold starts, fine if restarted within a few minutes, 5-8 seconds cranking required if restarted any time from a few minutes upward until probably around 12 hours or more.  Any comments appreciated.

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