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That damn stumble again!


Malc Holmes

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Hi all,

As some may have noticed, I have made a few posts over the last year or so about an anoying stumble that has always been a feature of my car since I have had it. To re-cap briefly, idle is fine, but touch the throtle and it stumbles for a second before the revs pick up. Also at light throttle openings and almost always below 60mph it seems as if the engine is stumbling and suringing slightly. Not a complete disaster and still very fun to drive, but not nice in town or heavy traffic (like last Sunday on the A11!). ALL sensors are new other than the O2 sensor. Freescan checked out by Dermot who pointed out a few minor issues, which I have addressed now but have not resolved the problem (does n=run a bit better in general though). Injectors also replaced recently with RC's.

I was speaking to a friend at work who has a Skyline R33. He had very similar symptoms of the stumble and serge at low throttle openings. He took his car to a specialist, they replaced the 02 sensors and problem went. As with the Esprit, at large throtle openings the 02 sensor is disregarded, hence it does not matter what the 02 sensor is saying, hence no problem when you are giving it a bit of welly.

My freescan logs seem to indicate the 02 sensor is OK, but can it just go out of calibration after a while rather than just pack up, hence say the mixture is correct even when its realy lean??

What do you recon?

Malc Holmes

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Hi malc,

I had a similar problem after fitting a new exhaust and cat with a new lambda sensor. According to freescan the new sensor was fine, in the end I put in a new one from LOTUS and the problem was gone. See also http://www.lotusespritforum.com/forums/ind...ost&p=78659 .

Freek

Edited by fjmuurling

Esprit Freak

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I had the same symptoms and replaced the lambda sensor, problem solved. Freescan on mine showed 0 for the reading on the sensor though so it was the obvious problem.

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

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Guest Troy Halliday

Is your Lambda sensor from Lotus or an after market replacement. I spoke to Brian this week about lambda and he pointed out that quite a few people have had problems with eratic idle and stumbling when using the non Lotus Lambda sensors.

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The anecdotal evidence on the forum point to exactly that too however I ordered mine from SJ's and it's still got a Delphi sticker on it!

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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Is that what I need on mine?

Possibly save your life. Check out this website.
http://everyman-campaign.org/

 

Distributor for 'Every Male' grooming products. (Discounts for any TLF members hairier than I am!)

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No. You do need a new TPS though and a MAT sensor I think. Your ECU is being asked by a faulty TPS to increase the revs as it would settle at either 0% or 2%, making it think you want 2% throttle and resulting in a high tickover.

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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Ahhhh, ok.....whatever you said :thumbup:

Possibly save your life. Check out this website.
http://everyman-campaign.org/

 

Distributor for 'Every Male' grooming products. (Discounts for any TLF members hairier than I am!)

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From the 100's of Freescan logs I have looked at over the past 6 years problems with either a bad or the wrong O2 sensor is by far the most common cause of poor running. I think if you get one from a good Lotus independent they are OK but if you try and save a few pence and cross the part to a generic you are asking for trouble.

You can do checks on the TPS with Freescan and reset the zero calibration point. This is very important for smooth performance. The are a few checks you can also do on the MAP.

All this issues are checked if you send me a log file.

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Thanks guys,

An order for a new O2 sensor is on route to Stratstones Lotus as we speak! I should get a chance to fit this and let you know the results before I leave for Japan.

I have attached the latest freescan log I have. This was the first run with both a new fuel pump and new RC injectors, so is a fair reflection of the set up as it stands at the moment. Please take a look and let me know what you think. BLM values are still high, though these have improved slightly with both the new pump and again with the new injectors. I am adding a new fule pressure reg to my order just incase that has a problem as well!

Kimbers. I can send you a new MAT sensor if you need one, let me know. I thought I bought a heap of correct new TPS's as well, only to find they turn in the wrong direction! If anyone has worked out how to reverse the direction on these let me know, and win a free TPS!

Thanks guys

Malc

Ps apparently I am not allowed to upload this type of file (Excel CSV file), am I doing something wrong? How can I attach it Bibs?

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Hi all,

As some may have noticed, I have made a few posts over the last year or so about an anoying stumble that has always been a feature of my car since I have had it. To re-cap briefly, idle is fine, but touch the throtle and it stumbles for a second before the revs pick up. Also at light throttle openings and almost always below 60mph it seems as if the engine is stumbling and suringing slightly.

Malc Holmes

Hi Malc,

Are you still running the factory SE chip? If so, changing to the S4 or S4s code will be a revelation...

Visit Sanj's Lotus Esprit Turbo SE pages

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You could have used Lipscomb or Nick Whales and got 10% off as a Club Esprit member! My O2 sensor was from SJ's as they had them in stock and I was in a rush. I think it was about

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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  • 2 weeks later...

OK,

This weekend has seen the addition of new O2 sensor, new fuel filter and fuel pressure reg.

O2 sensor made a significanmt improvement, sut not the others. Still mild stumble at low speed, low throttle openings and mild hesitation when opening the throttle from idle. Am I just paranoid?

The entire fuel system is now new (everything from pump to injectors) and the rest of the engine is in good shape, but my BLM's still go up to 150ish.

I will be trying a mild chip upgrade next to see what improvements that makes (still on stock SE chip at the mo).

In the mean time, can someone e-mail me a Freescan log CSV file from a totally standard SE (circa 1989) that they feel is OK, just to compare with mine. Perhaps I am just being over sensitive!

My e-mail address is [email protected]

Thanks chaps

Malc

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As soon as my turbo is back on I'll get some logs up, it's a stock '89 SE running perfectly bar the spiny thing at the moment.

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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Hi Yasuo,

Harness was fully checked when I put it in, only 2000 miles back (this car has had little use I am affraid!). The list for next weekends activities (other than packing ), is fit new coil pack, new plug leads followed by new ECU and new chip (starting with latest S4s code).

Is there realy no-one out there in LEF-land with standard SE freescan logs?

Malc

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I have now had a chance to have a look at the 2 logs I received and compared them against my own. I am pleased to say, mine does not see so bad after all.

Thanks to both Freek and Yasuo for your help.

By the way, new coil pack and leads went in today, so other than the Chip itself, everything else is new now. Should get a chance tomorrow to see if this lot makes any further improvement.

Many thanks

Malc

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