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Glutton For Punishment
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Discussion Starter · #1 ·
My car has been running great, except for what I consider a rough idle.

Car has the green dot pulleys. Idle is set at 950 but fluctuates between 900 and 1000. The car interior vibrates and shakes at idle. Car revs off idle very nice. The idle doesn't shake the suspension, and the motor doesn't wiggle harshly in the mounts, but it certainly doesn't purr.

I have checked the WUR pressure and it is correct.

I have cleaned the injectors twice, and they spray cleanly, but I haven't verified volume.

I have verified tps continuity at idle.

I have fooled with the air plate mixture and found the setting that has best all around performance which also has the smoothest idle.

Exhaust note sounds even, but lumpy. Idle just reverberates in the cabin and feels rather rough in the seat of the pants. Sounds like is just beginning to stall. Idle speed verified with test instrument. Bumping it up to 1100 solves the problem.

Is this a :tadts: moment?
 

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Wingless Wonder
1988 Esprit Turbo
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6,311 Posts
Exhaust note sounds even, but lumpy. Idle just reverberates in the cabin and feels rather rough in the seat of the pants. Sounds like is just beginning to stall. Idle speed verified with test instrument. Bumping it up to 1100 solves the problem.

Is this a :tadts: moment?
Assuming that your timing is set at 15 - 18 degrees BTDC:


Yep,

Too much valve overlap for really smooth running at idle which is normal.

Set it at 1100 and go accomplish another beer run. Or, 950 - 1000 with high beams on, and interior fan on high. (Which will also result in a no-loads idle of 1100)




An additional benefit of the higher idle, if you have the OE Valeo alternator, is that you will have more amperage at idle instead of running off the battery. Valeos have notoriously weak low-RPM capacity.

Another TADTS.
 

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Glutton For Punishment
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251 Posts
Discussion Starter · #3 ·
Thanks for the reply. Yes timing is at 17 btdc.

I have about 150 miles on the car, and just chasing down little issues like a leaking crush washer on the Return line connecton on the top of the fuel tank. Apparently pressure is fine but non pressure connections leak.

Seem to also have sprung a transmission leak also after an extended highway run, so I get to chase that down now. Passed inspection this morning but the county offices are closed so I have to wait on my metal plates.

I also just got my voltage regulator for my valeo alternator that has been making a solid 12v under speed and 11.5v at idle, so going to throw that in and hopefully get real charge voltage.

Front tires still flat spotted, which is lame since they had 0 miles on them (and 6 years of not rolling)

At least the idle is normal.
 

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I had this problem and just let it go for about 3 months last summer until I put it in my shop to do some other things to the car. After doing a lot to it and having no success, I checked my throttle butterflies and they were gummed up. I over looked them because I don't drive the car as much as my ordinary cars, and figured it would be a few years til I needed to clean them again since I cleaned them real good as well as the whole intake when I bought the car a year earlier. They were dirty, I cleaned them and it completely solved my rough idle, my idle was shaking the car. I just chalked it up as im gonna have to know now to keep an eye on the idle and when it gets "funky" to check them.

Another reason I over-looked them was it is a little bit of work to get to them, and figured it just wouldn't be that with as little (bout 2,000 miles a year) as I drive the car, but I do have a K and N filter, and it is a turbo, so its bound to get a little dirty there I guess.
 

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Super Moderator
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4,177 Posts
My 88 has 28K miles in 28 months and the idle is 'seasonal'.

While in San Diego 12/22-12/26 - it had a 'hot start' issue - would not start until I really floored it (yes - doesn't make sense).

Only once - the temp was 72F on 12/23 when this happened - went back to 'normal' (850-1000 RPM, lumpy, etc.).

Once in winter of 2012, it would have low idle (700 RPM), but back to normal in the warmer months past April.

Have tried Chevron fuel injection cleaner - not sure if it helped or hurt, but no obvious change.
 

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To have a really smooth idle each cylinder must be within 5% of the others so the engine is balanced. If one or more cylinders is not withing 5%, every time that cylinder fires the motor will slow down a little. The idle system does not react quickly and by the time it does the next cylinder is firing so it overshoots and the RPM's run up. Advancing the cam timing reduces the vacuum signal and accentuates the problem. You should not be adjusting the mixture screw to set idle, that affects the mixture linearly across the whole operating band. Do a compression test. Adjust the valves. Have the injectors cleaned and replace and carefully gap the spark plugs. If you cannot get your compression readings within 5% you will never idle smoothly. Techron can help if the injectors are not spraying right. Run your hand over the sidewalls and tread of each tire. If you feel lumps or bumps the tire is not flatspotted, you have belt movement and the tires will never run smooth. + - 50 RPM's is not terrible so don't beat yourself up over it, it is not a new car.
 

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Wingless Wonder
1988 Esprit Turbo
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6,311 Posts
I never had a sticking throttle butterfly in 21 years of ownership, FWIW.

I did have an intermittent low idle in the 5 years prior to my drivetrain refresh, and so during my refresh work, I have paid close attention to the integrity of all vacuum hoses and venting lines (replacing the marginal plastic Lotus jaw-clamps, with worm clamps).

We'll see. Engine is close to running. :up:

I'm running the OE style paper pleated air filter, and my engine has green-dot cam wheels (thanks to CarSalesman).

++++++++++

A properly operating Valeo should give you 13.5VDC over 1500 RPM. Less RPM than that, not so much depending on the age and tension of the alternator belt.

One thing I found recently while putting the engine bay back together: having the Bosch MCU (Mixture Control Unit, under the air filter box) in the wrong position can put a lot of strain on the fuel lines, especially that pesky return line from the MCU to the top of the fuel tank. I found that the 'sweet spot' for MCU position on my car was about 2/3rds towards the front on the slotted mounting bracket. (I didn't note where the MCU was originally, just ONE of my many errors when taking things apart...) <SIGH>

Turns out the "sweet spot" positioned the plastic fuel lines perfectly parallel to the engine bulkhead where they went left to right.
 

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Glutton For Punishment
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251 Posts
Discussion Starter · #8 ·
I had this problem and just let it go for about 3 months last summer until I put it in my shop to do some other things to the car. After doing a lot to it and having no success, I checked my throttle butterflies and they were gummed up. I over looked them because I don't drive the car as much as my ordinary cars, and figured it would be a few years til I needed to clean them again since I cleaned them real good as well as the whole intake when I bought the car a year earlier. They were dirty, I cleaned them and it completely solved my rough idle, my idle was shaking the car. I just chalked it up as im gonna have to know now to keep an eye on the idle and when it gets "funky" to check them.

Another reason I over-looked them was it is a little bit of work to get to them, and figured it just wouldn't be that with as little (bout 2,000 miles a year) as I drive the car, but I do have a K and N filter, and it is a turbo, so its bound to get a little dirty there I guess.
I think I will give this a shot. Probably should have done this with the motor out a few weeks ago. Certainly would have been easier.

Did you yank the whole assembly and bench clean them or just pull the plenum and spray the TB's out? I have a K&N that came with the car so some over zealous oiling in the past could certainly coat the butterflies with gunk.

Any gaskets involved?

Thanks for the tip. The more I drive the car the more I think this is not a normal idle. My diesels idle smoother.
 

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Integrator
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2,930 Posts
Could you be more specific with problem description?

Irregular idle (shakes) during the warm up cycle?
Or
Irregular idle (shakes)- when fully warm?
Or
Both?
 

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I just pull the air cleaner assy, and then the side of the plenum that faces the air cleaner assy (there is a gasket there but mine was easily reusable). Then just spray carb cleaner in it and operate them a few times open and closed. If I remember correctly I used a toothbrush also with the carb cleaner as they were pretty dirty right around the butterflies themselves.

Another reason I was hoping it wasn't my throttle body valves originally was I absolutely hate taking the air cleaner assembly off the side of the engine bay, well not taking it off, putting it back on with the filter in it can be a pain sometimes.

I think the K and N filter was definitely the culprit of this dirt as I have had K and N's on a few bikes I owned, and I remember cleaning my past bikes throttle bodies on more than one occasion. I had a Harley Davidson VRod that was notorious for dirty throttle bodies that often caused rough idle and it had a K and N filter.
 

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Smooth idling and 910 engines dont go together! This is even moreso if you have the green dot cam setup like I do on my '87 HCi. My car idles at around 850-900rpm when cold and a little lower when warm. It hops around and resembles half of an American V8 musclecar! Very lopey and "unsorted" sounding. I actually like it!

IMO, bumping the idle up to 1100 is NOT correct. Thats too high and serves no real purpose. Everyone comments on the idle of these cars being all wrong. Its not - thats what they do. Its unbalanced and entirely obnoxious. It wasnt designed by Lexus engineers :D

The car should idle around 900rpm, give or take 50rpm. Not 1100rpm.

Let her pop and hop.... it sounds COOL! :coolnana:
 

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Smooth idling and 910 engines dont go together! This is even moreso if you have the green dot cam setup like I do on my '87 HCi. My car idles at around 850-900rpm when cold and a little lower when warm. It hops around and resembles half of an American V8 musclecar! Very lopey and "unsorted" sounding. I actually like it!

IMO, bumping the idle up to 1100 is NOT correct. Thats too high and serves no real purpose. Everyone comments on the idle of these cars being all wrong. Its not - thats what they do. Its unbalanced and entirely obnoxious. It wasnt designed by Lexus engineers :D

The car should idle around 900rpm, give or take 50rpm. Not 1100rpm.

Let her pop and hop.... it sounds COOL! :coolnana:
Agreed - your car sounds bad-ass.
 

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Glutton For Punishment
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251 Posts
Discussion Starter · #13 ·
Well found my issue. Working to correct it now. Injectors are way out of balance. Just bought this beautiful injector tester / cleaner and look at the result.
 

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That looks VERY high tech! Expensive too! All you really needed was some cups and 1 graduated cylinder. Now you need an injector cleaner/tester. If you send me your injectors I can clean and test them. I did Atwell's and got them pretty close. Any Volvo dealer should also have a cleaner/tester and can do them.
David Teitelbaum
 

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Glutton For Punishment
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251 Posts
Discussion Starter · #16 ·
Tester and ultrasonic cleaner. Purchased for my motorcycle shop, yes it was expensive!
 

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Glutton For Punishment
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251 Posts
Discussion Starter · #17 ·
That looks VERY high tech! Expensive too! All you really needed was some cups and 1 graduated cylinder. Now you need an injector cleaner/tester. If you send me your injectors I can clean and test them. I did Atwell's and got them pretty close. Any Volvo dealer should also have a cleaner/tester and can do them.
David Teitelbaum
What chemical do you use? I have been using simple green in a ultrasonic cleaner, but just hasn't done the business as can be seen by the test results.

This last time I used the trick of copper wire around the pintle to hold it open, then ultrasonic clean, then back flush.

Thanks
 

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Wow...amazing tool to have access to!

Have been reading posts esp. the CIS thread with interest...my '86 idles very roughly, but I attribute that to the broken left (US drivers side) motor mount [by "broken" I mean "the rubber seems to have pushed through the metal surround" and the engine is sitting visibly lower to that side].

Otherwise, the idle of the car is lumpy and bumpy, indeed, a strange sort of blad-blad-pupple-bladdy-pupple-blad noise I thoroughly enjoy as it's so...odd compared to modern engines.

Now I'm rethinking putting on my new K&N. I searched ITG's website for comparable filters, but was unsure if any were the correct measurements for the CIS Esprit--certainly they have ones for the Elise et al. but not the Esprit.

David, when I get to my engine-out bundle of joy and anxiety, may I keep you in mind for injector cleaning? There's not a Volvo dealer anywhere near me!

Anyway, I'm watching this thread with great interest, as things like remembering to mark off the exact position of the MCU with a grease pencil (or other implement, accompanied by a photo) are always good advice.

Cheers,

Scott
 

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Glutton For Punishment
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251 Posts
Discussion Starter · #19 ·
Well after lots of cleaning and back flowing the injectors and cleaning some more here is my final result.
 

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Glutton For Punishment
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Discussion Starter · #20 ·
Question though. On my way home the car seemed to run worse. Wouldn't rev out over 5k very well. Pulled much better off the bottom. I may have dialed the mixture too rich based off the dirty injectors and now it is way too rich.

Does the O2 sensor loop learn long term trims or is it always adjusting the frequency valve on the fly, not based on previous data? Does a battery disconnect clear it or is there nothing to clear?
 
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