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1989 Lotus Esprit Turbo
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49 Posts
Discussion Starter #1
Gents,

After powder-coating my intake manifolds last Fall and reassembling to the specified torque settings (new seals from Dave Bean Engineering) the car idles at 1,600 RPM - once it is warmed up. It chooses to hang at 2,000 RPM at certain intersections in town as if it recognizes the opportunity to disrupt people enjoying a meal outdoors at one of our fine local restaurants (ha, ha). I've taken the manifolds apart and re-torqued to no avail. I began to address the situation by believing it to be a vacuum leak - replacing the following w/o seeing improvement:

Replaced and clamped vacuum lines tight to their connectors from the front and back plastic ports of the driver's side of the intake manifold and Fuel Rail diaphragm. Tested (and replaced) one of the one-way valves. Orientation of one-way valves is Black portion positioned closest to intake manifold port.
1. Turbo Boost Transducer,
a.) Checked that the Boost gauge and Transducer unit worked correctly by administering 10 PSI of air to transducer.
b.) Dropped the Transducer and MAP sensor and replaced the vacuums and rubber elbows. Cleaned electrical connections and added dialectic grease.
2. Capped off the vacuum line that services the EBPV and Throttle Jack Valves (Both were removed some time ago. I believe this line originates at the 'Y' vacuum lines located forward of the pass side buttress)
3. Checked the "Y" connection over at the ECU (area forward of the Right Buttress). Found that air pressure to the 1MM Inside Diameter hard plastic hose met resistance. Air pressure back towards the Vacuum Pump met no resistance and created a horn-like sound - assume it was the pump. (Should there be a one-way valve between the pump and the Y connection?)

Have not yet checked:
1. the line from the Intake manifold to the Charcoal Canister at the canister. Is there a tutorial on checking the valve here? 2. Nor have I inspected the lines directly from the vacuum pump under the car recently.
3. Crankcase Breather valve. How to do so?

Are there other areas I should be looking at or have I identified all of the vacuum lines that could effect idle and throttle stability? The car's throttle does feel uneven especially when attempting to maintain a constant speed. Unplugging the IAC Valve does not affect idle speeds.

Other items replaced:
Air filter
Spark Plugs - Gapped 0.035 INCH
New 8MM Spark Plug Wires
New Ignition modules
New Throttle Position Sensor


Thanks in advance,
Travis
 

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It's been a while, but there's some one way vacuum valves in there, towards the front of the motor, if I recall. Standard part, available at any auto parts store.

Does sound like a bit of an intake leak. Have you gone over every joint, spraying with carb cleaner while the motor is running and listening for a change in RPM?

Oh, and I have 6 wheels for your car if you're interested. 4 rear, 2 front.
 

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1989 Lotus Esprit Turbo
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49 Posts
Discussion Starter #3
Dr. Hess,
It's good to make your online acquaintance. I cannot count the number of times I have visited your Esprit Site amd reviewed your parts list! Thanks for the advice on exploring leaks with carb cleaner. I'm new to motor work so it's all a huge learning opportunity for me. I'll give it a try. When you say you have wheels, do you mean the 15" OZ 'Sawblades'? if so, I have two sets of them currently- one set in gold and the other in silver. I'd be interested if it were not for the limited selection of tires available. If you have another size wheel from the S4 or later I am all ears.

Thank you for responding to my post with a solution!

Travis
 

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I have the original back wheels that came on the car, the 15" OZ, plus a complete non-se OZ set. I bought a set of wheels sold as "SE" on ebay. Six months later when I went to get them mounted, it turned out they were non-SE wheels, identical to what I had on the car. Too late to biatch about it. I should have measured them when I received them.
 

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1989 Lotus Esprit Turbo
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49 Posts
Discussion Starter #5
Sorry to hear it. If it makes you feel any better I paid top dollar for a 'brand new' replacement rim from SJ Sportscars in the UK and received a bent rim that was also chipped up. I never was able to resolve the issue with Steve so I had the wheel refinished and straightened after paying full price for it. I'm disappointed by the lack of integrity out there!
 

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1990 Esprit SE
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31 Posts
the car idles at 1,600 RPM - once it is warmed up. It chooses to hang at 2,000 RPM at certain intersections
Hi Travis,
Check the throttle cable is slack at idle and the throttle screw resting on its stop.
If all of your vacuum pipes are in order, this has all the hallmarks of a badly set up throttle position sensor (TPS).
You say it's new, but is it adjusted correctly. If it reads over 0.9v at idle, it will cause an idle speed control issue.
I set mine at 0.5v.
Have you reset the ECU?

Andy.
 

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1989 Lotus Esprit Turbo
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49 Posts
Discussion Starter #7
Andy,

Thanks for your response.

Throttle cable is slack once the car is warm and the screw is resting on it's plate. I've removed the Intake manifold to confirm the butterflies are aligned and closed with the motor off.

Regarding TPS, I do not have scan software. Is there a way to check the voltage at idle w/o the software? If resetting the ECU is undoing the battery for a time. I have done so. Is this the reset?

Travis
 

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The scan software was available free, and the interface to the connector can be made for a couple bucks of parts, or bought.
 

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Have you checked to make sure the heat from the powder coat didn't warp your manifold?
 

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1990 Esprit SE
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31 Posts
Reading through your post, I assumed your car was an SE. I've just noticed that its "non SE" so I'm wading beyond my depth. Does it have the BOSCH injection?
 

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1989 Lotus Esprit Turbo
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49 Posts
Discussion Starter #12
Andy,

It sounds like I'm missing an opportunity to diagnose the issue properly with Freescan. I appreciate your input.

Travis
 

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1990 Esprit SE
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31 Posts
You need to check the voltage between the TPS blue/pink wire and ground with the ignition on.
Use a pin to pierce the insulation on the blue pink wire in order to measure the voltage.
Should be between 0.45v and 0.9v with the throttle closed if its the same an the SE.
If you've removed the TPS and refitted it in a random position, this could easily be your issue.

Andy.
 

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Is there also a throttle closed switch in the TPS? Toyotas have that. It tells the ECU to "idle." Sorry, too lazy to find my 89 non-SE shop manual and look it up.
 

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1989 Lotus Esprit Turbo
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49 Posts
Discussion Starter #17
Andy,
With the key in the ignition and motor off I get a reading of .77 on the multimeter. Should I rotate the TPS Assembly until I achieve a different value? If so, what should it be? I definitely did not place the TPS sensor in the same position as it was in before when I reinstalled it. I should have marked it when I took it off (hindsight is 20-20)
Travis
 

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1989 Lotus Esprit Turbo
Joined
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49 Posts
Discussion Starter #18
Is there also a throttle closed switch in the TPS? Toyotas have that. It tells the ECU to "idle." Sorry, too lazy to find my 89 non-SE shop manual and look it up.
The manual doesn't indicate that one exists. Not that it isn't there and I am unable to find information on it.
 

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1989 Lotus Esprit Turbo
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49 Posts
Discussion Starter #20
I ran a test sequence from the manual on the IAC harness and found 0.24v on the second and third connectors. 11.95v on numbers one and four. How do I trace back to find grounds or faults? I imagine these signals are sent to the ECM and I'm not seeing a schematic for the three plugs on the ECM. Does anyone have an idea of where this info can be found?
 
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