Richard123

You can also test with a multi-meter on the pressure switch (wires disconnected). If black-brown make on the first press of the brakes, then you have no volume in the accumulator (or a ton of air in the brake lines!). If they don't make, then you have a corroded or weak set of contacts in the pressure switch. As discussed, it should take several presses of the brakes to get black-brown to make (turn on pump) and then several more to get black-white to un-make (activate anti-lock light and get ABS computer to run the pump every time you hit the brakes).

Ah, fair enough. I thought your issue was the long time for loop closing. For interest though, has your exhaust back pressure valve been removed? I had one instance where the car would not run closed loop, occurring after I washed the engine seeking the source of an oil leak. It would sit and idle, but not take any fuel. Threatened to stall every time I touched the throttle. I let it cool to get it home, and replaced the O2 sensor with one of those Bosch 13030's. My O2 4-wire connector is long gone and a couple of the single connectors were more than dodgy, so I suspect getting the wires wet caused the issue though I can't confirm as the issue never reappeared. I'm betting your new O2 sensor cleans up your issue.

Robin, From the graphs, it seems that your issue is the same as mine. Your O2 sensor was hot (near max output) well before the ECU closed the loop. After the loop closed, your O2 sensor "wobbles" just fine, lol. So I don't suspect a bad O2 sensor. Yours is a 1995, so it came factory with the exhaust back pressure valve and throttle jack which were intended to allow the cars to go closed loop quicker, correct? And can I assume they have been removed? Mine are removed from my 1994 S4, and I am wondering if the 1200 rpm cold idle isn't throwing the ECU off, as it is expecting the throttle jack to produce a much higher cold "warm up" idle?? Might that anomaly cause the ECU to abandon the standard map and decide to wait for a specific coolant temperature before closing the loop? Just a theory, but if your EPBV and throttle jack have been removed, it may make some sense. I might test it by hooking up the throttle jack again and going with a 2400 rpm (or such) cold idle just to see what it will do.

I think I know this one. The O2 signal climbs from about 0.45 volts when cold up to about 0.9 volts when hot. The high reading is because the voltage output is higher when there is no oxygen (rich). Once it goes closed loop the ECU leans the mixture (less gas) until voltage drops (it senses oxygen), then immediately richens mixture until the voltage increases, then leans it, etc. The signal wobble is produced by leaning out every time the O2 reads high, and richening every time the O2 reads low. It's best to watch on an analogue voltmeter, the needle acts like a metronome! My issue is that I have a nice hot O2 sensor putting out a solid 0.9V and an ECU that is reluctant to close the loop, so certainly something else is at play. I'm pretty sure engine temps plays a part in my car, but not in others' Esprits and I don't know why.

Does anybody have any idea what all causes the ECU to go closed loop and if it can be manipulated?? My 1994 S4 used to close the loop in about 45 seconds but is now waiting about 4 minutes for a coolant temperature of 56.8C to be achieved. I put in a new O2 sensor (13030) and checked the 12V heater circuit, no codes thrown, drives fine though it idles up (say 2000 rpm) when rolling clutch in, then idles back down (1200 rpm) when the car stops, until warm. The O2 sensor still hits approximately 0.9V by 45 seconds. I tried the battery disconnect to no avail. I will try resetting the BLM's via Freescan, but figured maybe this was a familiar thing? (The car has never had the exhaust backpressure valve since I've owned it, and I've blanked off the throttle jack, so neither function.)

Best few dollars I spent was for the fitting to tee a pressure gauge into the oil line at the turbo. There is still that feeling of trepidation when you see the needle in the red, or the flicker of the red light as you first rev it up, but at least you know what you have. There is something to be done to solve this in 2018. of course. Buy a 2018 Lotus. They don't do it. Else, add it to the "Esprit experience".

Before you start buying parts, pump it empty (40 presses), leave it for a few minutes to dissipate, then turn the key to pump it all back up again. See if you get back to 5 or 6 presses.

OK, so rich mixture on all 4 cylinders. See the other thread in this section about fuel pressure regulator. Pull the vacuum line off it and see if it stinks of fuel, internal diaphragm might have blown so it might be leaking raw fuel into the manifold.

Sounds like you got a bad cylinder. Pull a plug at idle and see if one isn't contributing. A dead cylinder will pass plenty of unburnt fuel.

There is a very slight offset inwards. Measured from a straightedge to the bolting surface, was 1cm less on the front side than the rear side. (So 0.5cm from dead centered.) Maximum diameter of rim (outer edge) is 39cm.

Found it. Mine was fastened down under a couple of hoses, not easy to see. The +tive looked good, but the ground that went to the far side of bracket seemed loose. Fished for it with a screwdriver and snugged it up. Boost gauge back to normal, owner back to happy. (It's all this good living I've been doing. Give a few bucks to a homeless guy, and see how it pays out?!?!?)

So it's the thing with the hose and two red tagged wires running to it? I didn't see it when I was there, but once I saw the MAP sensor and the plastic hose running to it, I stopped looking! Thanks so much Ian, I really appreciate it. (Crossed fingers for a loose wire!)

Ah, so they are separate, which explains why the car seemed unaffected. So the device I found (above RH fuel tank) is the MAP sensor. Where might one find this gauge transducer? Clearly somewhere with ease of access and likely a commonly available and inexpensive part I assume?

My boost gauge never did zero, it always read a needles width up, but going down freeway yesterday it really started to act up. It would jump up to 0.5bar for no reason, then drop back. When I did dig in for some boost, it would over-read substantially. All the while the car ran fine and seemed unbothered by its antics. Am I right to assume the gauge gets it's signal from the sensor behind the carpeted right hand engine bay side cover? And that is also the sensor that gives the ECU it's information? So a quick Freescan should tell me if the sensor is failing? Since the car ran fine, is it safe to assume it's a gauge problem? If so, any ideas? The other gauges were fine. You think the gauge itself? Grounds? Anybody else have this issue?

On my 1994 S4 the spare is a 175/70R14.

Karl, I've always gotten that milky look in the reservoir when emptying the accumulator. I was told (by posters here or another Lotus specific site) that it is normal (cannot verify). I've also had that brake pedal that pushes back, which is definitely not normal. However when I had that happen, it coincided with a pump that would run on every pedal push.

It does get more familiar the more you have to work with it, unfortunately! I'm curious. How do you know when you get air in the system? The number of presses goes down? Or does the braking "feel" change? Do you bleed each caliper to get the air out, or just depressurize the accumulator?

It's an odd braking system that is sometimes difficult to troubleshoot. The accumulator and the pressure switch are common problems. I haven't heard much for actual pump problems, which is surprising since in many cases the pump cycles quite frequently! How many "presses" of the brake pedal do you get before the pump turns on? If the pump runs every press, then your switch, relay or accumulator have completely failed. If it's every couple presses, it may be a weak accumulator or air in the brakes. If it's every 5 or 6+, then your hydraulic system is good. Best to test with key on but engine not started, window down and front bonnet open so you can hear the pump easily.

Just to add a bit for anybody looking for possible culprits to that spring "oil burn off". The o-rings in the back of the cam tower get baked by turbo heat and often fail. Oil from there drip quite nicely onto the back part of the exhaust manifold. An easy and cheap fix worth looking into if you have the issue.

Why would you think that? In my thinking, I was short air on start-up (likely due to butterflies building up with crud over the years) and allowing more air via the throttle stop (air bypass) seems to have solved it? ("Seems to" being key, as I'd like more cold starts before I get too cocky, lol.)

I just went through a (potentially) similar issue. If start up idle isn't high enough, my ECU would call for a ridiculously high idle (around 2350 rpm?). The IACV would go wide open (240 counts) but ECU would drown it with fuel and idle would actually struggle all the more. Some relief would come when the O2 sensor finally closed the loop and my BLM integrator would be able to lean it out. The solution (I think, I have 3 or 4 good cold starts) was to drop the IACV count (mine is 29 hot) by opening the throttle (via the set screw, air bypass screw). With more air on start up, the rpm flares up immediately, then the IACV drops it to keep a nice 1400 rpm idle. The ECU never goes into that "panic mode" and I don't get that choppy ultra rich fuel smelly idle. Check your "desired idle" in a Freescan of a cold start. If you see a 2000+ rpm desired, you have the same issue as I had. Good Luck.

I think I got it sorted. Started with TPS of 0.73V and IACV of 31 when hot. Turned the TPS to get it lower and got 0.51V but IACV was in the 50's when hot. I turned the air bypass (which is just the throttle stop) a 1/4 turn and now TPS is 0.53V but IACV is back down to around 29 hot. The car now starts with a brief burst of RPM (like 1500) and settles to a relatively smooth 1350 or 1400 with a request in that area. The car is no longer requesting the high idle (+2000) so the IACV isn't pinning open (240 counts) and the ECU isn't over fuelling, so the car isn't nearly as rough. I may give it another 1/8 or 1/4 turn to get the the IACV a bit lower yet, but so far so good. Mornings still above freezing, but not for long.

I finally have Freescan working and thought I'd have you guys look over a "running" file to see if all looks ok. Around line 450 I give it a bit of a push going up the freeway ramp. It seems ok to me, but I don't know what a lot of the columns signify (BLM, load, spark, etc). Let me know if I should call a tow truck, lol. Richard up ramp and freeway sept 12.csv

I think I figured it out my wild idle via the attached Freescan file. On startup (line 130) idle is low so car sets desired rpm high (2387 rpm) and IAC goes full open (240), but car is WAY WAY rich on the map and has rough and low idle. At line 726 the ECU closes loop and immediately starts to cut fuel (pulsewidth drops from 3-2 which very slightly improves idle). At line 848 pulsewidth drops further to 1 as ECU continues to cut more fuel and idle continues to rise. (IAC still wide open, O2 sensor still rich). Finally at line 896 ECU has cut enough fuel to have O2 go lean and idle rpm is up around 1650-1700 rpm. It stays this way until 1338 when I lose patience and drive away. In my opinion, the problem is either that the fuel pressure reg is failed (unlikely as the car doesn't seem to overfuel at idle except at start-up) or more likely this is caused by the "oversized RC injectors" which the previous owner advertised the car as having. This is made more severe by us being at fairly high altitude. Does the diagnosis make sense to you Freescan experts?? start up sept 12.csv

You may be spot on. At first glance, the water temp sensor voltage and the coolant temp don't seem to jive. But desired rpm is never indicated up near 1800 rpm. RPM also rises and falls without throttle position or IACV count changing. I will record a proper start-up and drive tomorrow. (I was too lazy to do it for this morning's commute!)