3 Cylinder Elan?

[ESM]

[quote author=Paul.P link=board=help;num=1116161215;start=30#38 date=06/13/05 at 11:55:49]I know i'm thick, but what is the TPS ?[/quote]<br><br>TPS = throttle position sensor

[Candles]

OK - I've done it backwards, but I've tried the 'known good' sensor from my old engine and there's no idle improvement.  I'll just check the circuit now......<br><br>The TPS seems to be getting power but I can't set it up in the right place coz my laptop wont talk to the car any more.  I've got all sensible other feedback from the ECU but a continuous 'no reply' reported in Elanscan.  The red LED is flashing on the interface board.  Is the ECU dead?  Bugger.  I can't believe it could have just died now of all times    Maybe the ECU dying has been the root cause of all the snags.....  :'(<br><br>OK - I've been through the TPS harness with a multimeter and it is a bit weird.  The wire (BW11D for those who care) that I expected to be at ground as the reference for the sensor, doesn't appear to be grounded.  Where does it connect to ground, inside the ECU?  I'm confused now, but I have always wondered if this was a weird earthing problem, despite having checked all the earthing points over and over.<br>

[Candles]

Well, I messed around a bit more with it.  The laptop still isn't talking to the ECU but all other ECU indications are normal. At one point for about 4 minutes, the car sat there, everything connected in ECU-computed mode, idling smoother than it ever has, but then lump by lump and backfire by backfire it went to sh1te again.  <br><br>I am still convinced ESM is right and it is something to do with the TPS and the wiring to it.  For example, if I pull the rubber boot off the TPS and probe all the terminals whilst it is running at idle(comparing them to the engine block) the lowest reading I get is over a volt.  This surely should be 0.4v?  However, the reference line (the black one) seems to be at about a volt compared to the engine block, so that would justify the high TPS signal output.  Still doesn't make sense to me though!<br><br>Worst thing is, I now cannot get Elanscan logs anymore as the laptop and ECU aren't on speaking terms!<br><br>Candles.

[Candles]

Update:<br><br>It isn't the ECU (i've tried a good one), even though neither are speaking to my laptop which hopefully is another unrelated problem......<br><br>Still unsure of the TPS circuit.  I may 'simulate' an idle situation by applying the correct voltage to the harness with the sensor disconnected and see what happens.  <br><br>Candles.

[ESM]

There should be three wires to the TPS:<br><br>blue/orange: 5V<br>blue/red: TPS signal<br>black/white: analogue ground<br><br>The last is a reference on the ECU that may float relative to the battery ground, so measure the 5V and the signal output relative that wire NOT the block. Connecting the analogue ground to the battery ground could cause problems in its own right. <br><br>The blue/orange wire also supplies the MAP sensor<br>The black/white wire also references the MAT sensor

[Candles]

Thanks for that ESM.  I'll go and check it out now.  Why does the analogue ground float??  Or is that a deep question revealing my lack of understanding for the system!<br><br>Candles.

[Candles]

Probing the TPS gave me a chance to set it exactly at 0.4V and see that all the other wires are steady at the required voltages.  The signal voltage seems to be steady on a multimeter even when the engine is running roughly.<br><br>One odd thing:  When cold, it seems to be smoother.  I'm going to have a look at the CTS and other stuff now, although the CO is steady at about 2% - is that about right?<br><br>With the laptop not talking to the ECU I have really run out of ideas so soon it really will be sledge hammer time or the scrappie!<br><br>Candles.

[Doug]

yo Candles, I admire your perseverance, and have been following, but don't have any bright ideas to offer.<br><br>hopefully you've been over the engine install in your head enough to know it was all plumbed and wired properly ? ? <br><br>might be worth a paid opinion/help from your most trusted Lotus mechanic.  Het, does the factory still do service??  If so this might be your answer!<br><br>And if you do use the sledge, take some pics of the work  ;)

[ESM]

Candles, you ask some questions ::). Well you asked for it....<br><br>In any system where there are several metal objects connected by earth wires there can be differences in electrical potential between the objects because the connecting wires have some resistance (especially when there are electrical things like alternators attached to bits of it). These earth difference can lead to significant errors in the voltage read. In addition the digital circuitry in the ECU produces a lot of noise and it desirable to keep the analogue reference seperate from that. <br><br>Check the resistance of the signal, earth and reference voltage wires between the TPS plug and the ECU plug - the voltage might be 0.4V at the sensor but it wasn't being read as 0.4V by the ECU, going by the logs you produced before.

[Candles]

OK I'll try that now.....<br><br>Doug, I am persevering as I don't have a favoured Lotus mechanic.  I'm not doing it out of some fanatical love for the car but as I bought the car as a hobby, a challenge and something to tinker with.  I admit that this project has got me a little stumped - annoyingly right in the final stages which makes it all the more infuriating!<br><br>The most annoying thing is that my one window on the problem, Elanscan, has stopped talking to the ECU.  I'm hoping it is an unrelated snag but It maybe something to do with the wiring all together.  <br><br>The weird thing is that the car-side wiring has not been touched and worked fine before.  That is pointing me in the engine loom area, which I may simply swap in its entirety with the old engine!  Heck I might swap the whole plenum!<br><br>Thanks for your ongoing help chaps, and as always, keep it coming!  [grabs multimeter and walks out]<br><br>Candles.

[Candles]

Well, I spent a while upside down in the footwell probing the ECU harness and the unfortunate story is that 0.4v is getting through right the way to the ECU with the TPS at idle.  It is steady and the engine still runs like a complete bag of nails.  <br><br>I think it'll be off to a Lotus dealer soon, on a trailer as it runs too badly to drive  :'(<br><br>Candles.<br><br>ESM:  Have you got any of your ALDL interfaces 'in stock'?  I think mine is broken.

[Ashaman]

I like EMS's suggestion, and thought I would add on my  final thoughts before you cart it off...<br><br>I cannot remember, but is there a "main ground" the Elan uses for the ECU?  Since it is a fiberglass car, grounding is sometimes a difficult thing.<br><br>I think there were like 3 "ground" leads in the ECU harness, but I have never traced them out to see where they wind up.  I remember there are some grounding straps somewhere on the backside of the intake/engine I think, did they maybe not get hooked up?<br><br>If it were me, just to make sure this wasn't the problem, I would get some heavy cable (jumper cables?) and form a grounding chain.  Hook from the negative battery post to the engine block.  Hook from the engine block to the ground of the ECU harness.  Might sound kind of dumb, but I solved a problem on another car this way once (ECU to chassis was fine, chassis to engine was NOT).<br><br>After confirming it was a grounding issue, I just added a couple grounding straps and it never had a problem after that!<br><br>

[Candles]

I have double checked and the various braiding straps are connected, however I don't know they are working.  I'll try grounding the block and plenum manually.<br><br>Candles.

[Candles]

Grounding the block and/or plenum didn't work.  I noticed that the battery compartment has a little box marked 'Electronics Ground' inside it, so I checked that over.  It was fine with just a couple of Ohms to the battery -ve post.<br><br>Anyone got any thoughts on why the laptop interface doesn't work?  I've read through the ElanScan thread and not really shed any light on it apart from that my (AW) interface is broken.<br><br>Oooooh this makes me mad.....  [smiley=flaming.gif]<br><br>Candles.

[Sy V]

Oooooh this makes me mad.....   <br><br><br>Candles, put the hammer down and walk away from it!

[Ashaman]

What about ECU ground?  Seems like it has to be something like that...unless the two problems are unrelated?<br><br>Dunno man, this sounds like a tough one - you have my sympathy!

[Candles]

On the electrical diagram for the engine management, it shows three grounds.  They all arrive on the side of the intake plenum at the base of the PAS fluid reservoir.  It took me ages to find them!  Anyway, fiddling around there with the engine running, it suddenly went smooth.  Sadly, I think it was just random as no matter how hard I tried, I couldn't get it to run smoothly again.  I checked it all over and there was good continuity from there to everywhere else, so stumped again.<br><br>So, where am I at now?  Well, I've decided on a more logical approach.  This is it:  Car was OK before new engine.  Car is bad now.  Therefore, new engine is bad.  Now short of changing the block back (can't be arsed) I'm going back to the old bits.  I've done everything bar the engine harness, so I removed the old engine's one earlier (dead easy due good access) and I've nearly removed the installed one but I can't get the ba$t4rd secondary throttle connector off.  <br><br>I did however, jury rig the new loom across the engine, without CTS, IAC, secondary throttle & temp gauge and the engine seemed to run smoother, notwithstanding the fact that the IAC was right open and the ECU didn't know what the temp was.  So, once I get the secondary throttle solenoid connector off (need Hobbit hands and Golum arms - unless anyone has any tips!), I'll swap the whole thing and no doubt I can then take the sledgehammer to it.  If I have the patience, I'll then do the throttle body and then the whole plenum!<br><br>One area which I haven't addressed is a leaking plenum from some point.  When the engine is running, I can hear hissing from the plenum, but I think it is just coming from the throttle bypass.  Is there an installed test I can do?  I've tried shoving my hand over the inlet and it seems to stop the engine in pretty short order, so there can't be a big leak.<br><br>I would post a video of it idling as the symptoms must be quite distinctive to someone who knew what they were doing.  The timing is all over the place, even in diagnostic mode.<br><br><- Saved until another day!<br><br>Candles.

[Candles]

Well I managed to get a small electrical screwdriver into the secondary throttle plug and pop it open, so no need for the Golum arms.  While I was at it, putting the 'new' loom on only took a few minutes, so I did it.  Sadly, the engine didn't run any better!  Arrrgh..............<br><br>Back to the drawing board, or the scrapyard  :'(

[Monty]

Candles,<br><br>Can`t believe how much trouble u`r having :-/ I`m not of much help but check the wires to the CAS as one other member was having trouble and his CEL kept on flashing and seem to disappear when he moved those wires (bad connection)  ???

[Exbury]

If it is an air leak, if you spray a lubricant into the area then the idea is that this is sucked in instead of air, blocking the gap temporarily and improving the engine revs, you should hear a noticeable rise in revs, then drop as it starts to suck in air again.  Not an idea scenario and I believe we used to use an alternative to WD40, but a spray lubricant should not do any harm anyway will help create an electrical connection and relatively easy to test.  On hoses, around the plenum, injector seals are probably the best areas.<br><br>I presume you changed the plugs (sorry forgot to read) and double checked with a known good set, even new leads or plugs could have an immediate failure, unlikely but possible.<br><br>Best of luck - Jason