Running Out of Ideas

[Qavion]

Recap....

Gents...

I have had this very intermittentent stalling problem on my 89 SE for at least a year. It happens usually when the car has just warmed up on a first drive or has been warm from a previous drive. After sitting at traffic lights and pulling away (usually gently), the car either hesitates (no further acceleration for a few seconds) or simply stalls. Seems to happen more in warmer weather at relatively low speeds (from 10 ~ 50kph). After stalling, the car usually restarts straight away. Only on a couple of occasions has the car refused to start in a short time period (for up to 30 minutes).

Unfortunately, Freescan logs NO faults.

To try to fix the problem, I've replaced the following:

Spark plugs (found they were the wrong type)

Ignition leads

Coil Pack

ECU (but not the Memcal)

Oxygen Sensor (Lotus factory-sourced)

Throttle Position Sensor (and used Freescan to adjust it)

Fuel filter (twice)

Fuel pump

Fuel pump relay

6 fuel injectors

I've looked in the RHS tank for foreign objects which might be blocking the pump.

On the exhaust side (in case there was some restriction).. I've fitted a free flowing CAT and exhaust and removed the EBPV (and sealed off the hose from the frequency valve controlling it).

On the vaccuum control side, I've looked for leaks in some parts of the vacuum lines, but not all. I've replaced the charcoal canister (with control valve)

Cleaned and checked the crankcase breather valve.

Replaced some sections of vacuum hose.

Replaced one one-way valve on the vacuum lines and cleaned and checked another.

On the cooling side...

Along the way, I've replaced a chargecooler pump impellor (found slipping on shaft). The chargecooler was getting quite toasty.

Fitted a heatshield behind the coolant tanks to try to keep the heat away from the boot electrics.

Questions...

Would an intermittent or slightly out of tolerance signal from, say, the coolant sensor, vehicle speed sensor (if I have one) or flywheel sensor (or the wiring thereto) stall the engine, but not log a fault in the ECM?

Does the IAC valve also help stop the car stalling at above idle speeds? At above idle speeds, does it go to full open or full closed (or some fixed positon)?

I don't understand why the car only does this on some drives (I only drive the car once or twice a week and the problem sometimes doesn't occur for up to a month or so).

I don't know whether to keep randomly changing parts until I hit the right one... or put the car into a garage and hope they magically come up with a solution when the combined resources of the Lotus Esprit Forum and Club Lotus can't help me (at much lower cost)

Thanks for any suggestions

Cheers.

Ian.

Edited October 13, 2008 by Qavion

[superdavelotus]

Hi Ian,

Does the Se have a IAC valve? Not sure it does. I've had similar problems with my V8 but it's all fixed now. I never had an engine check light, not once. My IAC valve kept closing fully when hot which resulted in idle not holding when I restarted when warm.

Your engine temp sensor and connections should be the first thing to look at. A faulty one won't throw up check light.

The next is the green vacuum switch under your plenum. It has three vacuum pipes connected to it. Not sure what the name of it is but this diverts the vaccum when your car warms up. This advances timing when cold then retards the timing when the car has reached correct temperatures. If it's faulty then it won't retard timing when warm and you'll get a lumpy idle and it may stall.

Do you have any modifications to your car, dump valve etc? If so then let us know.

Take your earth strap from your engine to chassis and clean up surfaces and refit.

Dave Walters

ps. have to checked fuel pressure through the regulator? Iam not that familiar with 4 cylinders anymore so forgive my ignorance.

[Vulcan Grey]

Yes, the SE does have an IAC.

I would also start with that.

One test you could try is to pull off one spark plug wire at a time, and see how many rpm's drop. Put the last wire back on before pulling the next. The IAC should fight to keep the same rpm's.

Then redo the test after pulling the electrical connector off of the IAC. The rpm's should drop the same for each cylinder, and then engine won't fight to maintain the same idle as before you pulled the wire.

If in the first test, the engine is not able to idle correctly, or rpms are not fairly even, then suspect the IAC. If the first test is exactly like the second test, where the system doesn't compensate for the missing cylinder, then suspect the IAC...

[Qavion]

Thanks, guys.

I was thinking about changing the IAC, but I assumed this was only used during idle (although, I have to admit, my car doesn't always idle at the speeds I expect it to.. e.g. when the engine is cool (around 10C), it doesn't always idle high).

I'll run the IAC checks that Travis mentioned and see what happens. I might order both an IAC and a coolant temperature sensor anyway.. as they seem to be relatively cheap.

Also, adding to the list of things I've changed ...

Fuel Pressure Regulator.

No dump valve fitted, by the way, Dave. No modifications I can think of, apart from removing the EBPV. Not sure I have a vacuum switch, but I'll check the manual.

Thanks!

Cheers

Ian

[ozontour]

Hi Ian

sorry if this comes through twice guys, PC doing some weird s**t at the moment...

check the wires in the distributor that are on the top plate.

when you accellerate, the vacuum advance moves this plate to advance the timing and in doing so bends and straightens the wiring with every gear change, ( engine revs )

I had this in mine go twice now and is an easy fix. A jaguear part genuine here in australia costs $180aud and you only use half of the part...

HTH

Justin

[Tony94S4]

well IAC should not have efect after throtle plates open,

so my be some thing elese,

any vacum leak should bump the idle a little,

the vacum line leak to the map sensor can throw it of ,

also I think I was able to bump the idle with free scan while conected to see if IAC reacts,

I had a simillar problems before I replaced my coils

good luck

[Qavion]

check the wires in the distributor that are on the top plate.

when you accellerate, the vacuum advance moves this plate to advance the timing and in doing so bends and straightens the wiring with every gear change, ( engine revs )

Not sure I have all this stuff on my car, Justin (Is this part of the Delco engine management system?)

I'm also having problems with the Esprit Forum... The pages take 3 or 4 minutes to load.

Tony...

I've already checked the plumbing going to the MAP sensor, but I'll double check it.

Unfortunately, because the problem is so intermittent, checking IAC response, etc might not reveal anything. This is why I'm buying and changing components one at a time to see what happens. It's not like I can borrow components for months at a time from fellow Lotus owners

Cheers.

Ian.

[Tony94S4]

Ian if ur in US I can loan u any part u need for testing just take care off shipping,

I have my engine out and a spare one with all the accsesories,

if overseas not sure the shipping its worth it

[DanR]

Ian have you got an immobiliser? There could be a problem with that. If so bypass it.

Alternatively, it could be your key tumbler and a dry joint or so there. In which case hotwire it in anticipation of the next breakdown.

Neither of these would come up on freescan I think.

Edited October 14, 2008 by DanR

[ozontour]

Hi Ian

Mine has the GM ECU i think. It has Bosch K - Jetronic fuel injection and all Lucas electrics, ( YUK!)

no chargecooler.

wehn you remove the distributor cap and rotor button, (easier said than done), you should be able to see two wires that run from the top plate on the spring loaded section. these are the two wires that need to be checked. I think the only way to check them is with a multimetre as you cannot see inside the wires. by moving the wires you will see your reading change.

HTH

Justin

[superdavelotus]

With regards to the IAC valve not working, mine wasn't working properly on mine and it kept closing the valve completely when warm which resulted in the car stalling. Believe me this happened because I had a spare one and plugged it into the plug and saw what was happening. Mine turned out to be the ECU causing the IAC to close intermittantly. I've since had the ECU fixed.

BTW, mines a V8 so it's going to be different.

Dave

PS. If it turns out to be the IAC valve then pm me as I might have one spare.

[Qavion]

Thanks for the offer of spare parts, guys, but the IAC and coolant sensor are already on their way from the UK (Only 50GBP).

Danny, believe or not, I fitted a new immobiliser after this problem started happening (I didn't realise it, but this problem has actually been going for longer than I thought... maybe 2 years). I only hope there are no remnants of the old immobilisers (2) causing this problem

Justin, it sounds like we have completely different ignition systems. No distributor on my car

Anyway, I'll let you'all know if I have any good news with the new parts.

Cheers.

Ian.

[ozontour]

Hahahha...of course you do. well in that case, avoind buying the Jaguar part...unle3ss you want to sell the uselss thing to me cheap I know i will need another ina few thousand klms.

Guess you dont have Lambda sensor either then? I had an issue similar and it was a broken wire to the Lambda sensor...mind you this would show up on a scan anyway i would imagine

Justin

[Qavion]

Guess you dont have Lambda sensor either then?

Actually, I do. I just called it an "oxygen sensor" (already replaced... probably nothing wrong with the old one).

Cheers.

Ian.

[Qavion]

Well, a new IAC arrived in the mail today and I unpacked and checked it. There was a retaining clip on the "pintle" (extending plunger thingy). When I removed the retaining clip, I expected the pintle to extend to to the required dimension (length) of 20mm. However, despite there being a spring on the shaft, it didn't (readily) move. I had to pull on it reasonably hard to get it to extend. I hope I haven't broken it by doing this (it freed up a little after I moved it in and out a few times). I compared it to the old one and it the old one doesn't extend at all (when you pull on it).

Before I go for a test drive, I was wondering what is the norm... Should I be able to pull on the pintle to extend it (if not, how do I set it to the required dimension). Looking at the manual diagram, the mechanism looks like it's screw driven, but I couldn't get the pintle head to rotate.

Thanks for any insight.

Cheers.

Ian.

[superdavelotus]

I had a working one in my hands until yesterday. You shouldn't be able to pull the spindle out. It's pretty solid. I haven't got it now, toook it back to my Lotus garage. I got it incase you needed it but now you are sorted, I have no need for it.

Dave Walters

[Qavion]

Thanks for the offer Dave, but I'm still confused.

In the manual it says "Check that any replacement valve has the correct part number and pintle shape".

I ordered the part using the part number in the manual "A910E6942F" (paper manual), but I've just noticed that the old part has an odd number "59523 A0699-" stamped on it. The old one has a metal shaft and the new one has a white plastic shaft. The pintle looks the same shape, however.

The manual also says "The IAC valve plunger position is set in the factory and should require no adjustment before fitting. However, to check that no mal-adustment has occured in transit, it is advisable to check the plunger extension before fitment. In order to speed the "learning" process, if necessary, move the plunger in or out until the specified extension is achieved." (i.e. 20mm +/- 2mm)

If, as you say, the plunger is not moveable, then how are we supposed to adjust it? (out of the factory, the new part was nowhere near 20mm)

Thanks,

Cheers.

Ian

[DanR]

I think you're doing it correctly. Fit it set at 20mm and once connected the ECU notes it's position and calibrates from that 20mm setting.

[S4Esprit]

I wonder if it's happening before or after the car goes into closed loop?

I just had a similar problem:

At idle, closed loop stall was the O2 sensor. Is there any possibility your O2 sensor connector has a loose or bad connection anywhere?

You should NEVER have to adjust an IAC manually because the computer controls it.

Did you look in where the IAC sets to see if there was any sort of build-up of crud that might prevent the plunger from seating properly?

[Qavion]

I'd say after it has gone into a closed loop. Usually the car has just warmed up or is already warm.

I fitted a new sensor as part of faultfinding with no improvement, so the contacts should be ok (and wouldn't an error message be generated if they weren't?)

The manuals state that the adjustment helps the computer to learn, so I was simply blindly following the manuals. There was a thin film of blackness in the pintle seat, but I've cleaned that up. There was also a lot of blackness around the shaft and head on the old one (perhaps recirculated oil fumes).

I went for a test drive today. It took 3 turns of the key to get the engine to start, then the car settled into a rough idle. I went for a long drive and the idle improved, but no better than prior to the IAC change. At least the car didn't hesitate or stall on this run, but sometimes it can take over a month before the problem resurfaces.

Sorry, no more info to add.

Cheers.

Ian.

[Qavion]

Nutz.... The IAC seems to have improved the idling of the car, generally (even seems like the stumble when pulling away from a standstill has gone), BUT... my original problem is still there. When the car is warm and I'm accelerating, the engine just dies.

I'll change the coolant temp sensor next... then perhaps a few of the other sensors (MAT?). It's so weird that there is no Check Engine light, though.