Rough running S4S

[Guest Mutley00]

I've not had the car long, and just had a C Service but cant get the engine running quite right.

From a standing start if you take it through the gears quickly up to 5k revs in each gear its a wonderful drive, BUT, if you're pootling along in 2nd 3rd or 4th at 2-3k revs then gently accelatrate, it coughs and virtually stalls. Sometimes its so bad you have to slip the clutch, gun the engine & let the clutch out again. I noticed yesterday it was running really rich, the newly installed exhaust trim is black with soot already.

If it was my Elan Sprint, I would say the carb mixture was wrong and they were flooding, but obviously that can't be the case with the Esprit. Has anyone any ideas - is there something your average DIY mechanic (me!) could check, or is it time to try & find a specialist in England's 4th largest city but infamous black hole for Lotus specialists.

Its had the EBPV disconnected and that's firmly wedged open with the vacuum pipe blocked. Plugs and filters are new and the Engine Management light doesn't come on. The CAT looks as though its seen better days (better years if I'm honest), so I've just bought a bypass pipe from PNM but if that doesn't work its scratch my head time again.

Any ideas appreciated, thanks Andrew

[islandbloke]

My Lottie has been extensively modified by her 'interim' owner (chip, engine, exhaust etc) and also seems to run rich with a sooty exhaust so I don't know the answer, and you could spend forever chasing yourself round in circles. I'd take her to a good independent (PNM in Liverpool seem highly regarded although I've no personal experience of them). Good excuse for a blart over the Snake Pass to join the motorway network at Mottram...

[andydclements]

You're not far out with the Elan Sprint reference. There is a stumble at 2-3k on these ECU cars. Some modified chips attempt to reduce it, but it's still there. To gauge whether yours is worse than another would be impossible over the internet, but it may be worth meeting up with another owner of an ECU controlled car to gauge it, even if it's an SE. If yours is worse than an SE, GT3, S4 or another S4S then you know you have an issue rather than a niggle you'll have to live with.

Andy

[lrg_machine]

Check the vacuum pipes and connectors to the MAP sensor, I had similar problems as you describe and it turned out to be a simple as one of the vacuum elbow connectors was cracked and split.

[espritmania]

Was that the yellow cat c one from Soke.

[Advantage]

Freescan required.

[mr.oogieboogie]

I have an s4 in Mansfield so about 30 min drive from Sheffield if you want to compare pm me

[Guest Mutley00]

Andy - this isn't a stumble its a virtual stall. I used to own Robert Crooks magnificent SE so I know what you mean about the lag but this is far far worse.

Paul - Yes it was the Cat D one from Stoke - do you have some 'inside info?'

Jeremy - forgive my ignorance but how do I locate these pipes. Are they on the 'map' on the underside of the hatch.

Stu - Great minds think alike - I was thinking of PNM but a blart over the Snake isn't an option - although its only 15 mins from my house. I'm not sure I'd make it to Wallasey. Why Wallasey for Gods sake!!

GKP - I think its looking that way

Thanks for all your replies

[mr.oogieboogie]

clear your inbox

[espritmania]

I got the feeling that it had not been used for a very long time.My gut feeling would be that something was stuck or blocked.I hope that you get it sorted cheaply.Try to start at one end of a possible solution and just work your way along ,your time costs you nothing.

[lrg_machine]

Andrew

From memory the MAP sensor is located under the carpeted cover on the drivers side in the engine bay towards the rear, you'll see a thin black pipe going to it, check the black rubber elbow connections, they're probably split if they haven't already been replaced.

Mine was like driving a different car after replacing these.

[espritpassion]

Jeremy, you know if the MAP sensor is located in the same place you suggested in your last post also on the GT3 (last model V8 interior) ?

on my GT3, times ago I opened the bay which is located between the engine bay and the luggages bay, there is a black module that should be the vacuum pump which is sound like " trrr trrrr trrr "

what you say about ?

Thanks

Alessandro

[lrg_machine]

Alessandro

I'm not sure on the GT3 if the MAP sensor is mounted in the same place, is suspect it is.

If you have a look in the parts manual at page 43.03A the MAP sensor pipe and connections are marked as parts 60, 61 and 64.

It was the elbow connection on my car that was split causing all sorts of engine running issues, almost stalling when idling etc. soon as this was changed the problems went away.

[espritpassion]

Thanks Jeremy for your help, do you changed the the MAP or only the elbow connection ?

Im looking the parts manual that I have in pdf, please if is possible can you specify the exactly pageN# where look about

Thanks a lot

[lrg_machine]

I didn't change the MAP sensor, just the split elbow connector.

On the parts manual I have the section is 43.03A afraid I can't give you a page number, there aren't any, but you should be able to just do a search for MAP sensor and it'll be fairly obvious what I'm talking about

[RV_ABZ]

As suggested by GKP, I'd start with a Freescan diagnosis and maybe reset parameters (I'm thinking BLM) and faults reported. Then see what comes up after you drive the car.

I did have a frequent really bad stumble/very rough cough not long after I bought my S4s and it was always between 2.5 & 3k rpm when driving gently along in 2nd or 3rd gear. I can't say whether this was the same as your current problem, but in my case, a BLM reset cleared it away. I still have the odd "3k stumble" though, but nothing as bad as that rough cough.

Edited January 17, 2011 by RV_ABZ

[fesuvious]

Start with freescan.

But, chase the vacumn lines from the pump. Cracks/splits in the vacumn lines can cause lots of driving issues. I too found a split in the elbow at the map sensor and this cured a lot of issues.

Injectors were causing @15% of rough running.

I removed the throttle jack and associated lines and resealed all remaining vac connections. Plus of course chased all lines inc the boost line from the inlet manifold. All the vac lines are on the map diagram - yes.

If you're ever passing the midlands...............

[mr.oogieboogie]

This could also be a coil or lead breaking down

[fesuvious]

Coil would be intermittent. I had a coil breaking down; kept 'coughing' at random points.

For less than £100 all said and done though an Esprit owner still running the originals would be daft not to replace them with MSD's

[Paul93Lotus]

This sounds like it could also be two additional items not mentioned:

The Idle speed control motor may not be at the correct base setting (fix only via freescan)...especially if you have recently replaced the battery or the battery had been dead or removed more than a half hour it may have set itself wrong. Also, if the battery has been disconnected/dead, the ECU needs to relearn...thsi means driving at least a half hour at varying speeds in order for it to relearn the fuel trim tables.

On my S4s, several of those rubber elbows needed replacement(if the line comes off the MAP completely you will stall/major stutter once you hit boost...they are crap parts and should be replaced with something other than the lotus one as it will happen allover again. Ideally you should buy the correct gauge silicone vacuum lines, forget the plastic tubing and elbows and that issue will end forever. Also check all your evaporative canister lines, I think one or two connect to your intake and can come loose.