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fesuvious

Help! S4s issues - high idle and stumble

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Good Day!

I did my research first, but still have some issues.

My S4S has a high idle at hot, also accompanied by a stumble just as you touch the throttle from lowish revs.

I have effected the ram air mod and also built an exhaust. The exhaust is straight through 2.5" from the cat. The EBPV is there, but fixed in an open position. 

I noticed that the vac pump ran a lot, constantly on and off so today I removed the throttle jack, and the EBPV and connected the pump directly to the HVAC pipe. Massive success, no leaks at all, the pump comes on switches off, and then basically stays off but for the odd 'fart' to pump the system up.

I did all this becuase I figured the high idle may well be down to a vac leak. It obviously isn't.

Freescan has been run, I reset BLM and IAC to see if this would fix it, but no. Took her for a run and she idles at @1550 when hot. On freescan the desired idle is showing @1100 when she is idling at 1550.

The stumble is annoying also, lets say you are in second gear, turn round a corner at low revs, touch the throttle and cough! she stumbles and jerks before picking up. I also noticed this when manually twitching the cable earlier. The throttle cable does seem to have quite a bit of play - could this be it?

Freescan shows my throttle position at zero when it should be and I have checked the full range of travel and it shows 100% when it should.

From cold the car idles at @1100 (ish) just as it should and as it warms up the revs creep higher.

Something I have done has helped as yesterday she was idling at 1800!!!

Any experts on here got any ideas? The EBPV solenoid is plugged in as is the throttle jack solenoid.

ETA

Did I read on here that a braking issue could affect things? - ignition on, and just three pumps of the brake pedal will set the noisy pump thingy off...????

eta

sorry Bibs, I just wanted to see if I was capable of making an exhaust. Just had to test myself

Edited by fesuvious

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Did you state in the previous posts whether the throttle jack canister has been removed/ disconnected or not? It's the item that attaches to the throttle cam by means of a rod, it has a vacuum solenoid attached (looks like the bulbous bit on the EBPV), and should either not be there, or should have the rod removed from the accelerator cam.

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I had a similar situation with my S4s about a year ago, not the high idle but the stumbling, it turned out to ba a cracked elbow joint on the pipe that connects onto the MAP sensor. Apparently they age over time and crack the part cost 40pence and it was like driving a new car.

Maybe you should check yours, it's under the drivers side (UK) cover, where you've done the ram air mod.

Edited by lrg_machine

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Thnks guys, yes, the vacumn operated canister for the throttle jack I removed. The linkage part is cable tied as high as it can go to the inlet manifold.

The map sensor elbow....hhhhmmmm, this is wrapped insulating tape.... not by me... now this didn't affect the vacumn pump operation when I checked, but then I guess it wouldn't would it !

Could this be the cause of the stumble then?

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A leaky elbow wouldn't affect the vacuum pump (even the small pump rather than the mechanical one on earlier cars) but it is from a system linked by small-bore pipes, so a leak in any part can mean a drop in pressure differential in the engine control vacuum system.

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which could cause high idle and a stumble?

I am getting error code 26 TIP & a seperate 'quad' code, does that possibly mean anything?

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If the pipe to the MAP sensor is not a good seal the the ECU is going to be getting the wrong informtion, this is what was causing my car to stumble, it was so bad on mine I thought the car was going to cut out every time I stopped at lights etc. and it was a bugger to track down the cause.

Insulating tape does not sound good, and I suspect it's there cos the previous owner found the pipe was cracked :cheers:

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Yes, me too.

Il hunt through all the other lines, and, after reading through these forums; Il remove the TPS and clean it, can someone tell me where the IAC valve thingy is to clean too.

Im thinking just hunt through and check everything. Then Il download a file from freescan and pop it up on here (once I learn how to). Can someone run through with me, I saved a file to the desktop via freescan which was a txt file, but theres sod all in it - what did I do wrong?

Also, seems as though I have brake issues, oh the joy of buying a barely used car! Still, I enjoy the fault finding, even if I do expect better of Matty's.

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Getting there !

This afternoon took the IAC out, the gap is 17mm when the lotus manual says 20mm ideal. Cleaned it with leccy contact cleaner, lubed it and then refitted and used sealant on the mating face.

Replaced the elbow joint at the map sensor.

Took the sensor out of the chargecooler/inlet and cleaned this up with electrical contact cleaner

Car driving much much better, still throwing code 26! Stumble much reduced however after unplugging the TPS I now have a wierd hesitancy sometimes on part throttle. Now thinking my TPS is shagged. However somebody has rounded the top screw off so getting it out will be a bugger.

Any tips? Oh, and here (I think) is some freescan data, care to take a look?

esprit.csv

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Grind the top of the top screw off, remove sensor then remove the rest of the screw with grips.

Couple of other things to check...did you reset the IAC in freescan? Also, I believe there is one of those cheap rubber elbows at the MAP as well located in the rear pillar...though since that one is not exposed to heat, it may be cracked...might be good to take a look in there. Another possible item is to check the lines running from the intake to the evap canister...those can rot(from the fuel) or fall off. You might try disconnecting your battery for a half day or overnight and then reconnect and drive at least a half hour so your ECU can relearn without all the previous bad settings/possible vacuum leaks being accomodated by the ECU.

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