Hesitant around 2k and very low idle

[tejr]

Guys, a couple months ago I washed the car, the MIL light came on.. took it round the block to see if the water would clear out of wherever it had found itself and after a few days of sitting on the drive the issue cleared itself.. not sure what it was but maybe water in the coilpacks or lambda connector?

Anyway, the car was ok for a few months up until yesterday apart from a distinct shunt/hesitance just above and just below 2krpm but only on light load when cruising.. which wasn't present before the incident above...

Until Yesterday it drove ok (apart from the above hiccup)but things got worse all of a sudden, the car began to idle around 600rpm, if I try to throttle it up its very hesitant to bring the revs up, but after that it feels ok, but when driving around you get to around 2krpm and you feel a sudden loss of power/hesitance which clears above around 2200rpm and then the car feels normal after that (upto 3.5kish, not take it up any further in the revs)

Not sure if that MIL light was related but thought its worth mentioning in case...

Coil packs? lambda? t-pots? HT leads are relatively new

Edited by tejr on Saturday 5th November 10:33

[Jcerb]

I used to get this! Currently i have a issue in the post below "missfire" you may want to take a read of. I think the water runs into the coil packs, they can tend to crack around the edges, i would check that out as found mine are. Now i notice under load it missfires then clears its self! I am on a mission to find some today to try it out.

[Tanguero]

Sounds very like a lambda sensor or as you rightly say, water in the wiring for one.
A coil issue would show up more under heavy load and lambda is ignored over around 3k so tends to go away when you gun it.

Edited by Tanguero on Saturday 5th November 18:43

[tonywilliams]

On the way home from picking up my Cerb 2 months ago it started to idle very low and even shut down, hesitated around 2k RPM under light load and when cruising but was fine on acceleration or under a heavier load.

I found it was both of the Lambda sensors at fault so replaced them with Britpart ones from LRDirect (link below), part number ERR6729. Have had no problems since.

http://www.lrdirect.com/ERR6729-Lambda-Sensor-Rrds...

[tejr]

Cheers guys.. I have a hunch the its fueling related and possibly overfueling as thats how it feels (when you press the throttle the revs dip for a sec before they rise from the low idle).. So my hunch says lambda, but my hunches are rarely correct! lol! I take it there is a lambda sensor on each bank? are they relatively easy to reach?

One thing i forgot to mention, when i hold the revs around 1500rpm the revs will 'bounce' osciliate +/-500rpm and won't hold steady..

Edited by tejr on Saturday 5th November 19:15

[leman600]

Id still guess at the ignition side, but only a hunch. I think I am right in saying that if a Lambda reading goes down, its ignored and suplemented by the alternate lambda. Moisture is probably more likely to influence ignition and in particular coil packs and leads rather than plugs. Newer items are not always good.

[tonywilliams]

Fully agree with you about new items not always being good, both Lambda sensors removed from my car looked almost new but had failed.

With both Lambda sensors failed the car compensates by adding about 30% extra fuel I was told by Taylor TVR which would seem correct as mine had been running extremely rich as a result of both sensors failing.

[tejr]

I'll hook it up to the laptop tomorrow.. what should I be looking for? the lambda should switch between 0-1.8v right? And to check if there are any spikes in the ignition?

[Tanguero]

leman600 said:

Id still guess at the ignition side, but only a hunch. I think I am right in saying that if a Lambda reading goes down, its ignored and suplemented by the alternate lambda. Moisture is probably more likely to influence ignition and in particular coil packs and leads rather than plugs. Newer items are not always good.

I am fairly certain that ECU will not substitutes a lambda reading from one bank to the other (like it does if a throttle pot fails). If you unplug one lambda the adaptives on that bank go to maximum and stay there even if the sensor is reading correctly on the other bank.

[gruffalo]

tejr said:

I'll hook it up to the laptop tomorrow.. what should I be looking for? the lambda should switch between 0-1.8v right? And to check if there are any spikes in the ignition?

Yep that is about it, leave the lap top connevcted for a while, mine had an intermittent Lambda issue wich have us confused for a while and then when ticking over the drivers side dropped to 0 stayed like that for a while and then woke up again.

The exhaust will give you an idea, both sides should sound identical if one is a little fluffy sounding then that is the side to keep an eye on.

[PoleDriver]

gruffalo said:

The exhaust will give you an idea, both sides should sound identical if one is a little fluffy sounding then that is the side to keep an eye on.

What if you have a cross-pipe joining the two together?

[tejr]

Yeah, mine are linked but from the drivers window the exhaust does sound fluffy and poppy as though extra fuel is being dumped into the exhaust.. on medium load and cruising closer to 3000 the car feels near enough normal, its just cruising around 2000 and under as well as idling at 600rpm thats the issue.. i'm still thinking lambda but will put it on the laptop in a few hours..

I'll do a screen shot of the figures at idle, cruising at 2000 and cruising at 3000 to see the difference.. the car will be warmed up for all those tests too.. I will post back around lunchtime hopefully...

Thanks for the help so far guys.. I will need your thoughts on the ECU traces though when I get them

[gruffalo]

PoleDriver said:

What if you have a cross-pipe joining the two together?

You should still be able to hear which side is less hard sounding than the other.

[tejr]

Ok, sorry about the delay.. I drove it home on Tuesday and it began to behave and I left work far too late to get a chance to hook the car up to the laptop..

Well, I say it began to behave, it was the same rough running to start off with then after warming it up I kept the revs as close to 3krpm as possible to burn off any crap on the plugs/sensors etc (like I say, its been running in for 1000 miles so its been driven gently)...

But anyway, I put it on the laptop today to see whats happening.. I may be wrong, but from the readouts the adaptives looked good, the t-pots looked smooth but the lambda's looked lazy at times and from cold were barely moving..The ingnition trace looks smooth to me too? But I'm not expert and haven't analysed them properly (have literally just gotten back and uploaded them)

Cold idle (manually holding at 1500rpm) -


Logged faults which were cleared and didn't return -


After 1min of idling at 1500rpm, I was expecting the lambda reading to begin bouncing at this point? -


Driving around after a few mins of warming up -


More driving around logs taken over the next 30mins -











The car still has a little stutter at 2krpm, but intermittently (laptop ran out of battery at this point)

[Tanguero]

Did you clear the fault log before you took the screenshot? Those errors could be left from a previous problem if not.

I had a persistent problem with bad running and AFR faults after washing the car for a while. It would go away of its own accord after a day or two. It turned out to be water getting into the lambda sensor plugs.

[tejr]

Yeah, after the second screen shot the faults were cleared and didn't return..

[tejr]

So do things look generally ok in those plots? I have a little time to look at the car today if it doesn't start raining!!

[gruffalo]

Ignition timing looks out, I would expect to see 12-16 not 18 plus that I am seeing on the printout on the right of the screen.

Not an expert mind you, but I do know that 12-16 is what is normal.