Discussion
My 2.9 V6 S2 seems to have developed the hiccups. I've tried sneaking up on it and frightening it but that hasn't worked 
So I'm turning to the combined knowledge of Pistonheads for some ideas where to go next
Symptoms:
Acceleration and idling are fine but cruising along and occasionally under throttle it seems to hiccup. Sort of just misses a beat and then it's fine again. Happens intermittently but every few minutes whhen cruising down the motorway.
Checked the TP by unplugging it - if anything it's worse without the TP.
Had a look in the dark to see if there was any spark leaking from the HT leads and can't see anything.
I've put on the Gunsons diagnosis thingy but got nothing conclusive - one time only reported that the vane flow meter was giving a low voltage and another time that the tp was giving a low voltage but most of the time reports no error. I did try having the gunson tester connected on the continuous test mode and driving it which reported a problem with the vehicle speed sensor but most of the time the Gunson reports no problem.
Any ideas where I should start - I'm thinking of swapping the dizzy cap, leads and coil for starters but don't want to just swap stuff without some sort of idea whewre the problem is or I could be broke before I fix it
So I'm turning to the combined knowledge of Pistonheads for some ideas where to go next
Symptoms:
Acceleration and idling are fine but cruising along and occasionally under throttle it seems to hiccup. Sort of just misses a beat and then it's fine again. Happens intermittently but every few minutes whhen cruising down the motorway.
Checked the TP by unplugging it - if anything it's worse without the TP.
Had a look in the dark to see if there was any spark leaking from the HT leads and can't see anything.
I've put on the Gunsons diagnosis thingy but got nothing conclusive - one time only reported that the vane flow meter was giving a low voltage and another time that the tp was giving a low voltage but most of the time reports no error. I did try having the gunson tester connected on the continuous test mode and driving it which reported a problem with the vehicle speed sensor but most of the time the Gunson reports no problem.
Any ideas where I should start - I'm thinking of swapping the dizzy cap, leads and coil for starters but don't want to just swap stuff without some sort of idea whewre the problem is or I could be broke before I fix it
Colin Blues2 said:
Had a look in the dark to see if there was any spark leaking from the HT leads and can't see anything.
Despite following the advice of PHers, and instructing 2 seperate individuals to check the leads, my leads problem was only diagnosed and eventually sorted (with new leads) at austec, and I had a similar problem for a while.
Maybe check again in the light, just to be sure.
If you are certain the TP is OK then it is probably one of the following things...
Your leads, cap and rotor, or your injectors.
I too replaced everything else to find it is my injectors that cause jerking.
Symptoms are the same, only occurs under a light load. Pulling is fine and so is coasting along.
I found that doing the other bits has improved the jerking but I know I will have to sort the injectors.
The magnecor leads are very good as they withstand higher temperatures which can be the cause of failure of standard leads.
Do you also have a problem with hot starting?
I placed another post earlier about this and I'm certain it is another symptom of poor injectors.
Your leads, cap and rotor, or your injectors.
I too replaced everything else to find it is my injectors that cause jerking.
Symptoms are the same, only occurs under a light load. Pulling is fine and so is coasting along.
I found that doing the other bits has improved the jerking but I know I will have to sort the injectors.
The magnecor leads are very good as they withstand higher temperatures which can be the cause of failure of standard leads.
Do you also have a problem with hot starting?
I placed another post earlier about this and I'm certain it is another symptom of poor injectors.
shnozz said:
air flow meter?
shnozz is correct in saying that it can be this.
I also replaced my air flow meter (the bottom one that does all the work) but this was only because it showed as having a fault. Made no difference to the jerking tho!
Also lift the bonnet and have a listen as you flick the throttle a little, one of mine makes a ticking type of noise which in technical terms means it's knackered. This is more a mechanical fault than clogging.
You could try some injector cleaner but most are added to the fuel tank and are not very effective IMHO. I saw a fellow PH'er mention that he removed a fuel hose from his fuel filter and filled it with injector cleaner thus giving a concentrated burst to each injector and it worked for him. Sounds good in theory and worth a try but the location of the filter in an S2 is a bit awkward to say the least!
However, you could always add another metal inline filter before the EFi system and fill that up with cleaner.
WildfireS3 said:
Happened to mine, went down the motor way started missing a beat every half an hour or so (was going to London) then went very bad. Pulled over waited 30 min all was fine for 30 min then it stared. Was the coil, going.
That can also be fuel starvation, there's a pre-filter inside the tank and a normal filter outside. The in-tank filter can clog and starve the pump of fuel leading to pump failure if not sorted. Again, happened to me too!
Colin,
You're right as it's a good idea to replace all the serviceable items first as they are generally not too expensive, you then have peace of mind that they are all OK for a fair old time. I'd recommend for the leads that you give Tim Lamont at ACT a call (0870 7070110):- www.actproducts.co.uk/ignition.php
He's really helpful and the magnecor leads kit is excellent quality. It's not worth skimping on these really as a cheapo set will let you down much sooner.
If the problem persists, then it sounds likely that your injectors need a refurb, Austec can do these for you or if you are miles away from them most LSUK (that's Lucas to us) have a system for cleaning injectors (ASNU), fairly cheap to do at around £20/25 per unit. I'll be doing mine as soon as I have replaced my water pump!
You're right as it's a good idea to replace all the serviceable items first as they are generally not too expensive, you then have peace of mind that they are all OK for a fair old time. I'd recommend for the leads that you give Tim Lamont at ACT a call (0870 7070110):- www.actproducts.co.uk/ignition.php
He's really helpful and the magnecor leads kit is excellent quality. It's not worth skimping on these really as a cheapo set will let you down much sooner.
If the problem persists, then it sounds likely that your injectors need a refurb, Austec can do these for you or if you are miles away from them most LSUK (that's Lucas to us) have a system for cleaning injectors (ASNU), fairly cheap to do at around £20/25 per unit. I'll be doing mine as soon as I have replaced my water pump!
Well picked up some leads, a new dizzy cap, rotor arm and coil at lunchtime today and fitted them this evening, just swapped everything over rather than try individual components.
Waited for the rain to stop and took her out and looks like she's cured. Nice and smooth all the way out and back again.
Judging from the state of the rotor arm and the dizzy cap I think they were the prime culprits. The dizzy cap was filthy and the contact at the end of the rotor arm looked about half the thickness of the new one.
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