Cutting Out/jerking When Accelerating

[lagonda 42]

This problem has returned to annoy!

 

Car runs fine when cold, but once hot, & more so when very hot, it will cut out when you start to accelerate. Doesn't happen all the time, & is most likely to occur during heavy/stop-start traffic, or accelerating once a really slow git has finally turned off in front!

 

I'm pretty certain this time round that it's simply a bad connection somewhere...electrical resistance increases with heat. When I had this trouble 2 or 3 years ago, swapping everything in sight made no difference, but cleaning all terminals did. Trouble is, which one/ones was it?!

 

Advice as to which connections to concentrate on please!

[lagonda 42]

I'm wondering if any of the earth terminals...the yellow connectors either side of the radiator...are likely culprits.

 

Also the battery symbol doesn't always light...I know this means the system doesn't start charging until engine revs reach 3200 or so, but could that problem also cause the engine to cut out briefly in these circumstances after I've hit the magic 3200? Just thinking low or no charge at low revs; sudden demand for extra volts/amps causing temporary loss of spark until revs pick up?

[Tom Fenton 1,542]

Sounds to me a bit like a dead air flow meter. Car doesn't cut out as such- dip the clutch and it will idle- however trying to accelerate there is no fuel and hence no power.

[katmav 0]

I've had very irratic running when warm. Turned out to be the coil.

[AlexRS2782 136 1 Cars]

I had similar problems in the early days of owning mine. Changed to another known working AFM & also had the injectors ultrasonically cleaned and it cured the problem

[lagonda 42]

Thanks guys. Unlikely to be the injectors; had those cleaned & test report showed they weren't that bad before cleaning. Coil...may be, but AFM perhaps more likely. I had this problem a couple of years ago, swapped everything I could think of, no joy. The only thing I didn't have spare was an AFM...borrowed one...worked fine. Put mine in his car...worked fine (!). Put mine back in my car...worked fine...so perhaps it's that playing up.

[dandanger 12]

id say AFM but like you say could be a dodgy sensor connection or dodgy sensor itself

[Tom Fenton 1,542]

id say AFM but like you say could be a dodgy sensor connection or dodgy sensor itself

 

So tell us, which of the sensors on the 8v engine could cause the fault described?

[dandanger 12]

Water temp sensor...... does the 8v have a throttle position sensor?

[Tom Fenton 1,542]

Please refer to the forum rules, specifically the parts about "hearsay and guesswork". I appreciate you are perhaps only trying to be helpful, but guesswork helps nobody.

[dandanger 12]

consider my ass spanked!

[Tom Fenton 1,542]

Like I say I can see you are just trying to be helpful, but please stick to advising other folk on things you have got first hand experience of.

[Pug Rob 0]

Hi,

 

I'm very new to the Forum world, so please bare with me.

 

I think I might be suffering the same issue as Lagonda. I have exactly the same symptoms. Once warm the engine feels like is just cuts out for a moment, seems to be more likely under light throttle, although not exclusively and usually at quite low revs. So on pull away, or just after changing up a gear in traffic (i.e. not booting it). But it is very intermittent.

 

It hasen't cut for long enough to try dipping the clutch to see if it will idle, but I will give that a try that next time is does it.

 

I have recently restored the engine and engine bay, and in doing so I checked the loom for any wire damage (with the plastic shielding removed) and cleaned / needle filed every connector (yes every one!). The car has run perfectly for about 1000 miles between doing the work and the problem starting.

 

So my suspicions are with a component failing rather than a wiring issue, it's very difficult to tell if it's a spark or fuel issue (or both).

Initially I thought spark (because it cuts out so abruptly), so I fitted a new coil, but that has not fixed it (it had new leads, cap, rotor arm, and plugs during the rebuild).

Then while studying what was going on when it was cutting out I noticed that the rev counter is not affected, and also there is no backfire when it cuts back in again, so I then thought it more likely to be fuel. So today I have fitted a new Tachimetric (spelling?) Relay, but that hasn't fixed it either.

 

Hence the surfing of the forum for clues this evening!

 

The reading I have done suggest that the ECU gets the signal for the fuelling from the ignition system (distributor signal), can anyone confirm if that is the case? If so, an ignition issue would cut both spark and fuel, explaining the lack of backfire when it cuts back in, but not the fact the rev counter carries on reading?

 

So the next port of call reading the posts above, appears to be the Air Flow Meter, Does anyone have the resistance readings available, to check it's function? (although being so intermittent, I think I will be lucky to find anything). It could be some dirt / wear inside the 'black box'. Does anyone have any experience with restoring / fixing AFM's or is it simply a case of sourcing another one to try?

 

Another though I have is it could be the immobiliser, it has an old aftermarket Clifford system fitted, and that would certainly cut both fuel and spark, but again, I imagine it would also kill the rev counter?

 

I will look forward to hearing the thoughts of the wise!

Thanks in advance!

Rob.

[lagonda 42]

Well...no more jerky jerky! In view of past experience, whilst I had the AFM I gave it a reasonable but not life threatening thump on a wooden banister. Closed up all the "teeth" on the AFM connector, signal cable connector and ignition amplifier connector. Cleaned up AFM terminals with needle file. I also sprayed all the yellow earth connectors around the radiator with terminal cleaner, pulling them on& off several times to aid cleaning; but I understand these are unlikely to be the culprit. Oh, also found one of the 3 cables connecting vertically upward to the shunt box had been wrong slotted; cleaned those connections as well.

So...it could have been any of those...don't care which, just happy with car, so much more pleasant to drive now, & just in time for my UK visit.

Rob...if none of the above helps, suspect the immobiliser, they're often the cause of problems.

[Pug Rob 0]

Thanks for the advice Lagonda,

 

I have, like you, carried out a number of checks and changes in one go.

 

I took your advice and cleaned the AFR, ignition module and signal lead connectors and closed them slightly to make sure the contact was good, before re-fitting.

I also adjusted the ignition timing, something I have been meaning to do since the re-build, approx. 1000 miles ago. I built the engine using static timing, and it ran ok but i knew a dynamic check should be carried out at some point. I found it needed advancing by about 4 degrees. Which has given it a nice healthy lift of power in the mid range and has made the low RPM running much cleaner, by that I mean there is no hesitation at all, so before the combustion clearly wasn't optimal. Because the cutting out issue occurred mainly at low RPM I'm thinking the the timing might have been a contributing factor to the cutting out, although I cant see it being the root cause?

 

Anyway, the end result is four days of happy commuting without any sign of cutting out, with the added bonus of a much more eager engine, I really know why i bought the car now, it's awesome!

 

Thanks again very much for your helpful advice.

 

I would still be interested to know if anybody has positive or negative experience with opening and "servicing" inside an AFM. Just because they are so expensive, and the finger gets pointed at them for so many issues. The solution of buying a new one, just to try, isn't really palatable, and the solution of buying 2nd hand seems fraught with the risk that it could have the same problem!

 

Thanks Again

Rob.

[pyrrhic 14 2 Cars]

I am reviving this old thread because this seems very much like what is happening to my CTI 1.6.

 

I have one question, on "found one of the 3 cables connecting vertically upward to the shunt box had been wrong slotted; cleaned those connections as well."

 

Where is this shunt box located?

[Anthony 1,003]

It will be located between the battery and headlight - black box about 8cm long or so that is connected to the battery positive terminal.

[lagonda 42]

Well, I finally got so p'd off at how bad the car was getting (yes, my "repair" didn't last long!), I thought I'd take the afm off and have a good look at it.

 

With a multimeter, I found the resistance track was reading well over 1k ohms for the higher readings. Hmmmm. I've previously done the trick of repositioning the copper contact arms, so this time, I soaked a cottonwool bud in nail varnish remover, and scrubbed the resistance track vigorously with that. Quite a lot of dirt came off; result, maximum readings now around 800 ohms.

 

No jerky jerky....why did I put up with it for so long?!

 

But....question....will this prove to be a reasonably long term fix, or should I be looking at getting the afm reconditioned/a new one? Have had the car since 2003 so I don't mind spending out if it's a worthwhile and long term improvement. As far as I know, it's the original afm, supported by the date code, so it will have "done" around 211,000 miles.

[pyrrhic 14 2 Cars]

I found out my problem was a very thin, but 2" long split along the air hose from the SAD to the intake planum. I repaired the hose temporarily with butyl tape, but I am ordering a new hose tonight. With the butyl tape on right now the car is running unusually smooth, so I imagine that was the only leak I had.