Au2 Tickford: intermittent power loss under variable load and speed conditions

[peterljohnson55]

Hi Guys,

My AU2 Tickford auto, 130,000 kms, experiences sporadic loss of power under load, of less than a one second in varying circumstances.

These ‘flickers’ are inconsistent and the time between them is variable. Doesn’t always happen, either, but has been getting worse over last month.

Happens when:-
- engine is hot or cold,
- pedal down from standing start,
- on cruise control at 60 and 70 (suburbia) while driving up slight inclines;
- cruising at 110 on freeway while driving up hills (like on F3 toward Sydney).

Mechanic says
- could be one of the leads (which are most likely originals)
- could be bad plug the plug could (have) damage(d) the lead
- could be fuel filter or injectors
- could be the coil
- doubts it is the auto clutch slipping

Mechanic suggests the following action
- concurrent replacement of new leads and sparkplugs ($200ish).
- Suck-it-and-see approach: Probably due for new leads anyway so no great loss if don’t solve problem.

(Ford Spares trade prices ... plugs = $69, Leads = $40, Fuel Filter = $18.25.)

I am no mechanic so haven’t a clue....
Can the problem develop in a major malfunction?
Any ideas?
Do you agree with the mechanics approach?
What would you do?

Thanks,
Peter J, Newcastle.

[JC]

A miss is poor fuel delivery, too much fuel delivery - ie dripping/leaking injector, or poor spark. So the mechanic is pretty much on the ball there (don't you love the internet where a non-mechanic is able to validate that a mechanic is on the right track!).

I'd start with perishable/serviceable items first. If you are not sure if the plugs and leads have ever been changed, then they are due anyway, so might as well do them. If the miss never happens under light throttle, but always is under medium/heavywide open throttle, then I'd suspect leads and/or cracked plug.

If that doesn't fix it, then I'd change the fuel filter next (especially if you don't know if it's ever been changed).

Then I'd look at coil pack, though usually when they go, it is more of a permanent miss than an intermittent one, especially since it's happening cold and hot. But once again, they are a serviceable/replacement item, so if it's never been changed, might as well do it too!

lastly - injectors. Why lastly? Because they are fiddly to get off and are probably the most expensive part out of the list and they are not typically the cause of a miss, but if everything else has been checked, then the only thing left is the only thing left so it must be the injectors.

Very lastly, it could also be the fuel pump, but again, this is the least likely cause, but has been known to be the cause.

[AUIIPURSUIT]

6 or an 8?

if its an 8, clean the MAF first with contact cleaner / maf cleaner... can cause errorneous air readings and cause over fuelling... happened on my au s2 xr8...


As JC says, work your way up the expense and expendable chain of common issues...

ive replaced my spark plugs (ngk iridiums), performance leads (eagle), coilpacks (MSD) and cleaned the MAF to get rid of my sluggishness...

the MAF clean probably made an equal improvement for $0 as the others did totalling.. 400 odd dollars (and i got things cheap).

[sly]

If you work through that and still haven't fixed the problem, one thing to consider is the throttle position sensor. AFAIK they aren't a common issue with AU's, but a TPS with dodgy internal electrics could cause the sort of power drops you describe as fluctuations in its output voltage (unrelated to actual throttle movement) can cause over- and under-fuelling.

OTOH it would be worth replacing the exhaust oxygen sensor before the TPS as O2 sensors generally have a useful life of 100-150,000km or so. When they get old and "lazy" they respond too slowly to changes in the exhaust gas composition, also leading to transient over- or under-fuelling. Ford will charge hundreds for one, best price I've found is cyberspace auto parts, $60 or so.

I also had similar symptoms from a failing Cam Position Sensor, but they occurred consistently under full-throttle acceleration at over 3000rpm, when the car was 250,000km old. Unlikely in your case.

[mik]

sounds like a fair assessment by the mechanic,, not saying this is your problem, but the coil pack started playing up on my s2 xr6 vct at around your mileage , they can be found fairly cheaply if that turns out to be the case, i picked mine up new off ebay for $80 ish from memory.

[peterljohnson55]

Thanks to each of you for your advice. To start with, I am going to go for a replacement of plugs and leads – that seems to be the common thought - and see how that goes.

However, should I think about a new coil pack, up front? At least will get fitted with plugs and leads and keep labour costs down. Is that the wise thing to do, if I have the money?

JC, thanks for your very thorough reply – very helpful, and a good plan.

AUIIPURSUIT, I have a 6 so suppose I don’t have an MAF. I will get quotes for NGKs and Eagle leads, tho. FORD may be a bit pricey for parts.

SLY, your thoughts will be there if the present plan fails. Thanks for the level of detail.

MIK, as noted above, not sure if I will go for a coil pack at the moment, depends on money as I don’t have much. But will get a quote for a pack tomorrow.

[AUIIPURSUIT]

you should be able to swap all items youve mentioned yourself champ.. dont be afraid to get some grease under your nails and remember you are only ever one post away if you get stuck in the process

[badkiwi]

i had same on my au2, under presure would miss goin up hills an give it a bit an would miss, same as wat u say , an was coil pack braking down found after i did leads,plugs

[FGII-XR6]

I'm thinking fuel pump or coil pack. it's the right Ks for either of these to be on the way out

[peterljohnson55]

UPDATE ... And what can you make of this?

Thanks guys for your replies. Now here is the latest which surprised me.

Two weeks ago I took the beast for rip up country and thought I would see how bad the problem had become, for it had been progressively worse.

So, pedal flat to floor from standing start to 100ish, three or four times.

Amazingly, now I dont have the problem at all - it runs very smoothly!

Anyone care to advise what they think happened?

[badkiwi]

stumped, do it still do at low speed an on slite hill incline ???