Ignition Problem?

[Rob_the_Sparky 9]

Here are the symptoms: (on a standard 309 GTi)

 

When under load the engine cuts, then goes, then cuts, etc. Like a very severe kangerooing but happens at pretty much any rev, although much worse below about 3k.

 

If gentle with the throttle then no problem at all

 

Ticks-over perfectly (much better than most!)

 

Only happens when the engine is warm, again perfect when cold.

 

 

I'm thinking it has to be something ignition related but could it be fuel pump/tachy relay?

 

If ignition I'm thinking most likely to be the ignition amp but not got much to base that assumption on apart from the fact that it is worse when hot and I believe the ignition amp can suffer when hot.

 

Suggestions/experiences please

 

Thanks

 

Rob

[Richie-Van-GTi 72 2 Cars]

I recently had issues with mine under load, turned out to be lazy fuel pump.

[Anthony 1,003]

Ignition amp failures tend to be rev rather than load dependant in my experience, so I would personally say that the issue lies elsewhere.

 

Does the fault begin to occur as soon as the engine is upto temperature (ie when cold start enrichment turns off) or does it take a while longer than that (ie when componants are getting hot)?

 

Probably the easiest thing to do Rob is to just swap parts off the Black/Red 205's and isolate the problem - should only take 10 minutes to whip off the coil, dizzy cap/arm and leads and swap them over.

[Veero 1]

A vote for the ignition amp here. Kinda similar to what problems my 8v 1.6 had, AA man was perplexed, local garage said ignition amp straight away which I swapped for my Mi16 one and hey presto problem solved.

 

Veero

Edited April 19, 2006 by Veero

[Alex G 0]

id check the condition of the cap arm and leads, sounds similar to the problems i had, Albeit being on an Mi

[Rob_the_Sparky 9]

Problem starts before it is completely warm. It was running fine last week and has come on quite suddenly. Had the plugs out and 3 were heavily contaminated with oil. Cleaned most of that out and no better.

 

Going to play this afternoon but can't do a straight swap on everything as my 205s are phase 1.5 and the 309 is phase 2. Will let you know how things proceed.

 

Thanks for input so far.

 

Rob

 

P.S. Don't think it is fuel related as it is fine at full throttle once the revs rise.

[Rob_the_Sparky 9]

Quite right Anthony, it wasn't the ignition amp. Also wasn't the dizzy cap or rotor arm, despite them being well worn.

 

Tis worst when setting off (or trying to) from a junction. Only solution is to drop the clutch and then slip it like mad to get the car rolling. Last night it got so bad that when cruising if I tried to accelerate it started to kangeroo and would stop when I backed off - probably because the engine was hotter than my test runs today.

 

Beginning to doubt it is ignition...could a weak mixture cause this?

 

Rob

[Pug_101 0]

If you have oil on your plugs first thing to do is a cylinder compresssion test on all 4 bores. You need to find out were the oil is coming from. Remember to do each cylinder at a time and replace the spark plug before going on to the next bore.

Fuel can leave a type of varnish (which will reduce there sparking power) on the plugs and it could be this you are seeing which is almost imposible to remove completly so get some new ones and thats why you need to check the compressions.

 

If the compressions in all the cylinders are ok and it is oil on the plugs what could be happening is excess pressure in the engine caused by the breather system being blocked. As the oil temp rises and it starts releasing vapour it has no were to go and can force it's self pass the piston rings. for a quick check of this disconnect the crank & rocker breather tubes and leave them to atmosphere and plug up the pipe that leads into the intake system. Take it for a drive and see what happens, apart from being a bit smelly of oil.

 

You could have a air leak, so when the car is cold the enrichment system is compensating for it and when the enrichment turns off it gives you a lean mixture.

 

Of course any of the above posts could also be your problem

Thanks

Paul

[Rob_the_Sparky 9]

Yet another update. I changed the AFM for an old dirty item in the garage (one of your stock Anthony) and it is improved. Gone is the vicious on/off power effect so the ponder about mixture seems to have some substance.

 

It still is hesitant when curising with next to no throttle, e.g. 30mph on the flat in 5th. Feels like it is missing 2 or 3 times a second, not great but a whole heap better.

 

The air leak idea sounds quite likely to me. Either that or an ECU temp sensor?

 

Rob

[Anthony 1,003]

Anthony's AFM mountain comes to Rob's rescue again

 

If it's fine when cold start enrichment is running, fine at WOT (when it's running richer) and swapping the AFM noticeably reduced the problem then I'd say it's definately sounding fuelling related.

 

Probably not an airleak I'd say if it still idles spot on, although worth checking that there's no splits in the pipes that are getting opens when the engine moves (as it will do when you punch the loud pedal)

 

Unlikely to be the ECU temp sensor itself in my opinion, as it sounds like cold start enrichment is working, and even if it's knackered and stuck in cold-start then it'll still appear to run fine (just drinks fuel)

 

Might be worth trying yet another AFM, as the light throttle surge sounds like it's running lean to me.

 

If you're planning on keeping the car long term, then I'd spend a few quid replacing all of the consumable ignition parts (plugs, leads, cap/arm) as a matter of course - not much money, and then atleast you know that they're good and should last a while.

[Rob_the_Sparky 9]

Well whatever it is I can guarantee it is intermittant! Have been adjusting idle mixture and ignition timing during the day and seemed pretty much cured. Went out after leaving it for 1.5hours and it is undrivable. Almost impossible to get it to move (regardless of throttle) without severe kangerooing.

 

I thought it might be running lean and I'm pondering whether the AFM currently on is the one I used to MOT the red car (as its emissions were low with this AFM). In which case it is probably still a bit lean.

 

I'm currently baffled. Already changed the ignition amp, dizzy cap and rotor arm I guess it is time to start randomly replacing the rest of the ignition...not my preferred option but as correctly pointed out not an expensive one.

 

If it is running lean could that be the FPR? From my thoughts if the spring weakens over time then it will reduce rail pressure. However, I've never heard of this happening. Also if it were this then why would it be intermittant (or maybe just a part warm engine problem?????).

 

Not a happy bunny (and the red one needs a driveshaft so may have to do that next to ensure I have a running car next week).

 

Rob

 

P.S. After much fiddling it looks like the ignition timing was pretty good to start with, maybe a degree or so retarded but not bad.

 

P.P.S. Idle has raised as I enrichened the idle mixture so that would indicate lean mixture to me (agree?).

[Pug_101 0]

I've had a similar problem over the last couple of weeks just after changing the sparks and leads. Traced the fault to a loose + battery terminal, the terminal was fully done up but could still move on the post. Changed the terminal today and everythink running as it should.

It could be worth a look if you haven't already tried this.

 

Paul