a strange malfunction....i'd appreciate your ideas

[panic]

it happens, not always nor often, when the car is fully warmed up...the engine just drop revs and seems like if it's going to die, specially when the car stands (in a traffic jam)and you let it idle...then you floor the gas and goes up but like if there was missing spark or fuel (blocked injectors? not enough sparking power?...) then maybe for sometime no malfuntion at all, then suddenly you could be in a traffic jam and it starts again...

[Bluebottle]

I had this problem once and it was the coil starting to fail...the engine bay gets hotter when you are stuck in traffic and thats when my would show this sympton. But it could be the leads breaking down or the amplifier unit.
I would check for any signs of scorching or any other breakdown in the leads, and signs of oil seaping from the coil.

[CaptiV8ed]

Panic, I believe you and I are in the same extremely annoying boat. My car is hesitating and apparently missing under light or heavy load, or low or high revs. No pattern to it at all. I did discover something yesterday though. Yesterday in the afternoon, the car misbehaved. I drove back late last night and it hardly missed a beat. Today (hot and sunny) it's sh1te again!

So, I have turned my attention to what could be happening. Coil? I have read that they usually fail by being fluffy at low revs, but fine under load or high revs. Ignition amp? Dunno how to tell...
Oddly enough, my shift light (which just picks up spikes in the HT circuit) keeps lighting up as the car hesitates - could this be spurious behaviour in the amp / coil?

But what about the air flow meter? If it was just in tolerance on a normal day, then would it be able to be 'tipped over the edge' on a hot day when the wire is not getting cooled by hot less dense air, buggering up the fuelling?????......... Please help I'm at my wits end!!

[David H]

Panic, I had a similar problem once. It took a while to find the route cause but it turned out that the ECU was getting too hot, it was very close to or contacting the heater pipes. After moving the ECU a little the problem went away.

It probably isn't the same solution for you but it's an easy one to try.

Best of luck.

[panic]

Bluebottle said:

I had this problem once and it was the coil starting to fail...the engine bay gets hotter when you are stuck in traffic and thats when my would show this sympton. But it could be the leads breaking down or the amplifier unit.
I would check for any signs of scorching or any other breakdown in the leads, and signs of oil seaping from the coil.

blue, i've changed the coil for a better then stock one, the simptoms remained, just show in less occasions...

[panic]

CaptiV8ed said:

Panic, I believe you and I are in the same extremely annoying boat. My car is hesitating and apparently missing under light or heavy load, or low or high revs. No pattern to it at all. I did discover something yesterday though. Yesterday in the afternoon, the car misbehaved. I drove back late last night and it hardly missed a beat. Today (hot and sunny) it's sh1te again!

So, I have turned my attention to what could be happening. Coil? I have read that they usually fail by being fluffy at low revs, but fine under load or high revs. Ignition amp? Dunno how to tell...
Oddly enough, my shift light (which just picks up spikes in the HT circuit) keeps lighting up as the car hesitates - could this be spurious behaviour in the amp / coil?

But what about the air flow meter? If it was just in tolerance on a normal day, then would it be able to be 'tipped over the edge' on a hot day when the wire is not getting cooled by hot less dense air, buggering up the fuelling?????......... Please help I'm at my wits end!!

my problem occurs just sometimes, for long periods it does not happen and then suddenly, maybe after weeks or months, here it is. as i said to blue, i've changed the coil, i also have 2 different 20am bosch airmeters (both are fine), the plug wires are nearly new and uprated (act), the plugs are often changed as well, i have a few tornado chips that i change just in case... the car goes like a rocket when the malfunction does not appear, it seems to be a ghost sickness, many garage guys have searched for a solution but with little results...

[panic]

David H said:

Panic, I had a similar problem once. It took a while to find the route cause but it turned out that the ECU was getting too hot, it was very close to or contacting the heater pipes. After moving the ECU a little the problem went away.

It probably isn't the same solution for you but it's an easy one to try.

Best of luck.

where could the ecu box be moved? mine, like i guess all griffith's, is in the passenger foot well, on top of the battery...could it be a kind of short circuit caused by the inductive electricity of the battery maybe?

[David H]

panic said:

David H said:

Panic, I had a similar problem once. It took a while to find the route cause but it turned out that the ECU was getting too hot, it was very close to or contacting the heater pipes. After moving the ECU a little the problem went away.

It probably isn't the same solution for you but it's an easy one to try.

Best of luck.

where could the ecu box be moved?

To do the test just drag it out in to the passenger footwell area.

ETA: Just noticed that the problem does not occur very often so having the ECU laying around is not a viable option.

Check that it's away from the heater pipes anyway (or lag the pipes).

Edited by David H on Tuesday 5th June 22:37

[spend]

Are you describing the shunt from the cooling fans switching on?

Dave

[panic]

but then, why, if the malfunction is caused by the heat or short circuits because of the battery onto the ecu box...why it does only happen sometimes? if the conditions are the same, the same malfunction would have to arise every single time i switch the engine on and cruise around...(i've studied this in phisics during high school...)

[panic]

spend said:

Are you describing the shunt from the cooling fans switching on?

Dave

sorry dave, i dont understand what you mean here

[Seasider]

Try cleaning the plenum butterfly

[crackedfinger]

panic said:

it happens, not always nor often, when the car is fully warmed up...the engine just drop revs and seems like if it's going to die, specially when the car stands (in a traffic jam)and you let it idle...then you floor the gas and goes up but like if there was missing spark or fuel (blocked injectors? not enough sparking power?...) then maybe for sometime no malfuntion at all, then suddenly you could be in a traffic jam and it starts again...

I had the same thing, it was after the car has heated up it will tend to stall on idle, between gear changes and feel a bit grumpy sometimes, then fine other times.

Replaced the ingition amp from reading advice here that it breaks down with heat - fixed the problem for good

Edited by crackedfinger on Tuesday 5th June 22:58

[GarryM]

Just another possibility to add to the options. I remember something similar although it happened more frequently than you are experiencing - engine would nearly die when idling, I'd give it some throttle and it would run badly ("fluffy" was a description the mechanic used! ) up to about 3k revs and then it would clear its throat and run fine until it happened again. Didn't happen every time but probably once a trip. Ended up changing a throttle pot and had the ECU repaired. Apparently the throttle pot had malfunctioned and taken a bit of the ECU out with it. Pretty rare I would think but you never know!

[spend]

panic said:

spend said:

Are you describing the shunt from the cooling fans switching on?

Dave

sorry dave, i dont understand what you mean here

That is the stutter caused by the high electrical loads at the instant that the radiator cooling fans switch on. If you have a fan over-ride switch - does a similar thing happen if you manually switch the fans on at tick-over.

Dave

[panic]

spend said:

panic said:

spend said:

Are you describing the shunt from the cooling fans switching on?

Dave

sorry dave, i dont understand what you mean here

That is the stutter caused by the high electrical loads at the instant that the radiator cooling fans switch on. If you have a fan over-ride switch - does a similar thing happen if you manually switch the fans on at tick-over.

Dave

i wish it was but unfortunately it isnt...

[spend]

I would check all the hoses connected to the plenum, and clamp off the advance and purge valve pipes. You should be able to rule out unmetered air then, without too much effort or 'destructive' testing.

Dave

[panic]

thanks to all of you, i'll go through all your advices and will get it right.

[rfisher]

Another PH member who won't accept emails!

I sell or hire fault code readers - let me know (by email via my profile) if you would like one.

[panic]

[quote=rfisher]Another PH member who won't accept emails!

personally, i see no reason why not allow e-mails, i just never filled the profile properly, you can go ahead now...