7afe Engine miss at Speed

[Seedy Al]

Hey guys, we are having some issues with a vehicle at work, its getting my head very scratched.

Basicly its a Caldina with a 7afe in it, and it was a miss at just around 100km, from what the driver says its like a flutter. however it does any always do it, but when It does at around the same rpm etc.

From what i understand its been there for a while, and has had a bit of work trying to trace it out.

no Fault codes come up on the scanner, and so far the plugs, leads, coil pack, oxy sensor and Diafram in the tvis have been replaced.

Any thoughts? Experiance? burnouts?

Cheers in advance.

Seedy Al

[xsspeed]

I know 4age's are reknown for hesitation issues etc that stems from leaking capacitors in the ECU. Whether this is causes an intermittant problem, or not I am not sure.

[KKtrips]

My next plan would be to swap computer and recheck.. 2nd hand computer <$100??

[Vintage Grumble]

Yeh, could be ECU, but odd that it happens at the same RPM/speed, ECU problems are normally random as buggery. What about the pick up in the dizzy? Or maybe a fuel supply problem?

[peteretep]

My galant is doing a similar thing at the moment, under heavy load or near wot it kind of surges or something, maybe not a miss as such ( miss being like a jerk) but like a dip in power, except compared to your car, mine is carbed so can't be an ecu...

[davidian]

have the same issue on a mazda engine. around 103-105 kmh and from memory around 2300rpm. it only started happening since i moved the idle sensor thingy around, so Id look at that perhaps?

only happens when i let off the gas just slightly, so at that particular spot you either have to be accelerating or let right off, otherwise nothing is wrong. v strange

[Steelies]

nothing stupid like gammy cat converter?

[Bling]

If you run out of ideas, get the injectors cleaned, have heard through the grapevine thats a common problem on the 7afes

[UTERUS]

TPS?

Something blocking the airflow to the engine, flapping around in there giving it a fluttering type fault (i've had this).

Have you driven it and felt it?

[Hemi]

i second the looking at the ecu . ive had a few faults like that in older ecus i remember the 92 ish galants being prone to it and even one of my ca ecus had a leaking capacitor that caused it give me all sorts of weird and wonderful gremlins

[Seedy Al]

just took it for a burn. Seems to be happening at 3000rpm with the over drive off at about 90ish k.

tried to get to 3000rpm with over drive on but was traveling to fast

Odd thing was that the gu8y who drives it is saying it used to do it at about 2400rpmm with over drive on at just around 100km.

Might have to try the ecu i think, does seem odd that it comes and goes for no reason.

Allan

[Seedy Al]

Ok, so it wasnt the ECU.

lame.

Also it seems to be missing at a different time now than before.

getting more keen to Chuck SU's on this think

Allan

[Crownin_Round]

Yeah 4age head etc

[Truenotch]

Does it only happen when it's hot Al? Could be the coil having a spaz under load once it gets warm.

[Seedy Al]

Coils have been replaced, but no it doesnt really seem to matter what temp. Fucken over it to be honest haha.

might try the TPS even though that has been replaced I hear.

[sentra]

dont speed?

[barf]

is the coil different to the original type?

if it's a different coil, another possibility is that the dwell time (traditionally set by the 'points gap' in a kettering-style ignition system) could be too short, causing coil to charge enough for sufficient spark at low loads but at high rpm/loads there may not be enough spark for proper combustion.