need to know if my problem is fuel or ignition? plz

[ffjunior]

at idle my engine sometimes shutters so i changed my plugs,fuel filter, air filter my cel does not pop on and i was told if it was a misfire over a certain time the cel would pop on and it hasn't ive been reading posts and dont know if its a ignition coil prob or a fuel delivery prob any suggestions? oh and is there a way to check igniton coils outside of the car for problems i have 135,000 on a 99 q45t

[Q45tech]

Not really because the secondary winding has a diode making resistance measurements tough.

Plus positional differences vs engine plug well and operating temperature of coil.

The usual method is to do a power balance test or monitor exhaust purity to zero in on the weaker coils.

One uses BG44k and resistance measurements to absolve injectors.

It appears that more modern cost constrained coils have a finite time to failure of >70,000 miles ..........................Delphi states their some of their newer pencil coils only last 2,000 running hours....................that's only 100,000 miles.

Yet I know the 90 Q [price no object- very robust design] have lasted more than 10,000 hours on my Q.

Something to keep in mind is the coil is ~~0.5 ohms and draws ~~10 amperes for a few miiliseconds to charge. This is 10X higher current than an injector....................heat creation with no gasoline to coil it.

[maxnix]

Do a search on stumble.

Hope you used OEM NGK. But as tech says, if all else is in as new condition, usually a failed coilpack.

[ffjunior]

i used denso double platinum plugs gapped to specs is that bad or is the ngk a special plug for this car?

[maxnix]

The PFRG plug is specifically designed for the VH series. Denso are usually OEM Toyota plugs. Denso have not been shown to destroy VH engines like Autolite and Bosch. But neither have they been shown to perform as well as the OEM NGK in the VH series.

Got FSM? Read it.