Help Please ... Intermittent Serious Problem With Corolla G6

[White.Lightning]

Hi Guys,

I am hoping for some help and advice here. My wife's car is a 1998 Corolla G6 with the 1.3i 4E-FE engine. It has 111,000 miles on the clock. We have owned the car for 8 months. The car has been running absolutely fine for the last few months until a few weeks ago when on on few occasions my wife reported an intermittent splutter usually when she accelerated say on to a roundabout. At the time, I drove the car a few times and could not reproduce the problem. Yesterday things became more serious. She left for work. The car was driving fine for the first 5 miles or so of the journey until she got the motorway. She joined the motorway in 5th gear and accelerated. The car would not accelerate above 40mph and started shaking badly. This continued for about 5 minutes. During this time she had to stay in the inside lane of the motorway and could not get above 40mph. She resorted to using 4th gear during this time. The shaking then suddenly stopped. She then left the motorway and joined a dual carriageway. This time she accelerated to 50mph OK but as soon as the speed increased to 60-70mph the shaking happened again. Eventually, the shaking stopped and normal service was resumed. Since this the car has been absolutely fine again but I am now having to use it as my wife is frightened after what happened on the motorway and again I cannot reproduce the problem.

We have owned the car for 8 months now. Before that, it had the same owner for 13 years (one of my colleagues at work).

What I have checked so far today:

- resistance of both coil packs, I did this with the engine cold this morning and both were within spec (~12Kohm)

- checked for fault codes on the ECU, no fault codes reported (but CEL was flashing to confirm it was working)

In the 8 months we have had it, I have done the following service items:

- changed engine oil and oil filter

- changed gearbox oil

- replaced the air filter

- replaced the fuel filter

- replaced the spark plugs

- replaced the cambelt

This is all within the last 5,000 miles. I have also replaced the plug leads with a new set of genuine leads as one nearly fell apart when I changed the plugs.

At the moment, my best guess is a coil pack problem. This is mainly because a) the spark plugs are nearly new, b ) the ignition leads are nearly new and c) one of the two coil packs have been replaced already. Interestingly, one coil pack looks original (as it has 4 and 1 numbered on it for the ignition lead numbers) and the other has been replaced with what looks like an aftermarket part as it is black in colour rather than grey, does not have the ignition leads numbered on it, and is not a tight fit on the bracket like the original part.

So, advice please folks, is this most likely a coil pack problem or something else?

Thanks in advance for reading