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mj22 12-10-2012 09:39 PM

JRSC - hesitation/stumbling of engine at low rpm
Hi Guys,

Some of you may recall a month or so ago I had a post up about my car after having just installed the JRSC on my zetec and I wasn't able to get it to idle. It turned out this was all tune related.

The good news is the car is now driving, and has definately seen a decent improvement in how it goes.

My problem is with the JRSC and the new tune, the car has a hesitation or stumbling type problem from 1000 - 2200 rpm bit it is particularly noticeable around 1800 - 2200 rpm as this is cruising rpm in 4th and 5th gear.

Basically what happens is as I apply the throttle the car does begin to increase rpm however the rpm does not increase smoothly, as described above it has a hesitation about it. Once above 2200 rpm the problem disappears and the car revs very happily to 7k rpm without any hesitation.

Some notes about the problem:

It feels alot like an electrical/ignition problem.

I have changed through 3 sets of spark plugs:

- Motorcraft copper spark plugs (1 stage cooler)
- Denso iridiums, standard temp
- Bosch platinums, standard temp

When using the denso and bosch spark plugs the problem is reduced however the hesitation is still there.

The hesitation is much worse when the car is cold and at times it even seems like it gets worse the longer I have been driving the car in stop start traffic (this
is likely a mental thing as it all just gets more and more frustrating).

The problem is more apparent when the load on the engine is increased. ie. driving up a hill.

The coil and spark plug wires were replaced 12 months ago with an uprated MSD kit from CFM.

Finally, as far as I could tell from driving the car there were no problems prior to the JRSC install.

Can anyone advise if this appears to be an ignition related problem or tuning problem and if so could they offer some advice as to a solution?



ZXthrizzle05 12-10-2012 09:50 PM

usually hesitation is due to an ignition or fuel problem....who is your tuner? if its tom then he is going to ask for a datalog in certain things to correctly pinpoint whats going on inside your engine. my car did this a bit when I first got my turbo installed. after getting really tuned by a real official tuner such as tom and not some knock off person, it ran a lot better. and it helped to change the sparkplugs every 5k miles and with the correct gap as well

mj22 12-11-2012 01:03 AM

I am in Australia so my tuner is over here.

I had spoken with Tom about getting him to tune the car however in the first instance it didn't seem he would be able to and then once it appeared Tom could tune the car I'd already made payment to my current tuner. A little frustrating that I'd already paid my tuner as I am certain things would have been alot simpler had Tom tuned the car.

The plugs are gapped within the recommended spec. I have tried opening and closing the gap and it doesn't appear to make any difference.

I think I will try to talk to the tuner about reviewing the fueling at lower rpm.

The thing that really gets me is that the car is a blast to drive quickly, however isn't so fun as a daily drive.

ZXthrizzle05 12-11-2012 07:38 AM

Been in ur shoes before. Culd also may be ur IACV?

iceberg65 12-13-2012 01:42 PM

As unlikely as it sounds, that MSD "upgrade" could very well be your culprit.

I've read of several people that run into ignition problems that disappear when they swap their MSD coilpack/wires back to stock.

1turbofocus 12-13-2012 03:07 PM

Got a datalog you can shoot over to me ?


mj22 12-13-2012 04:06 PM

I will try swapping out the MSD coil pack to see if there is any change.

I will also send you across a datalog tonight Tom.

Thanks very much for the help.


burke_024 01-08-2013 08:56 PM

did switching your msd help i got one to ?

ZXthrizzle05 01-09-2013 09:03 AM

Please ditch the msd wires

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