Stumble when engine warm

Patty · Postby **Patty** » Thu May 26, 2011 8:32 pm

Hi Community,

My NB8A recently developed a quirk where ~15-20mins into my trip the power would disappear, almost like I took my foot off the accelerator, and then come on and off and so on. I pull over and turn on my heater (thinking it might be coil pack related) and after less than a couple of seconds it's gone and I drive the rest of the way home/work (with the heater on just in case).

This morning I changed the coil pack, ignition leads, and spark plugs (all new replacements), drive to work and the car is exactly the same. There's no CEL and when the power goes off the engine does NOT feel like it wants to stall so it's got me a bit baffled.

Just wondering if anyone has had something similar happen and if they can suggest anything to help diagnose? I've already been suggested fuel filter and o2 sensor by well meaning friends which I'll have a look at hopefully soon.

Thanks in advance,
Pat

Dweezle · Postby **Dweezle** » Thu May 26, 2011 8:59 pm

My NA6 suffered what sounds like a very similar problem.
A new single wire O2 sensor seemed to fix that.
Ohh also worth checking the water temp sensor, NA6 its behind the head.
Needed to remove the coilpack, that fixed a similar problem on my old NA.

Patty · Postby **Patty** » Fri May 27, 2011 12:41 am

Thanks Dweezle, I was hoping I didn't need to take off the coil pack again.

I have my parents Jazz until the weekend so will have to jump back on the mexy on the w/e.

jerrah · Postby **jerrah** » Fri May 27, 2011 8:48 am

Does sound like it could be spark related but I'm confused how turning on the heater would have any effect on the coil packs?

93_Clubman · Postby **93_Clubman** » Fri May 27, 2011 2:03 pm

May be fuel injection/ EGI relay (in the engine bay fuse box), or CAS (less of a problem on NB8A than NB8B) - see irwin83's 2nd last post on page 3, & last post on page 4 of following:

viewtopic.php?f=29&t=21462&start=30

viewtopic.php?f=29&t=21462&start=45

jerrah wrote:I'm confused how turning on the heater would have any effect on the coil packs?

Coilpacks on the way out are affected by heat, so perhaps turning on the heater disipates enough heat to assist.

Patty · Postby **Patty** » Fri May 27, 2011 5:02 pm

Thanks 93_Clubman I'll have a closer look when I'm not at work

93_Clubman wrote:Coilpacks on the way out are affected by heat, so perhaps turning on the heater disipates enough heat to assist.

Yeah I'm not really on the brains trust when it comes to coil packs but I have read they react unfavourably to heat and given my frustration I would have poured icy cold coke on it while hopping on one leg if I thought it would get me home in peak hour traffic.

Postby **NitroDann** » Fri May 27, 2011 5:20 pm

Protip: dont install the bottom bolt when reinstalling coilpacks. The top 2 hold it fine.

Dann

Patty · Postby **Patty** » Fri May 27, 2011 9:40 pm

jerrah wrote:Does sound like it could be spark related but I'm confused how turning on the heater would have any effect on the coil packs?

Oh I just realised where you were coming from with this. No I wasn't trying to say turning the heater on fixed it. Pulling over for 30s allowed me to continue driving. I just also turned the heater as a hail Mary attempt to help me get out of jail.

Patty · Postby **Patty** » Fri May 27, 2011 10:06 pm

93_Clubman wrote:May be fuel injection/ EGI relay (in the engine bay fuse box), or CAS (less of a problem on NB8A than NB8B) - see irwin83's 2nd last post on page 3, & last post on page 4 of following:

viewtopic.php?f=29&t=21462&start=30

viewtopic.php?f=29&t=21462&start=45

jerrah wrote:I'm confused how turning on the heater would have any effect on the coil packs?

Coilpacks on the way out are affected by heat, so perhaps turning on the heater disipates enough heat to assist.

Very interesting thread. Aside from the spastic tacho it sounds like what I've caught. And extra kudos to you for remembering a thread from 2006 :lol:

93_Clubman · Postby **93_Clubman** » Sat May 28, 2011 1:08 pm

Just having a look back at fuel inj/ EGI relay issues & if it's this it tends to kill power completely &/ or prevent restarting, so perhaps less chance it's this. Slight chance it's even the beginning of an intermittent fuel pump (caused by pump itself or in-tank wiring connections), but either or both of irwin83's issues seem more likely at this stage.

As you already know, new coil packs & ignition leads on an NB8A will cure most problems of this kind. Hopefully you identify the problem over the weekend.

Patty · Postby **Patty** » Sat May 28, 2011 2:46 pm

Dumb post alert...

Where is the CAS on the BP-4W? Because I'm reading up on a guide to change a 1.8L CAS (http://www.flickr.com/photos/pethier/227840486/in/set-72157594256422537/and mine's not there??! I can see the heater hose through the firewall on that photo so I'm pretty sure i can see the connector for the coil pack in the background so it's the exhuast cam side right? ... nothing but air on mine.

The back of mine looks like it just finishes, there's a cap and bracket there where the CAS is shown in the flickr photo. I can see straight through to the rear thermostat housing. There's another post from Gilly71 on page 2 of the thread you linked above which says it's under the EGR line but there's nothing but bellhousing under it and my EGR is also capped off with a large socket head bolt.... I think thats the EGR line...? My exhaust manifold is an aftermarket one which was there when I bought her so maybe the PO has done this. (Doesn't stop my idle dip either i might add).

I'm going to pore through the workshop manual now but if anyone could help me with this it could save me some grief.

93_Clubman · Postby **93_Clubman** » Sat May 28, 2011 3:37 pm

From memory on the NB8A it's inside front of camshaft cover. No EGR on NB8A either I think, started on NB8B.

Patty · Postby **Patty** » Mon Jul 04, 2011 2:11 pm

So the Cam angle sensor is on the front driver side of the cam cover. Changed that out as well as the Crank angle sensor (because I damaged it with too small a gap :oops:

) and no problems to report so far. Don't know which sensor it was but my bet was the cam sensor based on what I've read.

Thanks all for the help.

93_Clubman · Postby **93_Clubman** » Tue Jul 05, 2011 1:23 pm

Good to hear you found a fix so far, hope it stays that way.

Patty · Postby **Patty** » Thu Jul 07, 2011 11:35 am

Aah you just had to say it didn't you?

The problem reared its ugly head again last night... Running out of things to replace and I've had to explain to my wife that I didn't buy car parts in vain, they were preventative maintenance lol...

It seems not as frequent as before though. I might check the cas wiring and grounding points over the weekend. It's just so damn intermittent I can't poke stuff and see how she reacts. :evil:

Anybody have anymore ideas?