BlackThunder

Just put a new exhaust system (pacemaker headers, high flow cats and a twin 2.5" system) on my XR8 and it ran sweet for about a month, but now its running like a hairy goat. It shudders at low rpm and surges when held at constant revs. I've checked all the usual things, plugs, leads, filters, etc and all looks OK. I checked the exhaust output with an AFR and it confirmed that the mixture was cycling from lean to rich. I am unsure as to whether there is something I have missed when upgrading the exhaust, or as to whether the problem actually relates to the exhaust.

Any assistance would be greatly appreciated.

slipper

Maybe there is a problem with your oxygen sensors?

galaxy xr8

Does it do it all the time or just come's and goes?.

__________________
AU II XR8
Herrod mod's,mmmn.
XW Wagon 221-2V,
Laser a maser.

dodgie

I second new oxygen sensors.
Or at least give cleaning them a go.

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ED Fairmont Ghia 5.0L

blue66coupe

If it didn't do it for a month then forget the mods as they didn't cause it directly, didn't damage the HEGO wires/loom from more heat?

AUGhiaV8

Did the same mods, had the same problem, fitted new O2 sensors... problem fixed.

EB 5.6

Are these the large primary pacemakers using the header plate?

If so, the problem is simply plug tracking. You need to unpick the aluminium tubes that cover the rubber plug boot, use needle nose pliers. Then, when you have them bare, buy some thermal plug lead insulation, availible from rocket industries. Then cut approx 8 x 6 inch lengths, and slide them over the plug boot. That will fix the problem.

The pipes are a great header, but the header plate and header needs about 15mins work with a die grinder and a stone BEFORE fitment. Ive been through all this before.

Are you checking the AFR at idle? you wont get an accurate reading in either loop at idle. Check it under load, on the road or on a dyno.

It is unlikely that the oxy sensors will have logged a "hego not switching" code, but check the voltages to rule it out if necessary. Check it - dont rule it out. The above posts are great advice also.

If the headers are the 4099's with header plates - do this mod with the plug boots. if its not causing a problem now, it will save u a headache in the future.

redhot

did u use the 4 into 1 or the tri y headers?
The 4 into 1 headers are big for the 302 windsor that might be your problem. The tri y are the right size. Check to make sure that u have the tri y headers fitted.

galaxy xr8

I have the 4-1 header's and no such problem's for me,they are not to big for the 302, the difference between the tri y's and 4-1 is only torque.

__________________
AU II XR8
Herrod mod's,mmmn.
XW Wagon 221-2V,
Laser a maser.

012

I think what redhot was trying to say is that Pacemaker recommend fitting the 4-1 (part no PH 4006) to the stroked 5.6 or a supercharged 5.0 Windsor.

I'm also having the same issues as Black Thunder. Idle rough, surging, running rich (yes I know it's a V8, but 360-380 of mostly highway km's per tank is a bit much), etc.. I've changed spark plugs (Iridium and gapped to 1.0mm), and the oxy sensors, little better now but still not 100%. Next on the list is leads which I'll be doing in the next week or so. Getting MSD or Magnecor 8.0mm. Don't know what else to do if the leads don't fix this.

Hey EB 5.6, do you work through a shop? If so, can you PM me with your contact details please? You sound like a cluey bloke, and if this doesn't work, I might have to pay a visit. Went to Ford and asked them to have a look as they have all the diagnostic equipment etc, and all they did was increase the idle in drive!