AUIII XR8 massive misfire/hesitation - Page 2

madmelon · 13-09-2010, 08:42 PM

OK, as stated before, I've checked leads, coils and MAF. Leads are 2 weeks old (MSD from A1), coils are WeaponX, plugs are also WeaponX (re-branded NGK I think), I cleaned MAF twice in the last week, if anything it made things worse (rougher Idle).

Disconnected oxygen sensors, that seemed to help a little bit, as did replacing the fuel filter.

It's odd that cleaning the MAF didn't improve things, which leads me to believe it's a lack of fuel causing the problem. Fuel pump and oxygen sensors are highest priorities now...and on that note, has anyone got any pictures of a Walbro GSS341 installation? I think that's the right part number for the internal one- I figure I might as well upgrade while I'm doing it as a fuelmiser standard replacement isn't particularly cheap anyway.

madmelon · 13-09-2010, 09:34 PM

Actually, part number may also be GSS342 or 255

madmelon · 15-09-2010, 11:00 AM

So nobody has any input on the Walbro pumps?

JC · 15-09-2010, 11:50 AM

Quote:

Originally Posted by madmelon

So nobody has any input on the Walbro pumps?

Send an PM to RG - he put an after market pump in the XR8 that I now own, but i don't have any details - he may remember.

RG · 15-09-2010, 12:28 PM

Quote:

Originally Posted by JC

Send an PM to RG - he put an after market pump in the XR8 that I now own, but i don't have any details - he may remember.

Hello!

Yep I do, the original one was done by G&D and the second one (that is still in it) was a much better job done by none other than CAT600. It's basically a plug and play job but you need to use something to pack out the pump so it sits in the cradle correctly as the Walbro is much smaller than the factory one.

EDIT: I may actually have a photo of it somewhere, I'll have a look.

RG · 15-09-2010, 12:43 PM

I do have pics!

That's the one I got from CAT600.

madmelon · 15-09-2010, 05:13 PM

Awesome

Thanks muchly. Will probably take me a week to get onto that- flat out with uni and uni racing car.

Is that a 341 or 342 series pump (aligned inlet/outlet or offset inlet/outlet)? Probably doesn't matter but if something is already proven to work then might as well stick with it...

**CAT600** · 15-09-2010, 07:00 PM

Oh gawd Russ you're not showing off my dodgy swirl pot are ya?

Tell you what though, that thing might not look like much but I could launch a 420rwhp TS50 in first gear on R888 semis with under 1/4 tank fuel and no surge..... a real diamond in the rough that one.

I think it was a GSS341 from memory....

Daniel

madmelon · 15-09-2010, 07:37 PM

Quote:

Originally Posted by CAT600

Oh gawd Russ you're not showing off my dodgy swirl pot are ya?

Tell you what though, that thing might not look like much but I could launch a 420rwhp TS50 in first gear on R888 semis with under 1/4 tank fuel and no surge..... a real diamond in the rough that one.

I think it was a GSS341 from memory....

Daniel

Looks good!

How is it different to a standard car, ie your awesome launches without fuel surge?

**CAT600** · 16-09-2010, 12:07 AM

Put it this way, many of the factory AU's would get fuel surge in first gear with 220rwhp and regular road rubber once they got to 1/4 of a tank. What I did with that Walbro was mount it lower in the swirl pot cradle and then reposition the fuel bucket (part of the fuel tank) so that it stayed full under acceleration. Those couple of mods combined made the car almost surge-free.

Daniel

RG · 16-09-2010, 01:05 PM

Quote:

Originally Posted by CAT600

Put it this way, many of the factory AU's would get fuel surge in first gear with 220rwhp and regular road rubber once they got to 1/4 of a tank. What I did with that Walbro was mount it lower in the swirl pot cradle and then reposition the fuel bucket (part of the fuel tank) so that it stayed full under acceleration. Those couple of mods combined made the car almost surge-free.

Daniel

Worked on mine too, albeit with significantly less power.

madmelon · 16-09-2010, 02:56 PM

Quote:

Originally Posted by CAT600

Put it this way, many of the factory AU's would get fuel surge in first gear with 220rwhp and regular road rubber once they got to 1/4 of a tank. What I did with that Walbro was mount it lower in the swirl pot cradle and then reposition the fuel bucket (part of the fuel tank) so that it stayed full under acceleration. Those couple of mods combined made the car almost surge-free.

Daniel

Um how do you reposition part of the fuel tank?

**CAT600** · 16-09-2010, 03:55 PM

When the surge is out you reach in and swivel the bucket so that the lowest part is towards the front of the car... this keeps the fuel in there under acceleration.

I believe some cars are already like this and some arent?.... My T1 was not and had to be rotated.

Daniel

madmelon · 16-09-2010, 04:17 PM

Quote:

Originally Posted by CAT600

When the surge is out you reach in and swivel the bucket so that the lowest part is towards the front of the car... this keeps the fuel in there under acceleration.

I believe some cars are already like this and some arent?.... My T1 was not and had to be rotated.

Daniel

Ok. I haven't had any surge problems- even with the fuel light on and a hard ish start uphill.... It's probably fine how it is....

madmelon · 04-10-2010, 11:10 PM

Update: still has issues but making progress. Purchased and installed Walbro GSS342, installation took me 2 days after work- first day was removal of old pump and sender, bought required parts at work today (EFI hose, 1 big hose clamp), installed today after much fussing around. After re-reading above info and seeing pics again, I may take it back out and change how the hose goes in- currently rather kinked as the pump sits quite high. It really was a ***** of a job, thanks mostly to my lack of a 7mm spanner (took me 20 minutes to get the hose clamp around the tank lid undone, after looking for a tool for 30 minutes I used a 5c coin) then getting the pump and it's foam sock (was supplied with 400-949 install kit with perfect foam sock) into the holder was a nightmare coz it was very tight...but at least it's secure.

After what people have said about pump noise, I was pleasantly surprised to find it was only marginally louder, even without the boot cap in place. Once the engine is running, it can't be heard over the exhaust...

As for making a difference- it barely improved it, if at all. Lesser tendency to misfire and buck.

Having done all that, I did something I should have done earlier- removed (and blocked) the vacuum line to the fuel pressure regulator. After doing this, there was a noticeable decrease in performance below 1500rpm as it was no doubt rich as....BUT IT GREATLY REDUCED MISFIRING! Only time it had an issue was at low speeds (<1200 rpm) when i went from rolling at 0%TP to 100%TP and it'd miss a few times and take off instead of bucking around...

Still pretty unhappy that I spent 2 days doing fuel pump without first doing regulator but at least I've got the pump now i suppose... (excellent price too, $145 delivered...and yes, it's genuine with the metal gears and all...)

madmelon · 06-10-2010, 06:00 PM

Has anyone had experience with (a) blocked injector(s)? Dad suggested this to me the other day after telling him pressure regulator disconnect made a difference.

Also, vacuum leaks into one or more cylinders? The gasket between top and bottom halves of the manifold do have a bit of oil seepage, hasn't changed much since i bought it last year. Not sure why anything would be coming out though...

madmelon · 21-10-2010, 12:55 AM

RESOLVED:

Spark plugs. After doing a compression test (results below) I decided to put all the original spark plugs back in. Old ones didn't have any cracks that were visible and gap was actually below spec (~0.8mm) but putting in th 90k km old plugs resolved the issue.

Compression test:

1 165
2 157.5
3 158.75
4 165

5 160
6 150
7 155
8 157.5

Not too bad but they could be a bit more even- admittedly, that's with the engine cold- don't know how anyone could do that with the engine hot!

Also filled the car with fuel and discovered that i hadn't quite properly tightened that doughnut thing that holds the pump module in,... very smelly and a very painful/difficult job tightening it without a 7mm spanner and without any way of getting the fuel back out again...lesson learnt.

b2tf · 21-10-2010, 02:39 PM

So did you put TR55IX plugs back in or the Motorcraft ones? Id suggest in that case one of the new ones was cracked?

madmelon · 21-10-2010, 08:31 PM

Quote:

Originally Posted by b2tf

So did you put TR55IX plugs back in or the Motorcraft ones? Id suggest in that case one of the new ones was cracked?

The original 85k km Motorcraft platinums. Had a good look, can't see any damage of any sort anywhere on them. Also, I won't be putting the standard heat range plugs in it again- gets knock with them occasionally.