Series 1 AU XR6 still running rough

[XRG6SM]

I'll make the intro to this brief, I picked up a (no rego) series 1 factory manual XR6 with the VCT engine as a project. It has pacemaker 4499's, the cat has been bashed out of it and it was running a real dodgy duel gas system.

When first driving it home from the bloke's house that I got it, it was running ROUGH. Misfiring, engine cutting out (going 60kmh down a hill), low oil pressure warning beeping at me. There was a clicking coming from inside the dash that would cause all the electronics to work only as it clicks. (for example the windows would only go up or down in bursts as it would click)

In the last few months I have done a lot to the car. I found out the clicking was a short with the bem - seemed to have fixed itself after I pulled the dash out and readjusting the wires. (The previous owner had done a heater core on it) I found out the heater switches at the back of the dash that are vacuum controlled weren't plugged in so I fixed that big vacuum leak.

I also did new brakes and rotors all around, new brake fluid, new tickford rims with new tyres, flushed the cooling system multiple times to remove rust deposits, new petrol only intake piping with no cut outs. Plumbed up gas convertor cooling lines, and cleaned up old gas wiring. Removed the gas tank, and all the old wiring that was spliced in to the factory wiring. New boot lid as the old one was rusted out completely, all for road worthy.

And I have fitted numerous brand new items to make the engine run better such as

-New fuel pump (walbro 255)
-fuel pressure regulator
-fuel filter
-coil pack
-ignition leads
-spark plugs
-Serviced injectors with $20 ebay kit with filters and o-rings
-run a few bottles of injector cleaner
-New 98 in the fuel tank

After each new item I fit, the car would run better and better. And I thought the most recent item (coil pack and leads) had finally fixed it. This thing was purrrring! Honestly for a 6, this thing goes HARD when it wants to run properly. It has so much low end torque and I cant wait for it to be registered and my new daily.

But still, there's an intermittent misfire that will come and go. When it is in neutral and I rev it it will bog down for a split second and the car will shake and the exhaust will pop and almost sound like a back fire. And when I give it a boot while going up hill it shudders and pops and feels down on power for a few seconds.

I'm completely out of ideas at this point. The only thing that I can think of that might be the culprit is the extractors and the bashed out cat, and it is causing too much free flow for the exhaust gasses, and the ecu isn't tuned for it?? Or maybe I killed the injectors when I did the service on them? Or perhaps the engine is just toast and I bought a complete lemon that should have gone to the tip

I'm all out of ideas at this point and I don't want to keep throwing money at this car on items that might or might not fix the problems I am having. It feels so so so close to running right, and I don't want to give up on what seems like the final stretch

Does anyone have any idea where I should look or what else I should do??

Cam sensor? 02 Sensor? Maybe some crusty old wire that I overlooked from the gas delete? Can the low oil pressure warning have anything to do with this?

This is the link to the YouTube video I made showcasing the problem:

https://youtu.be/1JvHJ2svFs8

[XRG6SM]

I will also add that, being a series 1, the scan tool port does not work. I have tried 2 different elm327 scanners plugged in and neither have worked. So that isnt an option

[PG2]

Inlet manifold gasket.

Don't muck around trying to diagnose if it's the problem - it's probably the most common problem of these cars. For $20....

[XRG6SM]

Okay thanks! I will try that one asap. It's cheap enough to just do it as you said.

I will post update

[XRG6SM]

Originally Posted by PG2

Inlet manifold gasket.

Don't muck around trying to diagnose if it's the problem - it's probably the most common problem of these cars. For $20....

Hello again! I had replaced the gasket and it all seemed to be running right. I even drove it to my new house without any problems.

BUT now its doing it again!

Any ideas?

[XRG6SM]

Originally Posted by PG2

Inlet manifold gasket.

Don't muck around trying to diagnose if it's the problem - it's probably the most common problem of these cars. For $20....

Hello! Very late response. I just want to say thank you! After changing both intake gaskets the car ran beautifully.

With that being said the car ran perfectly for a few weeks, and then the issue came back. Mainly when going low speeds in 1st or 2nd gear, the car would pop and carry on and backfire through the intake. :( I assumed that since I had recently replaced them then it couldn't be the issue causing the car to run like ****.

Well as it turns out that some of the bolts going into the engine block on the manifold had come loose. I tightened up the ones that I could get to easily (particularly the ones closest to the front of the engine I was able to get a good 2 and a half turns on the ratchet!) Doing this has improved the problem by I would say about 80%.

I will be going over ALL the bolts on the weekend to ensure the problem is fixed.

Also, I found out that there was 1 fuse blown in the kick panel, after changing that I was able to get my scan port working properly again through Forscan. Neat little piece of kit I might add.

Thank you all for the suggestions!

[falconhell74]

Clean or replace your ISC (idle speed control) sits on top of the throttle body 2 x 10mm bolts, they gum up with carbon and can stick intermittently remove clean with carbie cleaner, you can see the shuttle valve inside once off, they can also ware causing these same issues

[XRG6SM]

Originally Posted by falconhell74

Clean or replace your ISC (idle speed control) sits on top of the throttle body 2 x 10mm bolts, they gum up with carbon and can stick intermittently remove clean with carbie cleaner, you can see the shuttle valve inside once off, they can also ware causing these same issues

Okay thank you! Will try that again on my days off. I do remember cleaning it when I first got the car but I will do it again just to make sure. Do you have any other idea what it could be? I was thinking maybe bad O2 sensor or crank angle sensor