VT 98 Missing on idle and acceleration after service

[azmodii]

Hi all,

A bit of background - Was not missing before the service, occasionally had a fuel smell in the front of the engine bay. Ran a little rich, but overall got about 600-700KM's to the tank. Had it stall once when coming off a highway, hard to start but eventually did (CAS?).

Its a VT Series 1 98 Model 3.8L V6.

Just did a few minor things to it.

• Replaced Power Steering Pump
• Replaced Idler Pulley (Above Compressor)
• Changed Spark & Leads
• Changed oil filter & oil
• Changed air filter
• Changed fuel filter

We overfilled the oil a little (Mate didn't know you couldn't just dump 5L in one go), but we drained the sump and re did the oil.

After doing the service it is now missing, in one or two cylinders. On idle and on load. Have checked purge hose, and checked codes. Was showing a 47, but after removing the battery terminals and running it for a while the code did not return (Guessing the 47 was when the car stalled, going to get CAS replaced soon). I've removed the Mass metre and cleaned, checked the air intake manifold (The thing thats a screw that opens the flange, I cleaned that, also tried with another, no love). I've tried to make sure that all the leads are contacting and the plugs are ok. Spaced the plugs with a 5c coin. I managed to bridge the wrong jumpers on the diag plug (After this issue started) & I blew the ENG Main CONT Fuse (10A). Replaced that and all seems to work thank god!

Where do I start?

Im guessing the general order of diagnosis goes a little like this.

• Leads
• Plugs
• Coil Packs
• DFI
• Injectors
• Fuel Pump

Is there a way to test any of this stuff?

I know the leads are working, got a mighty zap off each of them. But I can't tell if its firing in the correct order or at the correct time. Is there any way to check that it is firing at the correct time?

Is the only way to test the plugs by taking them out, plugging into a lead, holding with a glove and putting near a clean metal surface to see spark?

I know that I can test the coil packs with a multi metre, but where do I test, put neg on one side and positive on other? Im guessing that would #### the coil pack! I just need to know what part of the multi metre goes where on the coil pack. I think the OHM resistance is 5.5, can anyone confirm this?

Is there a way to test the DFI Module under the coils?

Is swapping injectors easy? And if so, how can I tell which injector is ok, and which is not.

What pressure should the fuel line be running at, and where do I test this?

I guess the other thing to note is that my mates can be heavy handed at the best of times, and one of the plugs was dropped after we took it out to check (But this problem was there before we did that). Should I just get a whole new set of plugs and leads, and try again, or start with a diagnosis and work my way from there?

[azmodii]

Another thing to note is that after screwing around with the leads, i took it for a run and it ran ok, after stopping engine and starting again, same issue?

[Mick1988]

Put your old leads back on and see if the problem goes away. If not, do the same for the plugs. I reckon you may have some leads mixed up somewhere.

[azmodii]

The old leads unfortunately broke when I was taking them out, so I can't try them. I'll get a new set of leads and plugs and try that.

[Brett_jjj]

Its heaps easy to crack the porcelain insulator on a new plug when installing them, especially if the plug socket you use to tighten them doesnt have the rubber "plug protector" thingy inside it. Its the same with silicon type plug leads, its so easy to stuff them too. If they get crimped/kinked a bit, or pulled a bit hard whilst they are being fitted,the carbon core inside the lead can break,which renders the lead useless.

[azmodii]

Thanks for the help guys, turns out the 3 plugs I didn't tighten (A job that I gave to my mate) were all cracked. He used a proper plug socket with the rubber boot, but overtightened them.

Thanks all Runs like a dream now!

[accentstencil]

Thanks for the help guys, turns out the 3 plugs I didn't tighten (A job that I gave to my mate) were all cracked. He used a proper plug socket with the rubber boot, but overtightened them.

Thanks all Runs like a dream now!

Ban him from working on your car. Some people think everything needs to be tightened is hard as it will go.