Car is missing when accelerating.

[Hayden]

Hey,

Car is a 1993 Holden VP Commodore 3.8 V6 Engine. (australian)
Dual Fuel (Gas and petrol)

The car I have is missing when accelerating. It bogs down for a bit then starts running normal when you accelerate hard. It used to crank for a while before it would start. I replaced the coil pack and it starts heaps better. It runs on fuel and lpg gas. It does it on both gas and fuel.

Any ideas what is causing this?

Thanks in advance, Hayden.

Topic

[Cameron]

If the engine is missing under load I would strongly suspect a failing spark plug lead.

First make sure the leads are all properly pushed home and re-check for the miss. If the miss remains I would replace the ignition leads alone initially and re-check.

[dan]

i would check the spark plugs pull them out and have a look at them, see what they look like that is a good place too start, i would ALSO check fuel pressure as well if you can, i would also check the procedure for checking codes and extract some codes and see if you can get any.

a maltitude of things can cause a missfire, its best to do some diagnosis and narrow things down.

[Ingvar]

You have plug wires, right?
Put car somewhere into a dark place, as in – dark. Prep a spray can of soapy water. Start the engine and liberally spray wires with soapy water.
Should you see any arcing from wires onto the engine block….
Also, I’d have located, removed, and cleaned EGR and any EGR tubes.

[Glenn]

I know you’re getting some good advice from people on the forum. It sounds like possibly an unmetered air issue. Check out the video in this link and parts 2 and 3 that follow. I thought this was interesting. Definitely something to look into..https://www.youtube.com/watch?v=fRwFYCSaTe4&list=UUBFI1mrpMg8EETeRZv0YTNA
Sometimes an unmetered air problem will disappear with higher rpms. Best of luck with this. Let us know what you find.

[Hayden]

Thanks guys. I have fixed some vacuum leaks and replaced spark plugs. Runs heaps better only on LPG gas tho. Still runs shit on fuel. I have new injectors to put in so we will see how we go. Any other ideas?

[dan]

it running bad on gasoline does tell me that it may be a fuel injector issue, however i would still check fuel pressure before you go and replace the fuel injectors!

[Bill]

Normally a misfire will show up on LPG (Propane) before it will on Gasoline as propane is a vapour and is harder to ignite. Depending on how much gasoline you run on I think you’re on the right track with partially plugged injectors. I would try flushing them with a strong injector cleaner and the correct equipment before replacing them. Make sure the gasoline in the tank is reasonably fresh also.

[Hayden]

Thanks guys it fixed now. just replaced everything as the car looks like it hasn’t been touched in years. Didn’t cost me much because i already had most the parts. New injectors, Spark plugs, spark plug leads, coil pack, interior light bulb and fixed vacuum leaks fixed it. Runs really good now 😉

[dan]

glad you fixed it 🙂

[Author]

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