91 VN Bad Idle

[nolim8ts]

I have a VN Commodore which has been sitting in the front yard for around 2 months. When starting the car, the engine rocks from left to right and when sitting in the car, it feels like your on a roller coaster . When i put the throttle done, the rocking does away and there is only a little bit of power then on releasing the throttle the car will stall. When reeving the engine, a sort pinging or back fire sound can be heard. I have changed the leads on the car, ran diagnostics and checked all fluid levels.

Also forgot to mention that when putting it in to gear, it struggles to take off.

[88GreenVN]

Did you put the leads back in the correct order - easy as to get wrong. Or was it shaking before you changed the leads?

[nolim8ts]

I purchased a new set of leads and placed then on the vehicle and the it idled really nice (no power loss etc). A relative then replaced the new leads with the old leads thinking that the new leads were the old ones and thats when the rocking of the engine started (It sorta sounds like it is back firing when revving) I matched the leads to the engine as the cylinders are numbered back to the coil pack numbers and still have the same issue. Is the a diagram of the VN engine just to make sure the numbers on the cylinders are correct?

[Not_An_Abba_Fan]

I think the passenger side front is number 1, if you look across the engine whichever spark plug is the furthest forward that is number one. They go 1,3,5 down one side and 2,4,6 down the other, as I said I think passenger side front is number 1. Firing order is 1 6 5 4 3 2.

[nolim8ts]

I was looking at the engine and someone has labeled the cylinders as follows.

Passenger side from front(Radiator Fan)

1,3,5

Driver side from front(Radiator Fan)

4,2,6

I thought should be:

Passenger side from front(Radiator Fan)

1,3,5

Driver side from front(Radiator Fan)

2,4,6

[Not_An_Abba_Fan]

1,3,5 down passenger side, 2,4,6 down drivers.

[samuels]

I purchased a new set of leads and placed then on the vehicle and the it idled really nice (no power loss etc). A relative then replaced the new leads with the old leads thinking that the new leads were the old ones and thats when the rocking of the engine started (It sorta sounds like it is back firing when revving) I matched the leads to the engine as the cylinders are numbered back to the coil pack numbers and still have the same issue. Is the a diagram of the VN engine just to make sure the numbers on the cylinders are correct?

sounds like firing order is out...leads on wrong
1...3...5..passenger side
2...4...6 drivers side
firing order is as not_an_abba_fan said
#'s are on coil pack to assist...whether it be the series 1 or series 2 coil pack
actually sorry firing order is 1...5...3...6....2...4

[nolim8ts]

Currently have the leads connected as:

1...3...5..passenger side
2...4...6 drivers side

Could someone have mucked around with the coil pack as well?

Looking at the front of the coil pack it is labeled below (Its a Choc Block CP)

6 2 4
3 5 1 -----> Connector on this side

/ \
|
|
Front Of Car

[Not_An_Abba_Fan]

I always thought the firing order was 1 5 3 6 2 4 then I found this.

[nolim8ts]

From previous posts, It looks like I have the leads connected to the engine and coil pack correctly. I checked the connection on the side of the coil pack (EFI???) cause it looked a bit loose so I cleaned it up and reconnected it (Waiting for the battery to charge before starting again). Could the coil pack cause the rough idle at startup and under acceleration cause it to splutter then stall after releasing the accelerator.

[vt1538]

A weak coil pack can cause all sorts of issues. Most notably a miss under power. Have you checked your spark plugs? If you had the firing order wrong a plug could now be fouled & causing the problem.

[nolim8ts]

Bit of update. I changed the leads and plugs on the car but the engine still shakes but not as much as before. Some on the plugs had a whole bunch of carbon on them and 2 looked like acid had eaten away at them (Green Coating). I also unplugged the 30A engine fuse under the bonnet for 30 seconds and left the battery off for 30 minutes and when reconnected revved the engine at 2,000RPM for 30 seconds. When taking it for a drive, it will keep holding first gear and is really sluggish (Will stall if not in neutral when coming to a stop). I managed to get it into second, but there was a bit of a thump when the gear changed.

Another update. Ran the diagnostic check after driving the car by shorting the black and white wires on the ALDL and it returned error code 12 (System Pass) and kept repeating it.

[Calais3800]

The engine could be rattiling coz of worn engine mounts, give em a check. Also backfiring could mean that yours rings have gone or the 5 and 6 cylinder exsuast valves have burt out. did u remove the bellhousing for extra power? this makes the motor run a little rougher and leans out the mixture to the back 2 cylinders makeing it run hot.

[nolim8ts]

No modifications to the VN. Will have to check the engine mounts but even if the engine mounts were loose, would that cause the car to idle rough and be really sluggish?

When I running the diagnostics, I could swear that error Code 33 - Manifold Absolute Pressure Sensor (MAP) - Voltage Too High and Code 13 - Oxygen Sensor (O2) came up but after switching the ignition off then on, only error code 12 came up. How would I go about checking those codes?

[samuels]

No modifications to the VN. Will have to check the engine mounts but even if the engine mounts were loose, would that cause the car to idle rough and be really sluggish?

When I running the diagnostics, I could swear that error Code 33 - Manifold Absolute Pressure Sensor (MAP) - Voltage Too High and Code 13 - Oxygen Sensor (O2) came up but after switching the ignition off then on, only error code 12 came up. How would I go about checking those codes?

you said a couple of plugs had a green tinge? were the plugs you pulled out in the same bank,and next to each other?
greenish tinge is a sign of blown head gasket,or crack in head or block....is coolant level stable?

[nolim8ts]

Greenish tinged spark plugs were on opposite sides of then engine. There's no radiator cap on the VN from what I can see, but the water tank is full to the marking on the outside. The greenish tinge has now turned to a a light Grey tinge on the 2 spark plugs. The rest have a black tinge which is mostly carbon build up.

Just found this on the forums and dont know if it could be of relevance.

VN Commodore Rough Idle

Faulty wiring connection. Black wire with Yellow trace - inside the engine bay coming from EFI control unit. Single wire splits off to two wires. Hold wire, squeeze or move wire at join and the engine should increase in idle then settle. In some cases, the engine may stall. Repair connection.

The above wires run to the Coolant Temperature Sensor and the Throttle Position Sensor.

Does someone have a diagram on where I can find the EFI control unit?

[nolim8ts]

From my previous posts, I followed a recommendation about checking a black wire with a yellow trace for rough idling. I was able to follow it back to the Coil Pack connector and everything looked okay but I could not access the rest as that would require me to take off the alternator and belt. What I found though is that when I turn the car off, I can here what sounds like a large sucking sound near the throttle body for 2 seconds (Dose not occur when idling unless my hearing is out). I also noticed that where the 3800 in red is painted on the top of the engine, there is a black tube on the drivers side running to a round small black cylinder. On the opposite side of the cylinder, is looks to be sorta dripping (The tubing below looks damp). Any suggestions??

[Not_An_Abba_Fan]

Ahhhh, fuel pressure regulator. The diaphram is split and it is leaking fuel into the intake through the hose. Does the dampness smell like petrol?

[nolim8ts]

I ran the engine in again, and then looked for any drips but could not find any. I then ran my finger over the both tubing clips and there was dampness coming into the fuel pressure regulator (Piping coming up into the Engine Bay) (It left a film on my finger but it did not smell like petrol). How much would I be looking at for a fuel pressure regulator?

[Not_An_Abba_Fan]

They are pretty cheap, around $20-$30. You won't find anything dripping, what it does when split is suck the fuel into the intake manifold. To check it, take the hose off and suck it a little bit, you shouldn't get a continuous flow, you should feel vacuum build up. If you can put your tongue over the end of the hose and it stays there by suction, then the regulator is fine, but it doesn't sound like it. It's a bit of a crude way to check but its the easiest.

[nolim8ts]

I removed the fuel pressure regulator and tried to do the suction test. I could sorta feel a vacuum trying to build up but i could not get the tip of tongue to stay on. Is the tubing that runs from the 3800 on the top of the engine to the fuel regulator meant to be damp inside or have any fuel in it???

[Not_An_Abba_Fan]

No, it's supposed to be dry. Can you smell fuel in it?

[nolim8ts]

I get a very strong smell of fuel from that piece of tubing..So the pressure regulator is mostly likely rooted causing the bad idle and for it to stall or have no power when in gear???

Also, if I reconnected the fuel pressure regulator and left the vacum tube off, would that cause any problems. I imagine that if it was disconnected and the regulator was rooted, fuel would end up leaking out...

[nolim8ts]

Thanks to everyone for the help. Finally found out what was causing the rough idle and stalling...

...(Drum Roll)....DFI module attached to the coil pack. Replaced the whole unit and now it is purring like a kitten...