1990 VN running rough & uning heaps of fuel

[rickl]

Hi all

Last week I purchased my first VN Commodore, after years of driving EA Fords (although I did have a VH years ago). The car is a 1990 VN Executive Automatic. I am having a number of problems with the car that I would like to sort out. The car seems to have been fitted with quite a few new parts very recently. These include the following

New Radiator
New Coil Pack (seems to be the VP style with the round coils rather than the VN square coils)
New Exhaust system

The car has the usual fuel guage not working until I thump the dash problem. I plan to look at the cluster today looking for bad solder joints.

When I first picked the car up it was very cold and while driving it home I found that if I accelerated hard and caused the transmission to kick down the car started to buck and miss. I had to accelerate slowly, without kicking down, or I had problems. Is there anything specific I should be looking for that might cause this behaviour?

I find the car idles very rough, worse when cold.

I find the car uses a lot of fuel,about 350Km to a tank. Most of this is highway driving so I would have expected much better than that.

I noticed yesterday that the temperature guage never gets above the fist mark. It seems to only get just above the cold mark most of the time. When it gets up to the first mark the car just cuts out. The engine seems to be quite hot when it cuts out so it appears I might have a false reading on the temperature guage and the car may actually be over heating.

The previous owner told me that the car might have a bad O2 sensor. Would this cause this much trouble? I would have thought it might cause bad fuel economy.

I would appreciate some general guidance in what I should be looking for to get my car sorted out.

Regards

Richard

[88GreenVN]

Welcome to the VN Dash Bashers LOL.

The fuel gauge thing is the voltage regulator - easy fix with the how to section on this forum.

Yes the O2 can give bad idle and make the car use too much fuel good place to start. Also run some injector cleaner though it - wont hurt it.

But also can be the TPS, bad leads or plugs, vacume leak, Many things realy.

And the temp sensor can tell the ECU that the engine is stone cold all the time and that pumps in the fuel. But the temp gauge on VN's will always sit at around the first mark.

I had a VN for 20 years and thats where it has sat all day every day, except when the welsh plug went and drained the car of coolant - then we had alarms and flashing lights from the L3 cluster going off

[The Darkness]

for the fuel, do the o2 sensor and try the fuel pressure reglator. almost double my economy lol. try another cluster for the temp thing could work

[samuels]

Hi all

Last week I purchased my first VN Commodore, after years of driving EA Fords (although I did have a VH years ago). The car is a 1990 VN Executive Automatic. I am having a number of problems with the car that I would like to sort out. The car seems to have been fitted with quite a few new parts very recently. These include the following

New Radiator
New Coil Pack (seems to be the VP style with the round coils rather than the VN square coils)
New Exhaust system

The car has the usual fuel guage not working until I thump the dash problem. I plan to look at the cluster today looking for bad solder joints.

When I first picked the car up it was very cold and while driving it home I found that if I accelerated hard and caused the transmission to kick down the car started to buck and miss. I had to accelerate slowly, without kicking down, or I had problems. Is there anything specific I should be looking for that might cause this behaviour?

I find the car idles very rough, worse when cold.

I find the car uses a lot of fuel,about 350Km to a tank. Most of this is highway driving so I would have expected much better than that.

I noticed yesterday that the temperature guage never gets above the fist mark. It seems to only get just above the cold mark most of the time. When it gets up to the first mark the car just cuts out. The engine seems to be quite hot when it cuts out so it appears I might have a false reading on the temperature guage and the car may actually be over heating.

The previous owner told me that the car might have a bad O2 sensor. Would this cause this much trouble? I would have thought it might cause bad fuel economy.

I would appreciate some general guidance in what I should be looking for to get my car sorted out.

Regards

Richard

does the cooling system have coolant in it ? this can also contribute to excessive fuel consumption if it hasn't,believe it or not,also as answered by others your O2 sensor and also a crank angle sensor that is about to give up the ghost will give you that cutting out.

[Ozzie]

im curious as to how it passed a roady with that faulty guage:S
or didnt it come with one?

[rickl]

Hi All

The car has plenty of coolant in it and the water pump appears to be circulating it fine.

What I did notice while testing yesterday is that the cooling fan never comes on. I checked the wiring and I can make the fan come on by grounding pin 85 on the fan relay. As I read the wiring diagram the ecu should ground this terminal when it wants to turn the fan on. If the fan is never being switched on of course the engine will over heat. I plan to try another coolant sensor and see what happens as it is looking like the ecu is not seeing the engine warm up.

Regards

Richard

[centy]

mate bleed the cooling system to. there is a how to.
have you gotten the error codes out of the computer yet?
the codes are a good place to start to.
Also general service, oil filter air filter plugs and leads.
The later vn's had round coil pack like the vp's and alloy covetrs over the injector.
Also later ones had the top rad hose running from just up near the powersteer pump an not WAYYYY outthe back like the earlier ones.

[rickl]

Hi All

I finally managed to get this sorted out. It turned out that once I replaced the O2 sensor and the coolant temperature sensore the car ran fine. With the coolant temperature sensore replaced the car warmed up much better and the engine cooling fan came on just as it should when the engine is hot.

While I was at it I gave the car a good service and changed all the filters, oil and coolant and now I have a nice running VN

Regards to all who offered suggestions.

Richard

[88GreenVN]

Hi All

I finally managed to get this sorted out. It turned out that once I replaced the O2 sensor and the coolant temperature sensore the car ran fine. With the coolant temperature sensore replaced the car warmed up much better and the engine cooling fan came on just as it should when the engine is hot.

While I was at it I gave the car a good service and changed all the filters, oil and coolant and now I have a nice running VN

Regards to all who offered suggestions.

Richard

That may be good news for all the VN's with the same simptoms