Engine Overheated / Very rough Idle / no power

[Louieg]

I hope someone can help me. Yesterday in the 40degree heat my VT commodore suddenly stopped. It seemed to have overheated (Hot indicator on trip computer) although only 5 minutes before the temp gauge was sitting on 1/2 way so it seems to have just shot straight up. Anyway I only drove probably 150m up the road and pulled over. The engine then ran very rough and then it stalled. I tried starting again but it wouldn't go. After it cooled, I checked the radiator and it was full. The coolant level appeared to be ok as well. I was able to start the engine, however it was running very very rough, and if I put my foot on the accelerator the engine would just stall and I could hear what I thought was a back fire of some sort. I started the engine again but this time I manually pulled the accelerator cable a little to give it a few revs...suddenly the engine ran smoothly again. However when I put the car in drive and tried to drive off there was NO power whatsoever (didn't move an inch) and once again it seemed to backfire . So it seems the engine runs ok if I carefully give it some revs, however under normal driving, the engine has no power and stalls

Does anybody have any Ideas ? Your help is much appreciated.

[MR_VX]

i would be replacing the thermostat from the factory 95 degrees to a 81 or lower. some people pull them out altogether, and then flush your radiator a few time and change the coolant, to help with the over heating not sure about the ni power tho!

[Louieg]

thanks MR VX I will give it a go. I just hope someone knows about the other problem cause that is another major concern. cheers

[Louieg]

I started the car again this morning and once again it ran very rough. Gave it a few manual revs and it starting idling ok. I found that if I slowly press in the accelerator the engine runs fine however if I put the pedal to the metal it basically craps it self

[Rossbx]

No power? possibly coil packs or DFI module (or both) have spat the dummy. Could also be plug leads. Check for codes to see if there are any clues to the problem.
If the radiator coolant level is good then I wouldn't worry too much. Have the cooling system pressure tested to make sure there are no leaks. Do a compression test on the engine to determine weather your head gaskets are ok. If you can't do any of these things then I strongly suggest that you take it to a reputible mechanic and have him look at it for you

[Louieg]

Thanks Rossbx....The unfortunate thing is that I can't drive it in the state it is in....I am not a mechanic's a**hole so I guess I can get a mobile mechanic to come out in the first instant to run the diagnostic on the motor and see from there what the next step should be. thanks again for your help. cheers

[VT Owner]

I had pretty much the same problem. I found it was my water pump - was only 1/2 working. Replaced the pump and all is well now (fingers crossed).

[Louieg]

Thanks VT Owner, is there any real way to check the water pump yourself? The reason being is that the water pump was replaced only a couple of weeks ago before I purchased the car. So were you having the Idle problems as well? Cheers & thanks

[Louieg]

Mechanic reckons I need to change the coil packs / plugs / radiator cap & thermostat....Thanks for all of your help

[MR_VX]

i would change the coil packs last, abit pricely lad

[VT Owner]

Thanks VT Owner, is there any real way to check the water pump yourself? The reason being is that the water pump was replaced only a couple of weeks ago before I purchased the car. So were you having the Idle problems as well? Cheers & thanks

Not really other than taking it off and looking. If it was replaced a few weeks ago, then I'd be looking elsewhere for the problem (thermostat, trapped air in cooling system etc).

This was mine. As you can see there is no backing to the rotor fins (it had worn away) which explained why it wasn't working efficiently:

http://img.photobucket.com/albums/v2.../WaterPump.jpg

[Louieg]

G'day VT ownder, yeah not it the best nick I see. Thanks for you help. I was going to get the new sparks & Leads & thermostat etc, before I even contemplated getting the coil packs as I found out how much the coil packs were. Basically the cost of the 3 coil packs are about half the price of a second hand engine replacement!!!! thanks again

[Louieg]

I changed the leads/sparks and the coil packs (managed to get some reasonably priced ones) but the problem remains. I cannot press in the accelerator quickly without the engine shutting off/back firing. If I press it in slowly no worries at all. HELP

[Louieg]

If anyone is interested the problem was the fuel pump.....got it fixed and no problems. I also found out why my car was overheating....I had a dodgy fuse in the airconditioning fan so the fan was only working intermittently....which caused the overheating....car running at a cool 85-91c now where as before I saw it get above 110c!!!!!!!!! thanks for all of your help. cheers

[VT Owner]

If anyone is interested the problem was the fuel pump.....got it fixed and no problems. I also found out why my car was overheating....I had a dodgy fuse in the airconditioning fan so the fan was only working intermittently....which caused the overheating....car running at a cool 85-91c now where as before I saw it get above 110c!!!!!!!!! thanks for all of your help. cheers

Glad you got it sorted.

Not sure what you mean by a dodgy fuse in the aircon fan however (was it blown or just not making contact properly?)? Also, how does a dodgy fuse in the aircon fan overheat the engine? Is this something I should check as well? Where is the fuse located - engine bay or under the dash?

I'm a little concerned that your car runs cool at 85-91c while my car regularly runs around the 98-104c mark. At 104c the thermo fans come on and drop the temp to below 100c but I'm wondering if my thermostat is stuffed. Should my car be running close to 100c all the time or cooler?

[Tsunamix]

Normal running temp should be 87 Degrees plus a few. Stock Thermostat won't open until 87 degrees. 105 means the water is superheated and generating steam. That steam will be held in until the system overpressurises and escapes past the radiator cap.

Lots of little thangs can be wrong here. Your temp gauge can be out of calibration - reading higher than it actually is (likeley). Your temp sender can be aged and not performing correctly. Your cooling system could be full of gunge that collects on intrusions (like the temp sender) and that stuff will act as an insulator making it slow to respond to elevated temperatures. Your thermo fan sensor could be incorrectly set.

I would - throw ins some barrs radiator clean and take a 20 minute drive with the heater ON. the drop the guts of the radiator in the gutter. pull out the thermostat, fill it up and throw in more cleaner and take another 20 minute drive with the heater ON. Dump the coolant, rinse, refill.

If anything runs hot after this, replace your temp sender first.

Dont forget to check your water pump is in good Nic.

[VT Owner]

I've recently replaced the thermostat and water pump from Repco as well as flushed the radiator. I'll remove the temp sender and clean it up. Not sure how to reset my thermo fan sensor though, however, it's consistent at coming on at 104c.

Might try a full radiator and engine flush while I'm at it. Anyone point me to where the knock sensors are located? I believe I have to remove them to flush the engine correctly.

[Louieg]

Hi VTowner, the fuse was not making contact all of the time so the fans weren't alway comming on. It was actually the ENGINE FAN LOW SPEED RELAY that was replaced which is in the engine bay. Now the fan always cpmes on when the air con is running...this helps cool down the whole engine

[VT Owner]

I might look at that. From memory, I've never seen the low speed fan come on - only the high speed one at 104c

[KimberlyB]

Hey Louieg, i have the exact same problem with my VT LOL! common problem i guess- just wondering how much it cost to fix that problem? Also, is your car Gas converted?

[Louieg]

Hi KimderlyB, If you are talking about the air con problem then it would be the cost of a new 'low fan relay' which cost me $30.00 from the auto electrician...If you are talking about the full pump, then that cost me around $380 installed. MY car is not gas converted.....

[Louieg]

VT Owner, how did you get on? The low speed fan only comes on when you turn on the air con.....

[VT Owner]

Found my answer here: Both Cooling Fan's Not Running? Help. I tested the relays and they passed ok. It appears I have an earlier VT in which both fans come on at certain RPM's instead of the newer VT's which turn one individual fans.

I also suspect that I had an air lock in the system which was responsible for the poor cooling performance. On my 3rd engine and radiator flush, I used a HP air flushing kit I made up from rubber bungs I got from Clark Rubber to blow out the radiator, engine block and heater core. The air forced the water to blow the crap out (took about 30 mins before the crap stopped coming out and this was the 3rd flush I'd done in less than 2 weeks). Cut up and used the straight bit of my old top radiator hose to aid in bleeding the air out of the system and everything seems to be working well now (fingers crossed).

[Louieg]

good luck with it mate....I probably should do the same thing given I do not know any history about my car whatsoever....cheers

[11gothevt11]

I changed the leads/sparks and the coil packs (managed to get some reasonably priced ones) but the problem remains. I cannot press in the accelerator quickly without the engine shutting off/back firing. If I press it in slowly no worries at all. HELP

Where did you buy the reasonably cheap coil packs????????
How much $?