3.0V6 engine problems

[Jonny(7)5]

Hi Guys, I hope you can help me with my problem.

My 12V 3.0 V6 is a track car that I’ve finally finished. It went to Donington a couple of weeks ago and performed fantastically, handling like a dream. The engine is standard apart from C&B cams. Towards the end of the day the water temps were starting to get higher (up to 100-110 rather than 80/90), so I took it easy and let the car cool down more. It was fine on the way home, but I took it out later and whilst pulling away from a set of traffic lights I noticed the car felt significantly down on power. I thought it was just too hot, so I left it for a few days.

Upon trying to start it a few days later I made the following observations:

Cold starting really poor. It takes probably 15 seconds to catch, normally it’s on the button.

It won’t idle on it’s own until it’s warmed up. Once warm it will start on the button as normal and revs freely whilst stationery.

There are no knocking noises or lumpy power delivery (once warm), however it just does not pull, and feels restricted with about 60hp! It will not pull through the gears, as though the brakes are being applied at the same time.

If I try to make any progress it seems to get hotter than it should.

The spark plugs are very sooty, but after taking them out last night they were white tipped as they should be.

Items checked so far:

The fuel pump and voltage to it have been checked- no problems.

Compression checked- fine around 175psi per cylinder.

It wouldn’t appear to be losing water but maybe it isn’t driven enough to be able to check that?

ECU has been swapped and this made no difference. I’m trying to remember what the smaller unit does? That hasn’t been swapped.

So does anyone have any ideas or the best way forward?

Thanks for reading.

Jonny

[ally]

Are there any signs of oil in coolant, or coolant in oil? If the radiator is not in very good condition, it is quite early to get the V6 very hot- too hot even. Sometimes the head gasket can be weakened due to corrosion arising from not adhering to the specified coolant changes. I've seen that a few times.

The leak can be so small that it is difficult to pick up by compression testing. Another way to check is hydrocarbons in the cooling system. Snap On do an expensive kit for this, or an exhaust gas probe into the coolant expansion tank can find this. Your have a problem if there is more than 40-50 ppm of hydrocarbons even for a couple of seconds. 200+ppm means a repair is needed now, and not in a weeks time (not that you'll run the 75 every day).

[Jonny(7)5]

I can't see any oil in there but obviously I'm not really using it now. I'll have a look into that if I can get it tested somewhere cheers.

[veesix75]

Air Flow Meter ?

[Gold]

Originally Posted by ally

Are there any signs of coolant in oil?

If his head's cracked and the coolant is leaking into the engine to make 200 hp feel like 60, he'd have a white cloud the size of Hiroshima coming out of the exhaust. His temps would be off the scale and steam would becoming out of the radiator/coolant tank.

To me it sounds like there's something wrong and the car is electronically preventing itself from running right. MAF comes to mind. Athough after having considered if it's getting fuel ok.

[ally]

A head gasket failure doesn't necessarily mean catastrophic failure as described above. What has been described is a major failure, and that usually only happens when a minor failure has not been attended to. However, any amount of white smoke from the exhaust is an indicator. Beware confusing this with normal vapour on a cool and wet day.

Best eliminate the potentially serious first. It could be an air flow meter, but I would expect a lack of power to be noticeable from the outset, when the higher coolant temps were originally occurring.

[Jonny(7)5]

Cheers guys, thanks for your ideas.

[alfaspence]

if the plugs are sooty, its running rich on something... fuel or oil.

petrol engines run on a fine line, you can lose a whole heap of power if your over or under fueling (something the g-boys umoungst us never seem to want to take into account)

but its rich... if it were lean, that would explain the power loss with overheating...

ignition timing also plays a major part in power loss and running temps, might want to check that.
AFM's always get bagged as being the fault, but this is NOT always the case... yeah the old flappy ones wear out eventually and a newer one will always produce results BUT, can also do a pretty good job at masking the real problem!!!

If its overheating, use extreme caution, failure to do so will have very expensive consiquences!

[Barbalatte]

Can you get your hands on a Jetronic 2.5 litre computer??
I have a GTV6 with a 3.0 12v motor from a 75. I run a 2,5 Computer. Much beter.
Try it and let us know. I recon it's a computer problem.

[giuliettaevo]

Also check the camshaft timing! if your belt skipped one tooth it runs like it has lost 30 bhp but it still idles well.

[Jonny(7)5]

Well I seem to have checked most things now, with no luck.
I'd already changed the ECU and checked the camshaft timing. Swapped over the coil, changed the FPR and I've just replaced the fuel pump and filter. I'm sure it must be something to do with the timing...

[75evo]

Hey,

We had a guy on GTV6.com who rebuilt his whole engine, replaced the wiring harness, then changed to Haltech because of a strange stumble and was low on power too. Turned out it was a bad in tank filter. Totally clogged. Do the euro 75 fuel tank have an in tank filter? Have you checked the actual fuel pressure?

[Jonny(7)5]

It doesn't appear to per the workshop manual unless anyone knows any differently?

[Shipro]

did you check if air inlet is OK? maybe there is a puncture or it is not sealing well. other thing to check are injectors - there must be O-ring for each one and if they are worn out or damaged it can cause bad idle.

you can check this with start spray or gas for cigarette lighter ... start the engine and then spray from the AFM towards throttle valve and around injector seats in the engine heads. if the revs go up - there is a puncture.

also, cleaning injectors with ultrasound machine will be helpful.

[giuliettaevo]

Not only the full pressure is important, the amount of fuel delivered is also important. If the engine is at load and the pressure drops performance will drop also. measuring fuelpressure at full load is not easy while measuring the amount off uel delivered by the pump is very easy. just take off the fuelhose before the injectors and hang he end of it in a large (petrol surviving)bottle, wire the pump to run for 30 seconds and look how much fuel there is in the bottle. should be a litre of fuel.

[Topkat75]

3LV6 engine problems.
Poor cold starts could be down to failure/blockage/disconnection of the 7th injector.Mine is currently suffering from this and as soon as I have time I will sort it,meanwhile against all the best advice, a short blast from the "squirt and sniff tin" up the air intake does the trick instantly.
Best of luck!