Overfueling !

[Spawn]

Hi all...

Any pointers on things I can look out for for this one?

For some reason my Cerb has started overfueling quite badly. Fuel is being consumed nearly twice as quickly as usual.. and no matter how fast I am traveling or what gear I'm in, I am getting constant pops and bangs from the exhaust.. (I think out would be cheaper for me to hang my wallet out of the window )

Any ideas?

Rob

[jonbarrett]

I had this once, turned out to be a lambda sensor.

[Ballsy]

Try pluggin in a laptop and see what values the lambda's are at

[Spawn]

Right, I have downloaded both the Old and New Software. I assume I need the old for a 97 4.2?

What else do I need or need to know before I begin?

[Toadusmodus]

Spawn said:

Right, I have downloaded both the Old and New Software. I assume I need the old for a 97 4.2?

What else do I need or need to know before I begin?

Read the help files with the software, and trawl through previous posts on here regarding throttle pots/lambdas/software etc.
This one is a pretty detailed one!

http://www.pistonheads.com/gassing/topic.asp?h=0&a...

[chim500nj]

Spawn said:

I am getting constant pops and bangs from the exhaust..

Can't see any problem with that.

[volospian]

Spawn said:

Hi all...

Any pointers on things I can look out for for this one?

For some reason my Cerb has started overfueling quite badly. Fuel is being consumed nearly twice as quickly as usual.. and no matter how fast I am traveling or what gear I'm in, I am getting constant pops and bangs from the exhaust.. (I think out would be cheaper for me to hang my wallet out of the window )

Any ideas?

Rob

I thought someone once said that the pops and bangs are actually from a weak mixture, not rich?

I wondered if mine was running rich because it snaps, crackles and pops so much, so I asked the question...

http://www.pistonheads.co.uk/gassing/topic.asp?h=0...

[VPower]

Take it to a specialist and get them to check it if you not sure what the laptop will be telling you.
It's easier in the long run!!!

Could be a number of things including that the cam timing has slipped!


The pops and bangs are caused by the valve overlap that allows fresh fuel/air charge into the exhaust.
This could be stopped with an engine management mod to cut fuel on zero throttle like modern cars, but it also helps cool the combustion chamber and exhaust port. So probably best left alone?

[Olly]

We had this for ages on our car 18ish months ago & it was eventually sorted out with a replacement coil-pack.

I would suspect either :
Coil pack/s
HT Leads
Spark plug
Or Lambda......

[Byker28i]

Be careful. I had a lambda sensor go and couldn't get it out so took it to my indy.

On the way the weak mix blew the cat on one side - HUGE roman candle affair of molten metal out the back.

[Spawn]

Thanks for the replies. I have the software and will use the old one as I assume that will be correct. Not sure the new one would work on 97 4.2...

Then i'll post back on here when I get stuck hehe :P

[Tanguero]

Spawn said:

Thanks for the replies. I have the software and will use the old one as I assume that will be correct. Not sure the new one would work on 97 4.2...

Then i'll post back on here when I get stuck hehe :P

Either version will work with any Cerb. The new version gives you slightly more features and in my experience is rather more stable. I use it on my 97 4.2 just fine.

[VPower]

Spawn said:

Thanks for the replies. I have the software and will use the old one as I assume that will be correct. Not sure the new one would work on 97 4.2...

Then i'll post back on here when I get stuck hehe :P

Just to add, mine failed the MOT on emmisions due to a throttle pot being broken.
Was running very rich and would stall if left on tick over.

Good Luck and let us know how you get on.

[Jasper Gilder]

My second 4.5 did this a few times - If it's really overfuelling it stinks of fuel and the oil pressure drops because of bore washing - so you use a lot of oil as well and the back of the car is black and it drives like s**t

I had - new plus and leads, numerous new throttle pots and a new engine loom. Turned out to be sticking throttle bushes, rebushed the throttles and all was well

[Spawn]

How odd. I left this post rather than pushing it back to the top of the list as the problem resolved itself shortly after posting.

Then last night.. for no reason it's started popping and banging again like crazy! So would it be safe to assume there could be an intermittent problem with a lambda sensor or a loose connection somewhere? :s

Looks like I need to go ahead and good the software up

[Moany]

I have just posted a question with a similar problem, that is when I come off the throttle (4.5 cerby)the revs hold for a short while the car wanting to keep going when I don't. Also I can smell petrol sitting in the car. The local dealer replaced the throttle cable but it has made little difference, the dealer is suggesting to take the throttles off the car and clean them up, does this sound right?

[Scrooloose]

I had that. One of the throttle return springs on the throttle spindle had snapped.

Peninsular managed to source me some replacements....

[Moany]

Thaks for the reply, this is my first used TVR, although had a few new ones. When you replaced the throttle return springs did you do any other work. The local dealer has been great but its an expensive affair when they are suggesting several root causes of the problem.

[Spawn]

Im assuming my can't be a spring that has snapped as the problem appeared to rectify itself and then reappear the other day.

Will be putting some fuel in later and going over to the gf's so will see how she goes then.

[Scrooloose]

Moany said:

Thaks for the reply, this is my first used TVR, although had a few new ones. When you replaced the throttle return springs did you do any other work. The local dealer has been great but its an expensive affair when they are suggesting several root causes of the problem.

I didn't, but it's an easy one to do yourself. You just need to remove the panel in front of the wipers, take the back hose or two off and swap the springs. Takes about 30 mins if you're doing it for the first time