I think i have a cylinder down..

[mrzigazaga]

Hi peeps..Noticed earlier after changing rad exspansion tank and warming the engine that there was a popping on drivers side exhaust that happens even once warm and if you rev it...When i put my hands in front of tailpipes the right side is blowing me hand away and the left is quite gentle...Rev hard..pop..sounds like fuel is igniting in exhaust?..Will check leads,plugs,etc....But do think i should of took the injectors out and sent off for cleaning when the car was at the garage..I hope they are not but is more than likely...cheers,Zig

[wild rover]

I would pull the spark plugs out first see if one of them is wet. If wet change it to another cylinder.Ignition lead or spark plug.Pull the wiring for the injector and check for a voltage.By running the engine with the injector wiring pulled in succesion may give you an idea which cylinder is affected.
Also check connections on the resister pack on the n\s wing for cleanliness.
Best of luck.Hope it's simple.

[Trickie Dickie]

Please bear in mind I am not technical on engines at all

I had a strange popping noise which I just thought was the manifold blowing
so took to my garage expecting a new manifold gasket and turned out to be
the cylinder head gasket. It had just broken out to the air so no water problems.
Surely this would also cause the same symptoms?

Hope it isn't too serious

Cheers
Trickie

[ihouston]

Sounds like air leak , fuel mixture or possibly a plug playing up - my car will pop when the fuel mixture is not set up right - does the engine feel a little lumpy when you are sat in the car - does it feel like it is missing - simple compression test will rule out head gasket.

[mrzigazaga]

Cheers chaps...Sorry if i wasnt very clear but the popping is coming from the tailpipe not under bonnet..Thought i heard a bit of ticking which would suggest there is a manifold leak but the pressure out the back of exhaust is more than the side that is quiet?..Im hoping it is a plug as i did put the older ones in when i was back tracking before i took it to the garage...The leads are new although thats no garauntee...It was suggested by the guy at the garage that because its been running for a bit that any little piece of creap that could of been in there might have logged itself in the injectors...Im am hoping it is just a plug or something simples..Ive got to go to a friends funeral monday and he loved classic cars and i promised him that i would turn up in it...If she lets me down its gonna be a big basil fawlty except it wont be a stick im beating with....Fingers crossed..Cheers

[MJG280]

The exhaust pipes are not seperate as they usually join at the silencer with two pipes out but it could have easily been one pipe out. Try blocking up each tailpipe in turn to see if there is an obstruction.

[jeff m]

Each pipe of a standard exhaust on a 280 is not from one bank of cylinders,it joins then seperates on its route to the back of the car.
Maybe one box has a little rust in it and is blocked or one has lost its baffle.

Re the popping and possible unburnt fuel.
Check intermitant arcing on leads. Always look for the cheapest first

CIS does produce pops and bangs, the 73 and onward 2.7 911s usually have aftermarket pop off valves put into their airboxs.

A few pops and bangs is usual with CIS on deceleration, it doesn't have a fuel shut off solonoid like earlier Bosche systems.
If it only pops during idle and stationary reving but runs well and accelerates smoothly, then it is possible you just have a lean miss at idle. That little screw that everyone wants to turn is your idle mixture (you know the one) If it is leaned out it can cause a combustion failure and will pump unburnt crap out into your hot exhaust. Not a big deal.

I had hydrocarbons over 200 with a CO of 2, increased the CO to 3 hydrocarbons down to 80, increase CO to 4, Hydrocarbons steady at 80. (not on a 280 of course, just an example of relationship between CO and Hydros)

I would be more concerned with how it runs, although it could of course be a problem with your UK MOT depending on how they test and what allowance they give geriatric cars.

[ihouston]

My 280 has two completely seperate exhaust systems - not joined at all - this is shown in the bible so the popping would indicate which bank of cylinders the problem comes from if Mark has this set up - I would concentrate on that area with the plugs first off - then may be look for a leak on the inlet manifold gasket and move on from there.

[benebob]

Another thought brought on due to your previous issues with the gas tank rust and sitting of the car is what about a weak injector spring or partially clogged injector allowing too much fuel to dribble out. Injectors are easy to remove and test. Oh and you'd know it pretty good if it was a dead cylinder. Try pulling one of the plug wires and you'll see how she runs.

[mrzigazaga]

Thanks guys...I went out this morning and it started ok..Pressure was even from both tailpipes..The mixture was set up and the guy at garage said it was set to 900rpm when it reads 1500..I did turn the mixture screw the other day about half a turn clockwise as the revs sounded high and thats before i realised that my rev counter is out..He used compressed air to give the injectors a blast as when he tested them a couple were failing..I think perhaps i will get them ultrasonically cleaned and a new fuel pump as thats been making a wurring noise..They were the only two things that needed doing..Now that ive been driving it about maybe it could do with a re-check and adjust of mixture although it doesnt feel lumpy or missing when driving..It did start doing it again just before i switched off about an hour ago,I will check the plugs tomorrow...Maybe its the cherrybomb mid silencers i had fitted,My system has been routed slightly differently and they are seperated from each other, My old rover used to pop and that had a cherry bomb..It was a cheaper option than to replace with the right ones,Maybe im just being paranoid..Also noticed i have a severe petrol leak from the filler neck to tank(again)..Except this time i cannot stop it leaking..There is a small damaged edge on the tank connection and ive tried two different pieces of fuel hose..New clips..This is very worrying as last time this happened i lost about £50 worth of petrol in a day plus its right above the exhaust...Any ideas..Many thanks..Mark
PS:On a positive note a lady pulled up next to me earlier when i was trying to sort leak out in a black convertible saab and said thats nice..Ive got a griff 500..Just about to ask her name when she had to go as someone was behind her...bugger

Edited by mrzigazaga on Friday 26th November 18:18

[MJG280]

My tanks have loads of black mastic round where the filler pipes go in. Don't know what it is called but googling fuel resistant mastic should bring something up.
With bad running, from the comments on here over the years, new pump seems to be often the cure. Mine buzzes like a box of wasps which is why it doesn't run at all now but it is tucked up now in the garage.

[jeff m]

Mark
Adjust your idle rpm with the screw in the air by-pass located just under the throttle butterfly (don't use the idle mixture screw, well you can but.....)

[mrzigazaga]

Cheers chaps..will look out for some petrol resistant mastic or sealant...Thanks jeff..I did adjust it by the big screw with the spring behind it, Is that the one you are talking about..Although i have put it back to where it was now,Well Almost..Will have another look at the leak as i do have some petrol hose that has wire inside the rubber instead of outside..Might be easier to clamp,,Will need car for monday(funeral)then after that will sort it for good with some sealant,Probably gonna get snowed in anyway,,,Wah...cheers..Mark