Bad Idle. Tapping noise...

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Postby grim_b » 10 Dec 2005, 13:03

Where are you going in Basingstoke?
The Chevette might make the conversation after all :lol:

Perhaps a fleeting glimps as I 'happen' to be parking up somewhere? 8)
I loved my car, but she has to go.... :(
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Postby Harry Flatters » 11 Dec 2005, 09:56

For lunch - at the Hilton! :lol:
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Postby grim_b » 13 Dec 2005, 11:47

Turned out that my son was ill, so no driving on Sunday :cry:
He is better now, but still feel like I missed out somewhere....

G.
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Different Knocking now!

Postby grim_b » 04 Oct 2007, 11:48

Hi all,

Hope your all well?
I have got a BIG problem with the car now and need your advice please.

Driving into work today, I could hear when accellerating, a loud tapping from in front of the steering wheel. (i.e in the engine bay) I think it is coming from the dashpot on the carb?

I cannot accellerate in any gear without the car sounding as though it is going to launch a three inche pin through the bonnet and into orbit? The more gas the louder the noise?

When slowing down to a roundabout the car sound as though it will stall and when I just tried her again, I cannot get the revs level and it won't idle at all?

I think it broke, but what bit?

Thanks,
G.

Has anyone had anything the same?
Can you suggest a fix?
I loved my car, but she has to go.... :(
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Postby Doive » 04 Oct 2007, 12:05

Have a good look at the carb diaphragm, these can split and cause rough/no running, poor idle etc. Not sure why it would make a horrendous noise though? If it's making no power at all, I'd take a look there to start with. Is it misfiring at all, or just generally running rough?

Hmmm. Alternatively, take a long hard look at your distributor, to make sure it hasn't slipped round about 30 degrees. When I replaced my condensor (again) a couple of years ago and driving the car having set the timing by hand, the engine would pink and rattle like a full percussion section on acid. Retarding it a bit at a time until it stopped pinking seemed to solve the problem.
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Not the diafram

Postby grim_b » 04 Oct 2007, 13:29

Hi Doive,

I have just checked the diafram (pooring dash port oil all over me and the engine!) and it looks sound.

I removed the air filter and checked airwaves were clear.

I now need to put more oil in the dashpot? any ideas what oil is best? I usually use 3 in 1 but have only got Halfords classic car engine oil on hand.

I had a look at the dizzy and found that the arm contact is scrapped, I sanded it clean again along with the contacts in the cap, started the engine; while it runs smoother, it will not stay running when off the throttle? As such I can not move the car to check the pinking from the dashpot?

Any ideas?
Thanks,
G.
I loved my car, but she has to go.... :(
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Postby Gordo » 04 Oct 2007, 13:36

Something y'all seem to be missing is there are TWO advance mechanisms in the distributor - the vacuum which advances the timing under light load and the mechanical (or centrigugal) which advances the timing as the engine speed increases.
Something that may be causing some of the symptoms is a head gasket which is blown between two cylinders - I've had this and the firing on one would ignite the mixture in the next. Not good.

There are a number of other things it could be but, as I've just realised it's after 1:30 AM here, that'll have to wait till later
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Dizzy cap + rotor changed - no better

Postby grim_b » 04 Oct 2007, 21:58

I have just got back from work after replacing the dizzy and rotor arm. Sticking more 3 in 1 in the dashpot, it still doing it!

I am going to try the plug and the HT leads tomorrow. But if you reading this and have any ideas why the engine "pinks" when under load and won't idle, please give your advice, experiences etc.

I really was looking forward to owning a 25 year old car (this Jan) but at the moment, it is looking likely to be the final straw. Same old story, the missus is preg, got two kids already, this car gets me to work and back leaving the missus her car for the kids outings to the various venues. If the Chevette does come through it leaves a pregnant woman walking everywhere :cry:

Doive, I will check the position of the dizzy when I go back tomorrow.

Cheers all.

G. :cry:
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Postby CancerWagon » 05 Oct 2007, 06:37

By your origonal description of the noise, mentioning sounds like it is going to be hucking parts into orbit... it may be major internal mechanical damage. Valves hitting pistons, broken piston rod etc.

Do a compression test if you have the means.
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Postby Gordo » 05 Oct 2007, 08:49

I just had a thought that it may be a loose distributor cap, but as you've had it on and off a few times, I figure you'd've noticed by now.
Does it make a difference if the choke is pulled out?
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Postby grim_b » 05 Oct 2007, 10:21

If I pull the choke out, it stalls.

I am thinking that CancerWagon is right. but the noise is only when under load, i.e pulling away, acellerating.

Going to do the plugs at 5:30 tonight.

Cheers, anything else?

:)
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Postby Doive » 05 Oct 2007, 10:25

Take the rocker cover off. Visually inspect all the valves, stems, springs, rockers, pushrods for signs of damage or bits missing. It's possible that a bit has broken and is stopping a valve from opening, or a valve may have dropped and is rattling around inside the cylinder! Although if that has happened, I would have thought it would have banjaxed the engine completely.

Start the engine with the rocker cover off and have a good listen to see if you can tell where the noise is coming from exactly. Rev by hand to see if it will do it at rest.
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Postby CancerWagon » 06 Oct 2007, 02:51

Doive wrote:Take the rocker cover off. Visually inspect all the valves, stems, springs, rockers, pushrods for signs of damage or bits missing. It's possible that a bit has broken and is stopping a valve from opening, or a valve may have dropped and is rattling around inside the cylinder! Although if that has happened, I would have thought it would have banjaxed the engine completely.


Good advice indeed.

I've had two journeys on rather destroyed engines. The most Epic of these trips was in a chevette. (1600cc) A white knuckle 100km journey, where the last 50kms were with one broken piston rod smashing about in the crankcase, and the final 5 kms was on a tow-truck, once there was a hole in the side of the block. :lol: Moral of the story: one can still operate an engine with surprising amounts of damage for short periods of time.
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Postby Gordo » 06 Oct 2007, 09:56

thinking on this this afternoon, rather than the knock causing the rough running, could the rough running be causing the engine to move around enough for it, or the exhaust or whatever, to hit on something.
I might also suggest you recheck the points/contact breaker gap as I've found some shafts and/or bushes and/or base plate bush have been worn enough to give inconsistent dwell and hence misfire.
Something else that can cause knocking is a faulty fan thermal coupling - this one drove me nuts until I traced it!
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Carb stripped and refitted

Postby grim_b » 08 Oct 2007, 10:07

Hi all,

I have (over the weekend) removed and cleaned the various parts of the Carb. When I fitted it back on the car and tried it again the problem was still there, pinking while under load going forward and backwards.

The sound only comes when the throttle is in the "giving more right foot than needed" area i.e accelerating.

I have noticed that the Dashpot cap leaks if I push the valve in the carb up, but I am told that this is normal as the oil (if overfilled) comes out of the hole in the cap threads.

I have just been told that I need to check that the dizzy is working well, by testing it by sucking on the pipe that goes to the carb. Problem is, that I have already tried this and found that there is suction on the pipe i.e it traps the tounge when testing, so the diafram seems good.

I am going to test that the plugs all spark today by removing them one by one and checking spark on ignition.
I also need to do a points inspection.

Cheers all for your advice.

G.
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Postby Gordo » 08 Oct 2007, 10:45

I'd also suggest a compression test - it may be blown between adjacent cylinders without getting into the water jacket. I may have mentioned this earlier as it's something that has happened to me.
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Postby Doive » 08 Oct 2007, 11:56

Pinking is a very distinctive noise, and I'd suggest that if the engine is only making the noise when accelerating under load and not at any other time then it is very likely to be pinking, and not mechanical failure that would likely show up all the time when the engine is running. Beg, steal or borrow a timing light/stroboscope if at all possible and check if your timing is close to where it should be. Pinking sounds like a squadron of little angry drummers all playing a 12/8 march on your rocker cover, and only happens when you bury the throttle under load. Check your timing before you go pulling bits of engine apart.
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Postby grim_b » 08 Oct 2007, 14:19

Well, I guess we will have to wait and see chaps (chapesses).

The car is now in THE GARAGE!!

Oddly though, before I braved the 2 mile journey to the garage, I losened the dizzy and twisted it slightly. This produced a better idle run, but the pink was still there. I drove it halfway to the garage where I had to stop to turn right and the engine stalled and would not start again!!! :shock:

I had to push it the rest of the way... God I'm hoping it will be ok, I love that car... :cry:

Thanks again people :)
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Postby Doive » 08 Oct 2007, 14:48

I wouldn't be surprised to find that they charge you £2.50 for a replacement condensor. When my timing was significantly out, the condensor failed and meant it couldn't be started. The only other thing I could think of failing like that would be a rotor arm, although as I found out recently they tend to fail at 70mph on the M6 rather than at a junction waiting to turn left. The fact of the matter is that the little 1256 is so electrically and mechanically simple, that whatever has gone wrong should be easy to trace.
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She is a goer!

Postby grim_b » 12 Oct 2007, 10:08

Well,

Long story short because I am at work, but the head gasket had gone between 1 and 2 and the gas of 1 was going into 2.


The new head cost £262 all in and the car seems to be (slower) but much more stable.

I LOVE IT :)

Cheers all for the help,

G.
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Re: She is a goer!

Postby Shellysowner » 12 Oct 2007, 10:25

grim_b wrote:The new head cost £262 all in and the car seems to be (slower) but much more stable.


Do you mean they actually put a whole new head on, or was the head gasket+labour £262?
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Postby grim_b » 12 Oct 2007, 12:30

No, just the gasket + work = £262
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Postby Doive » 12 Oct 2007, 12:57

Excellent, very pleased to hear you got it fixed. I think many people, probably myself included, would have been considering just buying another car at that point. I know if the Saab spat it's head gasket out of the pram, I can get an entire new car for the cost of having the work done. But I'd probably get it done anyway now I think about it. Good thing about the Chevette setup is that the timing doesn't get upset when you whip the head off, which makes the job less expensive. HG on the Saab would be £400+.

I hope the car repays your kindness with much reliability. A head gasket every 25 years is not a bad record.
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Postby grim_b » 12 Oct 2007, 13:11

25 years or every 57.5k :D

G.
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Postby Gordo » 12 Oct 2007, 14:00

Well, I was correct, unfortunately.
When mine went, I had a slight ly eroded bit on the block as well as the head and had them both skimmed. I suggest you take it easy at first till you're sure it's fixed.

BTW, there's a trick to getting the head gasket and head correctly aligned on the block. If you look carefully, there's a head bolt hole at each end that's slightly smaller in diameter, either buy a couple of long bolts or take a couple of spre head bolts, cut off the heads and cut screw slots in the ends. Screw them into the block before fitting the gasket and head and they'll be perfectly aligned. Fit the other bolts finger tight and unscrew the studs and replace with the correct bolts before torquing them down progresively to 55lbs ft.
ttfn

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