Knocking on full throttle from standstill / low speed.

[FCD]

I probably drive my 1988 Ford Escort XR3i a little bit too gently, it's my daily driver so it sees mostly just relaxed 50Mph highway cruising in 5th gear at 2000-25000rpm and city stop and go traffic.

The other day i decided to get a bit silly in an empty parking lot and noticed it makes a fairly nasty dieseling type noise when flooring it from low speeds, even in 1st gear, although only for maybe a couple seconds, i've always used 95 RON gas in it so i decided to fill her up with Shell V-Power 98 yesterday and the knock is definitely almost gone, i think i'll retard the timing a little too as i think it's a little too advanced perhaps, although i like running as much timing as possible because that way it idles nice and smooth.

The plugs look normal and are not worn or damaged, but i can see the top of the pistons look like they have a fair amount of deposits, i'll run a few tanks of V-Power through it and drive it a little more spiritedly to see if maybe it would clean up the deposits.

 

[FCD]

Bunus engine pic : 1988 Ford Escort XR3i engine by Lauri Lind, en Flickr

 

[Danno]

Piston buildup may have enough impact to raise your octane needs.
Drive it like you stole it, safely of course, might help.

 

[supton]

Don’t rule out other causes, like bad motor mount or something loose.

 

[SwampSurvivor]

Could it be an exhaust manifold leak?

 

[eljefino]

A water decarbonization may be what you need. I like using one of these to mist into the intake.

 

[frankbee3]

Your engine compartment is very clean! It looks like you take very good care of your car. Has the engine been overhauled?

 

[Astro14]

Possibilities:

Too much ignition advance
Not enough EGR flow (if the engine is equipped)
Lean mixture
Combustion chamber deposits raising compression ratio

Probably could use a combustion chamber clean up, but check the rest as well.

 

[Astro14]

Also- more a mechanical, maintenance issue. Thread moved.

 

[FCD]

Don’t rule out other causes, like bad motor mount or something loose.

They are a year old so unlikely.

 

[Hal-9000]

Possibilities:

Too much ignition advance
Not enough EGR flow (if the engine is equipped)
Lean mixture
Combustion chamber deposits raising compression ratio

Probably could use a combustion chamber clean up, but check the rest as well.

Incorrect. EGR is not activated at WOT

 

[FCD]

Possibilities:

Too much ignition advance
Not enough EGR flow (if the engine is equipped)
Lean mixture
Combustion chamber deposits raising compression ratio

Probably could use a combustion chamber clean up, but check the rest as well.

These engines don't have EGR, in most of Europe until the early 90s not even Cats.

I am going to try and retard the timing a little, i had to take the distributor off a while back when i changed the thermostat and gasket as otherwise one of the 3 bolts that hold the housing is impossible to get to so i might have set it a little too advanced.

The mixture is ok i think, the plugs aren't too light or dark, but it is easily adjustable with a 3mm allen Key on Bosch K-Jet.

I think carbon deposits are most likely the culprit and are causing hot spots, since for the past year ( about 7000 miles ) i've really not gone on any long road trips with it and have done a lot of city driving.

 

[FCD]

Incorrect. EGR is not activated at WOT

This engine does not have EGR and never has had an EGR, it doesn't have a Cat either or any other emissions equipment from the factory, cars only started having cats in 1992 here in Spain and less than 20 years ago leaded gas was still sold hah.

 

[FCD]

Could it be an exhaust manifold leak?

It's not, i changed it 3 years ago and it sounded more like a lifter tick than a dieseling type knocking noise.

 

[FCD]

A water decarbonization may be what you need. I like using one of these to mist into the intake.

I have done that on my 75 Capri and maybe it was just placebo but it did feel like it ran better.
The problem with Bosch K-Jet is that the engine will not run with the intake hose disconnected as it needs vacuum to lift the fuel metering flap for the engine to recieve any amount of fuel.

 

[FCD]

Your engine compartment is very clean! It looks like you take very good care of your car. Has the engine been overhauled?

Oh you should have seen it 4 years ago when i bought the car... i've probably scraped brushed and wiped literal pounds of gunk off of it, the PCV valve was 100% clogged and therefore the oil vapors seeped out of every little place they could and basically coated the entire engine in oil mixed with dust and general crap.

Not to my knowledge it has never had any internal engine repairs, and for 100k+ miles and being close to 34 years old now the fact that it doesn't burn any oil and does not use any coolant either is surprising.

 

[ARCOgraphite]

Plug heat range or loosness, or more so - extended tip? You can go back to a recessed tip will slow ignition without moving the dist.
I am NOT generally a fan of extended tip plugs in performance applications.
Also cavitation and or hot spots in the head relating to coolant flow and wetting.

Enjoy! That underhood pic looks stunning!

 

[FCD]

The plugs are the stock Motorcraft AGPR12C that it specs right in the Haynes Manual.

 

[FCD]

BTW This is what it looked like under the hood when i bought it in Jan 18.

Covered in oil everywhere, and yes the coolant tank was that color from the amount of rust that had built up inside of it, no trace of coolant in the system, just rusty tap water.

Before by Lauri Lind, en Flickr

 

[PimTac]

It sounds like timing. Something in the distributor perhaps?