I had an engine rattle (1.8 petrol QQDB) that I couldn't solve, so I took it to a garage. They rang me back, saying it's not a rattle, it's a knock caused by overfueling. They replaced the spark plugs, as they said they were cabbaged because of the overfueling, and said I might need a new fuel injector. They did some tests with the injectors and said there's no problem with them. Given that it's overfueling, they reckon someone has remapped the car at some point (2009 1.8 Zetec S). They said the best thing to do was to get someone to map it back to standard.

Before I get the car mapped, is anyone aware of any other reasons why it could be overfueling when there's no issue with the injectors? Also, what would be the best way to get an OEM map done?

Thanks

There's virtually no benefit to remapping a non-turbo petrol.  I would be very surprised if someone had remapped this engine.

It's not easy to get standard maps.  I used to save them all when I was mapping cars so I could put the originals back on.  So you can either ask a mapping company if they have a base map they can flash on.  Or potentially ask Ford to do a PCM update, which should over-write any non standard mapping.

Over-fuelling is usually caused by a faulty MAP sensor in my experience.

This was my thought too, why would someone remap a non-turbo car for at best 3bhp gain?

So, I found a highly rated local tuning company. I sent them a message explaining the problem and what the garage told me, and they recommended a local auto electrician. I've looked on their website and they seem to specialise in ecu diagnostics, wiring faults, engine management, etc. So I'm guessing the tuning company had the exact same thought as you. I'm assuming this auto electrician outfit will be able to find out if there's an issue with the MAP sensor.

I'll be over the moon if it just needs a new MAP sensor!

Thanks for your insight

 

On 5/30/2025 at 7:52 PM, TomsFocus said:

There's virtually no benefit to remapping a non-turbo petrol.  I would be very surprised if someone had remapped this engine.

It's not easy to get standard maps.  I used to save them all when I was mapping cars so I could put the originals back on.  So you can either ask a mapping company if they have a base map they can flash on.  Or potentially ask Ford to do a PCM update, which should over-write any non standard mapping.

Over-fuelling is usually caused by a faulty MAP sensor in my experience.

Given how much it would probably cost the auto electrician to diagnose the issue, I just thought I could get Forscan and the recommended OBD cable. Would Forscan enable me to pinpoint the issue, such as the MAP sensor, or would the auto electrician be doing something beyond what I can do with Forscan?

4 hours ago, ChaoticWires said:

Given how much it would probably cost the auto electrician to diagnose the issue, I just thought I could get Forscan and the recommended OBD cable. Would Forscan enable me to pinpoint the issue, such as the MAP sensor, or would the auto electrician be doing something beyond what I can do with Forscan?

An auto-electrician can physically check wires and plug pins.  Whereas Forscan is completely reliant on the voltage data reaching the PCM.

Even if Forscan does pinpoint a MAP issue, it cannot tell whether the sensor is faulty or whether the wiring is faulty.

Forscan is a great tool, but it can't replace an auto-electrician.

 

You can probably get a MAP sensor for these for about £20 if you want to take a punt on that before paying auto-spark labour rates.

4 hours ago, TomsFocus said:

An auto-electrician can physically check wires and plug pins.  Whereas Forscan is completely reliant on the voltage data reaching the PCM.

Even if Forscan does pinpoint a MAP issue, it cannot tell whether the sensor is faulty or whether the wiring is faulty.

Forscan is a great tool, but it can't replace an auto-electrician.

 

You can probably get a MAP sensor for these for about £20 if you want to take a punt on that before paying auto-spark labour rates.

Thanks for the advice, mate. I will pay the sparky to pinpoint the problem before I spend more money on parts I don't need. At least I'll know if there are any other issues I need to know about. If I had continued on my path before taking it to the garage for them to diagnose the overfueling, I would have replaced half the car, trying to get rid of this noise. I would have been an amateur DIY car version of Trigger with his broomstick 😂.

On 6/2/2025 at 8:12 AM, TomsFocus said:

An auto-electrician can physically check wires and plug pins.  Whereas Forscan is completely reliant on the voltage data reaching the PCM.

Even if Forscan does pinpoint a MAP issue, it cannot tell whether the sensor is faulty or whether the wiring is faulty.

Forscan is a great tool, but it can't replace an auto-electrician.

 

You can probably get a MAP sensor for these for about £20 if you want to take a punt on that before paying auto-spark labour rates.

Just got back from the auto electricians. They said the EGR valve is causing the pinking. They gave me a printout and took me through the issues they discovered.

Petrol injection Visteon 121 ESU --

• P0400 Exhaust Gas Recirculation System Flow Malfunction 
• P0571  Speed Control Brake switch circuit failure 
• P2121 Throttle/Pedal Position Sensor/Switch D Circuit Range/Performance
• P2126 Throttle/Pedal Position Sensor/Switch F Circuit Range/Performance
• P2127 Throttle Pedal Position Sensor/Switch E Circuit Low Input

Power Steer -- (EPS) Electric Power Steering control unit --

• U1900 Controller Area Network Communication Bus Fault

I will fit a new EGR valve, but he mentioned that the throttle pedal sensor/circuit goes through the dash and will need sorting at some point. So am I right in assuming this has something to do with the old soldering cracking on the instrument cluster and that there's a guy on these forums who is the go-to guy to fix old solders? 

Ah, I often forget these have an EGR valve.  Most petrols don't.  Well worth getting it diagnosed properly in this case.  

@rd457 is the guy for the cluster repairs.

I still took the gamble on the map sensor. The sparky couldn't see me until today, and a week was too long for me to wonder if it was just the map sensor 😂

I'll drop @rd457 a message. 

Thanks again for the help!

1 hour ago, ChaoticWires said:

P0400 Exhaust Gas Recirculation System Flow Malfunction 

That error may also be caused because of the strange Throttle readings that are most probably caused by the Dash fault.

The drama continues...

@rd457 re-soldered the instrument cluster, and I bought a new EGR valve. At this point, I thought, "In for a penny, in for a pound," and ordered a new PCV valve/oil separator case, a new PCV hose, a new intake manifold, and new spark plugs. I've also got the new T-Map sensor I bought earlier. 

Today, I finally had all the parts, and instantly got stuck on the EGR value 😂.

I removed the intake system, throttle body, and the big coolant pipe in front of the EGR valve, but even with the pipe removed, the elbow/joint is still in front of it, making access to the right rear bolt a nightmare.

My 1/4-inch wobbler is broken, so I used a 3/8-inch wobbler and extension. I got the socket on the right back bolt, but it won't budge. I can't figure out if it's seized or if 3/8-inch tools are too big for the space and it's jamming. I reluctantly put everything back together for now.

My dilemma is that I'm working on the car in an underground car park. So whatever I do, if it doesn't work, I need the car to start; otherwise, there's a whole new level of hassle getting it out of the car park.

I've come too far with this overfueling rattle. I need to get this sorted because the oil level is rising due to being diluted with fuel. What's the best way to remove the EGR valve, or should I get the local garage to fit it and continue with everything else?

The thermostat housing is just bolted on, you can remove that for access as well.  Ideally you should fit a new gasket when refitting it.

The new EGR valve I've got includes a new gasket. I thought the thermostat housing on the 1.8 QQDB was down by the drive belt behind the intake manifold. Are you referring to the plastic bell dome on top of the EGR valve itself, which has four screws? 

I've attached a photo, red line to the EGR valve, and green line to the hose and elbow that's blocking the access to the back bolt.

I just had a new 1/4 wobbler and u-joint arrive, so I will go for round 2 tonight. 

 

5 minutes ago, ChaoticWires said:

The new EGR valve I've got includes a new gasket. I thought the thermostat housing on the 1.8 QQDB was down by the drive belt behind the intake manifold. Are you referring to the plastic bell dome on top of the EGR valve itself, which has four screws? 

I've attached a photo, red line to the EGR valve, and green line to the hose and elbow that's blocking the access to the back bolt.

I just had a new 1/4 wobbler and u-joint arrive, so I will go for round 2 tonight. 

 

Technically it's a 'water manifold' as there's no stat inside it, but it's still just bolted on.  The gasket on that should be replaced if you remove it to prevent coolant leaks.

You're a legend, mate.

Luckily, I bought loads of coolant while on my spending spree. If I can't get it off with the wobbler and u-joint, I'll order a gasket for the water manifold and take it off. 

If I've got to drain all the coolant and take the water manifold off, I might as well do the water pump and thermostat while I've got everything off. Where's the best place to get part numbers for gaskets, etc?

I appreciate all this help 👍

No need to drain all the coolant for this.  But if you do want to replace other parts, catcar is the best one for free part numbers.  If you put your VIN into the main page then that narrows down the options to only those that fit your car (in theory at least!).

Ford - Catcar.info

 

This is precisely what I've been looking for. 

After removing the large pipe on the front of the water manifold, the coolant that comes out—is that essentially it, and a load more won't come out when I take the water manifold off?

I'm assuming that once I've put it all back together, I can run the engine with the coolant reservoir cap off and top up as necessary, and it will sort itself out without creating air pockets.

Yes, that pipe is pretty much at the lowest point of the manifold so no more coolant should come out.

Yes you can run the engine with the cap off until the stat opens.  (Which is probably pretty quick on these, unlike the diesels I used to work on!)  The proper way to refill the coolant is with a vacuum bleeder but most people get away with a standard cap-off bleed at home.

I managed to remove the EGR valve and fit the new one. I also changed the spark plugs and the oil, which absolutely stank of petrol and looked quite thin. To say I was pleased with myself is an understatement.

Took it for a test drive and it's still rattling 😐.

I've noticed some things while trying to fix this issue. The back of the throttle body is absolutely caked in soot. I don't mean like in all the pictures I've seen of petrol throttle bodies that need cleaning, which either have a light dusting or a light film of tar. I mean, this is caked like it's a diesel. It's also a very oily soot, not a dry powder soot. I tried cleaning it with throttle body cleaner, a rag, and a toothbrush. It's so thick that it made no difference. 

Inside the intake manifold, looking in with the throttle body removed, it's very oily and sooty, like a misting of oily soot that has built up on everything, and I can see a puddle of oil in there.

When I took the spark plugs out, cylinder 1 spark plug was nice and clean and looked new. Cylinders 2, 3, and 4 were heavily sooted, and the threads were oily. The car had brand new spark plugs less than 300 miles ago when the garage diagnosed the rattle as overfueling. 

Do these symptoms suggest anything other than just the EGR valve causing my issue? The car has just short of 130,000 miles on the clock.

I still have to fit the new intake manifold, crankshaft oil separator case, PCV valve, PCV hose, and the new T-Map sensor to fit. I'm hoping that with all this stuff replaced, it will fix it.

My OBDLink for Forscan arrived yesterday too. I'm gonna plug that in today and see what it says

There is a common issue on these with worn piston rings.  Hopefully it's not that, but excessive blowby and low compression (partial misfire/soot) do seem to be pointing towards that.

Do you get any blue smoke from the exhaust at all?  What was the most recent MOT reading for HC's?

There's no blue smoke. When I bought the car 6-7 weeks ago, it came with a fresh MOT that had no advisories or anything. When I look at my certificates online, they don't have any hydrocarbon readings. Is there any site that will allow me to see this information?

If it is a worn piston ring, can I remove the piston and put on a new ring, or is it just over at that point?

7 minutes ago, ChaoticWires said:

There's no blue smoke. When I bought the car 6-7 weeks ago, it came with a fresh MOT that had no advisories or anything. When I look at my certificates online, they don't have any hydrocarbon readings. Is there any site that will allow me to see this information?

If it is a worn piston ring, can I remove the piston and put on a new ring, or is it just over at that point?

It's not possible to see emissions readings online unfortunately.  They can only be printed out from the test machine at the time of the test.  

The rings are likely to be worn on all of the pistons rather than just one.  They can be replaced, but it also depends on how much damage has been caused to the bores.  If the bores are damaged badly enough then they need to be 'bored out' and larger pistons fitted.  Technically possible but not financially viable on these now.

Bare with me here...

I want to buy a nice Mk7 Golf GTI or a 2015 Focus ST3. Given the prices of used cars nowadays, all the ones that are in my budget are going to have 90k+ miles on the clock. The idea of spending £17k on a 10-year-old hatchback seems ridiculous to me. I figured if I buy a cheaper, higher-mileage GTI or ST3, I can get my turn out of it if I can work on the car myself.  

So I bought this Focus as a cheap run-around and to learn how to work on it myself. Granted, I didn't think I would be doing so much work on it straight away.

Let's assume it's the worst-case scenario. If I get some oversized pistons and new rings and get the auto machine shop around the corner to bore and hone the cylinders, and if I can do that for under £1000, I'd do it just for an educational project. 

I have a full range of Nortorque torque wrenches, a Milwaukee high-powered impact wrench, and full 1/4, 3/8, and 1/2 inch socket sets, which are short and deep.

I realise this is a serious escalation for a 16 year old focus with 130k on the clock. So, the question is, do you reckon I could do it for £1000 or less? 😂

1 hour ago, ChaoticWires said:

do you reckon I could do it for £1000 or less?

No.

Having searched online, I can't find a set of oversized pistons for this engine.

They make them for the 2.0 version as that's still popular in the Fiesta ST.

The 1.8 hasn't been produced for a number of years though and doesn't have much demand for modified parts as it wasn't in any performance models.

It might be possible to drop a good used 2.0 engine in for less than a grand.  You'd just need an unlocked ECU to go with it.  Most of the ancillaries should be the same.

However, my honest opinion would be to put that grand into a Golf GTi or Focus ST.  They'll hold the value.  Anything spent on this car isn't likely to be recovered.