[Blue_Bora_TDI]

Hi all,
I bought a golf 4 1.6 16v, 2003. Car seems to run good, plenty of power, but one annoyance is that the throttle takes long to close when letting off the accelerator.
When shifting you see the revs climb a bit before dropping and while driving you can feel the car still delivering power for a second even when you're off the pedal.
What can cause this? I'm doing a throttle body alignment later tonight to see if it helps, I have vcds and a vag com interface.

Thanks in advance,

 

[ttg4l]

Air leaks, sticky injectors, bad lambda sensor, exhaust leak (throwing off lambda reading), could be anything.

-Start with a good service, including plugs.
-Clean and adapt the throttle body.
-Check for air leaks
-Fuel system cleaner, and at the bare minimum make sure you're using 98+ octane fuel. These are a high compression engine, and need high octane fuel to match

 

[Blue_Bora_TDI]

Exhaust is completely leak free(original system too) so we can write that off.
Going to service soon but last service was 25k km ago, which included oil, filters and plugs.
Air leaks I haven't tested yet. What are the usual suspects? Throttle body to inlet manifold?
I'll give the throttle body a good clean too and adapt it in vcds.

 

[Blue_Bora_TDI]

Also, forgot to mention. When you stand still it's gone. As soon as you start moving, even in neutral or clutch engaged or both, as soon as the car is moving there is a solid 1sec delay between hitting the throttle and the revs actually going up.

 

[ttg4l]

Air leaks: brake booster line, intake manifold gasket, EGR gasket, EGR stuck open. Smoke test will reveal them easily enough.

 

[Blue_Bora_TDI]

Realigned the throttle body, checked for leaks; nothing.

Read a bit that this is just a golf 1.6 thing.. is there any way to change that?

 

[ttg4l]

They are a bit funny, my idles never been perfect, but it's the best it's even been. Few tankfuls of V-Power sorted my rev hanging and stalling issue.

The ECU is Italian, which may or may not have anything to do with it.

 

[Blue_Bora_TDI]

Yeah I noticed, they're made by Marelli. My bora's ecu is just german Bosch. Makes you wonder why they picked marelli.
My idle is also a tiny bit rough but still in tolerance. My mates fiat punto idles worse than mine lol.

I haven't filled up with 98 yet, will do once this tank runs out. I always fill up at BP, but the cheapest 95 petrol there is.

I'll try to toss in a bottle of injector cleaner aswell, maybe that helps.

 

[ttg4l]

It'll be worth doing a compression test, someone else on here had an idle problem that ended up being burnt exhaust valves - very common, and generally caused by using 95 octane fuel.

BG44K and Normfest OT100 are two cleaners I can recommend, if you're searching for one.

 

[alfiesadog]

Another thing if the revs hang excessively on gear changes, I'd suspect the clutch switch.

 

[Blue_Bora_TDI]

1.6 has clutch switch? I'll check that ASAP, my tdi had a broken clutch switch and acted the same way

 

[Blue_Bora_TDI]

Clutch switch and brake switches are good, just checked.

I tried running an open intake and it seemed to be a little less laggy and hanging in the revs. Also a bit faster, and gave it a slight bit more torque down low. Is that common on the 1.6?

 

[ttg4l]

Clutch switch and brake switches are good, just checked.

I tried running an open intake and it seemed to be a little less laggy and hanging in the revs. Also a bit faster, and gave it a slight bit more torque down low. Is that common on the 1.6?

Yes the air box is terribly designed internally, there's a separate passage that's blocked off on one end, but still lets intake air flow down it from the other end. There's also a restrictive cone on the end - but it can be argued that the cone helps air flow smoothly (at the cost of about 1cm of intake size).

It'll be worth sealing shut the hot air intake flap inside the air box if you get it open. It is based on a thermostat that opens to let hot air in to speed up warm up times, then close when the air coming in is too hot, but it is common to fail open and let hot air in all the time.

 

[Blue_Bora_TDI]

I was thinking of making a good Cold air intake anyway; is that better? I have a k&n CAI that fits perfectly with a 90° bend. I also have a k&n breather filter for the breather tube that connects to the airbox.

 

[northpole]

just modify the airbox and put a sport panel filter in it.... look in the how2 section... unless you want to loose some bhp because the kn will suck in to much hot air from the engine bay(unless you make sure it has an extra cold airfeed and built a box around it)

something you'd already know if you'd just take the time to read some of the tuning topics... the airbox design might not seem good but with a few little modifications to it, it'll be way better than most CAI systems, especially if you are still running the standard turbo, intercooler and boost pipes.

 

[ttg4l]

just modify the airbox and put a sport panel filter in it.... look in the how2 section... unless you want to loose some bhp because the kn will suck in to much hot air from the engine bay(unless you make sure it has an extra cold airfeed and built a box around it)

something you'd already know if you'd just take the time to read some of the tuning topics... the airbox design might not seem good but with a few little modifications to it, it'll be way better than most CAI systems, especially if you are still running the standard turbo, intercooler and boost pipes.

He's got an NA 1.6, so no turbo, but otherwise I fully agree. You'd need a proper heat shield built otherwise the K&N is just going to end up sucking in hot air and causing a bunch of detonation.

I was thinking of making a good Cold air intake anyway; is that better? I have a k&n CAI that fits perfectly with a 90° bend. I also have a k&n breather filter for the breather tube that connects to the airbox.

One thing to note for the breather, it's currently connected to the airbox, so there's a small vacuum pull on it from the intake, which the K&N breather filter assumingly will not provide.

I'd keep the stock air box, but delete the hot air flap mechanism, anything else won't really do much for the 1.6. Anything I've ever tried to free up air flow has just resulted in it drinking noticeably a lot more fuel, but hardly any gains to show for it - hence why I have the stock air box now. Of course you can go for the CAI if you want a bit of extra noise, perhaps some small gains, and don't mind the fuel consumption.

 

[northpole]

yeah i overlooked the op's question and basically replied to the first answer... but yeah non turbo engine, don't waste money... engine swap it 1.8t for the win or go stupid and drop in an r32

both will put big smile on your face (not so on the insurance though)

 

[Blue_Bora_TDI]

I just want a good daily driver. I have a tuned bora tdi to drive in for fun.
But the rev hang makes the car awkward to drive in the city; especially after being used to the direct throttle on the tdi.

 

[ttg4l]

The 1.6 definitely can be a good daily, it can easily get 40-45mpg on the motorway, and 35mpg around town. Cheap to service and maintain too.

Can you get a video of your rev hanging?

 

[Blue_Bora_TDI]

Just took a video. Incidentally, it actually stopped with the rev hanging today(sort of).
It now does it sometimes on shifts.
In the video, shifting from 1st to 2nd shows the rev hang. The rest seems normal shifting(I just hadn't noticed yet)