Terrible starting / poor idle / big flat spot / stalling / Hot valance with Mexican Beetle 1600i

[vwjim]

I'm trying to solve the following, on a low mileage 2004 1600i Mexican engine

Terrible starting both when hot or cold
Poor idle
Big flat spot
Stalling
Hot rear valance / discoloured paint

Someone previously has changed the following;

New throttle body
New air temp sensor
New TPS
New head temp sensor

I've connected up the laptop to the ECU and cleared the faults relating to the head temp & the inlet temp. These faults have not return.
I've replaced the ECU relay for a new genuine replacement

The TPS value at idle was 62 and not in the 40-60 range, so I've adjusted that so it is now 59
I've checked the timing as described on 1600i.de and it seems okay, though the engine won't idle for 3 minutes when in Basic Settings?

The resistance measured across both temp sensors, (and the old ones that were removed), are all virtually identical when the engine is cold

I've NOT yet checked the fuel pressure, as I don't have a suitable gauge yet.

I noticed at idle the injector time was anything between 4 - 5.1ms, where as the listed range is meant to be 2.5 - 3.5ms? If you move the throttle off idle the injector time reduces back into the listed range and runs much smoother?

The spark plugs look fine. All the hoses look fine. The rubber manifold connectors / hoses all look new. No leaks detected.

Anyone got a bright idea what might be the cause(s) of these symptoms......?

Thanks.

[ps2375]

To me, with the info you have given, it must be running rich at idle w/ the throttle closed. The cause...no idea. I have no clue what version ECU these use. Is the Fuel Pressure Regulator connected to a vacuum source and is it operating correctly? Does this have a MAF (like something from 2004) or an Air Meter like something from the early 90's?

[vwjim]

Thanks for your reply.

The fuel pressure reg' is connected to the manifold as per factory layout. And there's no leaks on the pipework, but as I've not got a pressure tester, (yet), so I've not been able to test if the pressure changes.

No MAF sensor. It has a TPS and MAP connection back to the ECU.

Regards,
Jim

[vwjim]

Tested the fuel pressure today. 3 bar with slight flicker in the gauge as the RPM increases or decreases. But generally very stable.

[Piledriver]

Is the thermostat stuck partially closed?
The late Mexican wax pill thermostats can fail closed.(not fail safe) unlike the German bellows setup.

I vaguely recall the vacuum hose going into the ECU occasionally leak in the ecu on that generation.
Line/ecu should hold vacuum.

[vwjim]

The faults occur on cold or hot engine, starting is bad all the time, but I will double check them up make sure the engine hasn't suffered a period of over heating.

No vac' leaks on ECU's pipe or the fuel pressure reg' pipe.

[Piledriver]

The cam on those it timed so low as you should be able to put a few psi (<5)on the intake and check for leaks.
It should hold for awhile, just slowly bleed past the rings.

Otherwise the low vacuum could just be a worn motor.
MAP setups always run richer as they age, since DJet, reduced vacuum is a sign of wear.

A weak ignition can also cause a rich look and "feel".
Those have same decent ignition as mid 80s Golfs, should bite hard if you get across it
Assume you have checked timing.

[vwjim]

Yes, checked the timing.

I'll see if I can rig up a way up leak test as you described.

Thanks

[Piledriver]

Yes, checked the timing.

I'll see if I can rig up a way up leak test as you described.

Thanks

Same setup as a boost leak check on a TDi, 2" rubber coupling and a pvc cap in one end, with a tire stem popped in.

[vwjim]

Perfect. Cheers.

[vwjim]

New coil pack sorted all those issues. Now the Injector duration at idle is within range, where before the duration was 3x too long.

Only thing now is the CO reading out of the exhaust is a bit high. HC and Lambda figures are within range.