16v 2.0 1995 lack of power after 1 minute of starting 'Help required please!'

[How's My Driving? 10]

Hello All,

 

I've recently bought my first Corrado 16v 2.0, (a long time ambition) and have just hit my first real big issue.

 

She'd been absolutely great for the first three months as I drive to work and back everyday (approx 25miles total)except for a few initial idle hunting issues then on the way home the other night, just as I was about to turn into my road I lost all power, the car revs were low and threatening to stall however putting my foot on the accelerator provided sudden, seemingly random bursts of power, I managed to limp her home and since this time the problem has persisted.

 

Every time I start up she runs fine for a minute or so then the the power goes to pot again with intermittent revving and she struggles to idle, eventually staggering to a stall. I did notice that there was a lot of oil around/above the spark plugs (embarrassingly this was the first time I'd checked them since purchase, a personal lesson learned there!) however I've cleaned this out and will be changing the rocker cover gasket so don't think this is related. I did also notice the spark plugs were black and charred so could be un-burnt fuel.

 

I've been checking various parts, Accumulator, ISV and will be replacing the fuel filter when it comes through the post however I've not been able to get to the root of the issue, does anyone have any suggestions?

 

Also whats the best way to test the two pumps?, Would just disconnecting them be ok to see if the same thing happens or will this mess up the fuel pressure/supply?

 

Thanks,

Frank

[Cong 10]

Have you checked the wiring to the throttle body? I found on mine that 2 of the 3 cables had weathered fell apart and once I replaced them poor intermittent idling and losing power was sorted. Just a thought?

[dr_mat 0]

Did you get a VAG-COM scan off it? If you can, get it scanned for faults and check the temperature readouts from the various temp sensors. The engines run on an enrichment program during the first minute after cold start and don't turn the lambda/maf on until afterwards so seems likely there's a fault with one of those.

[How's My Driving? 10]

Have you checked the wiring to the throttle body? I found on mine that 2 of the 3 cables had weathered fell apart and once I replaced them poor intermittent idling and losing power was sorted. Just a thought?

 

Thanks Cong, I've been chasing up every lead since I posted this. What seems to rule most problems out is the fact she runs fine for the first minute, I'm guessing while she's in cold start mode. This has led the trail to look at the Lambda sensor and/or wiring and the MAF.

 

Was your issue constant or did your car run fine for the first minute or so?

 

Thanks.

[How's My Driving? 10]

Did you get a VAG-COM scan off it? If you can, get it scanned for faults and check the temperature readouts from the various temp sensors. The engines run on an enrichment program during the first minute after cold start and don't turn the lambda/maf on until afterwards so seems likely there's a fault with one of those.

 

Hi,

Thanks for this, this is what I've been finding out when looking at the other blogs however none mentioned the temp sensor so I'll check this as well. Do you know the best way to test the lambda, MAF and temps or in fact their location?!?

 

From what I understand so far the MAF is in the front left (as you look at the engine bay from the front of the car) of the engine bay under the plastic cover that's over the fuel injector distribution thingy. When the problem is there all I need to do is disconnect and see if the problem changes at all. Same with the lambda but this is at the top of the exhaust.

 

As for the temp sensor I'm stuck on this as I'm not sure where to look for it. I've been told there are two of them, one for in car read out (some sort of RTD) and the other is a bigger one but I don't know where...

 

Anyone know what I should see if I put a multimeter or 12v supply across each of them?

 

(I did try using VAGCOM but nothing came up, starting to wonder if I used it properly).

 

I'll be trying this all out at the weekend so fingers crossed! (I'll post my finding on here as well) Also changing the Fuel Filter for good measure.

 

Cheers,

How's

Edited January 7, 2016 by How's My Driving?

[dr_mat 0]

Don't know the 16v engine myself but the easiest way to test the lambda is to read the measuring blocks in vagcom while the engine is running.

The temp sensors you need are on the thermostat housing on the VR6, but don't know where they are on the 16V. As before you can also read their raw values from vagcom...

[davidwort 0]

The 16v has temp sensors on the side of the head, around the water outlet flange, one for dash gauge and two others for ecu and idle circuit I think, with the ke jet system on the 2L if you disconnect the lambda and temp sensor to the ecu it should run in basic k jet mode, I.e. Ignoring the lambda input and if will use a fixed temp value built into the ecu. This can get around lambda issues for testing.

the 16v can have issues with the metering head if it gets water into it or has been tampered with, other favourites are poor pattern lambda sensors, hall senders on the dizzy breaking down and oil in the distributor. As long as the fuel pump isn't groaning or making variable pitch noises it should be good. You might also replace the fuel pump relay in the fuse box.

if you take the metering head top off the air box lift it up and check the air plate/fuel plunger moves freely and smoothly as this affects distribution of fuel to the injectors.

Also check for any splits in the inlet rubber connectors or any damaged vacuum lines, and check the idle switch on the throttle body is switched with the throttle shut and that the wiring to the switch is good, you can test the switch for continuity when pressed.

the 2l 16v has an electronic module on the side of the metering head that controls the differential pressure in the system, this affects fuel delivery by acting against the air plate plunger, it has basically the same function as the warm up regulator on a basic kjet 1.8 16v and allows fuel enrichment and I think ecu control from lambda input

if the plugs are black it's been running rich which could point to the temp sensor or lambda, seems more likely to be fuel delivery than the ignition side

you can do a fuel delivery test by pulling out the injectors and spraying them into jars for a few seconds, I've done this by jumping the fuel relay connectors and using the battery earth as a switch to power the pump, you jack the metering head/airbox top up and lift the air plate a little to open the fuel distribution, spray pattern and amount of fuel delivered by each injector in 30 secs or so will tell you a fair bit.

lots to go on there.

if I can dig out some old vag manuals I have they might have some more info on component tests and fault finding, but there's a lot you can do to rule out things.

[How's My Driving? 10]

Hi David,

 

That's a lot to think about, thanks for the info.

 

It has been running rich as the plugs are very black so I'll be checking the temp and lambda first. From what you say disconnecting either may change the engine running which would point to a fault with the sensor in question or wiring, good to know, thank you.

 

I did see a little oil in the distributor but not much, are they expensive to change?, (Actually are they the same as a Mk3 Golf?, I have one that I can rob parts off!)

 

I've checked rubbers and vent lines and all looks fine.

 

Also really keen on doing an injector test and if all looks good just giving them a good clean to get the fuel distribution spot on, anything to watch out for when doing this?, As I understand it the injectors are plastic and a pain to remove without damaging.

 

Any fault finding info would be great so see.

 

Thanks,

How's

[dr_mat 0]

(It has to be said I'm only assuming that the 2.0 supports OBD2 connection to vagcom..)

[Cong 10]

Glad your getting some very useful information, my issue was generally all the time plus any of the vacuum hoses can cause problems plus the air box can be an issue. good luck.