Running Bad Under Load ?

[VanhireBoys]

Gents
I have just driven my Turbo from Galway to my homeplace in Donegal ! Car ran no problm until I got about 2 hrs and 100 miles. All of a sudden when the engine is under load ie boosting or when I put the shoe in - it dosent want to respond.. It just misses and pops. For the last 50 miles I had to be very ginger on the throttle to avoid this...

If I really nurse it no problem - Starts and runs fine. What I am thinking is Dave screwed the emissions to 1.6% CO and left it without the lambda for the NCT. I I already cheked forvacuum leaks as I am inclined to believe its fuel starvation.

I am figuring its either fuel pressure ie pump or AFM. Is it known for an AFM to have a step change ?

I'll take any suggestion from you lads as I will have to get it sorted fairly lively !

Thanks Gents

 

[robwright]

Donal I had a similar thing once after doing the clutch on mine. It turned out that one of the plugs for the crank sensors was slightly dislodged. Still connected but a little adrift and not making a good contact. Resecured and all was well again. Might be a quick and easy one to check.

 

[944Turbo]

Have a close look at the rubber junction pipes to intercooler and onto the throttle body.

 

[Lowtimer]

If it suddenly started doing it after two hours of running, then something suddenly changed, and that does not sound to be like the AFM. You might indeed had a failing fuel pump or AFR, but my first port of call would be a complete pressure leak test of all the turbo plumbing, because I think you probably had air going where it ought not to go.

 

[PSH]

Hi Donal

If after checking everything the guys have suggested fails to find the problem check the function of the dump valve( recirculating valve) I suspect this may be your problem. If it is I'd recommend you upgrade to a Bailey DV30.

Regards

Pete

 

[VanhireBoys]

Thanks for the suggestions lads ! Reall appreciate it []

Well I started with the crank sensor ! No problem .. Disconnected the plug and checked connections - No problem nice and secure ! A failed crank sensor usually manifests itself as a non starter or above a certin rev the car will cut and mess irrespective of load... it was good to check this to rule it out !
All pipes and recirc valve checked and ruled out
Found a slightly loose intake pipe - Thought I had it .. No good - back to drawing board [:'(]
I checked the fuel pressure - No problem 2.5bar running and 0.3 rise at load .. Leakdown was no problem either
I took the car to an elderly VW mechanic who lives local - He loves the GTi Mk1 Golfs and done a tune on my 924. He connected up a co meter as he said she was running lean ! 1.6%CO at idle and 3.15% CO revving ! This proves no issue with the AFM

What I forgot to mention is that she will idle all day and if you really are gentle with the throttle she is fine
Sink the shoe or a load and she spits back through the airbox and backfires like a WRC ..
Had the dizzy cap off and there is no damp or cracks.. I replaced it a few years ago and it looks fine..!

I am going into my late fathers garage now to take the cap off again and see if I can replace the rotor arm ...

It seems that she is throwing sparks all directions under load and it will be fun tommorow if I have to nurse the old girl home with only half the power of a 2CV []

 

[peanut]

From your description it sounds more like a vaccum leak problem or low fuel pressure /flow problem to me. A vaccum leak would really upset the air/fuel mixture in the inlet manifold.[] How did you test the vaccum system ?
There are various ways to test the vaccum system but smoke is the best .
http://youtu.be/FfiQ7qWiG-M
If you want some excitment you could try propane gas or carb cleaner lol []

Your fuel pressure sounds low to me I take it it is a 16 valve ? I would have expected a higher idle pressure ? perhaps 3.0 Bar ? and at least a 0.5bar increase under load. might be worth checking the specs on your car as I am not sure what it should be.

Another potential problem could be the AFM . Might be worth substituting a spare to see if there is any improvement.

PS
here is the fuel pressure and flowrate for 87 onward cars. Looks like your fuel pressure is way down

 

[VanhireBoys]

WellGuys
Just a swift update for yous. I indeed had to nurse teh car 150miles form Killmacrennan to Galway.. It was 40mph on Lurgybrack hill and I overtook some git in a Suzuki jeep outside Charlestown. Not too bad in fairness... Got here now.

Dizzy cap and rotor will be here on Monday from the OPC as they have to come from Germany .
In the meantime I am taking out the DME and KLR control units tonight to test the Throttle position sensor and Airflow sensor back as far as the DME.
I will get another look at all the vacuum/pressure pipes again...

I will take the DME and KLR units themselves to work tommorrow or Saturday if I can get peace and check them for dry joints as just a by the way and another rule it out job.. I am very reluctant to start levelling blame on them but its one less thing to rule in or out. Just sommit to pass the tim until the Rotor and Dizzy come on Monday.

Dave, Sean, Dennis and Greg my trusted spanners in Fallons are going to have the pleasure of her company on Tuesday if I am not successful on Monday...! This will testr them !

I am also open for suggestions as welll lads.. Nothing will be disregarded... With this issue I have to keep an open mind so keep em coming !

 

[Lowtimer]

ORIGINAL: peanut
Your fuel pressure sounds low to me I take it it is a 16 valve ?

It's a Turbo.

 

[peanut]

ORIGINAL: Lowtimer

ORIGINAL: peanut
Your fuel pressure sounds low to me I take it it is a 16 valve ?

It's a Turbo.

are all the turbo's 16 valve ? don't know anything about turbos never been interested frankly.
However if that is the case then the OP's fuel pressure is well low which was my point[]

 

[PSH]

ORIGINAL: peanut

ORIGINAL: Lowtimer

ORIGINAL: peanut
Your fuel pressure sounds low to me I take it it is a 16 valve ?

It's a Turbo.

are all the turbo's 16 valve ? don't know anything about turbos never been interested frankly.
However if that is the case then the OP's fuel pressure is well low which was my point[]

Turbo's are 8 valve, gives them far more torque low down before getting the full benifit from the turbo. A standard turbo uses a 2.5 bar fuel regulator, modified cars need a 3 bar or better still an adjustable fuel regulator. OP states reading of 2.5 bar increasing by 0.3 under load, looks fine to me.

Pete

 

[peanut]

thanks Pete I shall remember that . I wasn't sure as i have had no experience of the turbo motor only 928, Lux and S2's but the Bosche fuel injection and engine management system is essentially the same in operation so the rest of my advice is hopefully useful..

 

[PSH]

ORIGINAL: peanut

thanks Pete I shall remember that . I wasn't sure as i have had no experience of the turbo motor only 928, Lux and S2's but the Bosche fuel injection and engine management system is essentially the same in operation so the rest of my advice is hopefully useful..

All advice is both useful and welcome, I wasn't picking fault, I just happen to have been here a number of times and thus passing on my own experience.

Kind regards..

Pete

 

[VanhireBoys]

ORIGINAL: peanut

thanks Pete I shall remember that . I wasn't sure as i have had no experience of the turbo motor only 928, Lux and S2's but the Bosche fuel injection and engine management system is essentially the same in operation so the rest of my advice is hopefully useful..

Deffo was peanut.. And thanks again to Pete and all you guys who are putting suggestions into the hat.

In teh meantime I tested the TPS right back to the ECU's and all good. Ranging from 3.89k - 456 ohm on one side of the pot to 568 - 4.01k ohm on the other side .. Throttle open contact was perfect as well

Airflow meter was all good. I tested at the ECU as well and put the meter on the dash facing out and moved the airflow meter by hand noting the results ... Wheres that bit of paper now....!

Both the KLR and DME control unit covers were removed and the PCB's inspected for dry joints and bad connections. Well they were in great condition - No nasties found and I looked under a big magnifying glass

Coil checked for breakdown. about 5 ohms on the 2 small connections and between one of the small and main connection about 10k ohms was noted

Roll on Monday when I'll change the cap and rotor. If that dont work I will change the coil ...[]

 

[VanhireBoys]

Well lads .. The bits landed on Tuesday.. I got the dizzy cap, rotor fitted... No difference ... Got the coil fitted .. No difference [:'(]

Its smoother on tickover as a result.

I nursed the car out to Daves on Wednesday where Dr.Rooney spent all day Thursday on it.. Sean is a real good troubleshooter and is a K and L jetronic guru. Still he is stumpted.....

There is only one route I can go now and I absolutely hate to even suggest doing it as it goes against all mine and Seans principles ... Change the ECU control unit and KLR for a known good one. Just to rule them in or out


This is the last roll of the dice .. The car has been down for a week now and the weather is superb... Typical

If one of you lads have an ECU / KLR knocking around I'll definately take them off your hands.. I'll cover whatever it costs.. Apparently the ECU is the same for a US car so it should all be fine but ill check it up anyway

 

[Dockrell]

Donal,
I have seen similar symptoms with an MGB after the oil level was checked - the dip stick was replaced incorrectly which allowed it to rotate and touch a plug and plug lead. This was only noticed late in the evening - when the bonnet was lifted there was a rather good light display from all the sparks.

Could not find a mention of the ignition leads being replaced - that could be the problem.

Mike

White 2.7 automatic

 

[PSH]

Hi Donal

Seems your not having much luck... Well I persuaded my son to read through all of the replies so far to see if he had any ideas. While he spent 10 mins reading through everything I also went over it all in my own head to see if I had missed anything. Now this may sound like teaching how to suck eggs and all that and something that both garages should have checked but the one thing that hasn't been mentioned as checked although it should have been one of the first things to do is the plugs? Have you tried replacing these, in case one has blown? anyway my son finished reading the thread and said " no mention of plugs, without seeing the car he'd go for blown plug, change plugs!"
So since both of us came to the same conclusion after reading what's been tried thought it best to pass it on just in case it had been missed...

Pete

 

[VanhireBoys]

Thanks a million lads .... I replaced teh plugs themselves when it happened first..The ones that came out were in good shape despite a wee bit of a gap... The leads themselves were also changed for a new set of BERU items last September before the 50th celebration.... Thanks for that Mike

We are starting to look at the ECU itself as all the fuel pressure/folw is normal from the pump and Sean reckons that its a weak mixture that is making her cough and backfire when you put the boot on. I theory that I have is the ignition is not advancing properly making it misbehave under load. The ECU controlls both ignition timing and fuelling so we are might go this was even though I am sceptical to say the least !

The AFM is working fine as well as this was checked right back to the ECU plug and the live readings are about 0.5v to 4.5v closed to open.

Really appreciate the help and suggestions fellas... Tell your son as well Pete I said Cheers []

 

[PSH]

I wonder if it's worth turning the ECU potentiometer one click clockwise which IIRC increases fuel by 3% and see if it makes any difference, there are other settings that give even more fuel plus advancing/retarding unfortunately I can't remember all of the settings.

Regarding the leads it is worth rechecking these as even though they are new they can be easily damaged when removing from the plugs. With the engine running does the rpm change or faulter when moving the lead cap from side to side. Be careful though for obvious reasons.

Pete

 

[sulzeruk]

Try a compression test as your head gasket could be on its way out.
Alasdair