ARH
28-10-2011, 05:33 PM
Can anyone diagnose this problem?
First, let me say how fantastic these forums are. I’ve been helped immensely - and saved a lot of money! - by diagnosing problems through reading about other people’s problems! This is the first time I’ve ever posted on a Forum, so here goes.
tdi 90hp with Bosch injection. 2002. ALH engine. 114K easy miles.
Last week I experienced starting problems – engine spinning over erratically like there’s no compression. Diagnosed it (from this forum!) as a sticking anit-shudder valve.
Examined the anti-shudder valve this morning – it was stuck shut. Inside, the EGR wasn’t too dirty, so I bought a can of Winns EGR Cleaner and sprayed it directly into the EGR valve to free up the anti-shudder flap. Worked fine – problem solved.
However, I noticed that there wasn’t a steady draw of air into the EGR – there was popping and blowback. As the engine was revved and I sprayed, there seemed to be almost as much air coming out as going in! Stuff was definitely coming out as well as going in because my hand and the spray can were black with oil and Wynns EGR cleaner!
This concerned me – I expected a steady flow of air rushing in. I clipped the hose back onto the EGR and took the car for a drive, and it drove and accelerated perfectly, as it always has. Yet, somehow, the 'blowback' from the manifold doesn't seem right at all!
Now let me back up three years. My dad owned this car from new, and had no trouble until 81,000m. It came back after the 80k service, but the following morning it belched large clouds of white smoke on startup and ran erratically. This cleared after a few seconds, and then it ran smoke-free and smoothly. It’s done this every morning since then - there's now 114k miles on it!
Nobody was able to diagnose the problem definitively at the time, but a competitor mechanic said it had been overfilled and that oil had gotten into the cylinders causing hydrostatic resistance and bending one or two of the con rods a result, thus shortening them fractionally. This in turn reduces compression,and it's expelling unburned fuel until it gets warm enough to fire on those cylinders – hence the smoke. Definitely plausible.
However, it still runs smoothly, accelerates well and it has done 33,000 miles since then without getting noticeably worse.
Further, I know that the original mechanic realized his fault before returning the car to my dad, so the excess oil was removed the same day it was put in.
Because of these factors, I’ve harboured a slight doubt about this diagnosis.
Now I’ve discovered this problem today – ‘blowback’ from the inlet manifold - I'm wondering if the bent con rod diagnosis is wrong - ?
Can anyone tell me what might cause the ‘blowback’ symptoms at the inlet manifold?
Could this be linked to the smoking problem?
My limited knowledge suggest some sort of valve trouble, yet the car ran smoothly and accelerated perfectly - ?
It would be just great to diagnose this problem accurately and with certainty.
By the way, the turbo failed at 97,000 (the bearing failed) and fractured the housing, filling the intercooler full of oil. Had it repaired successfully.
Any help/insight would be appreciated - thanks in advance for any/all interesting theories that might teach me something new!
First, let me say how fantastic these forums are. I’ve been helped immensely - and saved a lot of money! - by diagnosing problems through reading about other people’s problems! This is the first time I’ve ever posted on a Forum, so here goes.
tdi 90hp with Bosch injection. 2002. ALH engine. 114K easy miles.
Last week I experienced starting problems – engine spinning over erratically like there’s no compression. Diagnosed it (from this forum!) as a sticking anit-shudder valve.
Examined the anti-shudder valve this morning – it was stuck shut. Inside, the EGR wasn’t too dirty, so I bought a can of Winns EGR Cleaner and sprayed it directly into the EGR valve to free up the anti-shudder flap. Worked fine – problem solved.
However, I noticed that there wasn’t a steady draw of air into the EGR – there was popping and blowback. As the engine was revved and I sprayed, there seemed to be almost as much air coming out as going in! Stuff was definitely coming out as well as going in because my hand and the spray can were black with oil and Wynns EGR cleaner!
This concerned me – I expected a steady flow of air rushing in. I clipped the hose back onto the EGR and took the car for a drive, and it drove and accelerated perfectly, as it always has. Yet, somehow, the 'blowback' from the manifold doesn't seem right at all!
Now let me back up three years. My dad owned this car from new, and had no trouble until 81,000m. It came back after the 80k service, but the following morning it belched large clouds of white smoke on startup and ran erratically. This cleared after a few seconds, and then it ran smoke-free and smoothly. It’s done this every morning since then - there's now 114k miles on it!
Nobody was able to diagnose the problem definitively at the time, but a competitor mechanic said it had been overfilled and that oil had gotten into the cylinders causing hydrostatic resistance and bending one or two of the con rods a result, thus shortening them fractionally. This in turn reduces compression,and it's expelling unburned fuel until it gets warm enough to fire on those cylinders – hence the smoke. Definitely plausible.
However, it still runs smoothly, accelerates well and it has done 33,000 miles since then without getting noticeably worse.
Further, I know that the original mechanic realized his fault before returning the car to my dad, so the excess oil was removed the same day it was put in.
Because of these factors, I’ve harboured a slight doubt about this diagnosis.
Now I’ve discovered this problem today – ‘blowback’ from the inlet manifold - I'm wondering if the bent con rod diagnosis is wrong - ?
Can anyone tell me what might cause the ‘blowback’ symptoms at the inlet manifold?
Could this be linked to the smoking problem?
My limited knowledge suggest some sort of valve trouble, yet the car ran smoothly and accelerated perfectly - ?
It would be just great to diagnose this problem accurately and with certainty.
By the way, the turbo failed at 97,000 (the bearing failed) and fractured the housing, filling the intercooler full of oil. Had it repaired successfully.
Any help/insight would be appreciated - thanks in advance for any/all interesting theories that might teach me something new!