120 replies to this topic

[Jimbo]

There you go. Though to have a dump pipe blow out is some pretty serious pressure. Get that cat checked out!

[Ordex]

the blow out...

it is a bit rusty I guess

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[Ordex]

I have had a new secondary down pipe made up and installed a few days ago so I can again drive without gassing myself or melting the engine bay.

 

The intermittent boost is still there (limited most the time to 0.5 bar/wastegate pressure). The exhaust guy took a look at the front-side of the mid-pipe cat and said it was still intact. This doesn't rule out an exhaust restriction further down...

 

Not sure I mentioned this before as it didn't even register as being relevant, but it also starts from cold very rough most of the time (and has since I got it) - it will almost stall straight after kicking over and then almost stall on first few gear changes as well. After the first few gear changes it runs smoothly.

 

After doing some more reading around various threads it seems possible the ECU could have a sensor providing a dodgy value and be going into limp mode but never flash the CEL?

I've bought one of those expensive evo scan SSM1<->USB cables to do some interrogation of the ECU.

[Jimbo]

Usually the coolant temp sensor can do some bastard things. Its located behind the alternator and bolts into your coolant cross-over pipe.

[LukeFranky]

My first thoughts were coolent sensor as well. That or an air leak.

[Ordex]

I did accidentally break both the coolant sensor plug (just a little bit of the plastic) and crank sensor lead (it was stupidly brittle) when removing the alternator some time ago! I bought a new plug for the coolant sensor and repinned the loom into it (no soldering required), and re-soldered the new crank sensor plug on and heat shrinked it (as recommended). All up I thought I did a pretty solid job.

 

I can get hold of a OBD1 scanner in a few days (the evoscan cable will be weeks) - hopefully that will show up a dodgy reading?

 

Tonight I did the green/black plug diagnostic dance (everything clicking and appearing to work as it should). This must have also reset the ECU as the primary is making over 0.5 bar easily. Will see how we go tomorrow after a drive in to work.

[Miguel]

Shitty start is only in cold start, possibly starts low and lumpy then comes up to normal cold start high idle once it catches? I've had this happen a few times, both on the BG and my BC. Swapping out the AFM seems to have fixed it.

[Ordex]

Yep really low lumpy start when cold and then up to normal cold start high idle, but if I start driving straight away the first few times I go to change gears it almost stalls when I take the clutch back out and the revs drop.

 

This happened this morning when I drove to work, however I could make more than 0.5 bar boost - so it didn't cause limp mode.

When I jumped in the car at lunch time it did the lumpy cold start again and I was limited to 0.5 bar.

[Ordex]

Unfortunately the ECU scanner is OBD-II, so I'm going to have to be patient and wait for the evoscan cable to arrive which is SSM1.

Boost has been all over the place the last few days going from 0.5 bar limited one minute to full boost the next. I'm thinking electical gremilin given I've experienced how brittle some of the loom is...unless it's not haha

[Ordex]

Double checked my ECV rod this morning. Lock nuts were not locked on although the ECV itself wasn't rattling. Ran through the adjustment procedure again just to be sure. Hasn't made any difference

[Ewen]

Where abouts in aus are you? Im in melbourne i have a bg5 also. I also have a spare ecu for a twin turbo

[Ordex]

I'm in Hobart. I see by your other thread you have a 1996 BG5. I have a 7C ECU modified by Mines. What is your spare?

In case anyone is following along I've made a thread here about connecting to my ECU via the SSM1 cable.

[Ordex]

For some reason I decided to plug the black leads together and the CEL reported code 24 (ISC valve). YAY - a lead to work on!

Headed over to the YGTTT sticky and noted step 1 of troubleshooting - check intake is good.

 

Guess what, mine is not - duh.

The intake tract is joined to the primary with a silicon pipe. It has been like that since I got the car. I thought it may be dodgy and leak, and I guess the code 24 is occurring because it is - don't know why it never popped up before. Either way I think it would be best to replace the intake tract with a new part.

 

I read the entire manifold has to come off to do this job so what else do people recommend doing while it's off? Remembering everything in there is likely 20+ years old. I'm going to replace the remaining two coolant hoses I haven't done. What about fuel lines? Any gaskets? Anything else?

[Ordex]

So...the intake has been fixed (separate thread here).

 

While the intake manifold was off I replaced the coolant crossover gaskets and cleaned as much of the block as I could (found a hose clip, ball bearing and screws in all the grime!).

I replaced all fuel and vacuum hoses on the intake manifold itself, all PCV components (the brittle pipes broke as I removed the manifold) and removed, cleaned, tested and then re-wrapped the wiring loom (the original split tubing stuff was falling apart and covered in grime).

 

After some consideration of Jimbo's advice way back at the start of this thread I decided to source a VF14 secondary (with a wastegate) and put the original VF18 primary back on (see how it goes).

While I was waiting for parts to arrive I bought some 3.5mm nitrile hose from Advanced Fluid Solutions and did a full BBOD overhaul. I bought enough to redo just about all the vac hoses in the engine bay bar a few.

 

After spending a full day getting everything back together and double-checking everything I fired it up and idle was oscillating high/low and AFRs were all over the place. ECU had logged a code 24 (IAC valve)

 

I triple-checked all intake connections and decided to empty a can of UEC into the IAC, did an ECU reset and the idle was sorted!

Today I replaced the MAF with one of the other two spares I have and AFRs are looking healthier too.

I have only done a few short test drives, but it is feeling very smooth and boosting well. Fixing the air intake has also removed the ridiculously loud turbo spooling and BOV noises.

[Josh18]

Any more news on this? Great thread, I want to find out if you got it sorted in the end!

[Ordex]

Yes the saga continues!

My AEM AFR gauge slowly died and troubleshooting it, back and forth with AEM support, has been a big distraction. Finally got it fixed under warranty, so back to the real problem!

 

Injectors have been cleaned by a reputable shop, and I checked resistance and voltages at the injector plugs. Seemed ok, although grounds for both LH ones read about 0.5v (strange). Not sure if it should be concerning?

 

I gave the MAF a thorough clean and...wow does the car run smoothly off boost now! Smoothest since I bought it.

 

BUT...dispite this there is still a significant lean spot lasting for a number of seconds as manifold pressure goes north of 0psi.

When coming onto boost AFRs will briefly richen a little, then revert back to roughly 14.7, then richen fully and stay that way until manifold pressure returns to less than 0psi.

 

I can't tell if the car is bouncing between closed and open loop, or if it's always in open loop but just not able to deliver the fuel.

I tried disconnecting the o2 sensor to force the car to run open loop mode (couldn't think of any other way). The problem was still present, although AFR didn't revert quite as lean.

 

If anyone has *any* pointers about where to continue it would be much appreciated!

[Ordex]

Caught it on video

 

Boost gauge mounted on steering wheel. AFR mounted to right. Ignore the multimeter, I had it hooked up to the MAP sensor to check voltages were looking reasonable.

 

@ 0:05 it is on boost and AFR looks okay.

Then there is a gear change.

@ 0:11 it's back on boost but this time AFR initially richens a little then goes to poo.

@ 0:13 AFR it's back to rich.

 

I'm reasonably certain the 2 seconds of crappy AFR is causing knock and making the ECU fall into limp mode regularly.

[Ordex]

RESULT!!!

 

After more logging with a multimeter and evoscan watching engine load I figured everything going into the ECU was working as it should.

 

Based on this and pretty well most other causes being eliminated I decided it time to look closer at fuel system.

 

To continue the process of elimination I bought a walbro 255lph pump.

Today I opened the fuel tank and found a dirty and elderly walbro pump!

 

After installing the new pump initially things didn't look good. I went for a short test drive and AFR was all over the place. Rich then lean then rich. I was starting to worry I'd botched the pump install somehow and made things worse. But then it started to slowly look a little better. After a 30 minute spirited drive everything is looking spot on! AFR 14.7 in closed loop and moving straight to rich even before 0psi!

 

The car was 95% boosting correctly. Was surging a little right at the top, and hit limp mode briefly twice on the drive but fingers crossed this is something else and the main issue is fixed. Time will tell.

 

Thanks to everyone on here who has helped and offered advice! It's been a big learning curve and I'm sure there'll be more to come.

[duncanm]

great to see your making progress on this.. you certainly have perserverance!

[Josh18]

Well done mate!