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Discussion Starter · #1 ·
Haven't had a chance to look much at my car problems, but I'm kind of thinking it's not the APC that's the problem.

When I unplugged the solenoid, I get way less boost, so it is doing something.

When the car is cold, I usually get full boost until it warms up.

When it boosts, it seems to keep backing off, like the APC thinks there is a problem and is doing its job.

I took my old 2.3 turbo out for a blast at the weekend, just to keep it running, and one of the lifters had stuck or something... a horrible tappety rattling noise, like a diesel! And.. it drove _exactly_ like my new CSE does... same boost, same power. Eventually, the lifter started working, and suddenly... whoosh


All this makes me think that the cause of my problems are still a misfire, that was not cured by the new DI.

I probably will try swapping the APC solenoid just in case, but I don't think it will do anything.

Now I think about it that way, it sort of does feel like a misfire. Also, it does seem to stall easily when pulling away in 1st - that may just be the higher gearing though


I will recheck the plug gaps, since I used a nasty old set of feelers. My question is, what else could cause a misfire? Would I be wise to run a compression test while I'm checking the plug gaps?
 

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Mine regulary misfires due to the DI being on its last legs. When mine misfires, it feels awful. There's a real shakey grumble when you press the accelerator and the car shudders when at idle, however, it's not noticeable on over-run.

If it is a misfire, you don't want to be driving it while misfiring as unburnt fuel will go to the cat and that's the best way to kill it, causing your car to fail it's next MOT (and they aren't cheap either).

I find that when mine misfires, a short, sharp whack or two with the palms of your hand either end of the DI will normally fix it.

Hope this helps.
 

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Discussion Starter · #3 ·
Thanks for the reply... I bought the car recently, and I replaced the DI almost straight away because of a very nasty misfire. It certainly is much better since then... smoother, no "hiccup" on idle, more torque and power and sometimes full boost (never did that before new DI). But still not 100%, hence my post.

I'm just waiting for someone to say "burnt valve"...
 

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Alright, "burnt valve"

Do a compression check first though, as it could be any number of things.

What are the plugs like? And the plug bodies? (You are using NGK BCPR7ES11s of course!)
 

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Discussion Starter · #5 ·
Well....
the plugs are new, cos I fitted them right away, but they are BCPR7ES (i.e. not -11) gapped to (I hope) 1.1mm although I do intend to whip them out and double check with a decent feeler guage.

However, according to a recent thread there actually is a difference, other than the preset gap. I did notice how not-parallel the electrodes are at 1.1mm ... I wonder if it makes a difference?
 

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FYI - My misbehaving Aero (only mildy unhappy) was improved with the following:

New sparks (1mm gap)
IPT air filter (replacing tired old one)
Move to Optimax
Reset and adaptation run
Replace small vaccum hose to maifold and boost gauge which had a largish hole(!)

Now much happier - although still paranoid about the occasional , almost subconscious blip at tickover (predicting DI failure I suppose)
Boosts 1/4 into red
 

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John, as it seems to be temperature related, other possibilities are the intake air and coolant temp sensors.

Certainly a compression test will be useful in elminating/identifying possible causes.
 

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Discussion Starter · #8 ·
I've run a compression test, and all seems well, I think. How much do you guys turn the engine over when doing one? I gave it 6 turns about. Anyway, I got between 160 and 180 psi on all of them. Is that close enough?

Would a compression test detect a fault hydraulic lifter?

The plugs don't look sooty at all, and the gaps were OK. Can temp sensor (air or water) problems make the engine run lean too?

Can anyone point me to the procedures to test these two, as my searches haven't turned it up yet... thanks!
 

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Discussion Starter · #11 ·
Right, I found coolant temperature sensor resistances in a post by BillJ on The Other Board...

Bill said:

 
20-30 K ohms at -30 deg C
7.0-11.4 K ohms at -10 deg C
2.1-2.9 K ohms at 20 deg C
1.0-1.3 K ohms at 40 deg C
0.565-0.670 K ohms at 60 deg C
0.295-0.365 K ohms at 80 deg C
0.24-0.26 K ohms at 90 deg C
0.14-0.16 K ohms at 110 deg C[/b]
I measured:

2.6K @ 20C
1.3K @ 40C
0.7K @ 60C
0.35K @ 95C ish

Probably close enough I would say - anyone got any opinion either way?
 

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John, I would follow faero's lead and do the plug gaps a little tighter. The gap will open with time. 1.1 mm is the the maximum recommended gap, IIRC. Why set them at the maximum gap, if they're going to widen? I would try adjusting them to 1.0 mm and see if it makes any difference - it doesn't take as much effort as doing resistance measurements at the temp' sensor! FWIW, my plugs are set @ .9 mm, and I rarely ever get a misfire or a miss under acceleration/boost. Another thing: I, too, have witnessed plugs where the cathode wasn't properly aligned above the anode. I simply twist them back so they're centered directly above the anode.
 
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