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Old 07-06-2018, 11:03 AM   #26
lummert
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My LH 2.2 88 765 is very sensitive to any fuel system modifications. You could have several different issues adding up.
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Old 07-06-2018, 03:00 PM   #27
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So what do you suppose I should do? What should be my first steps of diagnosis?
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Old 07-06-2018, 04:16 PM   #28
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I feel your pain.

Have you checked the turbo for non-binding/free-spinning (cool, of course). A finder can check end play and rotation ease.

Our 230FT had melted catalyst in the converter, signalled by low vacuum; this after chasing too many other possible demons. That and undoing a PO's work in mistiming the cam finally ended my chase. What's two teeth among frineds?

I was easily able to look inside the CAT by undoing the front clamp and downpipe.
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Old 07-06-2018, 04:19 PM   #29
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Hey, thanks for your reply! I have checked the turbo and it seems to spin freely with ease, it only had minor side to side play (not hitting housing) and no in and out. I don't have a catalytic converter to cause any issues and if I check the cam timing again I'm going to go mad. About to try some new plugs and a junkyard knock sensor to see if that fixes the issues.
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Old 07-06-2018, 04:57 PM   #30
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Okay, but if the plugs 'read' okay and it runs okay with the knocker unplugged (unsure if that causes and ECU issues) it sounds like throwing parts like the madman these issues can make of us.

This reply is from a very helpful guy near PHX (ERI ) who knows these injection systems very well. His helpful tone is quite obvious.

"No work was done on the MAFs/AMMs other than testing, they both had the same 20 mV out of spec reading. They should be good for another 10 mV of drift, a bit over mid 30s mV out is where problems start. It is hard to say how long it will take for further drift to occur. Most enquiries that I get are from the Porsche 928 world. I always tell clients who have no nearby good mechanics who know Porsche 928s, that they should look for a mechanic who works on Volvos, as the Bosch electronics are “cousins” and a good mechanic should understand the theory.

Best regards, Rich"
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Old 07-06-2018, 05:24 PM   #31
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So... You're suggesting I change the MAF too? I do have a spare. I believe the ignition system resorts back to full retard when it stops receiving a signal from the knock sensor, therefore the fact that I saw no change when unplugging the knock sensor suggests that it is where the issue lies. With the head off the car while doing the head gasket job, I decided to clean the bowls of the head out with a wire brush on a drill, I left the spark plugs in. I am now worried that doing this may have changed the gap of the spark plugs which could be contributing to my issues, hence why I'm replacing those also.
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Old 07-06-2018, 08:57 PM   #32
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Ive definitely had my csi plugged onto my knock sensor and it went into a limp kinda mode...but it threw a CEL along with the code.
I'm having rich stumble/misfires while cruising that I was leaning towards knock sensor/AMM problems. Are you super rich while having these fits? As mine drops to <11.0 and stumbles at random while cruising.
I was also going to gap my plugs smaller, pregapped at .32 but I'm going to try ~.28.
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Old 07-06-2018, 09:07 PM   #33
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UPDATE:

I may have found the problem. While I was doing my head gasket I also swapped plug wires to some others I had around that looked to be in better condition. Well I checked the resistances of these "better" wires today and it looks like these wires are double the spec resistance. This would mean a much weaker spark. It actually would make sense if this was the issue. The power loss only really arose when my car was going full rich like in the 10s. I would assume it is harder to ignite a rich mixture hence why "rich misfire" exists. I believe the higher resistance plug wires aren't allowing for a good enough spark to fully ignite the mixture when it gets in these richer mixtures resulting in lower power. I'm about to leave to buy some new plug wires and then will install with my new plugs tonight.

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You could be getting a rich misfire at 10:1 of the spark is not hot enough to get a full burn.
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Old 07-06-2018, 11:19 PM   #34
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New wires were also out of spec. Swapped back in my old ones with the new plugs and voila! No more weird powerband flat spot.
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Old 07-08-2018, 02:21 PM   #35
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Good one! It's nice to figure weird stuff like that out. I've had plug wires look great and be out of spec or leaking spark. The factory spec is 500 ohms per foot. Even had fancy expensive plug wires let me down like that.
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Old 07-08-2018, 04:27 PM   #36
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The knock sensor has a proper torque spec. Get it wrong and it changes the output.
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Old 07-10-2018, 04:08 PM   #37
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Glad you got it solved. I'd checked and rechecked virtually everything,; changed parts, as you'd done, so I thought having both MAFs checked would give a firmer basis for eliminating one more possiblity. Neither are perfect, as my prior post says, but I was assured both are within spec. Hence, the issue had to be, an was, elewhere.
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