So with the AMM unplugged the car should resort the fuel injection to a sort of limp mode, where it injects fuel based only on RPM and throttle position. This can be helpful for diagnosing mechanical problems (rather than fuel injection sensor problems), since a plugged cat will make it misfire badly under load either way.

It will run badly, but if it will run under some load and at higher RPM's with the AMM unplugged that points you to a sensor issue. If it does the same thing it could be mechanical.

You didn't like leave a rag in one of the intercooler pipes, did you? I've done stuff like that too.

Quick update. Remove the exhaust and it runs fairly well at idle, light and medium throttle. Success thinks I. So I think I'll unplug the MAF and try that. Opps its still unplugged from last night. Plug it in and it will barely run at all and stalls.

Check the exhaust I removed and it seems perfect, zero obstructions at all.

Pics and vids tomorrow

OK, so as I said last night, I removed the exhaust and it ran the best it's run in over a year. I could actually drive it around the subdivision without slipping the clutch or a bucking bronco impression. When I got back I figured I'd try it with the MAF unplugged again per Drew's suggestion. Guess what, it was still unplugged from the night before. Plug it back in and it won’t run again.

So if you're following it would sort of run, but badly with the exhaust on and the MAF plugged in, but if you unplugged the MAF it would stall. Remove the exhaust and it's running 'well' when the MAF is unplugged, but stalls again when it's plugged in.

Right now I'm thinking it's a MAF issue. The plastic cover fell off when I touched it, so some foreign material could have got into it over the last couple of years. The exhaust is in mint condition, everything looks almost new, other than the studs that sheared when I separated the downpipe from the elbow the other night, every fastener and slip joint came undone with ease. I've never had an easier time.

So, i guess I'm looking for another air meter to try. Anyone got one for sale or return? Also since there doesn't seem to be a blockage in the exhaust I guess the seals on the turbo are gone from the gunk that was coming out of the flange in the video the other day. Si I suppose I need a $50 e-bay T3 rebuild kit then put the whole thing back together. I do have a spare, but unknown turbo I could put on.

Driving it. https://www.youtube.com/watch?v=AYqF9Bu0NNA

Pulling in https://www.youtube.com/watch?v=Wu71TZ4sca8

Cat is perfect


Pretty much mint exhaust


Shopping list:
Air meter
T3 rebuild kit
Sundry turbo and exhaust manifold gaskets
High temp paint

Thoughts?

P.S. Honestly I'm not a total mechanical ignoramuses. I've built engines, done engine swaps, fitted LSD's to FWD Trans, built one car from two etc. etc. This things is just killing me

If you look inside the AMM is the tiny little 'U' shaped filament broken?

The black plastic cover on top of the AMM, is it a Bosch one, or an aftermarket one, or is the cover blank? I've had aftermarket ones be bad out of the box before.

Adrian Thompson wrote:P.S. Honestly I'm not a total mechanical ignoramuses. I've built engines, done engine swaps, fitted LSD's to FWD Trans, built one car from two etc. etc. This things is just killing me

We've all been there.

John

FYI, the only good way to check the cat that I know of is to hold it up to a bright light and move it around in front of your eye so you can look through a few of the square tubes at a time.

I wouldn't worry too much about the turbo, at least not yet. A bad turbo isn't going to necessarily prevent it from running well (unless maybe it's jammed and there's a dead rodent blocking things). The gasket between the manifold and the turbo tends to leak until things have warmed up and expanded. It doesn't look like there was much oil there, possibly just exhaust gases. I'd call that typical for a C900 turbo.

I would try swapping in another air mass meter. They can fail and make it a real pain to keep running. Every time I've had a failure they've run super rich - black soot from the exhaust and a stink. I seem to remember the oxygen sensor provides mixture feedback to the ECU which then works into the AMM calculation so you could put an O2 sensor in it, a generic one is typically cheap enough.

Major vacuum leaks and major intake leaks can cause all the problems you have described too.

Crazyswede wrote:Major vacuum leaks and major intake leaks can cause all the problems you have described too.

That was my first assumption, not found them. Also if it were just an air leak somewhere why would it behave differently with the MAF connected and disconnected

Geoff wrote:FYI, the only good way to check the cat that I know of is to hold it up to a bright light and move it around in front of your eye so you can look through a few of the square tubes at a time.

I can shine a flash light though it, or hold it up and look through it. Deffinitly not blocked at all, it's in perfect condition

Geoff wrote:I wouldn't worry too much about the turbo, at least not yet. A bad turbo isn't going to necessarily prevent it from running well (unless maybe it's jammed and there's a dead rodent blocking things). The gasket between the manifold and the turbo tends to leak until things have warmed up and expanded. It doesn't look like there was much oil there, possibly just exhaust gases. I'd call that typical for a C900 turbo.

That's great news, I was feeling very depressed at the thought of having to pull the turbo and work on that as well.

Geoff wrote:I would try swapping in another air mass meter. They can fail and make it a real pain to keep running. Every time I've had a failure they've run super rich - black soot from the exhaust and a stink. I seem to remember the oxygen sensor provides mixture feedback to the ECU which then works into the AMM calculation so you could put an O2 sensor in it, a generic one is typically cheap enough.

I started the car and ran it over 2,500rpm per the Bentley manual, then shut off and looked at the MAF, I didn't see the element glowing as it says it should. But again, if it were just dead, why does it change when it's plugged in vs unplugged?

Does anyone have a spare known good MAF to sell?

BTW, it's not a Bosch MAF, it's an aftermarket one

'88 means LH2.2, right? The one with the adjustment dial on the side? If so after looking around I finally found this, it came with my old SPG and the PO said it was rebuilt or checked out by these guys:


Shoot me a PM if you're interested...

Maybe its a Lucas injection car.

I've seen those aftermarket ones before, but the more worrisome part is that protective cover has come loose. It's hard to tell from your photo, but it looks kind of like the electrical contacts are a bit corrode-ey.

We didn't get Lucas cars in the US. Although he does sound like he may have worked on something with Lucas electronics in the past

That "Fuel Injection Corporation USA" unit is probably a rebuilt Bosch part (at least that's why my rebuilt unit was from them).

Damn, I've run out of Lucas smoke, I'll get some more next time I'm back in England


OK, here's another pic of the guts. Still hard to tell.


No matter, the outstanding Mr Hutch is sending me the Bosch one he has. As soon as that arrives I'll be fired up and ready to go wont I

Not to worry, the 'Honey'Do' list is long for this weekend plus looking after my Grandson tonight and Sunday when he will watch and enjoy both the F1 and Indy car race with me Who care's if he's only 13 weeks old, I failed to make either of my daughters race car fans, I WILL conquer the next generation.

Just got back from the post office, I must have just made the deadline or something because they said it should be there on monday. Hopefully this is the final hump to getting the car running!