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, Wed, 13 Nov 2002 08:33:36
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I have an 86 Turbo 16V that I just rebuilt. The history is as follows. Three years ago on a mountain pass the pcv valve failed open and the turbo blew most of the oil out the filler cap. Once the oil was low enough the turbo bearings failed and the rest of the oil went out the tailpipe.
We added 2.5L at the toll booth, coast 60 86Kilometers down to the next town and added anothe 2L of oil. 100K later I added another 2L and we made it to the ferry terminal, onto the ferry, and then home.
A new turbo charger, a head removal and some exhaust manifold studs and 'Cherry' went back together. Ffor the next two year it ran reasonably well but did seem to be developing a slight knocking sound. From time to time as we had vacuum leaks we'd get the cold start surging too. That's when we start the car, it idles great for about 30 seconds, and then starts to hunt from about 1500RPM to stalling. A few minutes driving usually cleared that up once the engine warmed up.
After the two years we fnally pulled the engine and discovered 2 broken motor mounts. Oil still looked good as did the cut apart oil filter so back in it went with a new clutch, and assorted bits plus of course the new engine mounts. Hmmmm. knock was still there. I bought a Saturn loaner car for my wife and figured I get right at the car but now it's more than a year later and I finally rebuilt the engine.
Give how bad the #1 and #3 rod bearings were it's a wonder the thing didn't throw a rod. Dimensions were all within spec. I installed new rings, bearings, water pump and o-rings etc. and then lapped the valves and put in new valve seals. Again the guides were right in the middle of factory specs.
Once it was back in the car I turned it over without the injectors wired or the spark plugs until the oil light went out and the lifters sounded a little less rattly. Then in went the plugs and on went the injector wires and on the second try the engine ran like a brand new car. No rattle, smooth as silk.
Minor coolent leak from the drain plugs but once that was tightened up the engine seems just perfect.... until now.
We have about 120km on it. It still had the cold start surging so I started chasing it. Checking vacuum lines. All the rubber grommets and gaskets have been replaced. Lots of new vacuum lines. I used throttle body spray cleaner to clean the TB plate. After that, I put the hoses back on and started it up. Now I have an awful situation.
It starts perfectly, runs for about 30 seconds smooth as silk at just over 1000RPM. Then it starts to surge a bit but this time as I rev it up it misses something terrible and I almost get liquid fuel out the tailpipe. We are talking really rich. Black smoke, with some blue oil smoke too and it just doesn't run. All four plugs are black with soot where during the first 120km they were a nice brown colour.
The boost gauge goes from the 1/4 white up to 2/3rds white as the engine oscillates back and forth. If it were a MAP system I'd say that the higher manifold pressure would trick the engine controller into thinking that the throttle had been opened and it need the extra fuel for acceleration but obviously the the AIR MASS sensor must think that amount of fuel is going into the system.
With the AIR MASS meter disconnected (Engine light goes on), and the pipe from the TB to the intercooler removed the engine functions in limp home mode. I can block off the AIC and the engine stays running but there is definite suction there. Unblocking it causes a momentary surge and then the idle drops back down to running rough.
I've checked the O2 sensor after the engine warms up and it reads very low 0.1V up to 0.3V. Very very rich.
I'm kind of lost as to where to go next for diagnostings. The CAM to Flywheel timing was perfect. Any chance I might have jumped a sprocket? We've kept the RPM under 4000 and want to stay that way until 2000km.
Short of buying a new AIC or computer I don't know what to do now. I'm somewhat experienced at Fuel Injection as I designed a system that's used for Honda VTECs that are installed in Hovercraft and Aircraft. But there I used a MAP system and had a CAN bus link back to the PC that showed all engine parameters. Diagnosing problems there was easy but what confuses me is the first 30 seconds of engine operation are so smooth and nice and then it goes to hell.
Any thoughts?
Thanks
John
posted by 64.180.68...
, Wed, 13 Nov 2002 08:33:36
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