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Phil Thank you so much for your kind and detailed response , I really helps.
I was able to look at things on saturday as I got a little break in the weather and was off work.
I removed the plugs, they are the newer more expensive type ( iradium? ) with tiny electrodes, I did not see any real difference but I did note that plug #3 smelled like gas.
I undid the fuel line after it had sat overnight , there was no remaining pressure on the line so maybe it's leaking into cyl 3 I could check after an hour or two hours and see if there is still a squirt of gas when I undo the line. I think gas was leaking into cyl 3 and when I started and ran for the first block it would clear the cylinder out and I'd see a cloud white smoke.
I pulled the fuel rail and swapped the injectors from another 740. Just renewed the o rings. tried driving. no improvement there.
I had a look for any vacuum leak, I didd not get any gas from the line from manifold to the fuel regulator. I think the fuel regulator is working.
I checked the compression and got about 150 on each cylinder so I dont think it's a burned valve. my gauge is an old cheapo but it does seem to have compression.
I swapped the idle air valve. I do not have an EGR valve in this model I don't think.
I saw no change.
I checked the timing with a light. It was out a bit so I put it to about 12 degrees looking at the crank pulley and the plastic belt cover. it seems to have a 10, 15 and 20 degree mark so I put it as close to 12 as I can. that's what it says on the hood tag 12 degrees plus or minus 2 degrees. I did not seem to see the timing jumping all around in position. I think the timing and spark are ok.
I changed the mass meter from one from another car and drove it. It did seem to pick up and go much better. I floored it and it did have lots of power when I got it to open right up in sport mode. I got it up near 5 or 6 K and it pulled hard. I dont think the exhaust is plugged up.
when I removed the old mass meter I noted it was warm so I think it is pulling air from the exhaust preheater. maybe that valve is stuck but it wasn't really warm either.
I had previously tried cleaning the mass meter it had with mass meter spray but maybe that messed it up. I'm not sure if I'm supposed to use that spray on a mass meter with a preheater and I think this has the pre-heater. I did not use the spray on the one that's in it now.
the main problem now seems to be it has a very rough idle. Its not varying so much but it shakes hard at idle. I can get it down to 750 RPM but it shakes so much I insured my van to get to work because I don't think this engine shaking is healthy for the engine.
motor mounts seem ok it still shakes in neutral the shifter isn't moving about like it would if the transmission mount is bad.
I could try swapping out the 02 sensor, ECU, ICU, throttle position sensor, knock sensor. I could not find any cracks or air leaks in the intake system. I can try switching tmperature sensors or maybe test them in a pan of water to see where they open. I have a spare 02 sensor from another car and one that I probably replaced so I can try swapping them.
i removed the plastic intake from near the throttle plate and sprayed some carb cleaner in around the throttle plate with the engine running. did not see much difference.
I can hear the switch click when I take the throttle just off it's idle stop with the engine not running. I could check with a meter if that switch actually works or if it just clicks. I have a spare used throttle position switch so I can try swapping that out.
some great info was provided at the following link and i need to print that out and sort through it..
https://www.brickboard.com/FAQ/700-900/EngineSensors.htm
its a b 230F 1988 wagon with auto transmission.
I may be completely off but what I think is happening is that the ECU is missing some sensor input or getting bad input. at idle it is trying to compensate and it is sort of doing that about once per second or once per revolution, and maybe readjusting the fuel injector duration and that my engine is shaking because the computer is trying to compensate and can't establish equilibrium so it's constantly readjusting and not ever finding a happy place.
I have compression, I have spark, it gets gas, it runs, it starts ok, the plugs are not getting carboned up. Its running lean I think. fuel pump and fuel delivery are ok.
I could probably gain by having some tools like a gauge to check fuel pressure or an CO sensor to check if its lean or too rich.
I think the mass meter can be adjusted I've never tried, some mass meters have a plug over the adjustment. I don't think I've ever adjusted that. I dont think that's my issue now with the engine shaking so I'll leave that alone.
I might have solved the fuel leakdown issue, and I got the timing adjusted. swapping mass meters did seem to make a change. some hoses might be hardened up a bit. I put black tape where they go on to tighten them and a hose clamp. maybe I can source some appropriate line locally to renew some of them. I'm not sure where the cannister is. I can check it might be under the fender, drivers side. I think the EGR valve was used in a bit newer models. My van has one and it had issues with the sensors that report where the valve is moved to. I don't seem to have any of that on the Volvo.
I want to try pulling out the flame trap ,and clean it. its right under the intake manifold near the engine block. tihgt spot but I can see it.. I have a spare intake manifold gasket. It doesn't seem loose or anything..
its leaking some oil I think it's a pan gasket. the block seems clean and not oily. It isn't wet near the oil separator. I'll try to retorque the bolts for the pan gasket. oil leaks are not what I'm stuck on .
I feel like I'm going to find that ONE THING wrong and my methodology of troubleshooting might need to be improved to find it. I might be able to find a more systematic and logical approach and I know I'm all over the place with ideas. Im blessed with a few used spare parts and I even have a working pspare parts car I can go to .. so I can try swapping most things fairly quickly and look to observe changes.
I have an older oscilloscope , cod I connect that to the pulse at #1 injector? maybe I can learn about the injector pulse duration.
I'll try waving an un-lit propane torch around the intake manifold and hoses, maybe that could help isolate if I have a leak. I might see idle change if it can pull in propane due to a leak.
from the idle control valve to the plastic intake hose just past the mass meter there is a hose connection. I tried putting my thumb over that hose with it disconnected I have slight vacuum at that hose. I suppose I might hook a meter into the idle air valve and see if the thing is ever getting any power or a pulse. maybe it should get variable voltage, not sure. Maybe its not being "told " to work.
I'm completely lost but I think I just need to redirect my attention and perhaps Ive ruled a few things out. i think I had a stuck injector, time will tell if that's resolved, timing was a bit off but that's
I don't think its a mechanical issue, engine sounds normal, no knocks, valetrain sounds normal. I could check if the timing belt skipped a cog but it did have compression. i can try what you suggested and see if I can lift the belt cover so I dont have to remove the fan and alternator and drivebelts.
Thanks again to all who responded.
"the other Phil"
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