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"

ive been driving it to work dayly and seeing some patterns.

when I start it and pull out on the road I seem to have a cloud of white smoke following me and is very weak on power. at first I thought well it's just vapors from a cold engine, kind of normal but it seemed a bit excessive. I do not think it has a blown head gasket, no coolant loss.

Im wondering if I have a stuck injector and the gas is leaking past and giving one of the cylinders a spurt of gas and causing it to become flooded in that one cylinder? I know about the leakdown test but dont have a fuel pressure guage yet , but maybe I can crack the fuel line after parking and also after letting it sit overnight or for an hour or two and I'd expect to see a little spurt of gas when I crack the line open. If the pressure dissipates all on it's own maybe it can prove my theory of a stuck ( open) injector.

I have some spare injectors and got the parts, filter some o rings etc to rebuild them so maybe I can spend some time rebuilding my used injectors and then pull the fuel rail and swap them. Ill pull the plugs first and see if I have one that looks any different from the rest.

I think maybe when I get going it blows that excess gas out and runs sort of normal. Probably not great for the rings.

it seems really weak under about 2K and from 2K to 3K it has more power until it shifts and then seems weak again at the lower RPMS. Ive had lots of other volvos and none seemed this weak at the lower RPMS..

I dont think it's a clogged cat because it will make power and rev up.

i can try swapping the air mass meter from another volvo and drive it , and see if that makes a difference.

It idles at about 1000 RPM but seems to shake more than normal during idling. maybe its sort of pulling a bit but it's not lurching ahead when I take my foot off the brakes. It should idle a bit slower but I think that will make it shake more. If I can slow the idle a tad maybe it wont be pulling as much and maybe that contributes to the vibrations.

I should recheck the timing with a light. I could try to advance or retard the timing a little and see if that makes a difference in running. the distributor has only one way to go it so I dont think it s possible it is mis-timed by one tooth and there is only so much movement of the distributor ( its at the back of the engine)

I have a cheapo chinese copy of a volvo distributor I can try. maybe i can swap that in as a test. Ive had the sensors fail a couple of times but usually I found that would create a no start condition or maybe just die suddenly. It starts fine, I dont think this is a issue with that sensor. at one point I could buy the sensor from rock auto but they seemed to go into no stock and I bought he plate with the sensor before for about 100 bucks. when I tried to replace it again to keep that sensor in stock at home, all they had was this cheap distributor. it comes with the cap and rotor but when I saw the quality of the rest it was real garbage. I bet the sensor and plate can be removed and put into a volvo distributor. right now it has a distributor I simply pulled from a working car the same year.

the way it runs I wondered because it seems a bit like the distributor isn't advancing properly, that might cause low power at certain revs but most of that is determined by the ICU. i wonder if replacing he electrolytic caps it the ICU or ECU might change anything?

I'll do more once I can get time off with the car when its not pouring out or too dark. i should check compression and see if I have a weak cylinder or if they look even.
other than vibration at idle the engine itself sounds ok.. no knocking or anything unusual.

long thread and I appreciate the help and ideas. thanks Guys ! I'll report back once I can try the above things, that might give me better info on the symptoms and help isolate some things. I's not failing to start or dying in traffic but there is something not right with it and whatever the issue is I think it crept up on me slowly and wasn't a sudden failure. I don't think it's lost compression but this I can verify with a compression test.

it's an 8 valve. the distributor is at the back of the block and it has the TDC sensor in there , not on the bellhousing. no turbo, Its a Bosche system.

i have other cars with the newer system with the TDC sensor on the bellhousing and the little box to to check the codes. this is an 88 so it does not have the code reader box. I seem to recall there still being a way to check codes but you had to make up a little part with an LED?

it seems quite sluggish when cold especially. after running a couple of tanks of new gas it might be a wee bit better..
when it idles it seems to vibrate more than it should. It seems to shake the exhaust and that seems to sort of vibrate too but I dont think there is anything loose or abnormal with the exhaust..
head gasket is ok. temp is normal. I can' t seem to find any air leakage around the intake.

i dont think the cat is plugged I can get tit o rev up and go up hill and stuff but it just doesn't feel very strong or responsive.

I have a parallel post about the head gasket on my 240 , it has the TDC sensor but most of it is the same otherwise, different ICU. maybe I can swap the injectors or some other parts , maybe the fuel pressure regulator, to see what difference that makes.

good question, How could I test that?
the only time I had a problem with a cat, it fell apart inside and I had to bash it around and get rid of the porcelain honeycomb stuff inside, then it was ok, but that was a different car. I'm not hearing any weird noises but the exhaust did seem to shake a bit more than normal come to think of it. It seemed to have not a rough idle but I couldn't figure out why the engine seemed to shake more at idle than normal It's idling pretty steady but a bit high , maybe 1000 RPM but it also seems to vibrate in a way that's hard to describe. sort of a droneing noise rather than a happy tick tick tick..

I think I pulled the tranny mount out and looked at it , decided it wasn't broken and put it back in. I was wondering if I had backed my tailpipe into a curb or something and maybe mashed it a bit that way. thought maybe it was hitting the body somehow.

That's not something I've considered. Thanks for the idea.

good question, How could I test that?
the only time I had a problem with a cat, it fell apart inside and I had to bash it around and get rid of the porcelain honeycomb stuff inside, then it was ok, but that was a different car. I'm not hearing any weird noises but the exhaust did seem to shake a bit more than normal come to think of it. It seemed to have not a rough idle but I couldn't figure out why the engine seemed to shake more at idle than normal It's idling pretty steady but a bit high , maybe 1000 RPM but it also seems to vibrate in a way that's hard to describe. sort of a droneing noise rather than a happy tick tick tick..

I think I pulled the tranny mount out and looked at it , decided it wasn't broken and put it back in. I was wondering if I had backed my tailpipe into a curb or something and maybe mashed it a bit that way. thought maybe it was hitting the body somehow.

That's not something I've considered. Thanks for the idea.