RWD - A strange combination of symptoms

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A strange combination of symptoms 200 1988

help needed, sorry in advance for long read. TL;DR is at bottom.

Hello all. My name is Nick and I’m new to this site. I’ve owned two Volvo 200 series vehicles and have a solid amount of automotive experience. I’ve heard good things about this board and am hoping one of you guys can help me out. First things first:

Vehicle info: 1988 Volvo 240
Engine: (not so) Professionally swapped-in b230f from a 1993 Volvo 240.
Trans: M47 5 speed
Miles: 268K on broken odometer

I’ll start at the beginning. Picked up car and had a weird lope at idle like maybe a fuel injector was ever so slightly congested, you know, like an spaced out soft miss. Was not worried, it’s an old car and certainly the engine is not new. Even so, inquired about the sound and mechanic said it’s been sitting for awhile so it’s bound to run a tad rough. Touché. Drive about 3 hours home, once I’m in the RPMs (freeway driving) drives perfect, miss at idle is barely noticeable and only someone familiar with a well-running redbloco might notice it.

Fast forward several days, car has a few hard misses and no start instances. Mechanics had left MAF partially unplugged and battery had an internal short. Cleaned out corrosion on MAF and replaced battery. Everything is good, still idles a little wonky.

One day I start car in the morning and don’t let it warm up, have to get brother to school. Put it in reverse and start driving and boom dies right there. No start (cranking only) for about 10 minutes. Catches finally and runs fine. “That was weird, relay or something, maybe?” Forget about it. Fast forward two weeks or so. Only issue in those two weeks was long crank but always fired up and ran fine.

Recently driving back from lunch break. Start car, seems okay albeit a little rough at idle. Whatever. Suddenly starts idling VERY rough, as if there were an enormous vacuum leak or it was firing on two cylinders. At light throttle engine shakes violently, missing HARD. At speed it’s a bit rough but fine, no hard misses like I had encountered earlier with my disconnected MAF. When I come back down to idle starts running like shit, thick white smoke from exhaust. Appears to be running significantly rich but smoke is white, not black. Think fuel pressure regulator or MAF.

Get home and get to troubleshooting. First thing, replace plug wires and plugs. Plug wires are corroded as hell inside and plugs are black with soot, obvious red flag for the rest of the work on the car. That being said a lot of the work looks very tidy but come the f**ck on guys. Anyways, replace those, no success. Take car to auto parts store where friend works. On break we do some trouble shooting.

I replace MAF they had in stock for my motor—except for the old one is a hot-wire type and this new one has a little chip (like a computer chip) in it instead. Still has a 6 prong connector and housing is nearly identical so I figure screw it and throw it in. No change. Removing sensor puts car at default values and it idles way better. This happens with either sensor. MAF seems to be eliminated as cause even though symptoms seem to point to it.

I think, maybe it’s a huge vacuum leak. Spray carb cleaner on intake manifold gasket, around fuel injector ports, around flame trap, etc. and idle never stabilizes, at least from my input.

Do some research, thinking maybe TPS although the one on it looks brand new. We replace the TPS with one from a slightly older Volvo motor but with same connector and appearance. No difference whatsoever. I use a jump wire on the connector prongs to see if I can trick car, no change. TPS appears to be adjusted as faint click can be heard when moving cable slightly from resting position. Reinstall previous TPS.

Replace ignition coil, no change at all. Pull vacuum line off fuel pressure regulator, no drip or smell. Clamp 3/8 hose on back of FPR to see if the fuel is maybe draining back into tank due to FPR failure. Idle does not improve.

Clean connections on blade fuse by ignition coil with a wire brush, no change.

Inspect accordion hose to engine to see if unmetered air is getting past the MAF. At this point I realize a good amount of yellowish oil in the intake hose. I am initially extremely dismayed as it appears to be coolant contamination, although I figure there’s a chance it’s just nasty oil that mixed with some starter fluid and Seafoam throttle cleaner I had gotten all over the intake hoses. Check oil and coolant, neither appears to be mocha colored or cross contaminated. Obviously, gross oil mixed with white smoke immediately makes me think of a head gasket problem but I’ve had literally 0 overheating problems. None whatsoever. Coolant level has remained the same the entire length of this ordeal.

Oil in intake + aforementioned symptoms make me think vacuum leak from some part of the flame trap. Open up flame trap. Mesh screen is dirty but not super cruddy. Has black bits in certain areas but you can still see the entire surface of the mesh and tubing still allows air through. Oil separator box does not appear to be leaking.

Fast forward to this morning. Start it up to move out of my brothers way. Put it in reverse and mid reverse stalls completely. Won’t pop start, nothing. Cranking cranking cranking, nothing. New fuel pressure regulator is in the mail. Have no idea at this point what it could be. Any advice is VERY appreciated.


-in reverse on cold start will stall out if attempting to back up
-extremely rough idle, reminiscent of serious misfire or enormous vacuum leak
-large amount of engine vibration between idle and like 1/4 throttle (no tach in this vehicle)
-at idle on start up huge plumes of white smoke, gas smell
-after running fine at higher rpms, engine will almost idle out when you get to a stop but will almost always catch itself
-oil in intake hose

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    A strange combination of symptoms 200 1988

    Assuming the below (at bottom) is your current state (and I assume you have all 1988 components on a 1993 engine) I'd

    1. Inspect and pull the sender. Chance the intake tube is broken/ perforated inside.

    2. Test the main fuel pump.

    3. I'd pull the main pump and replace the fuel filter

    4. Check the connector on the distributor. That can break internally.

    5. Pull all fuses, keep in order, wire brush/ clean the fuse-box connectors and the ends of the fuses, reinstall

    6. Pull the spark plugs. If they were clean and are now soiled with gas ....

    7. Check for spark and see if it'll fire with some gas squirted into the intake

    8. Check timing belt.

    I just went through a 1988 240 (with a 1990 engine but that's irrelevant) that had been sitting 4-5 years. It would run OK, then run rough, stall, restart ... but not start again the next day. Plugs were wet with gas each time.

    Had, failing MAF; bad dist cap and wires, bad gas (owner had drained and filled but must have dissolved some old varnish), broken sending unit, clogged fuel filter, noisy main fuel pump, bad IAC, bad O2 sensor.

    "Update: the vehicle as of today will not start. No idling and dying, stalling, whatever; it will not start period. Replaced FPR, did not do anything as expected. Car is at near full tank."
    240 drivers / parts cars - JH, Ohio

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    A strange combination of symptoms 200 1988


    Very interesting thread going on here and with lots of information as Art said!

    It sure sounds like you have the 1993 engine transplanted in front of the original 1988 body.
    You have wires coming from the distributor and going into a harness. So that means they took the old one from the other engine so it all fit and runs.

    Since you do not know the amount of regular maintenance on this engine, I would consider not only the ignition tune up but a compression check just to see what you have on the cylinders for wear.

    Another thing, Peel back the top timing cover and look into for freshness of the timing belt too.
    If it doesn't look dry and brown or oily, try to loosen the tensioner nut, under the rubber plug in that cover and let it tension things up for good measure.
    Also, make a big note somewhere on the car, because your memory doesn't travel when sold, that this is a 1993 engine. The timing belt is different than the 1988 engine! It has rounded sprocket teeth in there!

    Since the car "sat for a while--??" He might have given you a warning?
    I would be real suspicious that the gas tank was near empty too!
    In that scenario, the gas ages more quickly due to the amount of air in the tank above the gasoline.
    Gas evaporated and oxides itself or at least all of the good stuff in it goes away.
    When the happens it starts to get thicker or even congeal.
    Consequently, This is not a good thing for the filter as it restricts output flow and leads to improper atomization pressure to the injectors.
    You drove the car for three hours and pushed a half a tank of fuel through the filter, so maybe, it's just now had enough jelly?
    This causes both symptoms of rich and lean misfires from the injectors and fouling of the plugs at any given time. If the pressure is low on the rail that is a big thing.

    I'm not sure this is going to be a "new one part fix!"
    Some TLC is needed to bring up the "vital systems up to specifications needed for the engine to run smoothly.
    Good luck on the FPR "only" idea.


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    A strange combination of symptoms 200 1988

    Hi Nick,

    I, for one, really appreciate the background you give, both on your skills, and the car. This information is so often kept secret from us until pried out in long sequence. TL;DR be damned.

    Only one question at this point, so we all know what we're working on: How much of the engine swap included engine management? Fuel and ignition systems are vastly different 1988 to 1993.

    And one comment. Having an FPR on order kinda tells me you're doing this as part-swap diagnostic. Do you have a means of measuring fuel pressure? A voltmeter to check A/F ratio at the oxygen sensor?

    Edit: Re-reading, I see one red flag. "Clamp 3/8 hose on back of FPR to see if the fuel is maybe draining back into tank due to FPR failure. Idle does not improve. "

    At idle, over 90% of the fuel pumped should indeed be flowing back to the tank. If you pinched the return hose shut, you should have felt the resistance to squeezing it, and the net result should have been to greatly enrich the fuel. Perhaps the regulator is stuck shut, which would cause the same extremely rich mixture, or the fuel pump is not reaching the regulation pressure, meaning nothing is being returned to the tank.

    Welcome Nick.
    Art Benstein near Baltimore

    I didn't like my beard at first. Then it grew on me.

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      A strange combination of symptoms 200 1988

      I’ve seen you answering a ton of people’s questions and I for am glad someone still goes out of their way to help a dwindling group of enthusiasts—especially in the US.

      I’m pretty sure the fuel system was changed. Has injectors that do not remotely resemble the kjet set up on my old ‘82 b22. As far as ignition system goes I’m not quite sure. What should I look for to identify the two?

      I’ve done a certain degree of parts diagnosing but that’s mostly due to both a lack of knowledge and lack of tools/work area as I recently moved. I do have a volt meter and I will do what I can according to advice given but I would need specific instructions as I generally avoid electrical problems like the plague—though evidently they are catching up to me. I will have my friend bring his fuel pressure gauge over this weekend.

      Another addendum, when I clamped the hose on the back the idle actually worsened slightly, but ever so slightly.

      Thanks for the replies!

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        A strange combination of symptoms 200 1988

        Most likely the '93 engine has all the '88 management, given the job of swapping the electronics is considerable.

        The '88 used Chrysler/Volvo ignition, timed at the dizzy. You can recognize it's control unit attached at the washer bottle. The '93's dizzy has no wires except the high voltage plug wires, and is timed at the flywheel.

        Also, you'll find the '88 had a three-pin idle air valve and its hot-wire AMM had a CO adjustment, where the '93 has a two-pin valve and no adjustment for the AMM, and if the LH2.4 came with the '93 there will be an OBD-1 diagnostic box on the left strut tower for emissions codes.

        Best book for these cars aside from the factory manuals is Bentley.

        I'm afraid anything made after 1980 begs a little interest in electrical, or it is just guesswork.

        Art Benstein near Baltimore

        Venison for dinner again? Oh deer!

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          A strange combination of symptoms 200 1988

          I does certainly seem like they kept the original engine management. There is a box by the washer reservoir labeleves “volvo” matching your description. My AMM was also hot wire type. Would putting in the AMM from a 93 not work, despite having a 6 pin connector? That’s what I did so if that’s not compatible I could definitely see it messing with my diagnostics of the AMM as the “new” part isn’t even correct.

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            A strange combination of symptoms 200 1988

            Update: the vehicle as of today will not start. No idling and dying, stalling, whatever; it will not start period. Replaced FPR, did not do anything as expected. Car is at near full tank.

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              A strange combination of symptoms 200 1988

              I have a carbed 240, so know that it will run without a lot of the additional electronics. It will run without an AMM.

              Basically, check for spark and fuel. And make sure the timing marks on the cams and distributor are where they are supposed to be at TDC.

              White smoke? Is water/antifreeze getting sucked in? How's the compression?
              1980 245 Canadian B21A with SU carb, M46 trans, 3:31 dif, in Brampton, Ont.

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              A strange combination of symptoms 200 1988


              You might want to take a look at this to kinda give you an idea of where you stand in the electronics arena on your car. Check out the AMM numbers to see what's up, if anything?


              Having the change out of the FPR, not doing anything, doesn't surprise me.
              It does help to hold the pressure consistent under all conditions.
              It does vary the amount of fuel held in the rail, especially, for times of acceleration or power demand. But it doesn't make more fuel available, if it cannot get it at all.
              The pressure must stay at a certain level or even go up slightly, when it varies the amount to the return line back to the fuel tank.

              To be more definitive, the need of getting rid of the rich/lean conditions that could be a faulty AMM model number or a bad functioning one. That's a hard window to close, definitively, without a truly good replacement.
              But the white smoke and black plugs are contrary to each other. IMHO there are too many fluctuations happening, within this self-tuning engine.
              We need to get it back to some basic system functions getting right.
              I remember you thought it was a vacuum leak symptomatic condition, so an intake manifold gasket would be a good start too. When cold it might be at its worse at low idle or engines speeds but never goes away! That's when I have read they are shot too pieces!

              Getting a pressure reading or a fuel quantity value established, along with a compression test, to see what we are working with.
              It's unlikely the injector screens are clogged, as the filters work good for a long time, but the pressure spray or cone shape has to be right.
              We need to tidy things up a bit.
              Finding out what was done, when and that is all we can do so far.

              Like Art I'm curious to what else is different about the 1993 LH 2.4 engine.
              I have one and they are a slightly different and I mean slightly different even from a 1992!
              It could be as simple as the injectors that are different, especially, if it came off a 1993 with the 3.1 LH system.
              It's anyone's guess and even more on my side!

              I don't know if they are different, but, I know the fuel rails changed features after '88 and they added a service port, for pressure checks, that's upside down!
              I'll never understand the reason to do that except to point any spray of fuel downward, for safety reasons and/or make it hard for any mechanic to fit something on there, with some cussing involved!

              Did your engine keep that special rail or even get the original manifold off the1988 LH 2.2?
              Hopefully, a new gasket was used, if that move was done?

              Keep us posted, as this is interesting!
              I Hope the link gives you insight to the changes over the years!


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