morgan;c-148474 wroteWhat happened to the 740 ? Looks super clean

OH, I did sell a number of bits off the 740 to recoup some of the cost, including the wheels, front snow guard, boot spoiler, radio/amp, etc. Wish I had kept the wheels but they’re in good hands now with the Nowatzky clan.
8 months later
Finally getting around to the long-overdue coolant flush and was going to change out the ECU coolant temp sensor. I had bought a new one ages ago...do you think I can find it? Not in the plastic tub where it should be, or any of the other tubs of new parts. Bugger! FCP order on the way. Ordered 3 to have a couple spares as they are only $9 each LOL!

I’ve been chasing a problem of running rich on cold start-up and even though the resistance of the sensor measures OK back at the ECU (at least it did a couple years ago when I tried to diagnose this issue) I figure it’s worth trying a new one. Also, I started the car up for the first time in a couple months today. Somebody mentioned start it up then turn it off and pull plugs to see if any look funny. Well I started it and it didn’t run too bad...let it idle for about 30 secs then shut off. Pulled plugs and they were all wet with petrol...would that be normal? Swapped in some new NGK Iridium plugs (very cheap from RockAuto if anyone needs some!!) I noticed the ipd spark plug boots (metal ones that have the little internal spring clip that pushes onto the threaded stud on the ends of the plugs) seem to fit very loose on the new plugs...hmmm. Also noticed that the plugs seemed very oily around the base of the plug and the threads, but no oil visible on side of the head (indicating cam cover leak) so not sure what gives there, unless I previously wiped the oil off the side of the head?? The plugs were some Bosch platinum 4-prong ones that I must have installed ages ago??

My OCD had been going nuts as the lower radiator hose had one of those stainless steel cheese-grater clamps on it at the radiator end, while all the other hose clamps are genuine Volvo ones. That will be fixed now! Was looking for my bottle brush thing to scrub out the radiator surge tank but nowhere to be found. There must be a black hole in the shed somewhere hiding all this stuff that goes missing!
I've heard iridium plugs to cause problems. I use bosch WR7DC factory fitment
I agree with ramrod iridium plugs are great for late model cars but they prefer a lean burn operating environment that 1980s fuel injection systems cannot offer with narrowband 02 sensors.
carnut222;c-162108 wrote There must be a black hole in the shed somewhere hiding all this stuff that goes missing!
They likely went to Narnia with your missing socks.

I dream of finding volvo's in this condition. It's great to know there are people like yourself out there who are prepared to invest the time and love to keep them in such great shape. Seriously, well done.
ramrod;c-162109 wroteI've heard iridium plugs to cause problems. I use bosch WR7DC factory fitment
timbo;c-162111 wroteI agree with ramrod iridium plugs are great for late model cars but they prefer a lean burn operating environment that 1980s fuel injection systems cannot offer with narrowband 02 sensors.
They were cheap and a few people on Turbobricks, Brickboard or Facebook or somewhere (LOL) mentioned they were good, so I'll see how it runs once I get the coolant sensor swapped out.
Shame on me - I see that I bought the car in 2010 and have never changed the coolant! Fortunately it didn't look bad and no corrosion on the thermostat housing or head, so WHEW!
Found the elusive temp sensor in one of the storage tubs (aka black hole). Took a bit of effort to get at it. Used two long screwdrivers to get the connector off, and had to undo a clamp for the main engine wire harness to move it out of the way. Then used a 19 mm deep socket with 3/8 drive extensions with a U-joint in the middle. Got the new sensor in and tightened but don’t have the connector on yet. Of course the rotational angle of the sensor is slightly different so the connector needs to be twisted about 30 degrees to reinstall, and no hand clearance, so that will be a challenge!

That car looks like it just rolled out of the factory Greg.. so nice! This build looks like everything I wanted mine to be. Watching very closely :) :)

So the engine going in, is it a earlier or later one than the one in the car?

    Vee_Que

    So the engine going in, is it a earlier or later one than the one in the car?

    The donor engine and M46 is from an 88 740 HP Turbo, but will be using LH2.4. No plans to upgrade the engine as I think 160-180 hp is plenty for my use in a 240! :)

      Success! I had to use 2 long flat blade screwdrivers like chopsticks to twist the connector around and get it seated. Not fun but it worked. Hate to think if I have to remove it again as the spring clip is now on the bottom! Grr! Still need to pick up a bottle brush so I can scrub out the coolant bottle before I can top up the coolant and take for a test drive. I doubt it will be any different but who knows?

      Vee_Que

      So the engine going in, is it a earlier or later one than the one in the car?

      Also forgot to mention that although the B230FT donor engine I’ll be using came out of an 88 740HP Turbo, it is a Volvo factory replacement engine that was fitted to that car in the 2000s I believe so hopefully a bit fresher than an old 88 engine. It ran great when I took it to the Winton Fun Day before I pulled it out of the 740T, but it has been sitting in a shed for about 10 years now!!

        thetrough

        What happened to the nice blue 740?

        It wasn’t that nice in reality (interior was a bit trashed, dents on exterior, non-matching bonnet. I stripped every ounce (gram?) of extra weight out of it and took it to the Winton Fun Day shortly after I bought it to test out the engine and transmission to make sure it was suitable for use in my 240 project, then pulled out the engine, trans, harness etc. and scrapped the body. That was probably 10 years ago - time flies!

          Well as expected, same symptoms after coolant temp sensor replacement. I knew that wasn’t it as I had back-probed ECU terminals and coolant temp resistance was within spec, but everyone says “coolant temp sensor” so I had to try it. Symptoms are on cold start, it fires right up but after a few seconds it starts running rough and black smoke out exhaust. Rev it a bit for about 10 secs and it smooths out (presumably when O2 sensor is warm enough and it goes into feedback mode). Sometimes when hot/warm start it takes a lot of cranking, but no rich running.

          So, I know it is NOT:

          ECT (engine coolant temp sensor for ECU) or wiring back to ECU

          Earths (have been cleaned and checked)

          MAF (have swapped with no difference)

          ECU (have swapped with no difference)

          Plugs, plug wires, cap, rotor (all swapped with no difference)

          Fuel pressure (checked and within spec)

          Fuel (car does not have stale fuel)

          O2 sensor (new one installed and no difference)

          Crank position sensor (new one installed an no difference)

          This car DOES have a cold start injector, but I have unplugged the wire connector and no difference.

          Only other things I can think of that I haven’t checked or swapped out yet are:

          Leaky injectors or bad spray pattern?

          Leaky cold start injector?

          Poor valve adjustment? Car runs fine once warm.

          Blocked catalytic converter (would probably not cause these symptoms?)

          Ignition coil

          Ignition power stage/amplifier

          Any other thoughts?

          Guess I will just live with the minor annoyance until I put the turbo engine in and hope it doesn’t do the same thing then?!!??

          ramrod

          Idle air control valve

          Thanks @ramrod definitely something I need to look at...my partner and I were just chatting about it. I guess if the base idle or throttle plate setting is too low, or the idle valve is not functioning properly, during a cold start when the ECU tells the injectors to run more fuel, the idle valve should bypass enough air to go with that extra fuel and bring the idle up. IIRC the idle does not seem to be higher than normal after a cold start, so definitely could be something there. I do know I’ve checked the TPS position and I get the “click” just off idle throttle position, so the ECU should definitely be in idle mode. More to look into, and while I look at the idle valve I can also possibly remove and look at the cold start injector since they’re both buried below the inlet manifold!

            4 days later

            Update. Haven’t had time to check the idle valve or throttle setting as we’re on the road, but I have started slightly applying the accelerator when I do a cold start, immediately bringing the RPM up to 1500-2000 for 10-15 seconds. That totally eliminates the rough idle and rich running issue I had been seeing on cold start...so definitely seems to be dumping in extra fuel that it couldn’t burn at the lowish cold idle speed, which fouled the plugs a bit until you revved the engine and/or the O2 sensor and feedback mode kicks in. @ramrod ‘s theory of idle valve is sounding more and more plausible. Where do I send the reward $$? :)

            Brief update on the cold start rich running issue. I did a bit of investigation into the idle valve at @ramrod ‘s suggestion. We just got back from a 300 km trip so the car was warm. I pinched off the idle valve hose and the car died, which indicated to me that the base throttle plate position was a bit too closed (idle should drop to around 500 RPM IIRC). So I removed the throttle link rod, adjusted throttle stop to open throttle plate slightly, readjusted throttle position switch and link rod. Now when I pinch off the hose the idle drops to around 550 RPM, and when I let off it flares to about 1500 RPM (as the computer probably has the valve wide open trying to bring the idle up from 500 with the pinched hose) then settles down to around 800-900 RPM. I have yet to try a cold start - will do that when I take the car into the car wash on the next fine day and report back. The idle adjustment was very subtle, and I doubt enough to make much difference, but we shall see! Fingers crossed but I’m not hopeful at this point...if it is cured I’ll be cursing myself that something so simple as a very minor throttle adjustment could have such a profound effect!

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