Hey ozvolvo peeps,

I’m feeling a bit bummed cos I’ve gone and taken a pressure washer to my 740’s engine bay and now it won’t run right. Car is 1990 740 Turbo with LH2.4. I only got the car a couple of months ago and had been having a ball fiddling with it and tuning it up.

I’d troubleshooted poor idle, misfire, hard start, no boost issues already and it was running like a dream for over a month. I should have learnt my lesson as I’ve had bad experiences with pressure washers before.

When cold, car starts and will idle, if a little low, around 600rpm. I can leave it to warm up some, and the revs slowly slowly start to drop. If I apply throttle it will rev up, albeit misfire a bit. Then when left to idle once more, it will drop off and stall.

Once the car is warmed up, it will start but only run for a second before revs drop and motor stalls.

Initially, it threw codes for

3-1-2

Signal missing for knock-related fuel enrichment

Wiring break between EZK terminal 4 and FI #28

2-2-3

Signal missing to/from idle air control valve

Circuit fault to IAC or faulty IAC valve

Engine difficult to start; low idle speed

I realised the knock sensor had come unplugged so I cleaned sensor and plug and reconnnected.

I also cleaned idle air valve connections. I had already cleaned the idle air valve last month.

I reset the ECU and tried again. Codes were gone and it did seem to idle a little better. But still would drop off once warm and fail to idle when warm.

At this point I also unplugged and cleaned ECT and TPS and MAF.

I tried unplugging the MAF and idle would come up to about 700-800rpm and idle comfortably. But bog when throttle applied. Is that Norma when MAF is disconnected?

I then had a code for:

1-2-1

Signal missing or faulty to/from pressure sensor

MAP Pressure sensor

I assume that is for having unplugged the MAF?

I inspected wiring and did find a couple of wires that had slightly exposed wires on an injector and on the throttle position sensor plug so I wrapped them.

I also checked the throttle switch. Is clicking with slight move off closed. So that seems right.

When I clamp off hose from idle valve to inlet, the idle drops and then stalls so I assume it’s working?

I tried unplugging the O2 sensor while it was running but made no difference.

The main loom that runs kind of behind the alternator with the wiring for idle valve, knock sensor, ect, injectors is a bit of a mess and covered with lots of tape. I sprayed a bit of contact cleaner on the wiring and the next time I went to start, it cranked for about 10 seconds without starting (only time it did this). So I’m thinking that there is maybe a short or exposed wire down there somewhere?

I don’t know where my multimeter is so I haven’t been able to check any voltage or resistance readings.

The car is supposed to be going to a workshop this week for an exhaust (it doesn’t have one) and a roadworthy. But at this point I don’t know if it will make it. Don’t fancy paying a tow truck to take it 1km.

I feel like it would be beneficial to at least try another MAF and maybe another idle valve before I go digging around the wiring.

The way it seems to be fine until it warms up makes me think it’s related to ECT or O2 sensor but would they throw codes?

I did also change the oil just before I degreased so the O2 may have gotten a little bit on it from the filter? But I wiped it off with a rag.

The main thing I haven’t checked is is to see if there is a water in the distributor cos it’s a pain to pull. The way ignition is breaking up when revved makes me suspicious. That is my next port of call but would that cause a difference in ability to idle cold and hot?

Any advice would be appreciated. So disappointing when you put loads of hours into the thing to get it running right and then it gets ruined by the temptation to clean.

The distributer and the tape covers wiring are obvious to me whenever anything gets wet....

    You have possibly got water in the AMM and wrecked it, don't worry I've done it before

      When I clamp off hose from idle valve to inlet, the idle drops and then stalls so I assume it’s working?

      With everything running right, the car should idle at ~500rpm with the ICV blocked off.

      But if the car was running fine before this, then it's probably water ingress. The state of your wiring loom doesn't spark joy. You can get contact cleaner and go through each plug in the harness and give it a spritz to clear out any water that may be trapped, if problem persists I'd go with what Ramrod said and check the AMM and go from there.

        Ex850R

        The distributer and the tape covers wiring are obvious to me whenever anything gets wet....

        Pulled the dizzy this morning. Was much easier than I thought when I realised I could undo the 2 bolts to undo the whole dizzy rather than the 3 bolts for the cap.

        It was a little damp in the cap. A small patch of white goo (water, degreaser and oil I guess) was removed. Cap and rotor are quite worn. But not much oil in there. Gave contacts a little emery and threw it back on. Will of course get new cap and rotor when I have the funds. (Has new plugs and leads)

        Reconnected battery and started it back up and it was initially hunting a little. Revs were around 500 then jump to 650-700. Then back down to around 500. Did this a number of times before settling around 500. Idled for a minute or so then gave it some revs. Misfire seemed to have gone under revs. If I slowly slowly reduced the revs it would just sit on idle. Low - around 500rpm. Then stalled. Started it back up, tried to move it and it was almost cutting out when I’d apply throttle unless I was super gentle with pedal.

        Threw no codes after this.

        ramrod

        You have possibly got water in the AMM and wrecked it, don't worry I've done it before

        yeah I wish I just had a spare sitting on my shelf to try. The item on the car actually looks a little like the plug doesn’t sit flush on the metal body so probably could easily get water in there. I read on another thread that the cheap Chinese models are just as good as Bosch items?? So should I just try buying a brand new el cheapo?

        jamesinc

        When I clamp off hose from idle valve to inlet, the idle drops and then stalls so I assume it’s working?

        With everything running right, the car should idle at ~500rpm with the ICV blocked off.

        But if the car was running fine before this, then it's probably water ingress. The state of your wiring loom doesn't spark joy. You can get contact cleaner and go through each plug in the harness and give it a spritz to clear out any water that may be trapped, if problem persists I'd go with what Ramrod said and check the AMM and go from there.

        Okay so when I clamped off hose from idle valve to inlet (behind throttle body) it shouldn’t stall?? Or should I clamp off the other hose? Would it behave differently depending on whether car is hot or cold?

        The fact that the car wants to idle at ~500rpm could indicate idle valve is not functioning? How would I test to confirm idle valve is functioning?

        I already went through each plug and gave them a spritz, as you say.

        Thankyou brains trust.

              @OdinsRedblock writes:

              It was a little damp in the cap. A small patch of white goo (water, degreaser and oil I guess) was removed. Cap and rotor are quite worn.

              Might be worth replacing the cap and the rotor button. This is why I believe in wasted spark - where these items don't exist and thus cannot wear out or get waterlogged. ?

              WRT to your IAC valve, how do the hoses look? Does the thing look gunky? They do gunk up, and the cheap fix for that is cleaning it up with a generous amount of carby cleaner. Unless they're truly stuffed, where the valve-thing isn't turning because of gunk, or because the motor inside it is cactus. Mind you, that 2-2-3 code could be a hint though that it's time to replace the IAC valve.

              You've already checked for vacuum leaks, of course, yes? Since they cause silly business - not as much as vacuum leaks on K-Jet, but problems nonetheless. And your plugs and leads are new /good, yes?

              Oh yeah - btw, if you disconnect the battery, the LH2.4 ECU 'forgets' all its adaptive maps including idle settings, so it's quite normal for the thing to 'hunt' for a new idle setting, which it then sets in the volatile memory.

              WRT to your IAC valve, how do the hoses look? Does the thing look gunky? They do gunk up, and the cheap fix for that is cleaning it up with a generous amount of carby cleaner. Unless they're truly stuffed, where the valve-thing isn't turning because of gunk, or because the motor inside it is cactus. Mind you, that 2-2-3 code could be a hint though that it's time to replace the IAC valve.

              The hoses look okay. They’re clean. I think I maybe cleaned them when I was going through and doing a general tidy up initially. But even rubber doesn’t look too bad. There’s a couple of tiny splits on the very top of one but only just on the edge above the clamp. Idle valve itself is nice and clean but the little flap doesn’t bounce up and down as loosely as the valve on my 850. So not sure if that is a warning sign?

              And yeah, did a rough check over for leaks. Replaced a few suspect hoses. Thing was running well before the clean though so I’m more invested in this being an electrical problem.

              When I got home this arv, I started it again and this time it wouldn’t even idle when cold. Pulled the maf and it was idling. Even idled up to about 700 this time: Again, clamped off the idle valve and it stalled. Started back up and ran fine.

              Plugged MAF back in and it didn’t want to idle.

              Gave me the 1-2-1 again but I would assume that is because I’d disconnected.

              At this point, I think I will put up a wanted ad for a MAF and an idle valve and go from there.

              Fortunately, the car was actually booked in for exhaust next week so I’ve got a little bit of time.

              6 days later

              Swapped in another MAF. No improvement. Then another Idle valve. No improvement.

              same thing. Is quite smooth for the first minute or so. Then degrades to the point where it bogs down and misfires when you apply throttle. Will idle at about 500rpm. Just. If you don’t apply throttle it may idle but mostly stalls as soon as you apply any throttle.

              I did manage to move it and it smells to be running lean. I was leaning (pardon me) towards a coolant temp sensor if these parts didn’t help. I actually picked up a new item today too. But don’t they typically run really rich when they go? Have a new PCV system too so was going to pull the mani and do it all in one swoop.

              I’m starting to think maybe fuel pump relay now. I couldn’t get the bloody graphic equaliser out when I had quick squiz this arv but I just stuck my hand up behind fuses onto what looks like green relay and felt clicking when I’d turn key. But the relays can fail in odd ways can’t they?

              Or maybe ECU fault. Don’t some of these cars have issues with ECUs, especially on the fuel side? When it stops running, the revs slowly just drop and drop and it putters out. A bit like it’s just losing fuel pressure. The fuel pressure regulator doesn’t leak when the vacuum line is removed.

              Car has a brand new main pump PO installed. Not sure about in tank. I do have a brand new item from professional parts designed for a k jet car. Does anyone know if they are the same in tank pump on a 90 740T?

              Of course it very well could be a wiring problem.

              I did find an earth on the firewall that was completely shorn. Does anyone have any diagrams or info on where the earths are located?

              The car is booked in for its exhaust and road worthy tomorrow. They’ve got it for 4 days. So I suppose I will get the thing towed and get them to have a look at it. They do a lot of fab and custom work on 80s/90s jap stuff so hopefully have the tenacity to tackle the issue.

              I’m starting to hate the thing so maybe it’s time a set of expert eyes take a look.

              That sounds like a vacuum leak to me - Have you checked for vacuum leaks

                ramrod

                That sounds like a vacuum leak to me - Have you checked for vacuum leaks

                Which part of what it’s doing makes so certain?

                I actually thought I heard a leak this afternoon.. under throttle. Like a boost leak. I double checked all my clamps. Went and got my partner and got her to try and keep it running while I used some throttle body cleaner and sprayed it on the hoses and around the connections and couldn’t see suspicious bubbling or anything. Most of the other hoses were replaced with new silicone lines.

                the little short connector on the turbo outlet is really stuffed and was going to replace it with a silicone kit from do88 when I had the thing on the road. A leak there would only cause it to lose boost, not run like shit to this extent though right?

                  Rich idle mixture.

                  How's the throttle body? Ever cleaned it? If not, try it, it's free

                  If the gasket tears upon removal I have new ones

                  Okay, it's now time to get the multimeter out and begin diagnosing

                  Do you have the LH 2.4 repair and diagnostics manual?

                    ramrod

                    Okay, it's now time to get the multimeter out and begin diagnosing

                    Do you have the LH 2.4 repair and diagnostics manual?

                    I was really hoping it wouldn't come to this @ramrod

                    no i don't have a copy. is there a pdf version available?

                      All the Volvo Green Books are on this site somewhere.

                      yeah, I found a copy online. Looks like a barrel of laughs.

                      @OdinsRedblock writes:

                      Car has a brand new main pump PO installed.

                      Uh oh. **alarm bells** What type of pump is it?

                      If it's a not a Bosch pump, throw it. One PO of a 745T wagon I bought had put a shitty Pierburg pump on it, and it wouldn't run correctly..... Later, I changed the main pump to the correct Bosch; problem solved.

                      Just because the PO put in a new one doesn't mean it's a correct new one - unrelated story: VE ute was throwing codes, 1st and 2nd shop wouldn't change the sensor because it looked new; 3rd shop changed it with the proper replacement and problem fixed, because whoever replaced it used a POS part.

                      If it's a Bosch pump, but not a 0 580 464 025 (aka 69594) which is the correct fitment for turbos, I'd replace it with one, and sell the old one. At 120 USD it's not cheap, but it's unlikely a genuine Bosch pump will clag out miles from nowhere in 6 months. In 30 years, maybe it might, but you never know what no-name stuff will do.

                      Can't hurt replacing the main pump filter while you're under there. either.

                      K-Jet in-tank lift pumps are a different p/n from LH2.x in-tanks, but it's just a lift pump and shouldn't make much difference as long as it's working.

                      Bad relays don't cause low fuel pressure, they cause no fuel pressure - intermittently, or permanently. Bad pumps cause fluctuating fuel pressure, and it's one failure mode of this type of pump.

                      If your car has the 6842434 late-type of injector rail, there's a valve on it at the end which points to the firewall for measuring fuel pressure.

                      7 days later

                      Okay sooo the car went into the shop last week and there’s been some progress.

                      They smoke tested it and there are no leaks anywhere.

                      It’s got good fuel pressure.

                      It has weak spark across a couple of cylinders so I sourced a new rotor and cap. Unfortunately, the rotor I got was ‘faulty’ so I swapped it for another. Then when I get a chance to sit and talk to the mechanic, it turns out it doesn’t even fit onto the dizzy shaft. The little ‘key’ inside the button is smaller in the new part. So it just spins on the shaft.

                      Does anyone know if there are different styles of rotor button for 740?

                      The part I sourced from GLT was a pro parts item. When I refer to their catalogue it does look like they have two part numbers for rotor buttons for 740s. Although the one I got as replacement seems to be closest in shape on the actual rotor to the part I am replacing.

                      Is it possible it’s a fault in the casting??

                      Anyway, apparently it did run better with just the cap alone.

                      Although they didn’t run it for long they said and my issue seemed to present once it had warmed up a bit.

                      Tbh, I’m a little surprised if it is simply the cap and rotor alone. I guess I’m showing my inexperience but I knew a bad cap and rotor could make a car run like shit but didn’t realise it could cause a car to actually stop running. But I guess just about anything can stop a car running if it’s bad enough. I guess if it’s just the cap and rotor I’ve dodged a bit of a bullet.

                      But what is it about washing the engine bay that would cause a cap and rotor that is performing perfectly well to stop functioning? I mean obviously getting wet.. but if I pull it and dry it and clean it, shouldn’t it run again? Well at least similarly to how it was before I washed it?

                      ANYWAY! We will see.. advice on this rotor button would be great.

                      The main reason the car went in was for an exhaust. I’m going a 3” 200 cell cat, 2.5” mild steel to a resonator then back to the axle with a little mandrel bend over the top to a flange and then a tail pipe with glass muffler. Going mild steel as from my experience it’s a nicer sound. $1200 seems quite steep but last time I had a quote on an exhaust was 750ish pre covid and I guess steel prices have gone up.

                      Here are some pics of the old rotor button I had in the car. No pics of the replacement unfortunately.

                      {"embed-external":{"data":{"url":"https:\/\/cdn.ozvolvo.org\/uploads\/8ZQMMFVYSKRG\/5bd5c183-fd8d-4a17-81d9-cd3d41c39006.jpeg","name":"5BD5C183-FD8D-4A17-81D9-CD3D41C39006.jpeg","type":"image\/jpeg","size":2761257,"width":1920,"height":1440,"displaySize":"large","float":"none","mediaID":25810,"dateInserted":"2022-02-20T10:50:51+00:00","insertUserID":1892,"foreignType":"embed","foreignID":1892,"embedType":"file"},"loaderData":{"type":"file","file":[],"progressEventEmitter":{"listeners":[null]}}}}

                      {"embed-external":{"data":{"url":"https:\/\/cdn.ozvolvo.org\/uploads\/IS112HGMMDBY\/d8af1ff8-f12c-4951-8df5-9e6fc66744a9.jpeg","name":"D8AF1FF8-F12C-4951-8DF5-9E6FC66744A9.jpeg","type":"image\/jpeg","size":3018738,"width":1920,"height":1440,"displaySize":"large","float":"none","mediaID":25811,"dateInserted":"2022-02-20T10:50:51+00:00","insertUserID":1892,"foreignType":"embed","foreignID":1892,"embedType":"file"},"loaderData":{"type":"file","file":[],"progressEventEmitter":{"listeners":[null]}}}}

                      © 2013-2023 Oz Volvo. All rights reserved. | Forum Rules | Privacy Policy