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1987 505 Turbo Revival


MGR550

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  • 2 weeks later...

Alrighty, I've got error code 4 "erroneous signal received from detonation sensor (check for engine speed above 3200 rpm)". Confirmed it does only activate the error once the engine goes above the 3200 mark after resetting. Got a new knock sensor and put that on, but no difference. I'm assuming is the knock sensor amplification module likely then.  Looking like it might be tricky to source a new one at first glance. Technical description manual has part # of 0 227 100 111 for that ignition setup and the one I just pulled out of the car is a 0 227 100 128. Others are referring to (what I think is) the same piece as a "ignition control module" and there's some off brand ones on RockAuto for ~$40 but not sure if they're that universal. Any ideas?

Thanks, 

Matt

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Those part numbers are for ignition modules, they are triggered to fire the coil and may or may not be in charge of dwell control (coil charging time) depending of the model and application.

On your car is it 0 227 100 128 or 0 227 100 123? Old 123 module have a blue cap and are made in germany but the newer ones are black and made in USA.

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Ah youre right, the module I grabbed off the car is the 0 227 100 123 (number had some dirt on it), but its a metal cap made in germany one; though it seems like that may not be the right part to replace for the error code I'm getting. Nonetheless probably good to pull it off anyways to clean the heatsink face and reapply some thermal grease. 

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It only does the constant flashing (4 flashes in a row, then a pause, repeat) once I rev it up to ~3k rpm then it holds that error code until I turn it off and on again. It picks up some knock every now and then if I go heavy on the throttle and if I haven't tripped the error code by going above ~3k, so I think it is working on that front. May be related but it doesn't seem to want to rev all the way out above 4krpm, afr seems fine, so might be ignition related and I'm suspecting tied to that error code; or maybe just a mouse nest in the exhaust😅.

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The document also suggests "Electrical circuit continuity" - you might want to test the continuity of the knock sensor wiring back to the ECU to make sure there's no broken wires or bad connections.  If you remove the sensor and just zip tie it somewhere and the error still shows up that would tell me the ECU isn't even seeing the sensor.  If the error stops with the sensor no longer on the block then it must be picking up knock - or something it thinks is knock.

It should also be revving out - put a timing light on it and see if ignition timing advances with revs.

Rabin

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So with the sensor off the block and just floating in air it does same thing; trips error code 4 when it revs up to 3k. Same thing again with the sensor unplugged from the socket too so it may likely just be a break or weak spot in one of the lines somewhere. Measuring resistance between the wires to the ECU I get open circuit, though I'm not sure what it should be normally (Not sure how measuring piezo sensors is done circuitry wise). 

Either way time to start tracing wires. Does the knock sensor go direct to the main ECU(s) behind the glovebox? The technical description doc has it as a knock sensor module tucked in behind the radio; though that's for the older model setup so I doubt mine is the same. 

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Pretty sure it’ll be direct to the ECU.  What does the sensor read directly?  It should read the same at the ECU plug.

I would verify the plug at the knock sensor is in good shape, check for corrosion in the wires.  If the wire has an issue it should be under hood with the elements, but could also be inside the car if there was ever mice in it.

Rabin

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Connector to the knock sensor was in good shape, no corrosion or breaks. Probed the wires back to the EZK ECU plug and the wires are fine as well. Brought the ECU board in to work and had an electrical engineer help me poke at it. Seems capacitor C100 on pin 13 (knock sensor signal) reads 0 capacitance and open circuit; ie has likely failed. Possible that this is throwing off the knock signal enough to trigger the error code so I ordered a new one and will update again once I swap that in!

Shoutout to the volvo forums for the pinout diagrams 😁

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Awesome find!  

I would have bet on wiring or a connnection LONG before the circuit board. 

Looking forward to seeing if that’s the fix.

Total aside - but that was another option I looked at, swapping engine control to a Volvo LH 2.4 ecu with associated wiring and stuff.  Volvo guys had it pretty well documented, and seemed pretty doable if you could get a hold of the parts.  In the end I decided stand-alone was the better option for all the work needed.

Rabin

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Well I swapped out that capacitor and tested it out - same issue still so that wasn't the main source of the problem; though I'm sure wasn't helping it any either. 

Paid a bit more attention to my blinky light and what causes the error code to trip, and it does appear to pick up some knock when I would expect it to, as long as the rpms are pretty low. Once it revs up some (lowest I've seen it at is ~2500rpm) then the error code trips. 

My current best guess it a bit of a long shot, but my power steering pump pulley bearing is all but destroyed (belt was removed long ago), so the pulley rattles around pretty noisily especially when it revs up. Maybe the mechanical vibrations from the pulley ringing around is sending some weird vibrations being picked up by the knock sensor that the ecu doesn't know what to do with? Could be coincidence that they pulley rattling noise gets to its peak around the same rpm as the error code trips... Maybe I'm just running out of ideas. Either way I should replace the pump so hoping its a two-birds-with-one-stone type thing. 

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I read the first reply and scrolled back up as I thought the same thing!  
 

If you test the board the same way does it still test OK?

Can you trace the board at all or inspect for cold solder joints?  Does sensor test OK?

Open circuit still makes the most sense.  What year is the car again?  Having another ECU would help troubleshoot it.

Rabin

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The short segment on the board did test fine after replacing the cap, though the sensor signal line feeds into a CA3080AEX chip that's some weird opamp style thing I don't fully understand, so the signal line is hard to trace after that point. Didn't see any burn marks or obvious cold solders on the board either. 

As for the knock sensor itself, the one on the car reads ~330kOhm, but a spare bosch knock sensor I have for another car of the same format reads 4.4MOhm, so I don't know if its just a general sensor difference or if mine is somehow dead. Car is an 87. 

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Took the car to a local mechanic to get the trans and diff oil changed out and to get the center driveshaft bearing greased up. There was a bit of a language barrier so I'm not entirely sure whey they all did. From my limited understanding of french, it seems the trans oil was in ok shape but they changed it anyways, and the diff oil was in very poor shape so they did that as well.

Somewhere along the line they took off at least the front left wheel and broke the center cap off the little metal clip that holds it on; seems like I can fix that with some JB weld or something so not too bad there. Also speedometer wasn't working so I'm guessing they nicked a wire somewhere. Where does the speedo pickup from? 

I think a bit got lost in translation and they went ahead and greased all the joints and stuff on the underside... Either way I'll have to check it all out next chance I get. Figured it would be an easy enough job and save me getting underneath the car in the snow, but maybe no more visits to the mechanic for this car

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  • 2 weeks later...

Was doing more reading on knock sensors and piezo elements stuff. Apparently while running, the sensor will produce ~40mV noisy signal corresponding to just regular small vibrations from the engine during normal operation. A knock event will send a voltage spike on the order of 600mV or so. I'm wondering if the ECU is expecting to see the smaller ~40mV noise signal as it's sort of continuity check (ie no 40mV noise, must be open circuit) which is maybe why it still triggers the error with the sensor disconnected and/or off the block. Could be that it doesn't trip the error code until is higher in the revs because its expecting that it would have seen some signal at that point, but if it doesn't then must be an open. I'm going to open up the ignition ecu again and go past that opamp chip I stopped at last time to look for another break somewhere downstream. 

Also checked my idle air control valve and its definitely not working (very rich on cold starts and idle isnt any higher than normal, but AFR settles back to normal once it warms up). Took the valve off and it moves if I poke it directly with a pick, but no movement from it when applying voltage, so looking around to find a new one.  

Coming up on warmer weather finally so I'll be able to get underneath it better and check out the speedometer issue. 

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Apologies as I’ve been out of commission due to a bad back - was a full stop on renovating and no trips to the garage for the last 4 weeks or so!

Mobility is much better now, so will try to make good on my offer to see if the manual has some detailed troubleshooting documentation.  Should be able to grab an ohmmeter check in at least two knock sensors as well.

Spring is coming here as well and I hope to make progress on mine too!

Rabin

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Glad your feeling better Rabin! 

Some updates:

ECU/ knock sensor; Cant find any more dead components along the path of the knock sensor circuit, so I touched up the solder on a bunch of the pins just in case they were cracked or something. I'll throw it back together this weekend and see how it goes. 

Idle air control valve; Confirmed dead, no response to any voltage, reads 330 ohm on the coil and was getting proper voltage from ecu. Opened it up out of curiosity (pics attached for anyone else wondering, the paddle arm down the long portion levers on the dark brown plastic piece, the arm is quite stiff) and I don't think I'd be able to repair it. Usual sources can't find a replacement (P/N AC361)... anybody got an old one for sale? or better yet has anyone tried swapping one from a similar era volvo in? 

Looking around for summer tires this weekend 😁. Also, how hard is it to find a pair of euro spec headlights? 

Matt

20220319_112450[1].jpg

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  • 3 weeks later...

Back again with good news! 

ECU: Was poking more at the ecu and found a store online that sells euro parts stuff and they mentioned a failure point on these ecus is that when the alternator/voltage reg goes, it can fry certain parts of the ecu which can cause intermittent ignition cuts, lack of timing advance in higher rpms, and other weirdness. Figured since I got the car with a dead alternator and have had every one of the listed symptoms, that was probably my case. I ordered an ecu from them; just arrived today and it seems to be working great with no error code so far! Tachometer seems a bit slow to respond, but not sure if thats related.. still not sure on the knock sensor if the 330 ohm one or the 4 mega ohm one is correct. 

Idle air control valve: couldn't find one meant for the N9TE anywhere, bosch or orther brands all out of stock. I found one meant for a 1988 BMW M5 that looked identical so ordered one and threw it on and it also works great so far; idle picks up for the cold starts to where AFRs are normal. Still need to adjust timing and everything again with all the new stuff just to make sure.

Electrical gremlins: Took out a poorly wired Alpine immobilizer and a rats nest of wiring and spliced connectors that was no doubt the source of my battery drain. One of the fog lights had a burnt out bulb and the other isn't getting voltage so 1 more wire to trace there, but at least the switch and relay are working. High beams will flash when I pull the stalk with the main running lights off, but wont turn on at all with the main running lights on, so I need to check the switch and any latches/latching relays for that. 

Hoping to get under the car this weekend to fix that speedometer drive and get the tires changed to start giving it a proper break in. Lots more to do but its almost ready to drive reliably now! Woohoo!

Also need to find a windshield if anyone knows where to get one that would be appreciated

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Nice work. About finding parts - did you contact Rob Courtier? he has a very large amount of parts for these cars, its where I almost always get my parts from.

10 hours ago, MGR550 said:

drive reliably now!

This cracked me up

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