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Chasing a slightly lumpy idle...still

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Old Aug 13th, 2018, 20:03   #21
AllHailKingVolvo
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You have a "secret weapon" in the fight against engine wear though Rob! As you run it on LPG, the oil stays much cleaner for much longer which reduces engine wear and clogging of the PCV system.

Also i suspect you are more attentive to any minor problems than the previous owners of Phils car have been, hence he has found so many "silly" things wrong that have all improved matters a little and combined have improved it a lot.
I think you’re right, Dave. I get the impression that my car had regular oil, filter and plugs but other than that it was just run as is.

Today’s been a productive day-being a musician by trade, I generally work Thurs-Sun, so the start of the week is car fettling time-the muso’s weekend!

I’ve cleaned the PCV, flame trap, IAC, all breather pipes and have replaced the vacuum tube from the flame trap to the intake manifold as it was split. I also replaced the distributor cap with a new unit, all of which has really helped the general grunt of the car and made it smoother still under power. The PCV wasn’t badly gummed up but had its fair share of crud as they usually do. The IAC was in really good shape but is cleaned and lubricated anyway. The dizzy cap made the biggest difference I think, the engine revs really cleanly now and hesitation under power is almost totally gone. The idle is still tiny bit uneven but nothing that I can’t live with. Just to complete the ignition system overhaul I’ve ordered a new ignition amplifier, and in the next week or two will also replace both fuel pumps and FPR too just to eliminate any of the usual consumables that tend to fail around the 150-200,000 mark.

After that, it’s just cosmetic work to do, barring the two rear shocks!
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Last edited by AllHailKingVolvo; Aug 13th, 2018 at 20:04. Reason: Grammar correction due to my phone autoincorrecting!
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Old Aug 13th, 2018, 20:36   #22
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Sounds like you've had a good day of rewarding tasks on the wee beastie Phil!

I think i'd be inclined to wrap the new ignition amplifier module in some bubblewrap and keep it with a tube of heatsink paste and the necesary tools in the car somewhere - it's one of those things that if it ain't broke, don't fix it! Just clean the back of the existing one and put some fresh heatsink compound/paste on it and refit and it should give you many more miles yet. They usually either work or not, no in between although an overheating ignition amp can give misfires at higher rpm and once in a blue moo at idle.

That split hose between the inlet manifold and the flame trap was probably causing a lot of the lumpy idle, did you check the stub on the inlet manifold was clean through the inside?
After that the dizzy cap although probably a 50/50 split between those two!

Might pay to remove fuse #1 (i think it's #1) for the ECU memory to reset the "strange" fuel trims it will have learned and give it a chance to re-learn from scratch on the new bits that are working well.
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Old Aug 13th, 2018, 20:55   #23
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I think you may be right re the ignition amp, I’ve just taken the belt’n’braces approach with the ignition system! I did clean and refit the existing one with plenty of heatsink paste as you suggested. The terminals were a little oxidised so I cleaned them up as best as I could and gave everything a good blast of contact cleaner, both terminals and plug, then refitted.

Excellent plan re the ECU memory reset-would disconnecting the battery for a couple of mins have the same effect?
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Old Aug 13th, 2018, 21:33   #24
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Excellent plan re the ECU memory reset-would disconnecting the battery for a couple of mins have the same effect?
It should do but make sure your keys are out of the car and you have the radio code etc.
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Old Aug 13th, 2018, 21:38   #25
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A seriously good sounding advice by Clifford Pope upstairs in the 240 section is to carry a spare amplifier mounted to a heat sink ready for use. If necessary connect it up and let it "dangle" until one say gets home to fix it up full good and proper. My words but I think I am doing justice to Clifford's far better way of explaining.
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Old Aug 13th, 2018, 21:40   #26
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It should do but make sure your keys are out of the car and you have the radio code etc.
Isn't there a procedure via the in built code reader to re-set things, or am I confusing chalk with cheese?
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Old Aug 13th, 2018, 21:46   #27
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A seriously good sounding advice by Clifford Pope upstairs in the 240 section is to carry a spare amplifier mounted to a heat sink ready for use. If necessary connect it up and let it "dangle" until one say gets home to fix it up full good and proper. My words but I think I am doing justice to Clifford's far better way of explaining.
That's why i suggested wrapping the new one in bubblewrap, carrying some heatsink paste etc. Letting it dangle can put unnecessary strain on the cables - other than that a good "get you home" idea.
However, the bit of preventive maintenance Phil has done (remove, clean and repaste) should be all it needs for another 20 years or so!



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Isn't there a procedure via the in built code reader to re-set things, or am I confusing chalk with cheese?
There probably is but as the Volvo system pre-2000 isn't true OBD-II, it's probably not as easy as doing a memory reset by removing power.
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Old Aug 16th, 2018, 20:27   #28
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Hello Dave,

Er. Bubble wrap has nothing to do with having the spare amplifier ready mounted to an equally spare heat sink, so one does not have to mount the amplifier to the heat sink at the roadside!

Dangling is obviously only "get you home" yes. I've not had to change a heat sink so I don't know how much is involved fixing it to the car. If Clifford suggests dangling, there must be a good reason. Famous last words, what Clifford says upstairs in 240 land seems to be the business.

Anyway to wrap a spare component use brown paper, string and sealing wax, far more classy! Or. All wrapped up in a five pound note.

I do think re resetting ECU memory I might be talking chalk and cheese. Barking up a wrong tree. I'm thinking of the fault code reader for LH2.4 as here https://www.volvoforums.org.uk/showthread.php?t=169603 and that has a specific inbuilt reset procedure.


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Last edited by Stephen Edwin; Aug 16th, 2018 at 20:34.
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Old Aug 16th, 2018, 21:17   #29
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Hello Dave,

Er. Bubble wrap has nothing to do with having the spare amplifier ready mounted to an equally spare heat sink, so one does not have to mount the amplifier to the heat sink at the roadside!

Dangling is obviously only "get you home" yes. I've not had to change a heat sink so I don't know how much is involved fixing it to the car. If Clifford suggests dangling, there must be a good reason. Famous last words, what Clifford says upstairs in 240 land seems to be the business.

Anyway to wrap a spare component use brown paper, string and sealing wax, far more classy! Or. All wrapped up in a five pound note.

I do think re resetting ECU memory I might be talking chalk and cheese. Barking up a wrong tree. I'm thinking of the fault code reader for LH2.4 as here https://www.volvoforums.org.uk/showthread.php?t=169603 and that has a specific inbuilt reset procedure.


.
Over and above unplugging the suspect ignition amplifier, it's two screws Stephen and clean the heatsink and smear some heatsink compound on the back of the new one. In fact, if you were to leave it dangling as a "get you home" measure, you could almost just plug the new one in without having it mounted on a heatsink - it will certainly work like that long enough to verify the fault either is or isn't the amp module - i used to carry one in my toolbox as a "diagnostic proof" module for that very purpose when i made my living at it.

There's nothing wrong per see with the idea of mounting a spare on a heatsink so it can be plugged in but for the sake of two screws, cleaning and then adding some heatsink compound, the entire repair is completed and doesn't need to be revisited to "make good" at a later date.

Brown paper etc might be more classy but won't protect the component the way bubblewrap will - i know this from experience!
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Old Aug 16th, 2018, 21:24   #30
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Over and above unplugging the suspect ignition amplifier, it's two screws Stephen and clean the heatsink and smear some heatsink compound on the back of the new one. In fact, if you were to leave it dangling as a "get you home" measure, you could almost just plug the new one in without having it mounted on a heatsink - it will certainly work like that long enough to verify the fault either is or isn't the amp module - i used to carry one in my toolbox as a "diagnostic proof" module for that very purpose when i made my living at it.

There's nothing wrong per see with the idea of mounting a spare on a heatsink so it can be plugged in but for the sake of two screws, cleaning and then adding some heatsink compound, the entire repair is completed and doesn't need to be revisited to "make good" at a later date.

Brown paper etc might be more classy but won't protect the component the way bubblewrap will - i know this from experience!
It sounds as if mounting the spare amp on a spare heat sink is a very good idea thanks. Why defer doing the compound &c. to be done at the roadside? Make it good when preparing the spare heat sink. Be prepared.

Sorry your brown paper failed. You forgot the string and sealing wax!

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