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adam73bgt
Club Retro Rides Member
Posts: 4,949
Club RR Member Number: 58
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More idle musings..
Checked all the intake joints for leaks and found nothing untoward, none of the hoses seem to have splits in them either
Took the IC off and had a look at the throttle linkages to make sure nothing was binding up or doing anything odd and it all seemed to be working. Didn't get a chance to actually measure the resistance of the TPS so thats a job for another day
Took it for a drive, cold idle was still non-existent but once the car was warm and I got back, it was idling nigh on perfect. But still doesn't return to idle smoothly, it will tend to dip under the ideal idle speed before bringing itself back up
Think I need to get to grips with the TPS..
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I have a similar problem, my cold idle isn't great. On first start it revs up to 3000 like its supposed to, then once it drops down it idles high for maybe 10 seconds and then drops down, on colder days it sometimes stalls, if not it idles really low. It smells quite fuelly so I wonder if my idle mixture needs tweaking. (even though we have fuel injection, we can adjust idle mixture and speed separately) Regarding your dip under idle, you may have a problem with your dashpot, its designed to cushion the throttle so it returns to idle smoothly rather than suddenly. More info here: www.rx7club.com/2nd-generation-specific-1986-1992-17/restoring-your-throttle-body-step-step-guide-what-takes-979364/
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The first thing that springs to mind is an air leak could be worth spraying around some brake cleaner or easy start on the lines when the engine is running and see if it picks up at all, but assuming all your vacuum lines are good then it could be a problem with the thermowax system. Where the coolant lines go from the BAC valve into the throttle body there's thermostat that pushes on a cam roller, and it pushes the throttle open a little bit to improve the cold idle, as the car warms up it slowly lowers the idle to normal levels, if thats playing up it could cause an issue. I've had issues with other cars with the cold start bypass. Most of my cars have been a wax unit that allows more air in when cold. On my most recent car I have removed this and installed a solenoid instead on a switch. I can then turn it on or off when required. This also nets a tiny amount of power by not having warm coolant circulating the tb
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adam73bgt
Club Retro Rides Member
Posts: 4,949
Club RR Member Number: 58
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Aug 10, 2017 18:12:04 GMT
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Cheers rotarypower thats another really handy link, now I'm torn half wanting to take the TB off and clean it all up but equally I really don't want to take the UIM off again From what it says about the dashpot on that link though, I think mine is doing something as the plunger on it pushes in and seems to return ok I'm not sure if the idle mixture can be adjusted on the S5 turbo, I think I've read that the earlier cars had some sort of mixture adjustment screw? I did find that my BAC valve idle adjustment screw does do something though. When the idle was a bit stable, I tried screwing it right in and eventually it did start to drop the idle speed a bit. But I can back the screw right out and the idle will still be too low so its outside the scope of adjustment that the BAC provides. Interesting idea ollieh17 , I'll be keeping my cold start stuff as factory but I hadn't thought of having a solenoid/switch setup with a bypassed system
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Tepper
Part of things
Posts: 381
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Aug 10, 2017 20:33:09 GMT
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I've recently stripped some of this stuff off my TB, you're welcome to it for the price of postage if you want but the condition is unknown!
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1989 Peugeot 205 GTi - stolen! 1983 Mazda RX7 1968 Rover P6 - also stolen.
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Aug 10, 2017 20:57:09 GMT
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Cheers rotarypower thats another really handy link, now I'm torn half wanting to take the TB off and clean it all up but equally I really don't want to take the UIM off again From what it says about the dashpot on that link though, I think mine is doing something as the plunger on it pushes in and seems to return ok I'm not sure if the idle mixture can be adjusted on the S5 turbo, I think I've read that the earlier cars had some sort of mixture adjustment screw? I did find that my BAC valve idle adjustment screw does do something though. When the idle was a bit stable, I tried screwing it right in and eventually it did start to drop the idle speed a bit. But I can back the screw right out and the idle will still be too low so its outside the scope of adjustment that the BAC provides. Interesting idea ollieh17 , I'll be keeping my cold start stuff as factory but I hadn't thought of having a solenoid/switch setup with a bypassed system I think only the distributor based NAs had the idle mixture screw. Your turbo with electronic ignition does it automatically using the O2 sensor. For myself I've committed to eventually switching to stand alone engine management, probably megasquirt. Then I can strip away a lot of the throttle body junk as it can be programmed in. Apparentlythey run a lot better and more economically with a modern ECU as well.
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adam73bgt
Club Retro Rides Member
Posts: 4,949
Club RR Member Number: 58
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Aug 10, 2017 21:31:04 GMT
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May take you up on that offer Tepper if you're not going to be using the bits, even if they don't end up being useful for mine they can end up in my box of FC spares rotarypower yeah, O2 sensor was new when I fitted the exhaust so I hope its still working fine! Although the issues I had with injectors saw me chucking a lot of fuel down the exhaust so I wonder if that could have killed it?... Standalone does seem to make the most sense judging by the responses of most 7 owners, its something I'd love to do with this but ultimately I don't think I'll ever get the chance to do it. Time, money and other projects in the way!
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ChasR
RR Helper
motivation
Posts: 10,266
Club RR Member Number: 170
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FWIW my Mazda used to almost cut out and then hunt albeit slowly.
It turned out to be a combination of the throttle body having a bit of gunk on it which prevented it from returning to the stop. but the TPS was the other issue ; it needed adjusting as per HBOL.
It was fiddly to do but the car idled spot on after that.
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Had idling issues with mine (obviously not a rotary!) which improved with plugs and leads but still wasn't right. I cleaned the MAF, IAC and TPS. That cured it, but I don't know which one, as I did them all at the same time!
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Last Edit: Aug 13, 2017 9:49:59 GMT by georgeb
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ian65
Part of things
Posts: 276
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Aug 13, 2017 10:38:09 GMT
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As these Rx7's were designed primary for the US market they came with all that emission junk and are very intolerant to having any of it removed.Even the Fb's came with the air pump, thermal reactor and rats nest which Mazda UK were too lazy to take off but being carbed they are easier to get running ok without the rats nest..... not so the later EFI cars... if the stock ECU detects that any part of the emissions system is missing/faulty then you'll have a whole world of grief..... they don't seem to be able to compensate for any variation. For a road car it's less stressful to either strip the lot except the bac and go to a stand alone or to just leave everything in place and run stock.
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Last Edit: Aug 13, 2017 12:05:36 GMT by ian65
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adam73bgt
Club Retro Rides Member
Posts: 4,949
Club RR Member Number: 58
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Aug 14, 2017 20:05:01 GMT
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ChasR TPS/throttle body is now my main suspect, I did give the linkages a cursory spray with spray grease as they'd been sitting in the garage for a while but it shouldn't be too hard a task to check out the TPS to make sure its in spec I partially agree with you ian65 . Yes in an ideal world, I'd strip the engine right back and run some standalone management but from looking at the design of the parts I've removed so far (air pump, cat, AWS, ACV) they shouldn't have any bearing on how the engine itself runs so I don't think the stock ECU should have too much of an issue. I've sort of taught myself to drive around the lack of cold idle at the moment and once its warm, it drives as fine as it ever did, so I'm fairly confident it shouldn't be too far off running well in all conditions with a bit more tinkering I do agree the other options would have been less stressful, although part of the stress in my case was misreading the info about the ECU chip that works with US and JDM ECUs but not the UK ECU, coupled with a real lack of UK model specific FC info on the internet/in books to glean information from. Edit to add: As a general update, its been a blessing and a curse being able to drive the 7 around as every time I take it out, it makes it harder for me to contemplate selling! In other RX7 related news, I've now properly built and torqued up two of the Rays wheels. Due to my... laziness and other distractions, I won't have all 4 wheels finished in time for the Gathering, but I'm going to forge ahead and get them done and on the car, it may be something to help the sale, and it will also just be nice to see them fitted on the car
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Last Edit: Aug 14, 2017 20:09:16 GMT by adam73bgt
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ChasR
RR Helper
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Posts: 10,266
Club RR Member Number: 170
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Aug 16, 2017 19:04:39 GMT
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It was the grease on mine which made it iffy ; I sprayed mine with carb cleaner to fully degrease it which also made the TPS alot easier to setup ; I suspect this was an issue previously with the last owner.
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adam73bgt
Club Retro Rides Member
Posts: 4,949
Club RR Member Number: 58
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Aug 21, 2017 10:20:14 GMT
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ian65
Part of things
Posts: 276
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Aug 21, 2017 17:13:36 GMT
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I saw this on the field yesterday.... it looked great.... you'll have no trouble selling it.... I was on the stand with the FB's... you should have parked up with us.
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ChasR
RR Helper
motivation
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Club RR Member Number: 170
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Aug 21, 2017 17:25:24 GMT
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I was going to say. It scrubbed up very well for the show! It was good to see a J bias across the Midlands stand .
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adam73bgt
Club Retro Rides Member
Posts: 4,949
Club RR Member Number: 58
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Aug 21, 2017 17:32:28 GMT
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I saw this on the field yesterday.... it looked great.... you'll have no trouble selling it.... I was on the stand with the FB's... you should have parked up with us. Thank you very much I wish I'd invested in a machine polisher as it felt like my arms were going to fall off but it was worth it haha I did have a chat with one of the guys from the FB stand as he came over while I was at the car but I didn't catch his name The FB's were all looking very nice, as was the Blue (If I'm remembering correctly) FD over in the retro parking I was going to say. It scrubbed up very well for the show! It was good to see a J bias across the Midlands stand . Aha cheers, I somehow missed your car on stand until I'd done a couple circuits of the field but it was looking good also, didn't realise you'd be selling so soon though!
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MiataMark
Club Retro Rides Member
Posts: 2,970
Club RR Member Number: 29
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Aug 21, 2017 20:56:43 GMT
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The FB's were all looking very nice, as was the Blue (If I'm remembering correctly) FD over in the retro parking If I've got my RX7 nomenclature correct it was silver and I parked next to it.
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1990 Mazda MX-52012 BMW 118i (170bhp) - white appliance 2011 Land Rover Freelander 2 TD4 2003 Land Rover Discovery II TD52007 Alfa Romeo 159 Sportwagon JTDm
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sb
Part of things
Posts: 725
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Aug 21, 2017 21:23:38 GMT
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I knew I recognised the plate! Saw it in the field and couldn't for the life of me remember whose it was at the time.
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adam73bgt
Club Retro Rides Member
Posts: 4,949
Club RR Member Number: 58
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Aug 22, 2017 11:05:53 GMT
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The FB's were all looking very nice, as was the Blue (If I'm remembering correctly) FD over in the retro parking If I've got my RX7 nomenclature correct it was silver and I parked next to it. Ah yes there was a silver one as well just down the row from the blue one I think
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