graearea Posted May 24, 2023 Share Posted May 24, 2023 My poor little Kali has a bit of a cough low down in the rev range and the occasional backfire out of the ITBs. this is currently combined with a high idle which means a constant burble when the throttle is off which means it sounds a little bit like I'm pining for my teenage years...I've swapped coils around (2 off, still misfires, swap the other 2, still misfires) and I've got some new plugs coming.I've checked the throttle cable and it doesn't feel tight, you can hear the roller clack into closed position when pedal released. is there something I can check with OBD? it's running at about 1.5k revs.any ideas before I ship it off to Rob?J Link to comment Share on other sites More sharing options...
John Vine Posted May 24, 2023 Share Posted May 24, 2023 What model/engine are we discussing?JV Link to comment Share on other sites More sharing options...
graearea Posted May 25, 2023 Author Share Posted May 25, 2023 2006 R400D Link to comment Share on other sites More sharing options...
John Vine Posted May 25, 2023 Share Posted May 25, 2023 Do you know someone with the MBE 985 cable for connecting the diagnostic port to a laptop running Easimap? That's the surest way way to examine what the various sensors are telling the ECU.Is the misfire confined to a particular cylinder? If it's #1 (the most common on a Duratec IME), check the coil-on-plug wiring where it enters the connector. Fractures are quite common in that area. Also check the connector terminals for arcing -- any black discoloration visible? If so, pull off and replace the connector several times (20 or so) to clean the surfaces.1500rpm is certainly a fast idle. It should be around 900.JV Link to comment Share on other sites More sharing options...
graearea Posted May 25, 2023 Author Share Posted May 25, 2023 I don't have one I'm afraid. I don't know how to find out which cylinder it is either. I'll double check the coils.I don't know anyone with an MBR 985. I've asked my local groups whatsapp group so we'll see if that helps.otherwise I'll have to see if anyone has one that they can post outcheers JohnJ Link to comment Share on other sites More sharing options...
John Vine Posted May 25, 2023 Share Posted May 25, 2023 To find out which cylinder is misfiring, you really need a digital pyrometer aimed at the primaries. Failing that, you can (carefully and very briefly!) touch each primary in turn with a wet finger.Normally, I could lend you my MBE985 (listed in the Equipment for Loan Register) but I'm abroad at the moment. For info, there's another one in the Register. Alternatively, you could buy one from SBD Motorsport, but they're not cheap.JV Link to comment Share on other sites More sharing options...
graearea Posted May 26, 2023 Author Share Posted May 26, 2023 ok. I'll go swap the plugs and see if there's still a misfire and dig my pyrometer out. it only really seems to stutter badly at low revs. makes me wonder if it is actually a misfire... I was fine keeping up with other R400s/R500s on monday :DI've emailed Spuddy on the register. we'll see if they're active.cheers again John.J Link to comment Share on other sites More sharing options...
graearea Posted May 26, 2023 Author Share Posted May 26, 2023 Oh dear Compression test later this arvo. Link to comment Share on other sites More sharing options...
John Vine Posted May 26, 2023 Share Posted May 26, 2023 That looks nasty. It certainly would explain your misfire. I take it the missing bit of electrode is no longer in there?is that the standard TR6AP-13 plug (FoMoCo/NGK)?"arvo"??JV Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted May 26, 2023 Member Share Posted May 26, 2023 "arvo"??Afternoon: Australian English and rarely spotted elsewhere. Jonathan Link to comment Share on other sites More sharing options...
graearea Posted May 26, 2023 Author Share Posted May 26, 2023 seriously? you've never watched neighbours? :Din the end there were 2 tips missing. I've replaced them with NGK TR6AP-13 I think the old ones were the same.I checked the bores and they looked ok. I compression tested at 160 150 130 125 from the back with broken tips on 1 and 4. don't know if that is good or bad.a few people have suggested that it's down to too hot. is it possible I should be doing something about this?obviously the car gets a hammering, I don't generally run for more than 20 mins on the trackdo I need to fit iridium plugs?still got to get to the bottom of the high-idle. that hasn't been fixed. (the misfire has) Link to comment Share on other sites More sharing options...
aerobod - near CYYC Posted May 26, 2023 Share Posted May 26, 2023 The plug colour looks good, John, nice and tan with no black bits, was the tip just melted as opposed to broken? If the piston crowns don't show any sign of pitting due to any localized melting, colder plugs may be the answer. The NGK BR7EFS plugs with a 0.9mm gap may work better and are quite cheap, they hold up well on my R400D for track use, sometimes for full 1 hour sessions in high 30C ambient temperatures. Link to comment Share on other sites More sharing options...
graearea Posted May 26, 2023 Author Share Posted May 26, 2023 OK. Maybe I'll swap to them then. People are saying they got too hot. Link to comment Share on other sites More sharing options...
aerobod - near CYYC Posted May 26, 2023 Share Posted May 26, 2023 Here is a link to a thread on 6 plugs I tried in the R400D back in 2017, before sticking with the BR7EFS since then: https://www.caterhamlotus7.club/comment/2228320#comment-2228320 Link to comment Share on other sites More sharing options...
graearea Posted May 26, 2023 Author Share Posted May 26, 2023 Thanks. I did read that but struggled to get a conclusion. I just ordered what caterham had on their site. Sounds like your choice might be less brittle. Link to comment Share on other sites More sharing options...
7 wonders of the world Posted May 28, 2023 Share Posted May 28, 2023 The plugs James listed are better suited to your usage and are a grade cooler, I would also consider a cylinder leakage test as 125 is very low, wondering if a portion of the errant electrode kissed a valve on its exit...?Not sure which way you number them but No1 is a the front on the Duratec Link to comment Share on other sites More sharing options...
graearea Posted June 9, 2023 Author Share Posted June 9, 2023 right. I've swapped out the plugs to the BR7EFS and I've managed to get a cable of one of our kind members.the throttle site is showing 1.8 when ignition turned on and 2.1 when running. I've recorded a log set of the car turning on and running up to 90degCdo I just screw out the idle stop to reduce the idle? to me that seems to be the problem.the throttle cable has a very small bit of slack meaning it's the idle stop on the roller barrel. max throttle is 15.1 which I think is correct.TIAJ Link to comment Share on other sites More sharing options...
aerobod - near CYYC Posted June 9, 2023 Share Posted June 9, 2023 Hi J, I would see if you can unwind the throttle stop slightly, but ensure there is still throttle cable slack when the engine is warm. If the engine doesn't want to run smoothly at idle when warm, then a small rotation of the TPS or balance of the ITBs may be needed. Aim for the idle Throttle Site to be in the range of 0.0 to 0.4.Your Lambda value when the engine is warm should be oscillating between lean and rich at a stable frequency with a status of "OK". Link to comment Share on other sites More sharing options...
graearea Posted June 9, 2023 Author Share Posted June 9, 2023 Hey James,oh so the oscillation is good? I read https://www.caterhamlotus7.club/comment/2139800 and wasn't sure.I'll back it out and see where I get to.how do I balance ITBs? do I need an airflow meter of some sort?cheers. John Link to comment Share on other sites More sharing options...
aerobod - near CYYC Posted June 9, 2023 Share Posted June 9, 2023 Hi John,Here is a throttle body balancing thread: https://www.caterhamlotus7.club/forum/techtalk/balancing-roller-barrel-throttle-bodies Link to comment Share on other sites More sharing options...
graearea Posted June 9, 2023 Author Share Posted June 9, 2023 cheers! I turned the limit screw half a gnat widge and got the site from 1.8 to 0.9 much below and it just conked out.J Link to comment Share on other sites More sharing options...
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