thetroughWhat happened to the nice blue 740?
It wasn’t that nice in reality (interior was a bit trashed, dents on exterior, non-matching bonnet. I stripped every ounce (gram?) of extra weight out of it and took it to the Winton Fun Day shortly after I bought it to test out the engine and transmission to make sure it was suitable for use in my 240 project, then pulled out the engine, trans, harness etc. and scrapped the body. That was probably 10 years ago - time flies!
Well as expected, same symptoms after coolant temp sensor replacement. I knew that wasn’t it as I had back-probed ECU terminals and coolant temp resistance was within spec, but everyone says “coolant temp sensor” so I had to try it. Symptoms are on cold start, it fires right up but after a few seconds it starts running rough and black smoke out exhaust. Rev it a bit for about 10 secs and it smooths out (presumably when O2 sensor is warm enough and it goes into feedback mode). Sometimes when hot/warm start it takes a lot of cranking, but no rich running.
So, I know it is NOT:
ECT (engine coolant temp sensor for ECU) or wiring back to ECU
Earths (have been cleaned and checked)
MAF (have swapped with no difference)
ECU (have swapped with no difference)
Plugs, plug wires, cap, rotor (all swapped with no difference)
Fuel pressure (checked and within spec)
Fuel (car does not have stale fuel)
O2 sensor (new one installed and no difference)
Crank position sensor (new one installed an no difference)
This car DOES have a cold start injector, but I have unplugged the wire connector and no difference.
Only other things I can think of that I haven’t checked or swapped out yet are:
Leaky injectors or bad spray pattern?
Leaky cold start injector?
Poor valve adjustment? Car runs fine once warm.
Blocked catalytic converter (would probably not cause these symptoms?)
Ignition coil
Ignition power stage/amplifier
Any other thoughts?
Guess I will just live with the minor annoyance until I put the turbo engine in and hope it doesn’t do the same thing then?!!??
Idle air control valve
ramrodIdle air control valve
Thanks @ramrod definitely something I need to look at...my partner and I were just chatting about it. I guess if the base idle or throttle plate setting is too low, or the idle valve is not functioning properly, during a cold start when the ECU tells the injectors to run more fuel, the idle valve should bypass enough air to go with that extra fuel and bring the idle up. IIRC the idle does not seem to be higher than normal after a cold start, so definitely could be something there. I do know I’ve checked the TPS position and I get the “click” just off idle throttle position, so the ECU should definitely be in idle mode. More to look into, and while I look at the idle valve I can also possibly remove and look at the cold start injector since they’re both buried below the inlet manifold!
Update. Haven’t had time to check the idle valve or throttle setting as we’re on the road, but I have started slightly applying the accelerator when I do a cold start, immediately bringing the RPM up to 1500-2000 for 10-15 seconds. That totally eliminates the rough idle and rich running issue I had been seeing on cold start...so definitely seems to be dumping in extra fuel that it couldn’t burn at the lowish cold idle speed, which fouled the plugs a bit until you revved the engine and/or the O2 sensor and feedback mode kicks in. @ramrod ‘s theory of idle valve is sounding more and more plausible. Where do I send the reward $$? :)
Brief update on the cold start rich running issue. I did a bit of investigation into the idle valve at @ramrod ‘s suggestion. We just got back from a 300 km trip so the car was warm. I pinched off the idle valve hose and the car died, which indicated to me that the base throttle plate position was a bit too closed (idle should drop to around 500 RPM IIRC). So I removed the throttle link rod, adjusted throttle stop to open throttle plate slightly, readjusted throttle position switch and link rod. Now when I pinch off the hose the idle drops to around 550 RPM, and when I let off it flares to about 1500 RPM (as the computer probably has the valve wide open trying to bring the idle up from 500 with the pinched hose) then settles down to around 800-900 RPM. I have yet to try a cold start - will do that when I take the car into the car wash on the next fine day and report back. The idle adjustment was very subtle, and I doubt enough to make much difference, but we shall see! Fingers crossed but I’m not hopeful at this point...if it is cured I’ll be cursing myself that something so simple as a very minor throttle adjustment could have such a profound effect!
Identical symptoms to my recent cold start issue. A combination of new ECT, idle air valve and deleting the cold start injector with a blanking plate solved mine. Good luck!!
buddyglitchIdentical symptoms to my recent cold start issue. A combination of new ECT, idle air valve and deleting the cold start injector with a blanking plate solved mine. Good luck!!
Thanks @buddyglitch I’ve done the ECT and disconnected the cold start injector (but if it’s leaking I’m not sure, so will have to have a look at deleting it - need some sort of cap for the port on the fuel rail?) The idle air valve SEEMS to be functioning, but whether it’s functioning properly is another story. I’ll see how it goes on the next cold start, and if no good will swap out the air valve and look closer at the cold start injector. Gonna get this resolved some day! Probably just in time to do the turbo swap. Grrr.
First cold start today after adjusting throttle plate. No real difference (still starts up fine, idles around 700-800 RPM and starts puffing out black exhaust smoke. Rev it up a bit and it clears its throat and all good. After warming up, letting the car sit for 20 mins while shopping, when I come back to start it (hot start) it cranks for about 5 seconds before firing up then revs flare to about 1500, then settles back to normal idle speed. Guess it’s time to swap out the idle valve to rule that out.
Also, I have stock exhaust system with rear muffler delete and pipe straight out the back. I noticed when it idles it sounds a bit like a V8, and not much in the way any exhaust pulses (just a very light exhaust flow almost like a person just exhaling). We always noticed that after a decent drive, when you pull into the garage it smells quite hot from the area of the catalytic converter. Wondering now whether the cat might be partly blocked? Time to swap in a gutted one and test that theory too.
Guess I could easily swap the fuel rail and injectors from the 93 sedan donor car and see if that makes any difference. Some day I’ll get this thing running perfect LOL!
I'd expect a partially blocked cat would show itself when you open up the throttle and you'd notice your down on power. I recently fixed a rough start condition by changing the Fuel pressure regulator and It was showing within spec pressure when I tested it. I'm not sure what the story was there, but it worked.
Can you just pull the cold start injector and the injectors out of the manifold and prime the pump to check for leaks?
Chasing gremlins like this can be a nightmare. I empathise with you. But it usually leads to a 'refresh' of components and a greater understanding of your machine, so it's not all bad. I hope you managed to sort this out.
ALVO360I'd expect a partially blocked cat would show itself when you open up the throttle and you'd notice your down on power. I recently fixed a rough start condition by changing the Fuel pressure regulator and It was showing within spec pressure when I tested it. I'm not sure what the story was there, but it worked.
Can you just pull the cold start injector and the injectors out of the manifold and prime the pump to check for leaks?
Chasing gremlins like this can be a nightmare. I empathise with you. But it usually leads to a 'refresh' of components and a greater understanding of your machine, so it's not all bad. I hope you managed to sort this out.
Thanks for the feedback @ALVO360 Yep, more work to do and more things to look at. At the moment we’re having to use it for any drives beyond range of the EV as I have the front axle out of the C30 awaiting a tool. Once the C30 is back together I can spend a bit more time on the 240 whether it be swapping out parts with the other engine I have on hand or testing the injectors etc.
More bits for the project arrived today from GCP...OE 240 Turbo exhaust system. Looks huge compared to the standard system...about 63 mm diameter. Yes it has “Mr Squiggle” tailpipe, but that’s fine...looks “sleeper” LOL! Will be interesting to see if it fits with the 86-later plastic rear valence panel.
Awesome stuff. Im keen to do the same thing on mine. I see theres only the rear muffler. Did you also get the other 2?
Cam205Awesome stuff. Im keen to do the same thing on mine. I see theres only the rear muffler. Did you also get the other 2?
The 240s only ever had 2 mufflers - one in front of the axle and one at the rear behind the fuel tank. Some 240 turbos had the front one deleted (according to the parts book these bits are for a B21ET, so non-catalyst 240 turbo. I already have a 2.5 inch downpipe from @DaiBrace at Classic Swede, so I’ll probably purchase a generic 2.5 inch catalytic converter, then will have to cut the front pipe on the new system short to fit the cat in. Unless of course the downpipe from Dai is exactly the right length to connect to the new system in which case I might umm, ahh, temporarily eliminate the cat for testing purposes...but seriously I want to run with a cat because I hate the stench of the exhaust when running without it.
See the pic below of the original B21ET exhaust system. The system I have replaces the front muffler and pipe with a straight single pipe. They must have discovered in later years (??) that the front resonator wasn’t needed, or it was deleted for some markets? Who knows...anyway I’m happy to get rid of it.
How does the GCP exhaust stack up against other options price wise? I'm beginning to think about an exhaust for my B230FT into GT242 swap. Motors in, gear box about to go back in.
Ok, did a bit more research...when I look at the parts diagram for the B21FT (240 T with cat) it shows no front muffler (pic below). So maybe the system I got is in fact the FT system, and maybe they decided they didn’t need the front muffler on cars with cat because the cat quieted it down enough. Anyway, I look forward to getting it on the car possibly before the turbo conversion because I deleted the rear muffler already and it’s too loud going straight out the back LOL!
Paul_RoodenrysHow does the GCP exhaust stack up against other options price wise? I'm beginning to think about an exhaust for my B230FT into GT242 swap. Motors in, gear box about to go back in.
about $450 including shipping if you include all the clamps and brackets.
I have a B230FT with a 200 cell cat and a single turbo muffler, 2.5" system with 3" downpipe, and the volume is very reasonable, has a nice warble to it but no droning and not obnoxious by any means.
jamesincI have a B230FT with a 200 cell cat and a single turbo muffler, 2.5" system with 3" downpipe, and the volume is very reasonable, has a nice warble to it but no droning and not obnoxious by any means.
Good to hear James. Thanks for that feedback. The system I have (OE Turbo) is also 2.5 inches...not sure I mentioned that for others who may be interested. I got the part numbers from a post on TurboBricks IIRC. I can post up if anyone needs more info.
Maybe a 3" cat in case you copy the downpipe , make a jig so 3 inch ones can be made off?
I would make some stainless ones if you want. I'm committing to build stuff....
