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4x4 YB running in a mk1 Escort - idle speed problems
Hi folks,
I've been on with a YB conversion in my mk1 for a couple of years now, it's finally at the point where it runs and moves under it's own power, however I've got a nasty idle problem that I can't track down.
Here's the full spec:
4x4 head and block, 2wd sump, standard 4x4 internals
4x4 T3 (uprated bearing and cut blades), -31 actuator, standard amal valve
2wd 3" mongoose downpipe and lambda sensor
Full MSD custom loom
Wasted spark with two new ignition amps and a new zetec coilpack, all new plug leads
Closed loop
knock sensor
L8 ecu
MSD Evo 320bhp chip
Standard fuel regulator (set to 3.5bar), Bosch 044 pump, 803 dark greens
It starts on pretty much first turn of the key, it sounds nice and smooth, it doesn't miss or rock around on the engine mounts. It sounds lovely, in fact.
However, it starts with an idle of 1800-2000rpm, it doesn't appear to drop down. And it also 'self rev's every so often, perhaps up to 3000rpm and then back down again, on very odd ocaaisions it drops down to something like normal idle speeds, but very rarely, and only for a few seconds. Sometimes when its changing rpm like this the amal valve can be heard to click, but not always.
What I've tried:
- Fuel pressure check; was slightly high at 3.8bar, dropped it back to 3.5.
- ISCV; original was seized solid, now replaced with a brand new one.
- Throttle cable; thought it may have been catching, so ran with it completely disconnected and back to the stops.
None of that seems to have made a difference. Every single sensor apart from the ISCV and TPS was replaced when I built the engine up.
Is there another sensor than the ISCV that can cause really odd idle problems like these, or cause the idle not to drop to the correct level after just a few seconds?
I did a quick video of the problem this morning - you can hear it revving now and again; at no point in the video did we even touch the throttle:
I found on mine if i ran relays to power the fuel pump the idle would be high. I traced that back to the ignition live being too high voltage as this is a sensing feed which needs to be connected to the car loom so when lights are on the idle stays stable.
We set the base idle today - without the ISCV plugged in we got it idling nicely at around 900rpm.
We found that the previous owner of the engine had bodged the adjusting screw - with traces of silicone around the top of the threads and tip of the taper. That's now been replaced with new o-ring seals.
Without the ISCV plugged in it sits nicely at 850-900rpm when warmed up. As soon as we plug the ISCV in it rises to around 2000rpm and flicks around a bit.
We can't find any air leaks. One thing we haven't checked yet is the CO - I've just bought a cheap gas meter to do this, but haven't got around to it yet. What should I set and see for a closed loop setup?
Ah ok closed loop. You need to follow MSDs instructions to set the co pot in the central c position that will give a ball park the use the gas meter you need to be around 1% co dont worry if its a little higher. BUT to get this the coolant temp needs to be over 70 degrees.
Ah ok closed loop. You need to follow MSDs instructions to set the co pot in the central c position that will give a ball park the use the gas meter you need to be around 1% co dont worry if its a little higher. BUT to get this the coolant temp needs to be over 70 degrees.
Reset the CO - hot and at idle it's fluctuating between 0.4 and 1.0. Probably about as accurate as I'm going to get with a Ł80 Gunsons gasmeter.
Without the ISCV plugged in it's quite stable now, but as soon as we plug it in, it goes nuts up to 2000rpm and drops down and back up all the time. Just did a second video showing it, this afternoon:
TPS is a red bodied PF09. Having now looked at some of the bodges that were made to the engine (silicone on the throttle body idle screw), I'm now feeling that may need a closer look and possibly re-adjusting.
Not silly at all. I think it's going to be a case now of doing exactly that - going over each and every sensor, making sure it's plugged in, and plugged in to the right connector on the harness. Fortunately MSD made it so easy to check.
Now that the ISCV has been changed with new, literally the only remaining original sensor is the TPS, everything else (crank, phase, ect, knock, oil pressure, act, etc) was replaced with new when building the engine up.
One thing I haven't got connected up yet is the diagnostic LED breakout from the MSD loom. I've got a dash warning light and a toggle switch ready for that. I guess it won't hurt to see if the ecu thinks there are sensor problems.
Haven't done either a voltage or resistance check on the TPS. Tried to get access to it today to see if we could try moving it and oh, it's going to be such a pain in the mk1 engine bay - we've got water pipes running under the inlet manifold which wouldn't be there in the Sierra or Escort Cosworth. Fun!
I think that's going to be next on the to-check list if I can persuade my wife to let me have another day working on the car tomorrow, instead of sitting in traffic waiting to go somewhere along with everyone else on bank holiday monday....
Unfortunately not, I'm based in the north east, somewhat between Durham and Newcastle. If I'd been closer to MSD I probably would have got them to do quite a bit of work putting the engine together and wiring it.
Just did a TPS test this morning - 0.07-0.1v with throttle closed, 4.60-4.65v wide open.
Going to have a good check over every sensor and make everything is tight and connected up correctly.
Can't see much more that could be at fault. Only other thing left to do is spray carb cleaner or something similar around the intake to see if it could be an air leak; I have my doubts since every gasket and seal on the intake and exhaust side was replaced when I built up the engine.
Everything else seems to check out okay now. It's just as soon as we connect the idle control valve up it starts to run erratic.
Tried from cold this morning without the valve and it started up fine, albeit running sluggish around 600-800rpm as it didn't have any assistance from the valve.
I can understand now why so many people leave them disconnected!
Fuel pump is a brand new Bosch 044 with a pre and post- filter. It runs directly from the battery (boot mounted) via a heavy duty relay, so only a few feet of cable. The MSD loom has a fuel pump relay output switch and I'm running that to the relay in the boot, so that line should have no load on it whatsoever:
Pre filter, Bosch 044 pump and big post-pump filter.
Fuel pump relay powered directly from battery. Triggered by low-load fuel pump output in the MSD custom loom.
Just did a TPS test this morning - 0.07-0.1v with throttle closed, 4.60-4.65v wide open.
Going to have a good check over every sensor and make everything is tight and connected up correctly.
Can't see much more that could be at fault. Only other thing left to do is spray carb cleaner or something similar around the intake to see if it could be an air leak; I have my doubts since every gasket and seal on the intake and exhaust side was replaced when I built up the engine.
Voltage is too low thats why you have clicking in your amal valve
Voltage is too low thats why you have clicking in your amal valve
So the TPS should be adjusted to bring the closed voltage up to what? The 0.3v figure? We can try that. I will say that with the ISCV disconnected and a warm, steady idle, the amal doesn't make any noise.
So far, in the last two days, we've done:
- Replaced seized ISCV with a new one.
- Reset CO screw and set to between 0.5 and 1.0% CO whilst hot and idle.
- Adjusted base idle to around 800-900rpm.
- Checked TPS voltage, which was 0.07-0.1v closed, 4.65v wide open.
- Checked fuel pressure; with vacuum blocked set to 3.5bar; it was 3.8bar.
- Found the idle bypass screw was gummed up with silicone, so replaced the o-ring.
- Checked all sensors are connected up to the right connector in the loom.
A couple of points of observation:
- The idle adjustment screw doesn't make very much difference at all (ISCV disconnected, of course); it seems to only affect the idle right at the very extremes of its range. With the engine up to temperature it will idle at 800-900rpm at almost any point of the adjustment range, other than the extreme points, where it either drops off to almost stalling, or increases up to 1200-1400rpm. It also hunts when you get to either of those extremes. This doesn't seem right to me.
- Tried spraying carb cleaner around the intake system to check for leaks; found no evidence of any.
- Without the ISCV it idles nicely when warm, revs willingly and is quite smooth.
- Even with the nice steady warm idle, hooking up the ISCV again immediately starts hunting and revs bouncing up and down again.
Again, the loom is all brand new, as supplied by MSD - so it's not been hacked or chopped in any way. There's a good solid supply to the fuel pump, direct from the battery and activated by the fuel pump output from the MSD loom.
Spark is good from the two ignition amps and coilpack.
Appreciate all the help so far!
Last edited by megatron-uk; 29-05-2017 at 04:13 PM.
Voltage should be around 0.20 volt,but sometimes need adjusted little higher if not have stable idle.This is important when idle is lean like lamda around 1,like you should have with closed loop chip.Also plug gap is important.
Originally Posted by megatron-uk
So the TPS should be adjusted to bring the closed voltage up to what? The 0.3v figure? We can try that. I will say that with the ISCV disconnected and a warm, steady idle, the amal doesn't make any noise.
So far, in the last two days, we've done:
- Replaced seized ISCV with a new one.
- Reset CO screw and set to between 0.5 and 1.0% CO whilst hot and idle.
- Adjusted base idle to around 800-900rpm.
- Checked TPS voltage, which was 0.07-0.1v closed, 4.65v wide open.
- Checked fuel pressure; with vacuum blocked set to 3.5bar; it was 3.8bar.
- Found the idle bypass screw was gummed up with silicone, so replaced the o-ring.
- Checked all sensors are connected up to the right connector in the loom.
A couple of points of observation:
- The idle adjustment screw doesn't make very much difference at all (ISCV disconnected, of course); it seems to only affect the idle right at the very extremes of its range. With the engine up to temperature it will idle at 800-900rpm at almost any point of the adjustment range, other than the extreme points, where it either drops off to almost stalling, or increases up to 1200-1400rpm. It also hunts when you get to either of those extremes. This doesn't seem right to me.
- Tried spraying carb cleaner around the intake system to check for leaks; found no evidence of any.
- Without the ISCV it idles nicely when warm, revs willingly and is quite smooth.
- Even with the nice steady warm idle, hooking up the ISCV again immediately starts hunting and revs bouncing up and down again.
Again, the loom is all brand new, as supplied by MSD - so it's not been hacked or chopped in any way. There's a good solid supply to the fuel pump, direct from the battery and activated by the fuel pump output from the MSD loom.
Spark is good from the two ignition amps and coilpack.
Voltage should be around 0.20 volt,but sometimes need adjusted little higher if not have stable idle.This is important when idle is lean like lamda around 1,like you should have with closed loop chip.Also plug gap is important.
I'll definitely give that a go - try to increase the closed voltage from 0.1 up to 0.2-0.3 or thereabouts. Will probably be the weekend now, as I don't have access to the car during the week (stored at my parents house at the moment, since my dad has a ramp and tools and stuff).
Also the after market ISCV have very weak springs in them, I've always found they open far to easily and cause massive idle issues. Work fine if you re use the springs from the old valve if they were OE.
I've had a similar reply from another forum member over on Turbosport.co.uk, where my build thread is. I still have the old valve so will try disassembling the two of them and swapping over the springs this weekend.
Okay so we swapped over both internal springs from the old valve to the new one - it has made no difference.
Also adjusted the TPS up to read 0.34v closed, 4.5v wide open. Again, no difference.
Still an erratic idle, still hunts and still revs itself with the idle control valve plugged in.
Something bothering me is why there is virtually no difference with the idle bypass screw almost for the entire length of travel until the very extreme ends. Why did the previous owner of the engine have the idle screw siliconed up?
Beyond replacing the idle bypass screw and a whole set of new engine sensors (all of which where new when I built the engine up anyway) I've got no idea where to go from now.
Even without the ISCV it's just not idling right, the idle screw just doesn't seem to do anything other than when it's all the way in, or all the way out. The 30-odd turns in between just don't seem to do anything. We had to take the throttle body off today to adjust the TPS (that was fun!) and I looked it over carefully - no stripped threads, no cracks, no damage to the spindle/butterfly, gasket is undamaged. Nothing.
Warmed up and with no electrical load, yes we can hit a sweet spot on the idle to get it around 800-900rpm. But I can't make it 1000rpm or 1100rpm, for example. It also wants to hunt all the time (I can't get it to sit at 800rpm for any significant length of time).
I haven't tried disconnecting the amal valve. I can give that a try. At this point I'm willing to try anything.
In addition to the idle bypass screw I have a new act and ect sensor coming. If I could get it running close enough I'd finish it, get it MOT'd and take it somewhere to get it checked thoroughly, but at the moment I don't think it's near enough running well to even get through a test and don't want to risk driving more than a short distance in case it's too rich or too lean.
There's a local Ford meet at Ryton this tuesday, I'll have to see if I can grab the attention of someone with either an original Escort/Sierra Cosworth or mk1/mk2 conversion and see if they know any knowledgeable local tuners.
Last edited by megatron-uk; 04-06-2017 at 05:07 PM.
In terms of testing the amal valve - I just leave it unplugged, correct? Obviously with the car static and no boost building it's not going to have any adverse affects in that respect?
I tried combinations of running the old bottom spring with the new top one, old top one with new bottom one, as well as both old springs. Tried different tensions on the nut as well, nothing seemed to make any noticeable difference:
Old and new ISCV springs.
The old spring is definitely stronger than the new one, but also significantly shorter.
Unfortunately I have no way of logging any data or checking AFR; I'm just using a standard narrowband Bosch sensor.
The old bottom spring may need a stretch, try to adjust its length so the piston sits about 2-3mm under the top of the iscv, before the top spring is fitted.
Dad called earlier to say that he tried extending the spring and it seems better - it doesn't seem to jump when the ISCV is connected any more and started from cold around 1400rpm, dropping down to something approaching normal, although it was hunting a little bit, it was only very slight, not the 200-400rpm surging that it was doing before.
We're both not convinced that it's completely solved, but it certainly sounds like a noticeable improvement. Still not a huge difference on the idle bypass screw, so we'll see if the new one fixes that one.
It's definitely looking like this engine would have had considerable running/idling problems and the previous owner has certainly had to bodge things to get it running.
28-05-2017, 12:18 PM
4x4 YB running in a mk1 Escort - idle speed problems
