25 replies to this topic

[Spherix]

Hi there,

I was really hoping not to have to post about this goose chase, having read many similar topics. Unfortunately, to no avail.

I've freshened up the SPI engine I had with the car by changing most gaskets, the oil pump, setting valve clearances and so forth. Gearbox was not separated. These are the first few runs I'm doing with this engine bar having driven it in/out the garage to change orientation a few times.

What I'm running in to at the moment is the idle seems to stick around 1200 RPM if I cold start it and leave it to warm up, but as soon as I touch the throttle it comes back down to just shy of 1300 rpm and stays there.

To rule a few things out:
- All vacuum lines are new, and re-inspected
- The loom was carefully inspected and some connectors have been replaced
- The lambda and flywheel sensors are 'old' (as came with car)
- The inlet manifold temp sensor is new
- The throttle body has partially come apart during resto/cleaning, where I've replaced the two gaskets of the spacer block. All looked clean and straight and nuts are tight.
- I have deleted the charcoal cannister and purge valve, the hose that runs from the breather rail is currently blocked off with a bolt, I was planning on hooking that up to the petrol tank breather pipe later; the purge valve connector hangs loose on the firewall.
- I followed the procedure of setting the stepper by having ignition in 2, pushing the mechanism fully in and letting it go while the gas pedal is fully depressed. After hearing the stepper do something, turn ignition off and confirm the adjustment arm is centered.

Before the first run, the stepper motor seemed to get stuck in a loop upon connecting the battery and putting ignition in setting 2. It went on for a few minutes and took a few randomly timed battery disconnects / connects & ignition key 0-1-2 changes for it to come to a stop. I've had this happen in the past while building the car, and couldn't find out if others have had this here. After it stopped, the stepper does seem to operate as expected and it hasn't reintroduced itself. The battery was very frequently disconencted while building the car fyi. See Https://youtu.be/_qWmAft9wFw for a recording of this.


The first run went like this:
- Engine cold
- Battery reconnect
- Contact to position 2
- Push in throttle mechanism fully while leaving pedal depressed
- Contact off; TPS lever sits centered
- Contact on, engine start
- Runs smooth ~1200rpm
- Leaving coolant to run up to 92 degrees, not entering closed loop
- Once I give the throttle a single push, rpms stick at 1400
- After restarting engine, RPM's stick to 1400-1600


Contact off & on again:
- TPS % is at 12
- Stepper Motor Position Steps reads 68
- Lambda reads 435
- Short term fuel trim 0
- Long term fuel trim -28
-> Engine start
- Coolant dropped to 89 degrees
- Idles at 1300
- TPS % at 10
- Stepper motor 0
- Lambda still 435
- No errors/faults
- Fuel trim values same
- Still no closed loop
- Blip the throttle and back at 1400+ rpms


Depending on the various of 3 tools that I've connected to see if that many any difference, some give a static lambda value of 435, others read a varying value in the 800's. Mems-Scan 0.5.2 read MAP errors, values between 36 and 40 at idle. It says it's indicating a leak, but as mentioned it's all new and inspected, including the brake servo and spraying brake cleaner around the inlet manifold etc.

Then later today, I took it for a drive around the block:
I Didn't bother to warm up fully before leaving, using the car as you'd normally drive off. The first acceleration had a slight stutter, but it pulled and ran beautifully smooth in a few laps around the block, although the idle still sits at 1200 RPM allowing the car to drive by itself with the clutch depressed in second gear.

Upon return to the garage it sat at 1200 idle again while opening the door, and after driving it in it somehow started idling at 1000 rpm. I connected the diagnostic cable to see what had changed, and noticed that the engine changes speed and needs a few seconds to get steady again upon connecting the diag cable only on the engine side. Not a clue if that's normal? Upon connecting diag software, I see no faults, the closed loop was actually working and the lambda seems to read a bunch of values as well. I hit the throttle once, and we're back at 1300-1400 RPM idle...

I've attached a log of the last minute or two of idling upon connecting the cable with the engine still hot, perhaps the more knowledgable people here can figure out where this is going wrong. I'll happily make more logs in different situations of course if that helps. I've also read that people suggest the ECU needs to learn it's own map, and you should drive it for a while to get that sorted. How much and what sort of drives should I be doing, and would that aid tjhis issue?

Thanks for the long read!

Attached Files

•  2022-07-26_18.22.txt   8.9K   8 downloads

Edited by Spherix, 26 July 2022 - 07:08 PM.

[genpop]

"Depending on the various of 3 tools that I've connected to see if that many any difference, some give a static lambda value of 435, others read a varying value in the 800's. Mems-Scan 0.5.2 read MAP errors, values between 36 and 40 at idle. It says it's indicating a leak, but as mentioned it's all new and inspected, including the brake servo and spraying brake cleaner around the inlet manifold etc."

 

 

Even you did all this already!

 

When looking to your logfile, i guess there is an air leak on the throttle body or brake servo.Check the replaced gaskets. Or spray some brake cleaner round the throttle body for searching where it soaks the air in. (caution: brake cleaner is highly flamable!) Disconnect all hoses to the throttlebody and close them, then tray again.

And ignition advance is a bit high but this may be due to the high rpm.Throttle angle is ok and IAC is at  zero because it tries to compensate the high rpm.According to hot idle it should be in the range of 28 under normal condition.

Edited by genpop, 27 July 2022 - 07:52 AM.

[Spherix]

Thanks! I had a quick look at the servo this morning and can at least rule that out. Pedal works as expected, pulling the hose from the grommet released a good pop of vacuum, and after blocking it off entirely at the manifold I hear no differences. Guess I'll take the whole intake manifold off today to inspect further!

[Tones61]

Air leak,
prob inlet gasket to head

[Spherix]

Some progress was made! I found out that the left hose here:

 

 

 

Had the wrong diameter and was pulling in false air. After grabbing a hose a milimeter smaller and putting a hose clamp on it for peace of mind, a slight hissing noise I thought was just the air filter also vanished and the car started idling at ~1000 rpm while warming up. The MAP reading error I had earlier also went away.

 

While going through a full warmup cycle having the engine idle, I noticed that some errors came up that I can't find much info on:

 

The RPM error gauge here indicates 'the difference between engine RPM and target RPM'

and was varying between 50 and 200 depending on engine temp and me hitting the trottle.

 

And on the errors page, I noticed the Idle Air position bottom(...) lit up:

 

If I blip the throttle, the rpm's won't go below 1200 again, but I noticed that if I let the clutch come up a bit to put strain on the engine, the RPM's would settle at ~950-1000 again. 

 

I've ran another log from the warmup cycle, I hope you can point me in the next right direction!

[genpop]

where is the log?

[Spherix]

Oh shoot, I keep missing the second button to upload

 

See attached; thanks for your time!

Attached Files

•  2022-07-27_20.15.txt   96.99K   3 downloads

[Spherix]

Adding another from a run just now after having made a small throttle cable adjustment (3 full turns of the nuts):

 

Before I hit start logging it actually went under 900rpm for about 20 seconds, but shot up a bit after without me doing anything. The log has a few start/stops in it fyi.

 

I'm not sure if it's related or a separate issue, but I noticed again that if I blip the throttle, RPM's keep sticking at around 1200 rpm. As soon as I now turnt on the lights and heater, RPM's dropped back to the 900'ish again. My alternator also makes a continious whining noise that I thought was a crappy bearing in a new item, but that noise vanishes once under load by the lights/heater. Could this be related somehow?

 

 

Attached Files

•  2022-07-28_12.07.txt   104.26K   1 downloads

[genpop]

Have you closed all the four tube connections on the throttle body?What happened then?

map is still to high about 40 should be 35. You must have an air leak.

On this side MEMSFCR.co.uk you may find a description for setting the Iac, but first find the air leak.

[Spherix]

Thanks for hanging in there! I wasn't sure if I logged that at the time, but just went ahead and did just that, bar the one going to the fuel trap. Result was that the car quite quickly went down to ~850rpm, even though the MAP seems unchanged. Blipping the throttle etc. made it still go back down to ~850 RPM. (see log)

 

Then, through process of elimination, I reconnected the hoses 1 by 1 and found out the previously mentioned hose (left in the picture) still seems the cause of the irradic behavior. I'm quite certain it seals very well now though, so it made me wonder if the other 3 hoses (the big one on top and the 2 next to each other) that connect to the breather rail are not always open, but the one giving me the issue is?

 

When I had it all blocked off I did notice an instant increase in crank pressure by leaning over the filler cap and getting blown in the face through the pinhole in it, should I be checking compression again?

Attached Files

•  2022-07-28_12.07.txt   180.59K   4 downloads

Edited by Spherix, 28 July 2022 - 11:59 AM.

[Spherix]

Ahhhhhhh I think I figured it out after looking at diagrams! I had switched around the two smaller hoses. The right one should connect to the left and plugs in to the crankcase breather rail, the left hose should connect to a smaller tube on the breather rail that connects to the purge valve. I was under the impression they were all connected, so didn't think much of it.

 

Switching them around means the left one only pulls air once the purge valve opens, instead of a continuous crankcase pressure.

[genpop]

When you look to the engine.The left one on the back  is for the fuel trap, the right one is for the air flap inside the air filter.

Have a look to the repair manuals.

[Spherix]

I did not mean the vacuum hoses at the back, I meant the two breathers at the front, as shown in the diagram pic I posted earlier. All seems to work fine now, although MAP still hovers close to 40 at idle

[genpop]

But your log is still not ok. map to high, iAC too low,ltftr too low, stftr too low!

Attached Files

•  spherix.JPG   79.35K   9 downloads

[Spherix]

While the values don't lie, I'm not sure what symptoms I should still be having then? It idles at 850, pulls smooth and fast, comes back to down to idle quickly as well.

When the vacuum & breather ports were blocked I also sprayed brake cleaner on ans around the throttle body, inlet ports at the back of the head and servo hoses without and change in RPM. What could still cause the values to be off?