8 replies to this topic

[garethkhill]

Hey All

 

My Japanese 1993 1.3 SPI with Cat has developed a rough idle in the last week or so. I have read & read & read as many of the posts as possible and tried to trouble shoot. I'd appreciate your support interpreting the following symptoms as well as readings I have obtained from a Sykes-Pickavant ACR4 with Rover Pod3.

 

Symptoms

 

 - A rough idle at cold that improves when the car warms up but is still noticeable.

 - The car drives and pulls well and intermittently the idle will drop very low and almost stall when coming to a stop.

 - When the car is at normal operating temperature I notice that the blower in the car only blows cold air e.g. does not blow hot even with the knob pulled out all of the way.  

 

What Ive Done So Far

 

I've tried to be as methodical as possible so:

 

 - Checked the breather lines and noticed one was quite loose; do these need to be tight i.e. with jubilee clips or just a pressed fit. 

 - Checked the vacuum lines and replaced the red one (just because I had a new one) as well as the one from the Fuel Trap (green) to the ECU. The one previously had been cut at the ECU end and there was a silicone vacuum line with zip tie securing it (PO not me)

 - Checked the stepper motor and reset it (by putting ignition on II and fully engaging throttle). I noticed that when the car was running at idle then the lost motion linkage isn't always in the middle. 

 

 

ACR Readings

 

So Ive measured these on two different days so that I can give a range of what I am seeing

 

ERROR COUNT                                         =   ZERO/ZERO

RPM (Engine fully warmed)                        =  967-1009 / 911-958

IDLE SWITCH Ignition On, Not Engine      = ON/ON (interestingly in the manual it says CLOSED/OPEN, I assume CLOSED = OFF and ON = OPEN?)

IDLE SWITCH Engine On                           = OFF/OFF

MAP SENSOR Ignition On, Not Engine     = 99/99

MAP SENSOR Engine On Idle                   = 28-30/ 28-34engine cold down to 28-30engine warm

ECT Engine Warmed                                  = 77/80

IAT Engine Warmed                                   = 51/37

BATTERY VOLTS                                       = 12.8/12.9

THROTTLE POT.                                        = 0.52/0.32

LAMBDA SENSOR                                    = 895-905/235-740

 

When the engine was warm the gauge in the car read just below the half way mark. 

 

I also checked the temperatures of various parts of the engine when it had warmed up, with results as follows:

 

 - Top of the Radiator 78

 - Engine block near a spark plug 73

 - The bottom heater hose 60

 - The top heater hose before the inline valve 60

 - The temperature thermostat housing 66

 - Air Filter 35

 

Your feedback and input is greatly appreciated.

 

Thanks and Regards

G

 

 

 

 

 

 

 

 

 

 

 

[garethkhill]

Hey All

 

So a bit more digging today and some interesting findings:

 

1. The Sykes Pickavant will record that the idle switch is "ON" or "OFF" rather intermittently

2. The heater now blows hot - I just don't think I let it warm up enough the last time I check

3. When I ran it today the Lambda sensor readings were high 800's and not dropping below this. Again sometimes it fluctuates within the range, others outside of the range.

 

Looking at the Sykes manual, it states that a vehicle with a faulty throttle position will not run correctly at idle. So do you think the Sykes manual is "telling" me that this is where the error is with the stepper motor? At idle (especially when warming up) I can see the stepper motor move forward and backwards. 

 

Thanks and Regards

G

[sonscar]

Not familiar with the Mini injection but the stepper motor moves in response to engine Rpm mainly to keep the speed in the range advised by the ECU map.Steve..

[Curley]

Sounds like an issue with the idle control. The stepper motor will open to let more air in, which the ECU compensates with additional fuel, to maintain a smooth tick over. If there is an air leak of the valve is staying open this would explain the Lamba being off. 

[FlyingScot]

Okay first thing to clarify is if the car has a throttle idle switch, easiest way is to look into the drivers footwell and check for it. In early cars this was used to tell the ECU that it should be throttle released.

 

The other thing immediately obvious is that the cars engine coolant temperature isn't/or hasn't in your data reached "operating temperature" which means that the ECU things the car is still needing excess fuelling.

 

Only when it reaches about 88C with the ECU detecting this with it switch to closed loop and use the lambda to adjust the fuelling.

 

Cold air from the blower when it should be hot is a sign all is not quite right with the engine cooling circuit and should be checked. Ideally you want to replace the thermostat making sure you fit the correct SPI 88C one and flush the system out whilst you are at it (I normally reverse flush with a garden hose myself).

 

Don't forget the usual service items (vacuum pipes and fuel trap) and if any doubt replace  although the MAP reading looks right. 

 

Breather pipes are mainly push on, but check for leaks.

 

Reset the lost motion linkage gap - its in Haynes or in one of the pinned links where you can download a factory manual.

 

Stepper motor faults are rare- ish, the car will adjust the stepper by itself when running, but what you can't see is that MEMS ECU also adjusts the timing. Its usually more concerning when it doesn't move.

 

FS

[garethkhill]

Thanks All

 

I appreciate the replies. 

 

Thanks FS for pointing out the throttle idle switch - I think that this is parts number NNS10001 - I will check the car tomorrow and report back. 

 

Ironically I used the car for work today and the symptoms were not present or at lease not to the same degree. 

 

Regards

G

[garethkhill]

Today I have inspected the footwell and accelerator pedal to see if I have signs of a throttle idle switch, which I don't see however the carpets were interfering in the accelerator linkage so I have cut some carpet to ensure no fouling. Also I read on another forum post that these were for the two plug ECU's and I have a 1 plug ECU. 

 

Car again today is not displaying the same symptoms, after waiting for the car to heat to 88 (it took a while to be honest) then the readings were as follows:

 

ERROR COUNT                                         =   ZERO

RPM (Engine fully warmed)                        =  926-959 no obvious fluctuations, was a fairly steady tick-over

IDLE SWITCH Engine On                           = OFF

MAP SENSOR Ignition On, Not Engine     = 99

MAP SENSOR Engine On Idle                   = 28-31 Although was very consistently at 30

ECT Engine Warmed                                  = 88

IAT Engine Warmed                                   = 38

BATTERY VOLTS                                       = 13

THROTTLE POT.                                        = 0.52

LAMBDA SENSOR                                    = 195-700

 

So I assume that the gremlin has disappeared, just a shame I didn't find the exact cause and hope it won't come back to haunt me. I have purchased some 3mm ID vacuum silicone hose that I will most likely swap at least the fuel trap to manifold as that has come off twice in about 4 months - roads in Toronto are very bumpy. 

 

Thanks for the input and advice, much appreciated. 

Cheers

G

[FlyingScot]

Yes with only one plug it won’t have the throttle switch - sorry it might have been easier to check this.

 

If the problem reoccurs check your engine coolant temperature ECT reading as this time it reached the 88C for the thermostat to open and for the MEMS ECU to switch to closed loop. If it doesn’t go this info it will assume the motor needs fuelling as if it were “cold”

 

FS

[garethkhill]

Hi FS
 

Will do, thanks again.

Regards

G