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[buznout]

Had an issue with the idle surging after a cold start up. Looking through the forum I found a resolution buried in a thread so thought I would post a quick knowledge base type post. Credit to all who post on here but mostly Sprocket for odd specifics about injection minis...

 

ISSUE: At cold start, idle would settle at 1000 then increase decrease up to 1500 and return to 1000. Eventually causing the engine to struggle and nearly stall. No modifications to idle screws, throttle etc. Was working one day then just stopped the next

 

CAUSE: Stepper motor should control idle while cold to increase idle speed but was not in this case. Surging related to CPU adjusting advance.

 

SOLUTION: With the accessories on without motor running, from the throttle body, fully actuate throttle linkage from closed to fully open 5 times. (In my case) It caused the stepper motor to reset, audible clicks heard similar to what it should do after engine shut down. Started the engine and issue resolved

[humph]

Have had the same problem as the op before, and the solution above is the logical place to start as it's zero cost.  Unfortunately my issue was more deep seated and costly, and initially intermittent so took a while to track down. My advice to anyone suffering from the issue above is to open their turn off any stereos & open their window/door before turning off the motor. As soon as the motor turns off you should here a series of rapid clicks and whirs, which as the op states is the stepper returning to it's start position, if these are not present there is a problem.

 

To resolve my issue we went through the following steps, with a few in between I've forgotten, start with the cheap checks.

• Reset stepper as above
• Check wiring loom from ECU to stepper - The stepper is a small circular device to the right hand side of the throttle body, the case has a series of holes in it. http://www.minispare...ic/JZX3062.aspx
• Checked the vacuum pipes as per Sprockets guide in the injection forum, this link is to a pdf version I think http://ukcooper.co.u.../Spi faults.pdf

• Checked the coolant temp sensor

• We then did some other checks, but ultimately the garage diagnosed a failed stepper, so this was replaced. But they were wrong, and I was out of pocket!

• With no resolution I sent the ECU off to a specialist who immediately confirmed that the stepper position being calculated was incorrect & had failed. Repaired within 24 hours and returned.

This ecu repair wasn't cheap (£150), and that was 6 years ago ish, so make sure you discount all the cheaper stuff first.