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Post Info TOPIC: Suzuki Vitara 1.6 8V Fast Idle problem


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Suzuki Vitara 1.6 8V Fast Idle problem
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So we think we have an air/vacuum leak, maybe the ISC is faulty? the idle looks to be a bit to low for that but we can test it anyway. For this test we needed to use Rhinoview and its RPM Control. First test was to set the idle speed to 1000RPM and see if the ISC could control engine speed when a bit more air was called for:

 

Engine Control by diagnostics on Suzuki Vitara

 

We can see that the ISC flow rate increased to 45% and the ECU was able to bring idle up to the target speed and was in control so the ISC is fully functional. Just for interest I set the idle speed to 500 RPM:

Suzuki Vitara no idle control

The results from that test confirmed what we saw when using TunerPro, in fact we could probably have just done this test but I wanted to present two different approaches. We have an air/vacuum leak, we just need to locate it.

 



__________________

1984 Suzuki SJ413K pick up, 1.6 16V Baleno engine
2000 Suzuki Vitara 1.6 8V, many mods
2004 Suzuki Ignis 1.5VVT 4Grip
2006 Suzuki Jimny 1.3VVT JLX+
and many more.



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The scaling of the history table may look a little odd but it is scaled the same as the VE map which allows this feature to be used for tuning VE values.



__________________

1984 Suzuki SJ413K pick up, 1.6 16V Baleno engine
2000 Suzuki Vitara 1.6 8V, many mods
2004 Suzuki Ignis 1.5VVT 4Grip
2006 Suzuki Jimny 1.3VVT JLX+
and many more.



Guru

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Posts: 1178
Date:
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This is a Suzuki Vitara with the 8V engine, its a 2000 model but is essentially the same as any 1991 through to 2001 Vitara. The problem is that it is idling at around 960RPM and has a hesitation coming off idle. The ECU is a 1112 type ECU and there is a comprehensive TunerPro adx definition for this model. The SDL interface was plugged in and TunerPro fired up:

 

Suzuki Vitara fast idle problem

 

The engine was warmed up for around 15 minutes, target idle was showing 800RPM but the idle was at 970RPM, 800RPM target and no CEL warning indicates that the ECU is not in a back up mode. The coolant temperature was showing fairly solid at 80C so no problems with the CTS. The O2 sensor was switching rapidly between 0V and 1V, this is unusual as it would usually show between something like 0.1V and 0.9V, the fuel trims were not moving and the rich/lean flag was indicating permanently lean, this indicates that the ECU is trying to control fuelling but cannot. IAC flow is quite low at 10l/min indicating that the ECU is trying to reduce air to bring down the idle, everything at this stage points to an air leak on the intake side.

As further test I created a history file to show fuel trims relative to RPM and Load (MAP in mBar). An air leak will have more effect at idle because there is less air flow, as the load increases so will airflow a leak will become proportionally lower. Graphing the fuel trims showed up an issue with the definition, the STFT ands LTFT values are swapped, the table below actually shows the STFT:

Suzuki STFT comparison table

The TunerPro definition outputs the decimal value for the fuel trim. 128 is equivalent to zero, below 128 means the ECU is running lean and above 128 means the ECU is running rich.

1000RPM/483 mBar is the load cell that the ECU is hitting at idle and as load increases the fuel trim returns to normal, another pointer to a vacuum leak.

One problem with using the history tables in this way is that TunerPro logs all hits- including those during fuel cut which can skew the readings, the history table is set up to average over 20 values so with OBD1 it only takes a few seconds for any spurious readings to be averaged out.

 

 

 



__________________

1984 Suzuki SJ413K pick up, 1.6 16V Baleno engine
2000 Suzuki Vitara 1.6 8V, many mods
2004 Suzuki Ignis 1.5VVT 4Grip
2006 Suzuki Jimny 1.3VVT JLX+
and many more.

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