Suzuki Forums banner
1 - 9 of 9 Posts

·
Registered
Joined
·
108 Posts
Discussion Starter · #1 · (Edited)
Hi everyone, I've got an interesting problem,

Auto, 2.0L, All stock, Second cat removed.

Problem #1: rough idle after warm up and under any load at idle. Shifting into gear causes idle to drop to 600 and not recover very much when shifting back to neutral. IAS motor? It seems to extend and retract when removed.

Problem#2: Surging while holding throttle steady. Only +-100 RPM and more noticeable under load while driving. I usually run with it disconnected for good driveability.

So far I've looked at the MAF, TPS, MAP, All are reporting correct voltages throughout their ranges while cold and hot without any change.

I think problem #2 is just the upper O2 sensor being slow as the fuel trim follow's the up and down surging of the rpms and its a smooth up and down every 2-3 seconds. It does switch from 0-1v on scanner.
It only started once I changed it out for a used one to test with. The original one worked but had a heater circuit malfunction.
With it disconnected the surging goes away. And so does my gas millage :p

The idle problem seems to have come on gradually over time but has become much worse with the weather now.


And something completely weird: If I blip the throttle just slightly off idle it will die down and then rev fine after that point. I can feather on and off the throttle in that range and it will actually almost stall out. This is the 10-13% TPS range Above that its ok. I just used a zip tie to set the TPS above 13% and live with it.


And something new that may be a symptom of the above issues. When letting off the gas to coast it feels like a standard because of the level of engine breaking. Its only when I hit below 17% TPS that it goes into engine breaking, If I keep it at 18% it coast's down just fine. But If I let off just a little bit more it surprises me.



I'll try anything to diagnose it.

I have access to a 99 ECU and all sensor's to try out. Any idea's ?

thanks
 

·
Registered
Joined
·
108 Posts
Discussion Starter · #2 ·
Also, I just changed the Cam position sensor, That didn't help anything but I got it for free and it was brand new, so why not :p
 

·
Registered
Joined
·
2,100 Posts
I think problem #2 is just the upper O2 sensor being slow as the fuel trim follow's the up and down surging of the rpms and its a smooth up and down every 2-3 seconds. It does switch from 0-1v on scanner.
It only started once I changed it out for a used one to test with. The original one worked but had a heater circuit malfunction.
With it disconnected the surging goes away. And so does my gas millage :p
A slow O2 sensor response is a sign it's time to buy a new one (or two if it's the 2.0l V6?) They have a limited life span and aren't designed to last forever.

Replace what you know isn't working properly and go from there. I had a dying O2 sensor in another vehicle and it caused all sorts of driveability issues- just like you've described. The "after warmup" also raises my suspicions as that's when the ECU would be switching to closed loop and using the O2 voltage feedback. It should respond immediately to mixture changes or else it isn't working properly.
 

·
Registered
Joined
·
108 Posts
Discussion Starter · #4 ·
It behaves the same at idle with or without the sensor attached.
I could watch the sensor show lean followed by an increase in STFT, After that it show's rich and a decrease in STFT. But with it disconnected I get the same idle problems but smooth drive-ability.


How sensitive is this engine to types and brands of O2 sensor's ? Is there one I should go for ?
 

·
Registered
Joined
·
108 Posts
Discussion Starter · #5 ·
Well I went ahead and bought a cheap O2 sensor for $25 off of ebay and installed it today.

Funny thing is that it actually worked and worked well!
It solved the surging while driving.

I was comparing how it switched compared to the old one on a chart and it would literally switch 3-4 times before the old one finished one cycle from 0-1V.

So it has good drive-ability now.

The idle has improved. I've put 500k on it since last resetting the computer and started using good gas with water remover along with a good throttle body cleaning.

Still hasn't fully learned the new O2 sensor though as its still burning slightly rich but clearing up faster each time I drive it.
 

·
Registered
Joined
·
108 Posts
Discussion Starter · #7 ·
The typical Denso or AC Delco that GM usually replaces them with is around $180 I suppose if it lasts that long its ok but I didn't feel like paying that just to see if it was the problem.

I figured I could get a cheap one and hopefully it lasts 40k. Even if it only lasted 10k each and I had to buy 6 of them, Its still cheaper than 1 OEM sensor.

Let the experiment begin :hyper:
 

·
Registered
Joined
·
12 Posts
The typical Denso or AC Delco that GM usually replaces them with is around $180 I suppose if it lasts that long its ok but I didn't feel like paying that just to see if it was the problem.

I figured I could get a cheap one and hopefully it lasts 40k. Even if it only lasted 10k each and I had to buy 6 of them, Its still cheaper than 1 OEM sensor.

Let the experiment begin :hyper:
Sorry for resurrecting an older thread, but OP any update as to whether the O2 sensor fixed your low idle issue? My 2000 has the same issue, low idle and vibrating when engine is at operating temperature, in drive/reverse.
 

·
Registered
Joined
·
108 Posts
Discussion Starter · #9 ·
O2 sensor fixed surging while holding throttle steady.
Did not fix the low idle problem.
I've even tried a new computer and idle is the same.
Tried another maf, tps, map... can't find the problem yet but one thing that helped was putting a zip tie on the spot where the throttle pully closes just so it opens the throttle a bit at idle.
 
1 - 9 of 9 Posts
Top