1128 and 1130 still... Idle is HORRIBLE

[stateofidleness]

Gents,
I've been chasing these two codes since I got the car it seems (several years ago). '00 base with Tiptronic - 77k miles

Just recently, I noticed the idle is VERY poor, and on deceleration to a stop, or stopping at a light/sign, it will dip to about 450-500 and bounce heavily between 500ish and 600ish until I give it gas. When I barely touch the gas, it seems like the RPM's will shoot up to about 1500-1700.

What's odd is that once it bounces around for a a bit, it will eventually "smooth out" and seem fine with only the occasional "hunt" like every 5 seconds or so.

This behavior is even worse and more pronounced if I have driven the car, parked it for a short while, and then go drive it again (shopping, errands, or going in to work, then leaving for lunch).

I have recently been hearing a "chirping" sound when it did this low idle bounce which the forum had suggested was a loose spark plug. So this past weekend, I changed out all my spark plug tubes, as well as re-tightened all plugs. It seems like this has resolved that issue as I have not heard a chirp since.

One thing I noticed while doing this was one of the rubber tips on a coil pack was almost torn off completely. Like 90% around was torn.

Some extra info: Car has secondary bypass pipes and a Che muffler and I DO have several small exhaust leaks at the different joints.

The car was recently in the shop for a transmission rebuild (Tiptronic $$$$) and no vacuum leaks or anomalies were visible by my Indy (who I trust a lot).

It seems like only recently this hunting has gotten worse, so I want to take care of it once and for all. What should my next course of action be? I was thinking of either doing O2 sensors (do I need all 4?) or all new coil packs. I was also planning on replacing my exhaust manifold gaskets next weekend as well. MAF has been replaced twice in the past year (both Bosch) to eliminate that as a source. Oil cap is easily removed with engine running.

Thanks!

[thom4782]

If the idle hunting was between say 600 and 1100 and all else was well, I'd suggest the throttle body needs cleaning. Did the idle return to this range when you re-tightened the plugs?

[MN 986]

Have you considered the AOS? I had the same codes recently and similar idle bouncing, and while I did not necessarily hear chirping, I have read that a failing AOS can make some odd noises. Mine actually made a light hissing sound when the car was warmed up. Check it by trying to remove the oil filler cap while idling. Difficult to impossible to remove indicates a failing AOS. I was amazed at the difference with the new AOS,,, the cap comes right off. I think my AOS was failing for a long time, but it started to smoke upon starting regularly about the time the idle bounce started. It all was resolved with the new AOS.
Good luck.

[jcb986]

My understanding is that O2 Sensors do not cause an engine to hesitate or idle roughly. Just disconnect one and see the difference for yourself. If you can or have someone with an extra coil pack, try changing one coil pack at a time and see if it is one of them. You can also clean the throttle body. There is a cam sensor that could be going bad and of course a vacuum leak, which is the hardest one to find. Now lets think inside the engine and what could cause the problem. One is a burnt value or a cam lobe that has worn down enough to cause the problem by not allowing the valve to open enough.

[ProjectM96]

O2 sensors could cause the engine to hesitate while accelerating.

Coils could definitely cause rough idle and misfire.
I would replace the coils, which should be replaced everytime you do a tune up.

[Topless]

Intake and exhaust leaks need to be fixed and your idle will smooth out. The codes listed are common for intake or exhaust leaks. The car is running lean.

[shadrach74]

Originally Posted by Topless

Intake and exhaust leaks need to be fixed and your idle will smooth out. The codes listed are common for intake or exhaust leaks. The car is running lean.

How does the ECU read an exhaust leak aft of the post cat O2 sensor? It seems to me that anything from that point back makes no difference to the ECU. If id does,please help me understand how leaky bypass pipes cause idling issues?

[BYprodriver]

Originally Posted by ProjectM96

O2 sensors could cause the engine to hesitate while accelerating.

Coils could definitely cause rough idle and misfire.
I would replace the coils, which should be replaced everytime you do a tune up.

My 2000 S with 102,K miles has the original coils. If they misfire it lights the CEL.

[BYprodriver]

Originally Posted by shadrach74

How does the ECU read an exhaust leak aft of the post cat O2 sensor? It seems to me that anything from that point back makes no difference to the ECU. If id does,please help me understand how leaky bypass pipes cause idling issues?

The ECU reads that the engine is running lean beyond the ECU's capability to compenstate. Exhaust leaks is 1 of many possible causes.

[shadrach74]

Originally Posted by BYprodriver

The ECU reads that the engine is running lean beyond the ECU's capability to compenstate. Exhaust leaks is 1 of many possible causes.

How does the engine read a "lean run" condition from a leak aft of the metered section of exhaust? There is no O2 sensor on the mid-pipe/secondary cat. The only leak the ECU would have the ability to detect would be between where the manifold meets the exhaust port or an actual hole in the manifold/header. I cannot understand your assertion that the O2 sensors are capable of sensing anything downstream of their positions...

[Topless]

Originally Posted by shadrach74

How does the engine read a "lean run" condition from a leak aft of the metered section of exhaust? There is no O2 sensor on the mid-pipe/secondary cat. The only leak the ECU would have the ability to detect would be between where the manifold meets the exhaust port or an actual hole in the manifold/header. I cannot understand your assertion that the O2 sensors are capable of sensing anything downstream of their positions...

Shad,
We don't really know where his exhaust leaks are for certain. We have not seen them and he "may" have more exhaust leaks than he is currently aware of. We do know that an intake or nearby exhaust leak will foul the sensor readings and contribute to rough idle. Simple process of elimination. Fix the obvious thing you are certain is wrong and move on to the next. This is always more effective than changing out perfectly good parts.

[shadrach74]

Originally Posted by Topless

Shad,
We don't really know where his exhaust leaks are for certain. We have not seen them and he "may" have more exhaust leaks than he is currently aware of. We do know that an intake or nearby exhaust leak will foul the sensor readings and contribute to rough idle. Simple process of elimination. Fix the obvious thing you are certain is wrong and move on to the next. This is always more effective than changing out perfectly good parts.

I see what you're saying, but he made it pretty clear that the leaks were around the bypass pipes. I'm not advocating changing out parts, I agree that the intake is the one of the places I'd look if I had a rough idle, slip joints at the mid-pipes...not so much.