Gen 2.5 lean condition help

[quailchaser]

I posted a while back about rough idle and acceleration after a rebuild. Some requested a video to hear the engine. I finally got it back together and even figured out how to use the torque app to check the fuel trim and 02 sensors. It showed the long term fuel trim on bank 2 at 25% with bank 1 close to 0%. I thought the down stream 02 sensor was bad because it stayed low while the upstream oscillated. I replaced it and no change. I did seem to notice a slight puff sound, though. I'm wondering if I could have an exhaust leak or some sort of leak around an injector. Any guidance would be appreciated.

The video is too dark to see, but hopefully you can hear the puff sound.

https://youtu.be/boznaFVf2xA

Frank

 

[Salonika]

How many miles do you have on the rebuild?

 

[Painted Mountain]

Typically a vacuum leak. Sorry i cant watch any videos now but use a hose as a stethoscope to locate exactly where the sound is coming from. Carefully of course. Smoke machines work great too! I have a federal emissions vehicle and I can have a exhaust leak without throwing a check engine light no problem. Not sure about Cali. emission but in that case the bank should direct you to the side of the engine you should be focusing on. Maybe someone else can chime in on that. On federal emission bank two is after the cat.

 

[quailchaser]

Thanks for the thoughts. I didn't think it was a vacuum leak and couldn't find one, but I'll look closer with proper test equipment. At least I now know it's one side.

I have less than 100 miles on the rebuild. I retested the leak down and get a little leakage by the rings, but consistent and low (under 20% on cold dry cylinders if I remember). I couldn't detect any leakage anywhere else.

FYI, the rebuild was due to smoke and 200,000 miles. One burnt exhaust valve was replaced and the cams ground. The cylinders were ball honed only (machine shop wouldn't even hone them as the machinist said they looked great and it would be a waste of time and money). Everything was checked for flatness, etc. and cleaned.

I'll update after the vacuum test.

 

[mike5]

If I understand / recall correctly, bank 2 is running very lean. As a result car is adding fuel. I remember something like if the percentage is greater than 8 it throws a check engine light per OBDII specifications. Are you getting any codes?

I'm no expert but I don't think vacuum works in a divided way between the banks. In other words a vacuum problem would effect the entire engine.

Given that it's on one bank I think narrows down the problem. Normally I'd say you might have a bad O2 sensor but it sounds like you took care of that. If there is a second sensor for bank 2 replace that as well. Nothing to lose. Having said all this could you have an injector or other fuel delivery problem on that second bank? I don't think an exhaust leak would lead to such a severe compensation in fuel trim.

On a side note, using short term fuel trim is also a good way to see under what condition it is dumping fuel. In other words even at idle and part throttle you have the condition or under load for instance.

 

[RyanY]

I'm no expert but I don't think vacuum works in a divided way between the banks. In other words a vacuum problem would effect the entire engine.

A leaking injector seal or lower intake manifold-to-head gasket could cause a localized vacuum leak.

I don't think an exhaust leak would lead to such a severe compensation in fuel trim.

An exhaust leak won't effect the O2 sensor readings - O2 sensors read the percentage of oxygen in the exhaust gas, not the volume. Losing some exhaust gas through an exhaust leak won't change the percentage of oxygen being read by the O2 sensor.

 

[quailchaser]

I did a quick spark test with a test light. I got spark from all coils but no idle change on cylinder 2. I'm thinking a clogged or bad injector. I'll test it tomorrow if the weather holds. I just hate having to take the intake off every time I mess with plugs or injectors.

 

[mike5]

For the leak, I was thinking more along lines...not hardware. But that of course makes sense.

With respect to my 96 SR, injectors have been one of those areas that required attention. I had to rebuild 5 of them and replace a 6th one. What I did was have them all removed and sent to RC Engineering. They tested all of them and rebuilt the ones they could. They also sent a report showing before and after flow and pattern reports. I may have at another point replaced another injector...but honestly I don't recall right now.

Here's a thought though (and why I like OBDII), if the computer is adding 25% fuel for a lean condition, is the O2 for bank 2 still detecting a lean condition? In other words you should have a code for a lean condition. And even if you don't, a good scan tool can get the voltage of the O2. So you can check the voltage on the downstream O2 for bank 2 and see what's going on. That'll be a clue.

Finally, if you have one bad injector, I would think dumping more fuel on the other 2 cylinders in that bank would make the mixture rich enough where the situation would be corrected from the computer's perspective. But if it is still running lean, then arguably you have an issue that is impacting 2 or 3 cylinders in bank 2. Again not a mechanic but I've around cars...

 

[quailchaser]

Still waiting to check cylinder 2 - its raining here. I did hear it clicking (used stethoscope) so it may be clogged. I also rechecked for air leaks, I found a small one at the manifold differential pressure sensor, but I also found a pretty good leak at the speed adjustment screw on the throttle body and also the gasket between the throttle body and intake plenum was leaking. I think I had it on backwards. Once it dries out, I'll tackle the leaks and check the injector for clogging. Hopefully that will fix the lean condition and the miss.
Frank in AZ

 

[snare]

What was the outcome?

 

[quailchaser]

Still working on it. Had a torn CV boot that led to new ball joints, etc. (don't ask). Anyway, it's back on the road and I should take it to the shop for full diagnostics in the next week or so.

 

[quailchaser]

Update: Took it into the shop after it threw a P0173 code again. Shop thinks timing may be slightly off. Hopefully that is all it is.

 

[Offroadmuch]

Update: Took it into the shop after it threw a P0173 code again. Shop thinks timing may be slightly off. Hopefully that is all it is.

How do you make minor adjustments to the timing on one of these trucks?

 

[Salonika]

I don't think you can make adjustments. It's either right or wrong.

 

[Salonika]

The downstream sensor doesn't oscillate as the converter evens out the exhaust gas mixture. Only your upstream o2 sensors play a role in engine mgmt. fuel trimming.
If you were that lean due to a bad injector, I'd guess that you should also have a misfire.