Testing Fuel Pressure, Spark (Chasing KR)

It's the first step in tracking down my mystery KR. I have 6 re-manufactured injectors and a new fuel rail sitting here - waiting for phase 2.

Have you tried putting in some race gas to determine if it is false knock. It may be your rockers or downpipe making noise. I would try to borrow a known good knock sensor and try that also. When does it knock?

Yes, I put in some 100 octane unleaded. It made the knock go down, but only a little bit. I also put in some 89 and got lots of KR in the same areas I saw with the premium. It's real knock, imo. Sometimes it's even audible. Almost seems like lack of fuel delivery. Just a gut feeling.

If your tune is the same, have you changed any thing else? I suspect you tried new plugs so maybe plug wires, Coil or possibly your MAF. Is it knocking in all gears? Is the knock boost dependant or mabe tip in knock? I know the frustration as I chased knock in my Turbo car, it turned out to be a head gasket.

Tune is the same. Only change is the tranny was rebuilt. I have not changed the plugs in a while. I will try that next. Wires are about a year and a half old. MAF seems okay, but I will clean it again to be sure.

It will knock in all gears, but usually not in 1st unless the engine is very hot and/or I mix lower octane. On straight 89 oct, it easily knocks in first. On 93 or better, I get a little (2-3ºKR) after the 2nd shift, then quite a bit (4-6ºKR) on the 3rd shift. On a hot day, it will just knock all through 2nd and 3rd gears. This is typical behavior for my car, but KR numbers are a few degrees higher than a year ago.

WOT downshifting from 55-75mph will usually show 5ºKR or more for a second or two. I've always experienced this, but it used to be 2º. Adding fuel doesn't seem to help, which has led me to think one or more of the injectors may not be performing 100%. I want to have them checked, so hopefully we'll know something.

The KR is absolutely boost dependent, and since it goes up with lower octane, It makes sense that it's not false. Thanks for the tips.

Chuck Leeper at www.codymotorsports.com is a good source for injector cleaning and flow bench work. Lots of Turbo Buick guys use him.

Sounds good. I'll use him, then. I'll make sure to say that you recommended him.

I've recommended him before as well. He did my injectors too.

Dennis, good idea suggesting to check the plugs. I needed to pull them anyway, as I usually do every 20k miles. It was about time. Tonight I found some interesting clues. I also want to make two important notes:

1) Scanning is important to do. Even if you don't think you have knock or any other reasons to scan, it can tell you things. If I had not scanned, there would be no way to know my car wasn't running 100%. It felt fine, idles fine, looks fine; it doesn't smell, smoke, or make any unusual sounds. It's also strong at WOT. But the scan showed slight KR, which isn't normal. This made me start with checking fuel pressure, then on to pulling the plugs.

2) Keeping plugs fresh is smart. Here is why I don't use platinum or iridium plug trying to squeeze 100k miles out of them - checking and replacing spark plugs frequently can reveal potentially serious problems before they get out of hand. Same goes for engine oil, imo. Why anyone would try to extend the life of $20 worth of petroleum for 10-15k miles is beyond me. Why not keep on top of things? Why take chances?

This image shows what the plugs in cylinders 1, 3, 4, and 5 look like. These plugs have seen lots of WOT activity, occasional knock, and both hot & cold weather driving. This is basically how all my plugs have looked every 20k miles for ~135k miles since I've owned the car:



Here is the plug from cylinder #2:



And here is the plug from #6:



Trying to figure out if these two are coated in carbon, ash, oil. or a combination. Possibly a lean condition from a clogged injector(s) made this happen?

I've not yet scanned for KR today. That info should be helpful in figuring this out. Anyone want to guess what #2 & #6 plugs are covered in, and what it means?

looks like oil on #6. #2 looks a drier, so I wouldnt say that one has oil on it. But #2 does look like a lean condition.

Yeah, I'm agreeing. I think both #2 an #6 are lean. #6 also has some oil. I don't like that, but not sure what I can do about it right now.

try this guide.

http://www.centuryperformance.com/spark-plug-reading-spg-192.html

Thanks, Dennis. After reading that, It really appears to be ash deposits, which could be caused by foreign materials inside the combustion chamber. I'm suspecting oil or coolant right now. I'm also hoping it could be from running lean because of bad injectors.

However, after scanning yesterday, the KR hasn't gone away. It seems less, but I don't think those plugs were the complete cause. The New injectors will go in cylinders #2 and #6, and then see if anything changes.

my.02- coolant leak. Are you running the AL104"s? Seems like a lot of deterioration for only 20kmi.

Very odd that just those two cylinders have all the deposits and the other four are normal.

Bert:tavis:

AA wrote:

Thanks, Dennis. After reading that, It really appears to be ash deposits, which could be caused by foreign materials inside the combustion chamber. I'm suspecting oil or coolant right now. I'm also hoping it could be from running lean because of bad injectors.

However, after scanning yesterday, the KR hasn't gone away. It seems less, but I don't think those plugs were the complete cause. The New injectors will go in cylinders #2 and #6, and then see if anything changes.

have you replaced your LIM yet? I dont recall you saying so in any past thread.

No, I have not. Depending on how quickly the plugs go bad, it may be time to do this soon. I'll see what they look like in 1000k miles.

AA wrote:

No, I have not. Depending on how quickly the plugs go bad, it may be time to do this soon. I'll see what they look like in 1000k miles.

You may have already done so, but if not perhaps you should have the oil analyzed.
Have you had to add any coolant to the system?

Bert:tavis:

Oil's in the mail....

AA wrote:

No, I have not. Depending on how quickly the plugs go bad, it may be time to do this soon. I'll see what they look like in 1000k miles.

cough cough ported SC cough

AA wrote:

I would like to remove it when I'm finished.

prolly a great idea

Ok, 6 new (re-man stock 36#) injectors are in. I was only going to replace #2 & #6, but at 162K miles, for all I know, all of them could be bad. With the new rails, if I need to swap any out, it'll be easier because I can do font and rear banks independently.

After installing the injectors, on the test drive last night I didn't see much KR, but I wasn't pushing the car all the way. I also had a fire extinguisher in the other seat. Something was different, though. It was more evident this morning on the way to work.

Today, I pushed the car a bit harder. Saw 1º KR under hard acceleration at high speed, and a few peaks w/ 3º max from 0-100 WOT. The difference I noticed earlier was now very obvious. I couldn't wait to stop and graph the acceleration scans.

For reference, here's a scan from last year, showing three near identical WOT runs at three different ambient temps:



Note that 85ºF was slowest, followed by 75ºF, and finally 55ºF was the best - as expected. These were all recorded in 2007. The yellow curve was copied from the above graph into the new one below, along with two new curves:



The red curve is a WOT run recorded last week; the blue one was recorded this morning, after installing the new injectors. And I'm now running pig rich using the MAF tables from the old injectors. I used to cruise at -1.6 or -2.3 LTFT on the freeway, now I'm between -5 and -9 LTFT. I'm assuming after I tune the PCM again, not only will it be even faster than it is now, but there will be some added benefit to fuel economy.

Look at that blue curve again. This is a HUGE performance gain! It feels like when I installed rockers... I probably I picked up 20 HP since last night. If your car has high miles, and feels sluggish, maybe it's something to look into. I still cannot believe the difference it made for me.

I've mentioned this before too. Most injectors are probably NOT working right on high mileage cars. They should be cleaned and flowed. A HUGE difference after installing injectors in my car (although I didn't record like you did. That's a great benchmarking idea!!)

If only I'd installed the injectors before last week's meeting with the EVO, that story may have turned out differently.