Dams76

Can someone take a look at my log file and provide some direction on what I need to do to get it running right. Attached is a log file from SCAN9495 of the car at idle. Also if I try to give it gas it tries to die out, this is not in the log file. I can take another log log of that if needed. Thank you for your help.

Here are my engine mods if it helps. Cam, port matched heads and intake, delteq, vortech s-trim, 60lb injectors, electric water pump, dual intank fuel pumps.

DavidS

Injuneer

I'll take a quick look at it, but I haven't reviewed a lot of forced induction tunes.

Opening the log, it's not really useful. Run time is only 92 seconds, not enough for the PCM to go into closed loop. Typically, takes 206 seconds (programmed time out value) to enter closed loop, and coolant temp has to be above ~120*F. Your coolant temp has only reached 108*. Third requirement is O2 sensors hot enough to work, and flags indicate both left and right sensors are ready. Are you possibly running an open loop tune? If it's not an open loop tune, you have to start it and run it for at least 5 minutes to get anything meaningful. Probably a good idea even with an open loop tune, to get the coolant temp up to "normal".

Idle had a cyclic surge pattern. Programmed idle is 950 to 988 RPM (varies with coolant temp). Your idle is cycling up and down over a range of 850 - 1130 RPM. The IAC is not responding to the surge. Not sure if that is typical for a FI setup. Who tuned it?

Are you running a 1-bar MAP sensor tune?

I've seen people post logs for review in the Forced Induction forum. Not sure is they get any responses. In this case, I think it would be a good idea for me to copy this thread to the FI forum. Normally we don't like a thread posted in multiple forums, but there is not a lot of traffic on Forced Induction any more. But there are a few smart FI guys that will help if they show up.

Dams76

Than you for the reply. It's an Ed Wright tune. I'll get another log file tomorrow.

DavidS

Dams76

Attached is the new file. It appears as though once it gets into closed loop the engine really starts surging, and then you will see that it starts jumping in and out of closed loop.

DavidS

Injuneer

I'll try and take a look at the file today.

Injuneer

Prelim review:

-it's dropping out of closed loop because the Bank 2 O2 sensor is going static. Sensor is extremely sluggish.

-Bank 1 O2 sensor never goes static, but it seems to be reading high when its cold.

-both banks have dropped the long term fuel trims to 108 (minimum possible with stock LTFT limits), so it's pulling at least 15% of the fuel out with the LTFT"s to keep it from running rich, and in some cases has to use the STFT's to pull even more fuel out.

Are the injectors high impedance or low impedance units with an outboard driver?

I assume DTC 16 is the result of the Delteq install. Why is DTC 48 for the MAF sensor there? Seems to be working fine. Did you unplug the MAF sensor at some time, causing that code to be stored? Pull the "PCM BAT" fuse for 30 seconds to see if it clears the code(s).

-very slow to heat up the coolant. Are you running a t'stat? Or is this just the result of the constant high flow from the electric water pump? I would think with even a 160* stat it would warm up faster than it does.

Who tuned it? Has it ever run right w/ the blower? I've seen a lot of unexplained problems with the Delteq. Funny thing is even the designer JC Hyde admitted that there were some cars it wouldn't work with, he couldn't figure it out, and gave up and refunded the owners their money back.

I'll keep looking at it.

Dams76

Thank you for taking the time out to look at this. I really do appreciate it.

The injectors are high impedance Siemens injectors. There is no driver.

I'll try to clear the codes later this week. I don't recall ever unplugging the MAF while the car was operating.

I have a 160 Stat as well as rhe high flow electric water pump.

The car was tuned on a mail order from Ed Wright at fastchips. I know it has run fine before with the tune. Although it's been over 5 years since I have had the chance to start diagnosing it. At first I thought it might be fuel so removed the vortec inline pump and added the dual in tank setup. It appears to be getting enough fuel now, but still runs bad. I honestly can't remember if it ever worked with the deltec or not. I was hoping to rule out all the sensors with this diagnosis before I started removing things. I am deffinately not adverse to removing the deltec and will if you think it could actually be the problem. Thank you again for taking time out of your day to help me.

DavidS

Injuneer

I'll try and spend some more time on the data log. Just too many personal conflicting activities.

Injuneer

You have two major problems.... the right side O2 sensor and the constant surge.

The right O2 sensor is either near dead, had a really bad/corroded/damaged harness connector, or it's simply not running hot enough to work reliably. There's a heater in the sensor, but if the heater or the 12V heater circuit was defective, you would get a code. The sensor sticks in the range of 450mV +/-30mV, and the PCM indicates it's not ready, and goes to open loop. That takes the short term fuel trims out of the picture, so the PCM can't tweak the A/F. And something I have never seen before, it goes into closed loop at exactly the time for the timer (206 seconds), and while both O2 sensors are ready and the flag indicates it's in closed loop, the flag is not set for the long term fuel trims being enabled. As a result, the LTFT's are stuck at 128, it's running rich, and the PCM has to pull the short term trims way down, and after a while of running like that, the STFT"s mysteriously reset to 128, meaning its seriously overfueled (if the O2 sensors are accurate. When fuel trims are enabled, the LTFT"s drop like an anchor to 108 on both sides, typical programmed lower limit.

At cold start, the PCM is commanding a high idle speed, but the idle air control valve is maxed out at 160 counts open, and it still won't reach the programmed idle speed. Check the throttle body for an obstruction in the IAC passage. Some aftermarket TB's have a restriction, and in extreme cases require an additional hole to be drilled. You could open the blades slightly, but the TPS voltage is already at 0.75V, and you don't want to go over 0.90V.

Again, even after more than 9 minutes of idling, CLT is still only 164*F, which seems like a long time to heat up.

Things that look OK - ignition volts, MAP sensor, TPS, ignition advance.

Then there's the surge.... a constant cycling up and down between well above commanded, to slightly below commanded. That happens whether it's in closed loop, open loop, O2 sensor not responding, etc. So the surge is not related to the O2 sensor/closed loop issue. I think it may be compressor surge, but I have not looked at other S/C applications, so I don't know if that makes sense. This is where one of the S/C guys need to help out. I did look to see if I could find a correlation between cycling MAP and cycling RPM, but if it's there, I can't find it. The PCM does seem to add a degree of ignition advance (27*->28*) in response to the upward surge in RPM, but that could be in the table of ignition advance. Sometimes you can play with advance to try and control idle surge.

Wish I could be more definitive, but like I indicated, have not spent any time with S/C application before.

Dams76

Ok I have made some changes and the surging seems to be better but the car still isn't running quite right. Below is a list of what I have done.

Replaced Passenger side O2 sensor
Removed Delteq
New OptiSpark
New Wires
Removed Aftermarked Airfoil from the stock throttle body
Cleaned throttle body and IAC with Carburetor cleaner


Removing the Airfoil and cleaning the IAC seemed to reduce the surging the most. Please see new log file. The car was already warm for a previous start when I took this log file. If I need to pull another one from when the engine is cold please let me know.
DavidS

Injuneer

Downloaded. I'll try and take a look at it today.

Injuneer

Right O2 sensor problem seems to have been solved. It's going into closed loop, and not dropping out. Sensor readings are cycling rapidly in closed loop, as they should be. There are some times in closed loop when both sides appear to go lean, and stay there for a period of time, with the short terms trying to pull the readings up but even though they don't come up, it does not increment the long terms. Doubt that is causing your idle problems.

It is actually very useful that you started it with the engine hot. In open loop, the O2 readings tend to be very steady. So it's easy to watch for unexplained changes. For the entire period of open loop, up to the expected transition to closed loop at 206 second run time, the left O2 is extremely steady. That side of the engine could not be running any better, except for the fact the average left O2 reading is 856 mV. We'll get to that in a later paragraph.

The problem is on the right side. Periodically there is a sudden drop in the right O2 sensor from reading the same as the left sensor (800-900mV) to dropping leaner. Sometimes it's just a frame or two of data dropping below 750 mV, which may indicate the misfire of a single cylinder. It's random, so it's not a single cylinder continuously misfiring. It's intermittent. Then there are other times where the right O2 drops into the lean area, dropping below 100 mV in the extreme. These upsets last as long as 13 seconds, although most last from 1 to 4 seconds. I would assume these are misfires of more than one cylinder. Would definitely appear as periods of a very rough idle.

In spite of locating the side of the engine, it's not possible to state which cylinders are the cause. Since it's so random and intermittent, could be a sticking valve, sticking injector, etc. A bad plug or wire would be more likely to be there all the time.

Once it goes into closed loop, since it is only idling, it goes into cell 16. And then the long terms start to drop, in response to feedback from the O2 sensors that it's running on the rich side. The left bank long term (LTFT) drops all the way to the stock programmed 108 limit (= subtracting 15.6% of the calculated fuel requirement), and the right side LTFT drops to 116 (subtracting 9.4%). The difference between the left and right sides could be explained by the right bank continuing to have fits of misfires, dumping air into the exhaust, making the right O2 report less of a rich condition than the left side. The perceived rich condition could be the result of the injector size/offset in the tune, or a faulty MAF calibration.

There still appears to be a +/- 100 RPM surge. That could be a response to the misfires, or something related to the compressor map.

Dams76

Thank you again for taking a look. I know it has run successfully with this tune in the past so I have a hard time thinking it might be the tune but who knows.

So if I am reading what you wrote correctly it could be a sticking injector, a spark plug or a bad MAF.

Looking for your feedback, what would be your next steps to fix the issue

DavidS

Injuneer

You have two distinct problems:

1). Intermittent misfires on the right bank at idle. Could be anything that affects spark (plug, wire), fuel (injector), or compression (sticking valve, faulty lifter, valve train issue). Maybe there are other things related to the S/C that affect fuel and compression. As I noted, I do not have much background in forced induction applications. I would think a faulty plug or wire would show a constant problem, not the intermittent problem you have..

2). Running rich on both banks, forcing the PCM to pull excess fuel out using the long term fuel corrections. Could be high fuel pressure, inaccurate MAF calibration (in PCM), faulty MAF, incorrect tune.