With the help of a friend I did get the datalog done on my car. Nothing stands out to me as looking crazy, but I'm hoping the knowledge of others will see something I don't. I'd like to find what is contributing to the low mpg and stalling issues I've been having.

 

I am by no means an expert, but the first thing that jumps out at me is the BLMs are very erratic, jumping around a lot both above and below 128. On average they are low though (115 ish), indicating a rich condition, which could contribute to stalling and certainly low MPG. Definitely pull the spark plugs to confirm. There are also some knock counts registering, which would hurt performance as well, if the ECM is pulling timing.

 

Thanks for the input. I'll pull a spark plug tomorrow and check. Any one else's opinion would be great too!

 

At light throttle your BLMs are at the minimum of 108 indicating you are extremely rich. This could be the cause of the stalling and poor mpg. As was said before there is also knock counts. These are showing up at WOT. At WOT your O2 sensor is NOT showing the extreme rich condition.

If this engine is mostly stock with the stock prom and not knowing any history of the car here is what I would guess to look at:

1. Ignition problems - check plugs, wires, cap, and rotor

2. Fuel problems - leaky injectors, regulator

 

History: 200+K miles, stock engine, all typical maintainence is done regularly. The wires, cap, rotor, coil, plugs have all been recently changed. O2 sensor and CTS are less than a year old. Other than the fuel filter, the whole system is stock to my knowledge, so I would lean more towards the fuel system at this point.

 

The rich condition at light throttle I agree would probably indicate fuel system unless there is a misfire that you have not mentioned. However, I doubt the knock counts at WOT is fuel related as you O2 sensor looks decent at WOT.

 

I punched it the other day and it poured black smoke out the back...id say its got some unburnt fuel sitting around...

Soon as the weather warms up ill pull the plugs and check them out. I was thinking the FPR how can i check it? Im assuming its vacuum operated can i just pull the vac hose off and see what happens? I dont even know how to check the fuel pressure on TBI.

Like she said all regular maintenance has been done. Only other mods are Open Element filter, high flow cat with a 3" catback.

Thanks for the help guys.

On a side note, it has been a little warmer the past week(right until yesterday now its hell out again) and we averaged 14mpg.

 

Stock tbi FPR is not vacuum operated. There is also no valve to connect a guage to so you need to get an adaptor to put into the feed line where it enters the tbi.
Is the IAT sensor put into the base of the open element air cleaner?
Also if the injector o-rings are leaking you should see fuel dripping from the bottom of the injectors at idle.

 

I would have Steve go check it now but it's snowing, so perhaps we'll do that tomorrow. Thank you for the help.

 

-Im going to try and get a fuel pressure adapter later this week.
-The IAT is not in the base of the open element filter. Can you tell me how this will effect the reading, back when we got it we were told it does not have to be in the base of the filter just hanging loose and not interfering with anything.
-Injector O-rings are not leaking.
Here are pictures of the #1,3, and 2 cylinders. I was lazy but needless to say they appear the same. They look pretty normal to me but id like a second opinion:

 

Steve, plugs look fairly normal, but I have never been great at reading plugs. The IAT sensor can effect both fueling and transient SA. The reason I asked was because at the start of the log file the IAT was in the 120 degree range. BLMs seemed pretty normal. As the car was driven the IAT reading went down to the 65 degree range. It also appeared that the BLMs went lower (rich condition) at the same time that the IAT was dropping. You might want to try drilling a hole in the air cleaner base and mounting the IAT sensor. But you may have more success mounting it to see a stable temperature in the 150 degree range like near the intake manifold.

On my setup with the open hood scoop I pretty much had to flatten all the IAT tables to kill there adjustments because of the wildly fluctuating temperature changes.

 

That makes sense but when we started the datalog the car was cold, like it had been cooled off for over an hour and was like 20-30 degrees that day. I find it hard to believe the IAT was actually at 120 degrees at start up then actually cooled itself off during driving? Its under the air cleaner close to the manifold if anything it would have been hotter i would have thought then if it was sticking in the air cleaner because there is no flowing air over it. Do you follow what i just said it might sound confusing.

This may be a possible bad IAT im gonna check out how to test it unless you know off the top of your head. EDIT - Resistance? How much is normal?

Thanks i appreciate your help.

 

Steve,
It may not be related to the IAT sensor but just a trend I noticed in the datalog. I have attached a graph of some of the log values which shows what I noticed. Also you can see from the graph that the Knock counts are occurring on acceleration.

The engine was still above 150 degrees at the start of the log so the IAT temp may well have been at 120 until you started driving and cool air flow drove the temps down. So I doubt that the sensor is bad. I do not have the sensor resistance spec at the moment.

Al