Hey guys, I've been trying to figure out what is wrong with my car for awhile now. I was driving it and I noticed the left o2 sensor was bad so I replaced both, the next day I went to start it and I was getting 9 degrees of igition retard and the car died after 10secs, so I took the plugs out and noticed they were fouled out and I started the car with the knock sensor unplugged, it ran fine but I heard the belt tensioner was making a knocking noise because the belt was too long, so I put on a shorter belt. Then I noticed I had the wrong plugs for the trickflow heads, so I got some NGK FR5s in them. The engine still has .3-.7 of retard as soon as I start it up. I ran it without the serp belt, and I used a mechanics stethoscope to listen for any noise. There is no audible noise that could be interprited as knock that I can hear. The one day that I drove it when the o2 sensor was bad it was detonating for about 1 minute, but the knock sensor didn't show anything so I though it was just a missfire of something.
Since I got datamaster and the cable I see that the car runs fine in open loop, with only .3-.7 of retard, then when it goes into closed loop it goes crazy. I know its running very rich becasue I turned up the F/P a bit just incase something was wrong with the new o2 sensors so it didn't run lean again. Also I know there is a DTC for the fan rely circuit but I didn't let then engine get above 210, and I don't think either of those will cause the knock sensor to go crazy.
The first log I tried I messed up, but when the engine was idling I held the throttle open a bit and it would rev up and slowly go back down while I was holding it. Then when it started to die I revved it again and it backfired once out of the intake.
The second time I let the engine run is when I got Datamaster to work.
I hope i saved it right, this is the first time I used it.
http://www.file.sc/4ae597/ihatethiscar.uni
I'm going to try to get the F/P right and fix the fans, then I will get another log. Please let me know what you guys think, I'm not very good with this computer stuff.

 

I forgot to mention my engine is 10.25:1 compression, and I only use 93 octane. Also its a brand new Knock sensor from Advanced Auto, I forget what brand it is but it wasn't AC, could that have anything to do with it?

 

Do you guys need me to post up a csv. file? I'm not sure if this is a knock problem or a fuel related problem, but its driving me crazy, all help is appreciated

 

Well I cant exactly tell you whats wrong but Ill point out the things that arent normal.

First the IAC count is "0" for the first half of the log.. then it goes into closed loop and the IAC jumps to 125... and last it goes back into open loop with IAC of 160 which is the max. It almost appears you have a vacuum leak judging by the IAC but then why is it 160 towards the end of the log... doesnt make much sense except that the RPMs are higher at the beginning of the log.

Next are your O2 sensors. They really arent working. They should be fluctuating from .000-.999 volts but I never saw them go beyond .400-.600... thats not right.

Your TPS voltage is kinda low too... it should be around .70 volts.

And last the MAF is showing up to 16 gps air flow at idle... thats WAY too much. I wouldnt think youd see more than 10 gps at 900 rpm.

But Id say first you should fix the O2 sensor problem. Go find yourself some AC Delco O2's. Then turn the TPS sensor so its at .70 volts OR maybe try killing 2 birds with 1 stone and crack the TB blades a little to bring the IAC counts down around 50.

 

if its open loop will it still show what the o2 sensors are doing? when I actaully tried to drive it down the road I saw the o2 sensors fluctuating up and down so I didn't think it was the o2s, but I'll get some AC ones anyway. I'll open the TB more, but will the PCM think i'm pushing on the gas becasue the voltage is higher then it was each time I ran the car or does it compansate for that? Also, what would cause the MAF to be like that? Thanks for the reply

 

I wouldn't be worried about the TPS voltage (0.45V is withing the accepted range) or the MAF readings. The fact that the O2 sensors seem to have no range of movement at all, and the DTC for high MAP showing up at record 455 shows some sort of issue either with the MAP sensor, then it goes out of closed loop at record 480.

The PCM seems to think its running excessively rich, and its bottomed out the long term fuel corrections in Cell 16. But even though its pulling out the max value of 15% fuel, it never really seems to have affected the O2 sensor voltage. It pulling the fuel because the O2 sensor voltage is above 450mV.... but if it was so rich is needed to pull 15% of the fuel, the LT's should have been near 1000mV when it went into closed loop.

Find out why the O2 sensors are reporting correctly. Find out why the MAP went bad in record 455. If the MAP really went that high for no reason at all, its like the valves were sticking open or something. That would also explain the high MAF reading, since a lot of the air is just blowing through the open valves (but that is not showing up in the O2 sensor readings). Things were fairly stable, until approx record 350 and on, when the MAP started climbing on its own, reaching 97kPa at one point. The knock retard almost seems to track the MAP. That makes sense, since as MAP goes up, the advance should go up..... but none of this should be happening at idle, with the throttle completely closed.

 

Does any of this indicate a vac leak? Could the Bosch o2s have gone bad already from it running so rich? The MAP sensor is brand new with a new gasket, but I will check the connector, maybe its loose.

 

I think the reason that MAP was reading so high and threw the code was because the idle had dropped to 300rpm at one point... motor has no vacuum so the MAP reads high.

In fact heres how it all played out as I see it...

First quarter of the log the idle was high, vacuum was great, IAC was zero. Then it went into closed loop... almost immediately the RPMs started to drop and drop and drop till about 300rpm at which point the IAC kicked in. I dont know if this was because the motor was running too rich or too lean b/c the O2 sensors arent working! BUT its obvious to me that it wasnt getting enough air which is why the RPMs slowing died down. IAC didnt respond very fast but fast enough the motor didnt completely stall. But then the computer went back into open loop and the idle looked great, vacuum was great, IAC was really high now though but the RPMs were a little less than before. Everything is looking decent till the very end of the log you see it goes BACk into closed loop and started stalling out again.... you ended the log just a tad early though but you can start to see the pattern.

Replace the O2 sensors and crack the TB blades. Then have a beer.

 

Ok, I ordered some AC Delco o2s from gmpartsdirect.com. I'll open the TB and replace the o2s and set the F/P so its not running extemely rich. what I don't get is why i'm getting knock when it first starts up, then it goes away for a few seconds and then comes back strong, is that all because of the o2s and its not getting enough air?

I'll go get another datalog one first startup so the engine will be cold and I can run it a bit longer.

 

ok, I lowered the F/P, opened the TB more, TPS was .52 then. Started the car, and it ran like crap, o2s didn't move, IAC never moved either. Then it finally died. Here is that dataloag http://www.file.sc/686f94/test2.uni

then I charged the battery becasue it was hard starting the first time, then I start it, it has much less ignition retard, and towards the end the o2s actaully start working when it goes into closed loop, the engine was running fine in closed loop, but the IAC was still at 0. http://www.file.sc/eeec16/test3.uni

so i let it sit more, i replaced a leaking tranny cooler line, and fixed the fans. so i started it up again and it ran perfectly, i didn't have the laptop hooked up but my scanmaster was on, the o2s were working great, the fans came on and the temp went down, i let the car idle for about 15mins. Since everything was working i let ot off the jackstands and drove it around, everything was working right except the IAC, it was always on 0. when i would come to a stop it sort of wanted to die but i just put it in neutral and it got back up. I'm quessing it was becasue of the IAC not moving.
So it seems like the car doesn't want to run on cold starts. Could it be the forged pistons slapping when they are cold cause the knock retard? I'm clueless at this point, but the this car feels a bit too fast for the street

 

In the 3rd test it looks to me like the O2 sensors are working properly. Also looks like you cracked the TB blades too much which explains why the idle is so high and IAC is sitting at zero.

Heres what you need to do if you still want to do more testing... I beleive the new O2 sensors will help a lot though.. I have never been a fan of the Bosch ones.

But what you should do is turn the key to the "ON" position so you power up the O2 sensors. Now just let it set like that for 10 minutes to allow the O2s to heat up.. they have built in heaters... then fire up the motor and get a log. What this will do is make the O2's sensative to ARF in open loop and youll get a better idea if the motor is running lean/rich. Because right now all I see is its running perfect but obviously its not.. the .500mV reading is a perfect A/F ratio but they are cold so they arent reporting the correct readings.

 

I'm sorry I forgot to mention on the 3rd test I noticed the idle was at 1200-1300 so i adjusted it to 1000rpm near the end of test3, but the IAC still didn't move

 

Close it enough to see movement in the IAC... like I said about 50 is a good target to shoot for. Its nice to have datalogging software b/c you can easily set the idle.

 

I got another datalog today. The battery that I had was bad, I got it tested at Autozone and they said there were 2 dead cells, so I only had a old AC Delco battery that is also bad so I had it hooked up to a charger while starting, and it was difficult to start.
In this datalog it took the o2s a while to start working even though I had run the car for 5 minutes before. Now I'm having the opposite problem, the IAC is at 160 instead of 0 like all the other times. I tried revving it to see if it moved. Then I opened the TB more with the idle set screw and the idle got higher but the IAC didn't move. So I lowered the idle again and revved it some more times. Once the o2s start flucuating the car runs fine, just the IAC doesn't move at all. Its a brand new IAC, could the plunger be stuck? When I view it as a csv. file does IAC TGT mean the target position that the PCM is telling the IAC to go to? Also at idle, should the STerm percent be as close to 0.0 as I can get it by adjusting the F/P?
Here is the datalog, it a bit long, maybe close to 10mins.
http://www.file.sc/49180c/test4.uni

 

The data log doesn't tell you what the IAC motor is actually doing. The data log shows you what the PCM is telling the IAC motor to do. It has no way of knowing if the IAC is working or not.

You want your long terms at "0%" and you want them to stay there. The ST's will be 0% if the LT's are stable. A ST of 0% with the LT at any more than +/- 5% is not what you want.