Hairy W Bush

If anyone has Scan9495 please try opening this file. http://www.megafileupload.com/en/fil...03119-csv.html I am having problems opening them myself. But here's the issue: after a cold start after a minute, it will idle down a lot if I raise the rpms, and a lot worse when i turn on the ac. I cleaned the IAC, MAF, air filters and it helped. I even replaced the IAC and it persists. After it's fully warmed up I don't really have a problem with it. This morning I turned on the ac during this cold start and it just kept stalling.
From the scan, at idle my tps voltage is .69. At WOT it is 4.47(100%). An MAF line trouble code keeps flashing in and out but I believe it's just related to the issue which is possibly the tps. Is this adjustable or does this sound like a bad tps to you guys?

Cliff Harris

CSV stands for Comma Separated Values. You open this kind of file in Excel. Open Office (NeoOffice for Macintosh) can also open these.

You can open it with a text editor, but the result will be a scrambled mess of numbers (which is the reason you need the correct definition file when you're using a scanner program).

I could not open the file or download it from that link.

Hairy W Bush

oh I expected it to replay in the same program like datamaster does. I see what you're talking about now. I selected 'commas' on the import window when it asked and now it's clear. I also just downloaded it from the link so the link is working. This is from yesterday when it kept stalling so it says RPMS at 45 but it's really at 0. I don't know why it says that.

Cliff Harris

From what I could see, you need to be registered with that web site to download anything. I am not. I am registered with many web sites and get too much junk from them so I avoid registering with sites that require it.

Hairy W Bush

that's weird because neither am I. try this http://www.filedropper.com/dlog-save...yy22p1s5103119

jsiddall

Try disconnecting the MAF (with ignition off) then starting the car. If it runs better then your MAF has likely gone flaky. MAF codes are almost certainly the MAF and not TPS related.

As with all computer related stuff also double check all the grounds (PCM, MAF specifically) because bad grounds can cause all sorts of untraceable headaches.

Hairy W Bush

Ok where's the ground? It goes inside so I highly doubt that's it. I'll try tomorrow morning when it's cooled off to unplug it.

Cliff Harris

The ground associated with engine sensors is either on the side of the block above the oil filter or the upper bell housing bolt on the driver's side. The location changed from year to year.

Mine's on the side of the block. My buddy's '89 is on the bell housing bolt. It's actually a double stud -- I don't know the name of that kind of fastener. It looks a stud with a nut in the middle.

Hairy W Bush

I just got under and checked that ground. It's fine. I don't think this is a ground issue.
I checked the data again and it looks like it's going to closed loop really early. That and the 02 sensor volts vary very much. Th parts in the graph where the idle is stumbling, the left bank gets .1xx volts at idle while the other side gets double that.

Cliff Harris

The O2 sensor voltage is very low when it is cold. It rises as it warms up and the ECM assumes it's working if it goes higher than some threshold value. I think it's 0.450 volts. Once that voltage is reached the ECM switches to closed loop mode. This assumes the mixture is rich enough in closed loop mode to make the O2 sensor output go above the threshold. I think if the mixture were too lean it would never go into closed loop mode.

Once the sensor warms up, the O2 sensor voltage varies between about 0.200 volts and 0.800 volts (200mV to 800mV if your scanner program uses millivolts). The ECM varies the injector pulse width to make this happen and the cycle takes about 1 to 2 seconds. The mixture is always varying from rich to lean to rich.

Hairy W Bush

Gotcha. So that does mean something is up right there. Line 88 for example in the graph shows bank 1 02 WELL under .45v and it's in closed loop. Bank 2 is also even under .4v. So it's doing the opposite of what you're saying. Starts high and goes low. The engine temperature is only 111 so why is it in closed? I thought it changes when it gets up to temperature. It starts right at line 70 and that's exactly where the idle starts to go down.
What I don't get is why code 48 is throughout the scan. I disconnected the MAF when the car goes into this trouble mode and it just made it worse.

Cliff Harris

The ECM has certain parameters it checks to determine when to go into closed loop mode. My car only has one O2 sensor, so it might work slightly differently with 2 O2 sensors. Here are the parameters for my car:

Coolant temperature > 40.7°C = 104.4°F
Engine run time > 300 seconds (cold) if startup coolant temperature < 58.5°F
Engine run time > 206 seconds (warm) if startup coolant temperature > 58.5°F and < 158.5°F
Engine run time > 50 seconds (hot) if startup coolant temperature > 158.5°F
Oxygen sensor reading between 0.195 and 0.686 volts for > 10 seconds

From this it looks like I was wrong about the .450 volt threshold, but the idea is still the same -- the O2 sensor needs to heat up before the ECM goes into closed loop mode.

From what I've seen, the O2 sensor is the last thing to meet the conditions above. The engine run time will time out long before the O2 sensor is ready.

Hairy W Bush

it went into closed loop at 1 minute 44 seconds from cold (temperature > 58.5°F and < 158.5°F) so that is 104 seconds not 206.

Hairy W Bush

so nobody has any idea...
I replaced the tps and the issue is still there. I though maybe the tps volts were too high but they only dropped .02 at idle so i guess that's normal then...
I should probably mention that whatever it is it is affecting my mpg.

jsiddall

Does your temperature look sane? What about disconnecting the MAF? You may eventually need a scan tool to know what your engine is seeing.

Hairy W Bush

yes and i said i disconnected the maf and the issue is still there. I do have a scan tool and have provided the data log in this thread.

jsiddall

So you did. I looked at the scan tool data and something is very wrong somewhere because the data is all over the place. At 10:28:35 the intake air temp is 90 F in one reading but 177 F in the next. Baro pressure dropped in half and TPS went up to 45% at the same time. These occurences of strange data happen in many readings and often the MAF reading goes crazy too. Also disconcerting is that, where the data looks sane, your BLMs are ~145 which means that the computer thinks your engine is running very lean.

So either the data is corrupted by the scan tool or the computer is sending out crazy stuff. If the computer is sending out crazy stuff it is often because of one or more bad grounds -- including sensor grounds. If you are confident in the power/grounds and can get your hands on a spare ECM to swap in that might help determine if the computer itself is faulty.

One other thought: from what you have said it runs better when in open loop so one easy test is to disconnect the O2 sensors and reset the PCM (to get the BLMs back to 128). See if it has any effect.

Hairy W Bush

I tested the MAF wires and they were in spec. I looked at both ground locations behind both speaker kick panels and they looked great to me. I see what you're taking about but it also sends a wack signal when it dies which is 45 rpm on that chart for some reason. Could have been the tps though which i just replaced.
How would I reset the PCM? On the scan program I am using there is a button to reset fuel trim (BLM) will that work?
here is another log I took if you want to get a better understanding of what is going on.
http://www.filedropper.com/dlog-save...yy22p1s5103119
This was a few days ago.

Ozzstar

Have checked for a vacuum leak? The correct way would be to do a "smoke test". That is the direction I would go at this point.

Hairy W Bush

did that too and saw no smoke