reading scanner question

[grazi]

94 TRans am...So I just logged about ten minutes on Datamaster and I'm trying to analyze why my car is stumbling and missing at half throttle. Why are certain boxes such as LTerm counts and EGR DC highlighted pink and or yellow sometimes? Should I ever have spark retard???
Thanks

[WildBillyT]

Pink in an Lterm means you are running rich. What do your Sterm counts look like?

[grazi]

Theyre generally the same as LT around 125 average number

[WildBillyT]

Can you take a screenshot of datamaster and post it up? Or host the file online and post a link?

[grazi]

I'd love to, Just have to figure out how. Give me a few minutes. Appreciate the help

[grazi]

Sorry cant figure out how to do it now. Anytime im under 50% Throttle position, LT is almost always around 120. At full throttle they are both 129....The Injector voltages went up to 86 and turned pink also if that means anything

[grazi]

I was just running the histogram on Datamaster. It shows I'm running really rich around 1600-2000 rpm when MAF sensor reads 20-30 gps. That is exactly when I'm having my missing, stumbling problems. I ran it for awhile with the MAF unplugged with no change at all. Does anybody have any ideas as to what may be causing this.

[WildBillyT]

It is definetly running rich

Couple basic questions just to get them out of the way:

1.) How old are the plugs, what type and gap?
2.) How old are the O2 sensors?
3.) No tears in the intake tract?
4.) Can you hear any exhaust leaks?
5.) Did you trace for any vacuum leaks?

For other guys, here is his scan:

http://www.njfboa.org/WBT/AutoLog_001.uni

[grazi]

Dont know much about the plugs.
O2 sensors are most likely original (102,000 miles)
Definitely no tears in intake. Stock bellow-SLP cold air intake
NO exhaust leak
Almost positive no vacuum leaks.

[JL8Jeff]

If the EVAP stuff starts going bad, it could basically act like a constant vacuum leak. Maybe try plugging off the EVAP hose. But it could be time for new O2 sensors as well. Do you know if there was any type of custom tune installed?

[grazi]

All of the vacuum lines going to the charcoal canister were bad so I replaced them. Could the canister be bad or plugged??. Im pretty sure there wasnt any tunes on it, an woman owned it since 95 or 96.

[grazi]

To plug the EVAP hose should I just unplug from TB and put avacuum cap on TB? Should I plug hose, too?? I didnt know I could run like that

[sweetbmxrider]

Just on the throttle body will do it, the other line will still vent fumes though. I let mine dump at the tank. I don't think that is 100% your problem though but I don't have datamaster on a working computer at the moment.

[S.J.SLEEPER]

stock ecm/pcm? stock chip? tuned?

[grazi]

No mods. no chips. no tunes. no nothing besides slp cold air intake. So if I unplug evap line and still runs rich and misfires would that rule out entire evap system??

[JL8Jeff]

No mods. no chips. no tunes. no nothing besides slp cold air intake. So if I unplug evap line and still runs rich and misfires would that rule out entire evap system??

That would rule out a vacuum leak in the EVAP system. Go over all the vacuum lines like the power brake booster, the PCV, etc. Maybe try swapping the MAF out with someone else to see if that is going bad. If the MAF is faulty, the stock programming may cause it to run rich to protect the engine from leaning out.

[grazi]

I have a spare MAF that I can swap.But I have the same runnung rich problem when I disconnect my MAF. Doesnt that rule it out?? Is it possible to have a vacuum leak from brake booster internally. maybe i can idle and wave around an unlit torch around booster to see if it changes idle

[JL8Jeff]

I have a spare MAF that I can swap.But I have the same runnung rich problem when I disconnect my MAF. Doesnt that rule it out??

Actually, I would think it should run differently with the MAF disconnected. It sounds like you're running in speed density mode or it's in limp home mode. The computer should be making changes based on the MAF readings, so no MAF readings and the same result sounds like the MAF could be bad. I would swap to a known good MAF and see what happens.

[grazi]

Good point. Ill try that later on today. Thanks

[WildBillyT]

Actually, I would think it should run differently with the MAF disconnected. It sounds like you're running in speed density mode or it's in limp home mode. The computer should be making changes based on the AMF readings, so no MAF readings and the same result sounds like the MAF could be bad. I would swap to a known good MAF and see what happens.

To Jeff's point, even if it's not throwing codes the MAF can be bad. I had that happen to me.

If the O2s are still original you may want to replace them just because you are due. Denso or AC Delco only though.

[Pampered-Z]

If you don't have any codes stored I'd start with a basic tune-up. Stumbluing at part throttle is also commonly caused by a stuck EGR or PCV valve that causes a basic vacuum leak and they won't throw a code.

Plug the hose between the ERG and the relay ( golf tee works nicely ) so that the ERG is blocked off. See if that helps. Also check the PCV valve is working properly.

Yes, you will always see some spark retard.

[grazi]

The PCV valve is working. One thing I noticed about my EGR when I took it off to clean it the other month, when i manualy squeeze it together, the shaft binds a little bit. I will try to block it off though.
When I talk about stumbling and missing at part full throttle, its not like a light miss or non noticeable type thing, sometimes it pings real bad and shutters like crazy.Its pretty undriveable. I will try to log on datamaster when it does it bad. The log that is on this thread hardly cut out that much on me.

[sweetbmxrider]

Try sticking a fuel pressure gauge on it? What kinda of fuel have you been using?

[grazi]

I cruised around with fuel pressure gauge the other day. Have 40-42 at full throttle and mid 30's at idle and cruise. Going off memory

[grazi]

Ive been using premium 92 or wahtever it is. I dont drive the car often so it has been sitting for maybe a couple months but happens even with good gas.

[grazi]

So I just another logged another run while my car was running horrible like I mentioned up top. Hopefully WildBilly T or somebody can post up the Datamaster log but I am getting 15 degrees of spark retard at full throttle!?!? My short term fuel trim go as low as 105 and as high as 145? shouldnt they be steady around 128?

[JL8Jeff]

Did you swap the MAF for that run? It sounds like a vacuum leak with the fuel trims jumping around that much. Your EGR might be stuck open causing the extra air to get in leaning it out (and causing spark retard). I think it will add fuel until it hits a limit (25% I think). Do you hear any type of hissing or whistling like a vacuum leak?

[grazi]

Hey Jeff, I swapped the MAF for this run. I also plugged the vac line coming from EVAP purge solenoid valve(not sure who reccomended that). I dont hear any type of hissing. I sprayed some carb and choke cleaner around pcv valve, brake booster, throttle body with no change in idle.

[sweetbmxrider]

While looking at the datastream at idle, note the fuel trims. Then bring the rpms up steadily to about 3k and see if they change. That should help determine vacuum leak or not.

[JL8Jeff]

The EGR still sounds suspect especially since you had it out and noticed it binding. If it's not closed all the way, you'll basically have a constant vacuum leak that the computer doesn't know about.

[sweetbmxrider]

Definitely. Throw it out.

[WildBillyT]

http://www.njfboa.org/WBT/run2.uni

When the EGR valve gets activity you go pretty lean shortly after and the knock retard comes in. I'd look at the EGR valve as well.

[grazi]

OK Guys, Ill try to do that this weekend. The EGR was gummed up pretty bad when I took it out. I figured I'd try to clean it. I used to clean and reuse the EGR on my 6.0 diesel ford all the time. Can somebody explain why a sticking EGR would make so much retard. I understand the EGR not opening would make the motor think its getting air when its not and make it run rich but what tells the motor to retard? Its all retarded......Thanks guys.

[WildBillyT]

If the mixture is off it may ping and that causes the knock sensor to go off, and the computer will pull timing.

[grazi]

Oh, so I guess first thing to do is Plugs and Wires , replace EGR , and o2 sensors.

[grazi]

Could it be a bad knock module?

[JL8Jeff]

If the EGR is leaking you will be lean which will cause the pinging, the computer will pull timing and richen it up which will lead to the rich condition. The computer doesn't know the extra air is getting in and can't really compensate for it correctly. Same thing would happen if the EVAP purge was leaking, but there might be a sensor that can detect the flow in that situation, I'm not sure.

[grazi]

Update, replaced EGR valve, egr solenoid valve and vacuum lines, pcv hose and ccv hose and o2 sensors. Can somebody with datamaster look at the link on post 8 and look at rec # 1537, 1465, and 1618. Doesnt it look like my tps may be acting slow. My MAP pressure goes up to 12 or 13 before the tps registers anything. Also On 1465 my map goes from 10 or 12 to i think 28 for a split second. also in 1618, i start jumping through fuel cells funny before the tps even registers. Thanks for looking.