MAF sensor?

[TSiTalonawd96]

I'm going to be as clear as I can about my symptoms but im down to a few things and my guess is a MAF sensor or IAT sensor(which is built in). So heres what its been doing..

Ever since the second day I bought the car when it was cold after driving for about 3-5min it would load up real bad( boost would go up, AFRs were in line, it just felt like you hooked a semi to my back bumper and it wouldn't go anywhere. If you let off the gas pedal and shifted it was fine). If I let it idle for 5-10min after I got to work on a cold morning and went to start it up later on it would be load up real bad. If I stomped it through first gear it would clear up.

Well now its doing it almost every day and for 10-15min at a time. Its black smoking, poping out the exhaust, doesn't do anything until about half throttle, and has no power. Then out of the blue it will clear up and run perfect.

I have done many BLTs and found some very minor almost negligable leaks.

Also I am getting crazy amounts of knock at all rpms. (I have a knock sensor on its way because mine is still the original one, just so I know its not the sensor).

Anyone think its the MAF, IAT, or something else i'm forgetting?

 

[gofer]

throwing any CEL's? sounds to me like your running pig rich and the knock your seeing is rich knock. is your mod list up to date?

 

[cabbageman97]

Won't be the IAC, hence *idle* air controller. Your MAF may have shit on you, but it sounds like you have a bad boost leak, where are the negligible leaks at? But it is something with an input to your fuel control/metering.

OH! nevermind, disregard... IAT not IAC.. Hook it up to a logger and see what your inputs are reading.

 

[white92talontsi]

Won't be the IAC, hence *idle* air controller. Your MAF may have shit on you, but it sounds like you have a bad boost leak, where are the negligible leaks at? But it is something with an input to your fuel control/metering.

OH! nevermind, disregard... IAT not IAC.. Hook it up to a logger and see what your inputs are reading.

He said IAT not IAC. I would pull the MAF try a known good one.

 

[cabbageman97]

Haha I know I corrected myself. Sorry.

But Ill say Maf or possibly even the Map sensor

 

[TSiTalonawd96]

Im supposed to be getting a good used one tomorrow. My mods are basically 14b turbo with 16g internals at 15psi. Stock fuel, Front mount, greddy type rs bov, thermal catback exhaust, gutted cat, blah blah. I have evoscan, thats how I found the knock count. What should I log now to figure this out?

My very small leak was coming from the throttle body. If you move the butterfly open and closed it will get louder and quieter so im thinking its the shaft seals. I will also replace the gaskets to be safe when I do it. (just replaced the IM gasket yesterday). Other than that all my leaks are fixed now...

Our cars don't have MAP sensors, we have MDP sensors. There pretty much usless, they just monitor the EGR valve and make sure it functions properly. (found that out today )

 

[delta448]

You've already answered your own question.

I'm going to be as clear as I can about my symptoms but im down to a few things and my guess is a MAF sensor or IAT sensor(which is built in). So heres what its been doing..

Ever since the second day I bought the car when it was cold after driving for about 3-5min it would load up real bad( boost would go up, AFRs were in line, it just felt like you hooked a semi to my back bumper and it wouldn't go anywhere. If you let off the gas pedal and shifted it was fine). If I let it idle for 5-10min after I got to work on a cold morning and went to start it up later on it would be load up real bad. If I stomped it through first gear it would clear up.

Well now its doing it almost every day and for 10-15min at a time. Its black smoking, poping out the exhaust, doesn't do anything until about half throttle, and has no power. Then out of the blue it will clear up and run perfect.

I have done many BLTs and found some very minor almost negligable leaks.

Also I am getting crazy amounts of knock at all rpms. (I have a knock sensor on its way because mine is still the original one, just so I know its not the sensor).

Anyone think its the MAF, IAT, or something else i'm forgetting?

It helps me to have read your other thread. Because of that, I know you have extreme amounts of knock showing up randomly in your logs.

When the ECU reads high knock counts, it retards the ignition timing in a last-ditch, run-away-screaming attempt to save the engine from becoming a boat anchor.

When you reduce ignition timing below the optimum, you lose a lot of power and efficiency. Also, if timing advance is reduced enough, the spark plug fires so late that the charge is still burning and increasing cylinder pressure as the exhaust valve opens and the piston starts moving through the exhaust stroke, and this is why you hear the popping (backfiring) out the exhaust along with gobs of black sooty smoke. In essence, you're experiencing the same thing a rally car does when it's anti-lag function activates. Boost hangs or increases due to the extra heat and pressure of the still burning cylinder charge passing through the turbine.

 

[nightgamer]

tps?

 

[TSiTalonawd96]

You've already answered your own question.



It helps me to have read your other thread. Because of that, I know you have extreme amounts of knock showing up randomly in your logs.

When the ECU reads high knock counts, it reduces ignition timing in a last-ditch, run-away-screaming attempt to save the engine from becoming a boat anchor.

When you reduce ignition timing below the optimum, you lose a lot of power and efficiency. Also, if timing is reduced enough, the spark plug fires so late that the charge is still burning and increasing cylinder pressure as the exhaust valve opens and the piston starts moving through the exhaust stroke, and this is why you hear the popping (backfiring) out the exhaust along with gobs of black sooty smoke. In essence, you're experiencing the same thing a rally car does when it's anti-lag function activates. Boost hangs or increases due to the extra heat and pressure of the still burning cylinder charge passing through the turbine.

^True, but I think its unrelated... I still have a fair amount of timing. 30 or so at low rpms and in the low 20's to high teens at high rpms. According to other people thats about what they usually see.

I also forgot to state that it only does this usually once a day if that, when its cold. It does it then its clears up and runs great for the rest of the day.

 

[delta448]

^True, but I think its unrelated... I still have a fair amount of timing. 30 or so at low rpms and in the low 20's to high teens at high rpms. According to other people thats about what they usually see.

Attach a datalog in your next post please.

Look at your log, look where you see the knock spikes. What's the ignition timing look like during and immediately after that knock spike? Are you sure you're not reading a negative timing advance?

 

[TSiTalonawd96]

I'll have to save them to a flash drive from my other computer, but the timing does go down according to the knock count (at the same time).

 

[TSiTalonawd96]

So I got my new MAF sensor, the car runs great now! (much faster) No more stumbling, black smoke, ect. I haven't had a chance to log yet but i'll let yall know tomorrow. Keep your fingers crossed.

 

[white92talontsi]

Thats great too hear. I would pull the plugs and see how black and sooty they got from the MAF problem. May be worth cleaning them and re using them.

 

[TSiTalonawd96]

Ok, so I logged today... Im only getting 10-20 counts of knock. Now I think its lean knock. My afrs are 11.5/1 --13.5/1 according to my wideband. On the way home its just pegging completely lean(so its possible something is wrong with it(dirty). It may just be reading wrong.

It ran great last night at about 15psi. I woke up this morning and it wouldn't do anything under WOT. It was just backfiring and poping and bucking(fuel cut??) so I turned the boost controller off and ran stock boost(about 10-11psi) and it does fine.

By the way, all of my logging was done on the stock boost.

So either my wideband could be reading wrong, timing could be too far adavanced, or the used (new to me) MAF sensor could be fudged too. Any suggestions? Im so confused. I shouldnt be hitting fuel cut at 15psi or running any leaner than 9.5ish to 1.

 

[gofer]

a log will tell us everything. with a log we can see your AFR's, timing, & exactly when its knocking and how many counts. only 10 - 20 counts of knock huh? thats a ton, there should be none or your seeing phantom knock. if AFR's are as lean as you say they are then add fuel, get them to 11.0 ~ 11.2:1. after you see a solid AFR in the low 11's and its still knocking start pulling timing 2* at a time at the RPM your seeing it knock. repeat until it stops knocking and then add a degree to see if its still good. before you do all this reach under your intake mani and make sure that knock sensor is in there tight. if you can get a good visual on it make sure it doesn't look burnt up on the back either. you might want to consider rewiring your stock fuel pump, that could be why your leaning out a bit as well.

 

[TSiTalonawd96]

^^That is good information but when I log the AFR ratios evoscan shows 9.5to1 but that is just want the ECU THINKS it is. My AEM wideband shows differently-its only about 6 weeks old.

My knock sensor is fine, I just had my IM off the other day and I checked it out.

Also note that with these logs I was on stock boost. I should be running 9.5to1 AFR's with 0 counts of knock.

My base timing is 8* without a jumper

Oviously something is out of whack... I ordered a brand new MAF sensor today to eliminate that out of the equation. If that doesn't change anything my next step will be the fuel pump- either a rewire or a 190lph. If that doesn't fix it then I will replace the FPR. Then lastly would be my TPS. Anyone have any other suggestions or think I should replace these in a different order?

 

[delta448]

Just keep throwing money at the problem. You'll get it eventually.

Seriously. Post a log. Or at least attach the file.
You have knock issues. It's that simple.

If the ECU is seeing knock it will reduce spark timing advance for a short period of time. It doesn't care what's causing it to get a knock signal, it just does as it is coded for when the signal occurs. And it doesn't pull timing forever, there is a small rate of decay for the pulled timing. After that short amount of time passes the ECU will be running at full timing advance again. With a knock count of 20-30, I imagine you'd be back to full timing in about 10 seconds or less depending on engine speed, as long as the ECU didn't read more knock during timing retard decay.

Retarded timing and misfires cause all the symptoms you describe. Remember, a wideband reads quite lean when there are multiple misfires (feel any hesitation/stumbling?) because of all the unburnt oxygen in the exhaust.

Take your laptop with you, set it on the seat and capture a log. When you feel the car start acting like you've described, stop the log and look at it. Then see what the timing and knock signals look like in the log at the time that corresponds with the onset and departure of the symptoms.

Want to see if it's phantom knock or real? Read your spark plugs for knock, look for tiny pitting on the insulators, look for any melting or operation under extreme temps, deformity of the electrode, look for any physical damage, look for white or very light discoloration. Not satisfied? Go fill up with some high octane racing gas, preferably around 110 octane or higher. Still have knock? -Then it's probably 99% a phantom knock issue and you know the solution to 99% of your problem is finding the source of the phantom knock. There's no way in hell you should ever see real knock at a stock boost level, on stock timing and stock fuel tables while using race gas.

Want to test whether it's phantom knock coming from the engine or chassis? Sit in the driveway in neutral and hold the engine to rev between 2000-5000 rpm. If you see knock doing this, it's probably internal to the engine, and I'd start with using a mechanic's stethoscope on the valve cover near the lifters.

There are lots of things that can cause phantom knock, not just the knock sensor. Bad lifter tick causes it, loose suspension parts with worn out bushings contacting each other, torn motor/trans mount inserts, loose exhaust piping hitting metal, -you get the idea.

I really believe this is the only problem your car has. You don't have to believe me, but throwing more money and parts at the car without determining the cause only works for people with too much money for their intelligence or patience level.

 

[TSiTalonawd96]

Just keep throwing money at the problem. You'll get it eventually.

Seriously. Post a log. Or at least attach the file.
You have knock issues. It's that simple.

If the ECU is seeing knock it will reduce spark timing advance for a short period of time. It doesn't care what's causing it to get a knock signal, it just does as it is coded for when the signal occurs. And it doesn't pull timing forever, there is a small rate of decay for the pulled timing. After that short amount of time passes the ECU will be running at full timing advance again. With a knock count of 20-30, I imagine you'd be back to full timing in about 10 seconds or less depending on engine speed, as long as the ECU didn't read more knock during timing retard decay.

Retarded timing and misfires cause all the symptoms you describe. Remember, a wideband reads quite lean when there are multiple misfires (feel any hesitation/stumbling?) because of all the unburnt oxygen in the exhaust.

Take your laptop with you, set it on the seat and capture a log. When you feel the car start acting like you've described, stop the log and look at it. Then see what the timing and knock signals look like in the log at the time that corresponds with the onset and departure of the symptoms.

Want to see if it's phantom knock or real? Read your spark plugs for knock, look for tiny pitting on the insulators, look for any melting or operation under extreme temps, deformity of the electrode, look for any physical damage, look for white or very light discoloration. Not satisfied? Go fill up with some high octane racing gas, preferably around 110 octane or higher. Still have knock? -Then it's probably 99% a phantom knock issue and you know the solution to 99% of your problem is finding the source of the phantom knock. There's no way in hell you should ever see real knock at a stock boost level, on stock timing and stock fuel tables while using race gas.

Want to test whether it's phantom knock coming from the engine or chassis? Sit in the driveway in neutral and hold the engine to rev between 2000-5000 rpm. If you see knock doing this, it's probably internal to the engine, and I'd start with using a mechanic's stethoscope on the valve cover near the lifters.

There are lots of things that can cause phantom knock, not just the knock sensor. Bad lifter tick causes it, loose suspension parts with worn out bushings contacting each other, torn motor/trans mount inserts, loose exhaust piping hitting metal, -you get the idea.

I really believe this is the only problem your car has. You don't have to believe me, but throwing more money and parts at the car without determining the cause only works for people with too much money for their intelligence or patience level.

^^ I fixed my knock problem. I took out my greddy boost controller and put it back to stock boost a no counts of knock now. Then 5 min. later it did the running ridiculously rich thing(so its unrelated) as I thought. I was logging when it did this and the two things I found that were out of wack: after letting off the gas going down a hill in gear(when the fuel should have been cut off) my injector duty cycle was 25% and my 02 sensor was reading 5 times higher than normal.

 

[delta448]

I was logging when it did this and the two things I found that were out of wack: after letting off the gas going down a hill in gear(when the fuel should have been cut off) my injector duty cycle was 25% and my 02 sensor was reading 5 times higher than normal.

I'd still love to see a log.

The narrow band or AEM?
Does the TPS log 0 when your foot's off the gas?

 

[gofer]

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[TSiTalonawd96]

I have been logging but its on my other computer. My tps is 14.7% at idle. It is adjusted properly, I checked it and readjusted it to make sure. I haven't got it to run rich again to check other stuff yet but I did notice that my AFRs according to my log is spiking back to 14.7 around 4500rpm then going back down to 9.5-kinda weird.

 

[delta448]

Kinda wierd... maybe, maybe not.

But we won't know until we can see the whole picture with a log. I'm done replying to this thread until you post one. I don't think I can possibly help you any further without seeing it.

Log TPS, airflow, timing, knock, front O2, wideband, engine coolant temp, rpm, STFT and the LTFTs.