? about MAP sensor

[2002 v6 camaro uncharged]

I didn't get any answers in Gen Tech so I will try here.

Can a MAP sensor be faulty and not throw a code. At idle with my MAF sensor unplugged my MAP readings are in the mid 30s, my timing hangs around 4* to 6*, my O2 sensors look good and the car seems to idle fine. At idle with the MAF sensor plugged in my MAP reaidng are in the mid 40s, my timing jumps around (I saw readings anywhere from -2* to 20*), and my O2 readings bottom out at 0mv to around 40mv and the car idles horrible.

Is it possible that there is something wrong with my MAP sensor and it is conflicting with my MAF sensor readings?

[98Camaro3.8]

Those MAP values don't sound correct at all. With no boost and a closed throttle, you should be seeing like 10-15 inHg at most. Mid 40s is like 7 lbs of boost....definitely not an idle reading.

What units does the scanner display in, maybe it's not inHg?

The MAP reading shouldn't change by unplugging the MAF sensor....unless the car is changing the IAC pos and altering the idle vac.

[2002 v6 camaro uncharged]

The MAP readings are in kPa.

[98Camaro3.8]

Ahh, sounds right on then.

If the car idles differently with the MAF unplugged, the MAP is just showing that there is indeed a different idle condition.

[2002 v6 camaro uncharged]

Thanks for the response Matt.

The different idle condition is horrible, with the MAF plugged in the car bucks back and forth and smells like gas. I throw the P0171 & P0174 fuel trim lean codes at idle until I unplugg the MAF then everything is fine.

I have been struggling with this for about 2 months now. I have tried replacing the MAF, had it to the dealer, tested many things, and taken numerous scans trying to find differences with the MAF unplugged and plugged in. I can not get this problem solved.

If you have the time would you look at a couple of scans if I emailed them to you in Excel format.

[98Camaro3.8]

Originally posted by 2002 v6 camaro uncharged:
If you have the time would you look at a couple of scans if I emailed them to you in Excel format.

Sure, I can take a look at it. I doubt I'll find anything, but I'll look.

[ssms5411]

Have you check your bypass valve? Try running it without it hooked up. Also if you have messed with some of the tables using Hptuners, you might want to reload your stock tune and start retuning from there. If you want, send me your bin. file and a log where it is acting up and I'll take a look at it.

[2002 v6 camaro uncharged]

Originally posted by ssms5411:
Have you check your bypass valve? Try running it without it hooked up. Also if you have messed with some of the tables using Hptuners, you might want to reload your stock tune and start retuning from there. If you want, send me your bin. file and a log where it is acting up and I'll take a look at it.

By-pass valve has been removed because the diaphram was torn but that happened last August.
This problem started like 4 days before I even got HP tuners.

I had the stock tune back in the car when I took it to the dealer a week and a half ago and it ran just as horrible as it is now.

I will definately send you my bin and logs and I really appreciate you taking the time to look at them. I will send them to you sometime tomorrow morning when I get to work.

[2002 v6 camaro uncharged]

Originally posted by 98Camaro3.8:
[/qb]

Sure, I can take a look at it. I doubt I'll find anything, but I'll look. [/QB][/QUOTE]

Thanks Matt, I appreciate it. I will email my Excel files to you tommorrow morning.

[2002 v6 camaro uncharged]

I just pulled my MAP sensor out and the tip of it was slightly wet with gas is that normal or do I have a FPR leak. But if I had an FPR leak wouldn't that effect the fuel pressure?

[2002 v6 camaro uncharged]

Well Its not the MAP sensor, I give up

[98Camaro3.8]

Where exactly in those scans is the problem? Don't really have the time to sift through a 30 minute scan.

Originally posted by 2002 v6 camaro uncharged:
But if I had an FPR leak wouldn't that effect the fuel pressure?

I think that would depend on how bad of a leak. A little leak may not be enough to cause a drop in pressure.

Originally posted by 2002 v6 camaro uncharged:
I just pulled my MAP sensor out and the tip of it was slightly wet with gas is that normal or do I have a FPR leak.

I guess it would depend where it's coming from (obviously). Could be from PCV or EGR, or it could be coming from FPR. I wouldn't expect it to smell strongly of gas, unless you were running real rich and getting it through PCV/EGR. Could you check the line at the FPR to see if it's wet also?

[2002 v6 camaro uncharged]

In both scans the problem is at idle.

In the scan with the MAF at idle the O2's bottom out and stay between 20mv and 40mv, the short term fuel trims lock at 19.5%, the MAP reads in the mid 40s (never use to), the timing jumps around (seen it go from -2* to 20*). The PCM thinks it is running lean but I don't think it really is because when I am at idle the car smells like fuel big time.

In the MAF unplugged scan at idle the O2s go up and down like they should, the MAP reads in the mid 30s, Short term fuel trims stay around 0%, timing is around 4* to 7*, and it idles fine.

If it is my FPR wouldn't it affect my car all the time and not just with the MAF plugged in.

I have the throttle body PCV bypass done for my supercharger so it can't be my PCV valve.

I guess my next plan of attack is to see if there is a problem with the EGR system.

[2002 v6 camaro uncharged]

At idle with my MAF sensor unplugged my vacuum reads on the gauge at a consistant 20 when I plug the MAF back in the gauge drops to between 16.5 to 17. It jumps around but mainly stays between those numbers and if it runs smooth for a second or two the vacuum will slowly rise to around 18.5 but as soon as it starts chugging it will drop back down to 16.5-17 again. I just don't understand how just plugginng in the MAF can change so much. Why would that change the vacuum?

Can anyone lead me in another direction with this new information.