Never had these symptoms before. Long list of codes

[LJRuddy]

Gonna try to make this post as detailed as possible...

Yesterday evening, I noticed that after the car had sat for a while (either over night or for 5 minutes) the CE light would pop on until the car reached operating temps. Also, I noticed that the secondaries were open throughout the RPM range when the CE light is on and for a short (20-40 second period) after the CE light turned off. During this time, the car ran normally except for a loss of power at low RPMS due to the secondaries being open.

This evening, things got worse. Pulled out of the parking lot after letting the car sit for a few hours. CE light came on and the secondaries were open. Only this time, there was an extremely strong buck coming from the engine. I was accelerating in 1st gear and at about 3k RPMS, the engine lost all power for about 1 second and when power was restored, the shock was enough to break the drive wheels free for a second or 2. I noticed that this strong bucking sensation ONLY happens about 5 seconds before the CE light turned on and about 5 seconds before the CE light turned off. When the CE light is off, the car runs like normal. Then, a strong buck when the CE light comes on. While the CE light is on, the secondaries are again open but now the engine is running very rough and sometimes a misfire can be heard. Also, if I go WOT in any gear during this time, the car will sluggishly accelerate to 4k RPMS and the engine will cut out until the RPMS drop to around 3800 and the cycle repeats until I let off of the gas. If I use 75% throttle or less, I can accelerate all the way to redline. Also, when the CE light is on and I hold the RPMS at a steady level while in netural and not moving, the engine bucks horribly and misfires are present in what seems all cylinders. Again, once the CE light turns off, all is back to normal.

So I pulled codes tonight after work. Here is what happened. During the KOEO test, I recieved a:

157- MAF circuit below minimum voltage.
551- IAS circuit failure.
557- Low speed primary fuel pump circuit failure. (roomate stalled it learning how to drive a stick)

During the KOER test, the engine could not hold a steady RPM. It was ranging from 500 to 1500+ rpms throughout the entire time. During this time, there was minor misfiring coming from the engine. I recieved:

158- MAF circuit above maximum voltage.
159- MAF out of self-test range.
411- Cannot control RPM during self-test low RPM check.
536- BOO circuit failure. (known bad sensor. I have a replacement handy)

Im guessing that my MAF is going out which is causing a false reading making the engine run all sorts of A/F ratios which therefore cause my bucking sensation. But why is my engine cutting in and out? and why does my secondaries stick open when my CE light is on?

Please help! :wave:

 

[hawkeye18]

Seriously, it's your MAF.

Since your MAF is out, the computer has to rely solely on the TPS, IAT and O2s to determine what kind of fuel it should be giving the engine, and it will default to a very, very rich setting to keep from destroying the engine.

When you go to WOT, you enter closed loop operation, which takes the O2s out, and the computer just has absolutely no idea what kind of fuel it should be giving it, so it tries to extrapolate a value based on Throttle position and RPMs. The ECU will be dumping so much fuel in that I'm surprised it doesn't just upright die.

Clean the MAF with either MAF cleaner or Electronics cleaner (please don't use carb/engine cleaner!), and if that doesn't fix it, replace the MAF.

Also, your engine can't keep an idle because your IAC is messed up (IAS, whatever). Clean or replace that as necessary.

I wouldn't worry about the secondaries for now... fix everything else, and if the secondaries still won't close, then post again and we'll work on that then.

 

[Kens1992mtxSHO]

X2. Get the MAF code squared and report back with any developments.

 

[jthod]

...that bug I put in is finally working....

 

[LJRuddy]

Update!!

I went to unhook my MAF to replace it with a known good sensor and I noticed that the connection was not all the way seated. As I pulled the connector off, I noticed that the bottom clip was broken off completely enabling the line side connector to come loose from the bottom. This was causing a loose connection which explains why my symptoms came and went. Im happy to have found my problem.

Oh, and this 58 degree weather here in town has brought all of the power back to my SHO. With my Falkens up front, I was able to break 1st gear loose on a WOT run this morning on the way to work. I could have even sworn I heard a 2-3 chirp getting onto the highway.