DX'ing a MAF Condition ....

DriVer · 05-28-2011, 06:19 PM

On my way back from Bethpage last week I was experiencing an annoying little pop on acceleration - (just 1 millisecond of a pop) but not all the time. I've driven this thing when it would just keep popping like a pop corn machine but this was different. Accelerating again - no pop. Cruise for a little while and then apply a little throttle "maybe" a little pop but nothing to write home about.

I called in some resources to help me figure this out (Jon) and we were of the opinion that I should clean my MAF sensor. I went to the store and bought another can of CRC Mass Airflow Sensor cleaner and went to town on this thing.

So I let the thing dry out and put it back in the tube and plugged in the modular connector. I have the rectangular part of the MAF up at the 1 o'clock position and the plug is at about the 2 o'clock position. There is a square key but I disregarded the suggested position. The airflow arrow is pointing toward the engine and the screen is facing the filter.

I went inside to start the engine and turned the key and you should have been there. The engine barely started and it would not run very much if at all. The RPM at idle were wildly oscillating at about 450 or so ... much too slow. Throttling up typically got no response. Oh OH! What did I do ... I must have drowned the sensor I'm thinking.

$220.00 later I got a new sensor ... same thing!

Now I'm thinking I compromised the wires in the modular plug! I'm having visions or splicing in a new plug yada yada and OH my!

Just for the heck of it I disconnected the plug from the MAF. I went inside and the engine started right up, it idled OK and it had a good throttle response.

Now I'm really confused! No connection to the MAF and this thing is running ... well it ain't supposed to.

So I got back on the phone and we brought in the expert, Steve Brazel, and he diagnosed the issue from almost 3,000 miles away and was 100% accurate. Steve said to pull the doghouse and check the upper connection of the inlet pipe - it's disconnected.

What it turned out to be was that the upper part of the air inlet tubing that connects to the intake manifold had come loose and was off of the of the manifold's collar. Pushing the tube back on and securing same, I turned the key on and engaged the starter and without hesitation the engine fired and assumed a normal idle speed. Throttle response is normal.

Here is what happened. The reason why the engine ran at all (disconnecting the plug) is because it was getting air from an alternate source. When the plug was restored back onto the MAF there wasn't enough airflow past the MAF to allow it to function properly so the engine performed poorly.

There was an pungent odor from the exhaust system but I was unable to ascertain if it was too rich or not. I believe it was.

I am expecting that the tube may have been working it way loose and that's why I was getting that annoying little pop. When I went and removed the MAF and manipulated the pipe, it came off the inlet of the manifold. That's what made the situation worse.

I was able to return the new MAF and I installed my old one and it's running just fine. My old MAF is actually #2 since the original one got a hole in the screen somehow. Honest I didn't do it.

So there you go ... IN THE EVENT this happens to you .... now you know where to look 1st!

DX by the way is a medical term for diagnosis.

I hope this will help someone - somewhere. If I were ya'll ... I'd check to make sure the pipe was tight on the manifold the next time you got under the doghouse.

I'm knocking on 92,000 miles

PS: Throughout this event my Scan Gauge II did not set a DTC.

Davel · 05-28-2011, 07:34 PM

Mike,

Thanks for the write up.....you know what it says on the tee shirts. This may help someone else, because you know it will happen to somebody, sometime.

Dave

M&EM · 05-28-2011, 11:54 PM

Mike, I recall you recently posted an issue with your fan shroud. On mine the air induction pipe from the MAF is supported at the top shroud to help keep it in place. A plastic pin is all that holds it to the shroud. Yours may have loosened up before or during your fan shroud repair.

Marty

DriVer · 05-29-2011, 06:52 AM

Quote:

Originally Posted by M&EM

Mike, I recall you recently posted an issue with your fan shroud. On mine the air induction pipe from the MAF is supported at the top shroud to help keep it in place. A plastic pin is all that holds it to the shroud. Yours may have loosened up before or during your fan shroud repair.

Marty, Thanks for taking the time to think through the different scenarios about the upper connection.

During my installation efforts after the MAF was installed, I actually reached up as far as I could and yanked on the tube. At that time is was solid. As you suggested the connector up there must be doing its job since there was no movement by the tube that I perceived.

All of these bites of information are useful for anyone who would undertake this maintenance routine and being able to see what could happen collaterally in invaluable.

The upper shroud in my opinion wasn't involved in the separation that I wrote about.