I recently replaced my MAF sensor for a light pinging issue (which the dealer diagnosed as the MAF giving incorrect readings).

I bought a brand new Delphi unit from Rockauto, whereas the original is a Denso. It seemed to make a big difference, but I'm also concerned the transmission is not shifting as smoothly as it did before. Most of the time it's great, the pinging is greatly reduced, engine is quiet and MPG is better. Occasionally I get a strange shift--one time in traffic it did some bizarre up/down/up shift that jerked the car. Has not done that since or anything like that.

The battery was reset when I changed the part, and I have given it about 250-300 miles to re-learn everything. It has certainly improved since then, but still seem to feel the 3-4 shift at low speeds. Also sometimes get a delayed downshift when turning corners.

Maybe I'm just begin paranoid. Maybe it's working just fine but I had driven so long with the worn out MAF and short/low rpm shifts that I'm simply not used to the way it's supposed to work? It definitely keeps the car in a lower gear longer than it ever did before, which is a lot better than it was (no it isn't in sport mode).

I still have the original MAF so I can always put it back in I suppose.

 

I asked a question about Delphi MAFs on the S-Type forum but did not gather any real data. I bought one as a spare, but was a little disappointed to find it wasn't a GM Delphi, but rather an East Asian knock-off. I have not had need to install it.


I would install it just out of curiosity, but I am in the south of France for a month.

 

It's not a GM Delphi? That's the only reason I went with the brand! *sigh* I had no idea there was a different Delphi brand.

This one is not bad for now, but maybe I will start scouring eBay for an Denso original.

 

Delphi is on everything, so I doubt that has anything to do with you shift issue. The question I have why your engine is pinging? It will compensate for low octane, but not all the way down to 85. Are you going with low grade gas?

 

I do know the shift is very dependent on the MAF. Just cleaning my stock one fixed all my transmission lurching.

 

That would be the $1,000,000 question. I've posted here and talked different people over the years and heard everything from carbon, intake gaskets, knock sensors, MAF, to "it's normal" etc.

No, I only run 93 octane. 3 years ago around 50k miles the dealer did a PCM flash (based on a TSB for pinging) which helped some, but never cured it. Brought it back last month and told them "find out why it pings" they said it's a bad MAF and they wanted to do the fuel system cleaning. The newly replaced MAF did stop 90% of the pinging, but it's still there under some conditions. I've done several courses of BG44k.

One more item to look at--I feel like there may be a vacuum leak around the PCV valve. Will check that over the weekend.

On the upside, the shifting seems to have smoothed itself even more the past few days. I've been doing more driving in various conditions. I can't say I've felt anything odd, it's just different than it was with the previous MAF.

 

Maybe the knock sensors are bad.

Oil is very low octane, so there is a chance the PCV system leak is connected to the pinging. A vacuum leak would also cause a hot combustion and possibly cause pinging..but that SHOULD generate a lean code.

Are you getting any codes at all? If not, I would lean towards one or both knock sensors being bad. That would cause the ECU to generate an advanced timing curve, and not know when to back off of it. It's even possible that the sensors were not tightened down to the block, so they can't read the pinging properly, even though they are still good.

 

Hey Guys, question on pinging sound. I cant seem to find a good video on the sound of pinging. anyone help?

 

Working on the pinging issue now myself coupled with a slight rough feel at idle only felt while my hand rests on an open drivers door not the steering wheel(annoys me) I don't use cheap gas and I hate using additives for cleaning fuel/injectors. Ive had all 8 injectors flow tested and sonically cleaned. I'm going to test coils next for resistance to see if any are weak since I've seen a few posts on failed ones. The shifting issue you mention though may or may not be related to the engine. I replaced the MAF with new and only solved alittle of my rough running issue(Ive had many). The ZF tranny uses solenoids inside that are also know to fail on certain vehicles. Most who have this problem get a Trans fault light eventually that sticks there car in 4th gear. Normally you just pull over and turn off and on the car to reset, but it could be the issue starting to rear its ugly head. The solenoids can be replaced but they aren't cheap from what Ive found (200-300.each). Love to hear what you find for the last 10% of your pinging though

 

Well tested coils and they are fine. Have extra 8 coils and all 16 are the same at least when checking ohm's. Replaced fuel filter and tried filling up at Mobil from near empty.....nothings changed. Time to get the OBD hooked up and check fuel trims I guess and O2 sensor readings. I've replaced every hose on this car with new ones and didn't expect this problem though. Pinging on heavy throttle and rough idle at cold start up...once warm idle is better but still bounces a little which you can feel when leaning on door. I know don't lean on door and turn the radio up...cant do it. Wonder whats next?

 

Car: 03 STR quartz in color, bought from one owner, dealer serviced, all records inc. the window sticker. Bought with 112K and 4 months on a new dealer installed ZF trans....fore and aft.

Hello Gent's, I'm new and can't seem to figure out how to start a new thread so until then I'm going to hitch hike on this one. BTW....I've owned my STR for 13,450 miles or about 18 months.....and I just love it....I also enjoy working on it. I've replaced all of the ignition coils and plugs as well as taken off the front of the car to replace the head light bulbs. Oil changes of course with a fuel filter R&R as well. My first car was a 1957 XK140 DHC.....37K original miles, red, XKE wires (bought it like that) beige interior with matching English Linen top......loved it.

MAF question: My Factory trained indy says I'm getting a lean left and right bank code due to a faulty (worn out) MAF....no vacume leaks.

I've resisted buying the Jag dealer MAF at $279.00+ and have now tried several 'other/off' brands. Having spent 35 years + and 490K miles in 'P' cars before returning to El Gatto......I've never had to deal with MAF's ....so it's all new to me.

Not unlike our friend above these off brands produce odd trans shifts and 9.8 to 10.2 mpg vs. the 15.6 to 23 mpg with the OE Denso MAF. The codes for lean left and right bank have however not returned but I do run into 'RESTRICTED PERFORMANCE' with my foot 'in it'.....(then again that's why I bought an STR....'foot in it') shutting down the motor and almost throwing me into the front windshield....not a happy thing.

Q: I can't seem to find an original equipment DENSO MB197400-3031 MAF online but keep being redirected to a Cardone 74 -50078 at $178.00ish from Amazon.

So questions:

#1, Does any one know where I can get the DENSO OEM replacement?

#2, any thoughts on the Cardone #74-50078 as a 'stand in' for the OEM DENSO model

and #3, do I need to disco the battery to re.... the computer on any or all of these models in order to have them work properly?

Any and all help/ suggestions / direction would be appreciated.