Car Hesitation at higher speeds

[alex840]

hypothetically speaking, if an 840ci car was accelerating and would not pass 100mph because engine hesitation, what would be the recommendation of start of a trouble shooting. There are no miss fire or check engine or OBD warnings.

1) check spark plugs
2) coil packs
3) fuel lines are upgraded, maybe fuel pump?
4) recent fuel filter change
4) clogged cats
6) Any other ideas or suggestions?
7) car has a valve cover gasket leak that will be addressed soon

[Timm]

If you don't have idle problems, the first on the list is MAF followed by blocked cats

[dragon850]

Yep, i second that. But in your case I would fo clogged cats then MAF since we already know car has trouble passing smog

If you don't have idle problems, the first on the list is MAF followed by blocked cats

[alex840]

Thanks Timm. I know CATs got issues, Ed (Dragon850) gave me all the part numbers for a complete exhaust overhaul. MAF, I cleaned it out a couple of weeks ago, but might still be an issue. I was told all the replacement MAFs that are being offered are just refurbished, in essence they are using the same coil.

Love your website.

If you don't have idle problems, the first on the list is MAF followed by blocked cats

- - - Updated - - -

Ed, I got all the goodies you refferred. Be in your neck of the woods to get exhaust handled in a couple of weeks. I will call you up.

Yep, i second that. But in your case I would fo clogged cats then MAF since we already know car has trouble passing smog

[Corellian Corve]

840 MAF's are not refurbished you can get new Bosch units anywhere. The V8 M60 / M62 units were widely used and readily available. It's only the V12 ones that are rare and remanufacutured.

[alex840]

Good info. Thank you for clarification.

840 MAF's are not refurbished you can get new Bosch units anywhere. The V8 M60 / M62 units were widely used and readily available. It's only the V12 ones that are rare and remanufacutured.

[alex840]

Just for future reference if anyone has the same issue, almost two years later the issue resolved:

Vehicle Speed Sensor on the on the differential. Got the code on scanner, and checked the archives on roadfly and that was it!

FYI, I did go down the list of all the goodies on original post.

Part # and Pic:

62168357020
343849_x600.jpg

[Timm]

So, your car did actually go past 100MPH but the speedo didn't register it!

[alex840]

Hello Timm,

Firstly, thanks to you and everyone's help on getting to the bottom of this. I changed, CATS, All Coils, Spark plugs (NGK), Fuel Filter, and checked the fuel pumps, and changed out the MAF but still same issue. The problem was I was not getting any Check Engine lights and INPA was not reading it, I used DIS and the code was there that was not registering with INPA.

Not exactly, so you might be able to shed some light on why the below and my case happens. I was experiencing the same exact thing as below:

http://forum.roadfly.com/threads/124...-cause-misfire

Quote"Cleaned the car" ??? did you wash it ??

"My experience with the rear diff speed sensor.- caused the car to drive normally around town, more or less. but once on the highway the car would buck and jerk- then die down like it was stalling, then when I put I foot down- it would take off like a bat out of hell - then it would repeat the same scenerio. My Peake code reader was able to pull the code and I pulled the diff speed sensor and replaced it. I then found out you just have to wipe the filings off. Doh..
Regards ,Walt"

So, your car did actually go past 100MPH but the speedo didn't register it!

[ChrisFuture8]

...interesting. Subscribed to this thread. Thanks for the update, Alex.