To owners of 93-95 GM 3.4 conversions

[limey222]

Recently my car has developed an annoying stumble if I let the revs drop too low while lugging around town in 2nd and 3rd.  Previously I was always amazed by its low end torque and it would pull away in 2nd and 3rd as long as it was moving forward at the time. Now when i go to accelerate there is a stumble like it is going to stall and almost a misfire before it recovers and accelerate normally.  All sensors were replaced just over a year ago. New coil pack and base about 6 months ago. New injectors and fuel regulator valve two months ago.   No codes are showing up on my laptop.
Any ideas?

[Scott Costanzo]

Did you go with the stock flowing injectors or the greater flowing injectors you mentioned you wanted to go with?

[limey222]

OK, Here is what might be considered a strange question. Should the ECM controlling a 94 GM 3.4L engine conversion always be powered up?
The reason I ask this is that I have a hidden, dual pole battery isolation switch installed which disconnects both + and - of my battery.
Got to thinking about this and I need to know if this means that my ECM is having to re-learn every time I drive the car or does it have an internal protected memory for the settings

[88v8]

Even if it does, these ancillary batteries are not ever-lasting

Ivor

[Scott Costanzo]

It will do a re-learn if you disconnect power from the ECU.

[mstemp]

Rather than using the disconnect you could,wire in a battery tender. Try that as a test to see if it solves the running issue. I use that on my rover FI V8, only fully disconnecting battery for longer term storage as the ECU has to relearn and caused some poor running for the first few full warmups.

[limey222]

 -- moved topic --

[DiDueColpi]

Have a look at your MAF Michael.
I'll bet that you have a buildup of contaminants on the sensor elements.
The smallest amount of dirt can throw these MAF's out of range and never produce a fault code.
Over oiled gauze type air filters will also gum up the sensor
Take a small soft artists brush and some carb cleaner to clean up the sensors. Be very gentle as they are fragile.
The difference in running is sometimes dramatic.

Cheers
Fred

[Tremelune]

I don't know about the stumble, but I'm seconding the recommendation for a tender. Much better for the battery than merely disconnected to prevent vampire drain. A battery Tender Jr is like $25...I've got one hooked up to any vehicle that won't be driven in the next few days. Really helps the battery last. If it solves your stumble, it's a free lunch!

[Sidecardoug]

If you are using the factory ECM and fuel injection, this guy may be able to help - I recently contacted him
about reprogamming the ECM for my '58 Volvo / 3.4 Camaro 4L60E to better optimize the shift points to compensate for the significantly lighter weight of the Volvo.  He said the ECU SERV # is in the range he can work with. ( Listed on his website - it may take him a week or so to get back to you, as he's pretty busy.)

www.PCMperformance.com