D Jetronic low to mid throttle surge

Hi, I have a 1974 Alpine A310 in Australia with d Jetronic injection.
It has started a low to mid throttle surge. It's ok at full throttle but uses lots of fuel.
I changed MAP sensors to a spare i was given. It runs better but not perfectly. I checked the original MAP and it holds pressure and readings with the multimeter seem fine.
Can anyone suggest where I start looking for the issue?
We don't have many old fuel injection specialists left here!
Thanks Tim.

Hi Tim,

low to mid throttle surge sounds like broken MAP sensor. If both show different results, I would be supicious. Also leaking cold start valve could be an issue and of course fuel pressure and engine temp sensor. We once discussesd a case here where someone in Australia had drilled into a Citroen MAP sensor and then repotted it like that.

Hi Tim,
did you check the Bosch part # of the other MPS?

It has to be the 0 280 100 055 - no alternatives.

Vacuum leaks (maybe the hose towards the MPS, maybe other leaks) would cause a rich mixture, too.

Regards
Norbert

Thanks guys.

The MAP that came off probably was on an R17 Gordini originally. My car had been converted to carbs, but was rebuilt back to factory in '92 when it came to Australia from New Caledonia.
The one I have on was from an A310-4 that was converted to a modern computer and multi-throttlebodies.
The original has 0280100048 stamped into it, not sure what's on the one now fitted.

I'll work through the sources of vacuum leaks, then fuel pressure. I have a spare original regulator too.

A modern computer and sensors are on the wish list. Been told $A5500 plus labour and dyno time. That's come with the 1800cc upgrade.

My engine

Hi Tim,

a 0 280 100 048 MAP sensor? That is a type 1 from Citroen. You should have a 0 280 100 031 or 055 as you can see from chapter 4 of my compendium

Please start in verifying component nos of all your components:

• ECU
• MAP sensor
• injectors
• throttle switch
• fuel pump