19 replies to this topic

[brivinci]

UPDATE:

So, I recently drove my car and it was revving through the RPM range beautifully! Although I am not a fan something fixing itself (as its bound to come back) it was so nice to be able to enjoy the car as intended. Later, doing some maintenance, I noticed that the newer fuel trap that I installed was broken! Don't get me started on the terrible quality of everything these days. I had to completely remake the damn thing. The top was barely glued one, it was garbage. I got it all back together and assumed that maybe its being broken was the issue with my car. I reinstalled and the car regained its stumble between 3-4k. So, I pulled the vac line off that comes from the MAP sensor and it drives lovely again!!??

So, what would you say the issue is? With the MAP sensor piped in, the car will NOT rev cleanly through the rev range and has a wildly noticeable stumble between 3-4k. Like, if you are in that range going up a hill, it might not be able to get past 4k and feels like there is a misfire. With the MAP sensor vac line detached at the fuel trap, the car runs perfectly. This is not idea. How bad is it to run with the MAP sensor detached? I do have another ECU from a 95 Cooper that I can swap in to test....just have to drive an hour to get it. Thoughts?

[sonscar]

If you have the sensor pipe open to atmosphere the ECU will assume max fuel all the time?Steve..

[68+86auto]

Note: I have never touched an EFI mini

 

A few things to do:
 

• Test the vacuum signal on the disconnected hose to ensure there's nothing crazy there (is it connected correctly).
• Test the electrical signal from the MAP sensor.
• Determine what is actually happening when the fault occurs. The ignition secondary scope pattern will likely give a good indication.

 

Obviously all three of those require test equipment instead of just guessing. Unless test equipment is used you'll be constantly swapping parts until you find the problem.

[brivinci]

I am not sure if I could test all that as this issue only occurs under load and mainly in 3rd and 4th, so moving at a decent clip.

I have the connection to tab into the ECU and scan. I guess I need to hook it all back up and run a log while driving and get the car to replicate the issue. What MEMs app would be best to determine this issue, assuming it has something to do with the MAP sensor?

[brivinci]

One thing to add: I DID finally get around to changing the fuel filter! Might be my least favorite job to do as no matter what I do, I end up getting fuel all down my arm at the very least. 

With that changed, I saw no improvement in the 3-4 stumble. I did this before the above post about the fuel trap breaking and it running without stumble. So, I am still in the same place BUT wanted to keep a list going.