29 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.

[brivinci]

I pulled the motor tonight to sort a few issues. One of which was my starter chewing up the flywheel ring gear! Awesome. Realized that when I pulled the starter, there were lots of metal bits, then sway teeth crewed up. Well, I pulled the motor and removed the crank sensor and there was a piece of the ring gear stuck to the end!! Magnetized to the tip. Who knows how long it’s been there but wonder if it could be throw in signal off?? I guess I won’t know in until I put it all back together.

[Pee]

Just to throw some recent experience into the mix. The good old MEMS relay pack / connectors was responsible for a misfire on my 94 SPI. Usual process of elimination on these cars led me down a fuelling or firing issue. I should learn that it always ends up being electrical 😄

Also these inline fuses need to go! (I’ve been saying that for 10 years)

Edited by Pee, 25 March 2025 - 07:34 PM.

[68+86auto]

Just to throw some recent experience into the mix. The good old MEMS relay pack / connectors was responsible for a misfire on my 94 SPI. Usual process of elimination on these cars led me down a fuelling or firing issue. I should learn that it always ends up being electrical

Also these inline fuses need to go! (I’ve been saying that for 10 years)

 

Not many people seem to understand that the fuel system should be tested last and the electrical system first. That means the starting and charging systems BEFORE even the ignition.

[brivinci]

Interesting you mention starter. So, my car is in very nice knick. I have owned it since 2005 and was essentially the second owner, with Wood & Pickett being the place I bought it from as a dealer. The car was 1000% original, including the wiring...which is the best gift ever. I know a lot of owners are dealing with past owners bodges. 

That said, the car is 31 years old so things can start to break down. One of which was the starter as mentioned above. It really did a number on the ring gear teeth and there were metal bits all inside the flywheel housing. Non on the flywheel but around. That large piece was stuck to the end of the crank sensor. Now, it might have just got there and it might not have the strength to stay on when the motor was spinning but who knows. 

Mini Spares order is actually due in today so I can get it all sorted. New starter will accompany my newer alternator. Once I have it all back together, I will certainly see if things are the same, or have improved.

[brivinci]

Pee, with your misfire, was it at a specific point in the RPM range or all the time? Mine is so specifically between 3-4k. Like, from 3-4k. Revs clean up to 3k, struggles to 4k, and then rips to redline. If you redline it and keep the RPMs from dropping below 4k RPMs, it feels perfect and very strong.

Also, plugs are all burning nicely. 

[Pee]

Pee, with your misfire, was it at a specific point in the RPM range or all the time? Mine is so specifically between 3-4k. Like, from 3-4k. Revs clean up to 3k, struggles to 4k, and then rips to redline. If you redline it and keep the RPMs from dropping below 4k RPMs, it feels perfect and very strong.

Also, plugs are all burning nicely. 

 

I cant say I noticed the specific RPM. It was a nightmare lower down, pulling out of junctions etc, but if you kept the revs higher it was ok.  The plastic clip underneath the relay box had broke years ago and I think its cable tied position was causing minor strain on the "big fat plug". I took the relay box lid off, cleaned all the connections, attempted to put a little more tension on all the connectors and plugged it all back in and resecured it a much better position. Its a simple enough thing to check and rule out. Just my experience 

[brivinci]

Like many I am sure, my clip had broken as well...and I zip-tied it to the bracket! Not too long ago, I would a 3D printed kit sold on eBay (I think) where you glue a new clip to the bottom and it works like the original. Simple and brilliant! Works like a charm and had held up with me needing to remove it a couple times already. 

I'll have a look at mine more closely and see. I have never opened it but might be a good thing to do, just to be sure/future proof things. Was it difficult to get into?

[brivinci]

To answer mine own question, it was pretty easy to use something thin and strong to get under the edge of the 2 pieces and pry gently. I did a good search and found someone checking a customers relay box from an MPi (slightly different outer box) and it showed some burning on the relay contact. 2 of mine showed signs of it, one being worse than the guys on the video. I took some time to clean the contacts with some fine wet/dry paper and liberal use of electrical contact cleaner. No idea if this will do anything BUT I have learned what the inside looks like up close and now know the contact points are nice and clean. 

Side question: Are all 4 relays used inside of this on a 1994 SPi? 2 of them looked brand new. They are not used, I would think that these could be swapped to the used ones.

[Pee]

There's a really good sticky in here that explains its function and pin out - SPI Relay Pack Functionality - Injection Mini Specific - SPi/MPi - The Mini Forum

 

It would read that all 4 are in use, assuming some more active that others maybe the reason for 2 of yours looking cleaner? Signs of burning don't sound to healthy though!

[brivinci]

Correct, I looked into a bit more and all 4 are used. 

What is interesting is that the one with the most scaring/burning was the starter relay. My started recently started chewing up the ring gear from (what I assume) is it not retracting quick enough. I wonder if the relay had something to do with this? I have a new starter in-hand and really happy that I opened this up and gave all the contacts a really good cleaning. I will keep the original starter (as I did the alternator) as each are dated to the cars year....and they both look so much nicer than the new units. Can't match the castings of the originals.