Troubleshooting odd engine surging, what else is left?

[wkohler]

Have you considered going back to the AFM? It seems to be one of those few things left. I'm not saying its the cause, but it might be worth a shot. I imagine you could just put it all back with butt connectors, or you could do it by desoldering and soldering again if you'd prefer, of course depending on your method of initial installation.

[m.olennick]

Have you considered going back to the AFM? It seems to be one of those few things left. I'm not saying its the cause, but it might be worth a shot. I imagine you could just put it all back with butt connectors, or you could do it by desoldering and soldering again if you'd prefer, of course depending on your method of initial installation.

I would be more likely to consider reverting if this same issue wasn't affecting someone who has the stock setup. It is still a possibility in any case.

Another thing I was able to rule out today, the MAF sensor itself. I sourced a new getup and still experienced the same symptoms.

I believe a phone call is going to be made in attempt to get Dan Miller back out here for 1) some more tuning on one of our project cars and 2) to shed some light on this problem. Initially I tried installing the MAF unit, however I had the instructions for a different unit version and consequently reverted to the AFM setup until Dan came down and installed everything himself.

I pulled the ECU connector apart today to inspect the soldering. I didn't find anything in terrible condition, however there were a couple exposed joints -- not in contact with anything else. I will see if we can ensure this wiring is fully intact.

[dauer]

I'm currently awaiting an ecu. Once arrived I'll swap it in and cross my fingers. Other than that I'm at a loss. The best way my condition can be described is as a lean surge. My inspection's due in June and I hope I have the issue resolved by then, otherwise I'm concerned it may not pass smog.
One thing worth mentioning is that it seems like my fuel pump is making more noise than usual. The other day I was unloading tools (I'm a carpenter) from my trunk while the car was running and the pump noise was more audible than I ever recall. In fact I never recall noticing any noise prior to this. Is one of the symptoms of a failing pump increased noise?

[whatareyoulookingat]

I've heard that a dying fuel pump will make more noise, but I've never experienced it. You might be better off buying a fuel pressure gauge and monitoring it when the symptoms occur. If you have low fuel pressure than the fuel filter, regulator and pump are suspect. I would replace the filter at the same time as [either] pump anyway.

[m.olennick]

I'm currently awaiting an ecu. Once arrived I'll swap it in and cross my fingers. Other than that I'm at a loss. The best way my condition can be described is as a lean surge. My inspection's due in June and I hope I have the issue resolved by then, otherwise I'm concerned it may not pass smog.
One thing worth mentioning is that it seems like my fuel pump is making more noise than usual. The other day I was unloading tools (I'm a carpenter) from my trunk while the car was running and the pump noise was more audible than I ever recall. In fact I never recall noticing any noise prior to this. Is one of the symptoms of a failing pump increased noise?

Don't hold your breath on the ECU

I'm hoping (for simplicity sake) that it doesn't work and our many minds may make light of the work.

[draztik]

mabey your purge valve?

[Funfive]

mabey your purge valve?

Worked for me! Thank you draztic!

I tried it based on draztik's excellent explanation and field work. 'lectric for 533i and pneaumatic for 535i.

Causes a lean condition, crappy idle and warm starting problems, since at 45 degrees from the coolant sensor it opens the purge system from the fuel tank vents.

Yours may be stuck open.

[whatareyoulookingat]

please explain more... Pictures? Where is the purge valve located?

[Funfive]

please explain more... Pictures? Where is the purge valve located?

Right near the charcoal cannister behind the passenger headlight area, down in the deep well that looks like it will accomadate another battery.

First check for cracked fuel vapor lines and the operation of the valve itself. My 533i is an electronic version, clean contacts and test operation.

An easy check is wait for engine to reasonably warm up and try unplugging the elctric connector first, if no change is detected plug it back in than remove the upstream fuel vapor hose heading to the intake manifold and put your finger over it. If the engine smooths out you know what to fix.

This is one of a myriad of things that can cause a lean running condition as it's unmetered air running into the engine.

[draztik]

http://www.mye28.com/viewtopic.php?t=46 ... rough+idle
Towards the bottom of the page theres info on the evaporative purge valve

[David Hunt]

Well, it seems the only thing left is to ring out the wires in that ECU harness, and get some contact cleaner on that connector in the glove box (and on the ECU pins.)
You seem short handed, so you'll be needing a partner, but it sounds like you are getting some help that way. And I would mark clearly the numbers with a sharpie so there is no confusion.
Get a brush after the pins with the contact cleaner, and even if it evaporates pretty fast, but I might hit it with some clean air (or canned computer stuff) and still wait for a bit.

[m.olennick]

Well, it seems the only thing left is to ring out the wires in that ECU harness, and get some contact cleaner on that connector in the glove box (and on the ECU pins.)
You seem short handed, so you'll be needing a partner, but it sounds like you are getting some help that way. And I would mark clearly the numbers with a sharpie so there is no confusion.
Get a brush after the pins with the contact cleaner, and even if it evaporates pretty fast, but I might hit it with some clean air (or canned computer stuff) and still wait for a bit.

After checking and cleaning every minute connection and module that I could find, I have eliminated all signs of the surging. I cannot feel it in the car anymore. Hopefully it stays this way!

[dauer]

I've been away from the boards for a bit because I've been flat out with work and got a puppy, which as I'm sure some of you know can be a full-time job in itself. I've also bought a new truck which I've been using for a daily driver, therefore the urgency has been toned down a bit. That being said I wanted to give a quick update regarding the surging issue I've been experiencing with my E28. I replaced all the parts related to the evaporative purge valve and while it softened the surging it's still detectable to me at least. Although this issue has been present for so long I'm not too sure how smooth it was running prior to this. I'm going to do a compression test, valve adjustment, and check for vacuum leaks for the umpteenth time. I'll keep y'all posted. I'm sure you're waiting with baited breath .

[spinedocab]

I know this is an old thread, but it seems revived and so here you go...

disclaimer: I haven't read the entire thread because I am just too tired, so if this has been covered please forgive me.

Disconnect your thermo-time switch connection. I know you know which one it is, but for those who do not, it is the connector next to the coolant temp sensor. (LOL). Disconnect the connector and just leave it hang there.

Anyway, do this and then see how your surge is, and whether your MPG goes back up. Bet it does...

I was chasing a similar situation, and could find nothing wrong until I went after the TTS. Voila', MPG up about 3.5-4 and more power, no surge, better driveability.

HTH,
Andrew.

[dauer]

I know this is an old thread, but it seems revived and so here you go...
Disconnect the connector and just leave it hang there.

Anyway, do this and then see how your surge is, and whether your MPG goes back up. Bet it does...

I was chasing a similar situation, and could find nothing wrong until I went after the TTS. Voila', MPG up about 3.5-4 and more power, no surge, better driveability.

HTH,
Andrew.

Andrew, thanks for the advice. Unfortunately I just replaced the thermo-time switch with little results. However, I will try disconnecting it because at this point I've got nothing to lose.

[87royal]

I'm having this issue, hope I can sort it out.