M104 loses power/ feels "stuck" after holding throttle

Isved · Oct 2, 2014

Wow, thanks so much for all the insight everyone!! I've been busy with some things. I will read through the thread carefully and reply later today.

Quick note: I purchased the car already swapped. The problem randomly happened once or twice in the 10 or so thousand miles I've driven it. The consistency of the issue did not develop until very recently. Even when I am holding throttle around 3k RPM for 5-6 seconds, it very clearly "switches" and goes into what I can almost compare to limp mode. The car still drives and revs but does so with "hesitation. I turn the car off, turn it back on, and it's back to normal until the next time I decide to hold an RPM for more than a few seconds. Very weird. Here are my uneducated guesses (keep in mind that I haven't carefully read all of your suggestions yet).

1. One of the fuel pumps shuts off for some reason?
2. Diagnostic module being disconnected throws the ECU into some weird limp mode?
3. Throttle body doesn't properly register something and malfunctions?

Thanks for everything so far, I owe you all a beer.

humblejoe · Oct 2, 2014

I'm in Limerick....So I may look to collect

Limp mode becoming progressively more problematic?

Sounds like ETA (throttle body) to me.

dtsdig · Oct 3, 2014

Floobydust said:
...

Flooby, can you share your source for the armored cable protection that you used?

Floobydust · Oct 4, 2014

dtsdig -

The spiral cable armor is the kind used to protect hydraulic and electrical wires on industrial equipment. I got mine a my local auto parts store stocks it because they also do custom hydraulics and harnesses for snowplowing equipment. I'm not sure of the manufacturer and/or type, but I will check with them and see if I can find out.

- FD

Floobydust · Oct 4, 2014

Isved -

One other thing I would suggest is to carefully inspect the "splices" and harness from the transplant installation. There are several input lines to the ECU that need to be either grounded or connected to +12 in order to "fool" the ECU into thinking it is still home in the donor car. The transmission overload switch input needs springs to mind - if this connection is faulty (or has become so), the ECU can "think" the transmission is "overloaded" and reduce engine output. Of course, there is no such switch on a manual box.

- FD

Isved · Oct 4, 2014

I decided to start with the very basics, and bought a can of seafoam and seafoam spray. Put some seafoam in the gas tank, some through the brake booster line, and the next day sprayed the spray bottle into the throttle body. Just got back from doing a good old Italian tune up and the car seems to be fixed! I'll put in a set of new f8dc4 plugs for good measure and will report back. Hopefully the car had a good amount of build up from sitting for a while. Thanks for all the help everyone!!!

Isved · Feb 10, 2015

I don't mean to revive an old thread for no reason, but the problem is not gone.

The engine harness was redone when the engine transplant was done, which is why I am under belief that the problem is in the throttle body harness as that was probably left original (all contact points with the seller are no longer functional).

As you all are probably more familiar with M104 specific quirks and issues, would you say it's plausible that the throttle body harness causes the car to appear to lose power after the throttle is held applied for a few seconds? the easiest analogy would be to imagine that there is a point where it is similar to a "switch" and the car goes from ~200hp to ~120hp. BUT if the car is turned off and turned back on, it's good to go until you once again hold out a gear longer than a few seconds.

Thanks for all the help once again, I am just looking for confirmation that I am going in the right direction before I shell out for a rewired throttle body.

NobleTruths · Feb 10, 2015

The typical eco-junk ETA symptom is best described as "limp mode." No matter how hard you press on the accelerator, all your car does is limp slowly down the road due to the lack of response by the butterfly valve in the ETA.

However, much more than the wiring can go bad in the ETA. The internal motor can fail. The internal gearing can strip. And internal springs can break.

Testing these components is not too complicated, but doing so requires removing the ETA; and if yours is still the original eco-junk, then that process alone will trigger the onset of total wiring self-destruction. Sounds like you are at the point of replacement no matter how you look at it.

Isved · Feb 10, 2015

Agreed completely. Just wanted to hear some agreement to the fact that the ETA seems to be the most likely culprit.

Thanks!

M104 loses power/ feels "stuck" after holding throttle

Isved

humblejoe

dtsdig

Floobydust

Floobydust

Isved

Isved

NobleTruths

Isved

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