14 MPG and Poor Power

[Gdub]

I bought this car a week ago and I thought I was getting all the power out of it. But yesterday I test drove my buddies car which is an identical 1990 535i(not chipped) and I was amazed at the power I am missing out on. I have a clean air filter, the engine runs fairly smooth, the check engine light has not come on, and new plugs and wires 30k ago. My engine runs smoother than my buddies also. Any Ideas?

[smcgowan]

Do the stomp test to see if any codes are present.

[632 Regal]

and then do a reboot and see what happens :D

sometimes the reboot is simply magic!

[SharkmanBMW]

and then do a reboot and see what happens :D

sometimes the reboot is simply magic!


search for "shogun reset procedure" and it will be in the result list, easy to follow details.....

may help you, post your results!

[infinity5]

oxygen sensors! somehow. maybe the engine just hasn't decided to turn the check engine light on yet, its taunting you.

Manual or automatic?

definitly do a Stomp test like they suggest. it should be around the forums somewhere, just search. you'll probably get back some codes that will tell you whats broken.

or, if you don't feel like searching, do what Regal suggested and disconnect your battery and touch the leads together for at least 1 hour. turn the ignition to pos2 (i believe) while you do this, too.

[SRR2]

"... disconnect your battery and touch the leads together..."

You know, you need to be *really* careful how you phrase this. A clueless newbie could interpret this to mean somehow touching the BATTERY leads together, which, obviously, can have catastrophic results. *I* know what you mean, *you* know what you mean, but a newcomer might not. Besides, the process of "touching the leads together" isn't necessary anyway. There's nothing in the car that won't bleed down all on its own in a couple of minutes.

I hope this kind of ambiguous advice doesn't show up in the archives.

[SharkmanBMW]

"... disconnect your battery and touch the leads together..."

You know, you need to be *really* careful how you phrase this. A clueless newbie could interpret this to mean somehow touching the BATTERY leads together, which, obviously, can have catastrophic results. *I* know what you mean, *you* know what you mean, but a newcomer might not. Besides, the process of "touching the leads together" isn't necessary anyway. There's nothing in the car that won't bleed down all on its own in a couple of minutes.

I hope this kind of ambiguous advice doesn't show up in the archives.


this is what is written for the Shogun rebbot procedure...

"shogun computer reset where the car battery is disconnected for at least 10 minutes with a neg and pos battery cables shorted (battery is out of the loop) with the key in #2 position will cause all the computers to reset to base values"

maybe someone should specify which cables to ground together, because it does sound like the battery!!!
what a mess!

[infinity5]

Sorry guys :) I'll keep that in mind from now on.

[waltersa]

Sorry I have been thinking about performing the reset procedure but wondering how it would affect an EAT chip, would it "erase" or somehow reset a performance chip. TIA

[632 Regal]

will not erase the chip.


Sorry I have been thinking about performing the reset procedure but wondering how it would affect an EAT chip, would it "erase" or somehow reset a performance chip. TIA

[Kalevera]

The check engine light could be "on", but the bulb could be missing. Not uncommon for shady sellers to pull bulbs and advertise it as "no lights on!!!!1"

There are tons of things to look at. First thing I would do is get a vacuum gauge on it and see if the cat is clogged up. Idle should read between 15 and ~ 26 inches (most I've seen are at the lower end of that spectrum). As the engine revs up, it should drop slightly (gets closer to atmospheric as the engine starts going). 0 inches under load is indicative of a clogged cat. There's a lot of info to know regarding interpreting a vacuum gauge result, but generally -- a steady reading with no boucing around is good. Everything should be smooth.

best, whit

[genphreak]

Check and/or replace; Vacuum leaks in pipes and fittings, (sometimes even gasket faces), O2 sensor, AFM, ICV. Clogged cat (as Whit said is very possible) if so you'll need a new O2 sensor anyway.

AFMs can loose smoothness as they open, if this bad you probably have intake leaks around the rubber boots to boot.. buy new ones (replace them all if old, fitting them very carefully- the way Dieter would at the factory as leaks are death for economy. A lot of people tend to over-tighten the aluminium sealing surfaces chasing vacuum loss.

PS I suggest doing a compression test and inspecting your plugs as your injectors might not be tip-top. :) Nick

[Gdub]

I did the stomp test and got a 1222 code. bentley manual said check for leaks in intake, or reasons for lean/rich mixture. i looked for and felt for leaks and couldnt find any. i have not done a reset yet but will do tomorrow. what are the reasons for running lean/rich? O2 sensor?

[genphreak]

Did you remove all the hoses, intake pipes etc and thoroughly check their mating surfaces? What about the little pipes that go from the FPR to underneath the intake manifold? And the rocker cover pipes?

Is the AFM flap moving smootly?

How does the vacuum gauge move when driving (smoothly?- chk Whit's sage advice on that..)

Is there a leak around the non-return valve that is in between the intake manifold and the brake booster? It has a little pipe that often breaks off underneath the middle section. If you still have it good, but it needs to be plugged shut with a rubber blank! (**Be careful** checking it, this little pipe is very brittle and snaps easily when old)