85 318i Hunting Idle

[Welfare Racing]

I have a 85 318i that i have been working on getting running smoothly so I can get the suspension and brake systems worked over before I do a s52 OBD1 swap. Background on the car is lots of PO modifications, it has rear disc brakes, 5 speed trans, bumper swap, and sport interior. I have been trying to fix the problem of a surge in power under acceleration, low power, and a hunting idle. things i have done/tried;

-ecm
-iac
-idle controller
-full tune (cap,rotor,wires,plugs)
-air flow meter
-vaccum leak test repairs (smoke tested)
-fuel pump(s)
-baro sensor
-tps
-cleaned/disassembled TB
-valve adjustment
-timing
-coolant temp sensor
-fuel filter
-ignition control

odd noted symptom, the SI sometimes is red flashing 3 leds, one orange, or an INSPECTION light, i reset, and then with the car running, the lights spazz out and go to inspection again, could this be an, or the issue?

Im gonna go nuts trying to get it running, only to pull the engine to put in the s52, i dont know what else to try. I have had the ability to test most of this stuff as I am a service manager in a shop that is a major Worldpac buyer. I know all the parts ive tried where good, so I dont know where else to look, any suggestions? Any ideas would be useful because Im about to loose it.


-brandon

[Welfare Racing]

Anyone? Illl be going over to another shop a friend owns today to see if he has any ideas..

[PiercedE30]

try replacing the SI board since it is aparently going/gone bad. it will atleast eliminate that headache.

[Welfare Racing]

Ok, went to friends shop, found that when moving engine harness (above fuel rail,portion of firewall area) that engine idle and speed changed, went home cut into the harness to look for cut,damaged,corroded wiring. found a few wires damaged, cut, spliced and soddered and heat shrinked connections. Still reving as if a cammy '60's v8, kinda lobe-y type cycling. then also noted o2 sensor connector broken, now in the middle of rewiring that...anyone have any ideas?

SI board would only cause the lights to be annoying right, its not gonna make it run like crap and have a loss of power,would it?

-brandon

[PiercedE30]

nah......it's just "one of those things" (in reference to the si board)

[Welfare Racing]

Rewired o2 sensor, still the same, then on a hunch started car with o2 disconnected, it actually runs better than with it connected, is it burned out to the point that it makes the car "limp" so bad that it runs better disconnected?

[BimmerBall]

that may be the source of your problem, i'm narrowing down the same thing and i looked at the o2 wiring and its all kinds of fucked up. I should be replacing it within the week. i'll let you know

[Welfare Racing]

Well, after this evenings o2 sensor replacment, the problem is gone, but now after fixing this problem I now decided that knowing the o2 sensor was bad that there must be some wear to the cat. It looks like it was replaced some time in the past 3+ years, I might as well replace it too. The car runs well, but lacks any kind of low end acceleration, and at high RPM's it looses it too. I'm going to replace it tomorrow in hopes of finally having it running well. thanks for the inputt those above, Ill let you know how it goes.

[Welfare Racing]

cat and resonator being removed now, will update with how things go...

[Welfare Racing]

runs well now, i just have a timing adjustment to make, thanks to all above who helped me with suggestions, hope this post may help someone else with a similar problem.

-brandon