Injector questions... Gurus needed!

[TouringDan]

I am deep into deciphering the cause of my misfire. It is completely random - and does not seem to hit on the same cyl. Sometimes it'll go for a few seconds without a miss, and others - it's like a popcorn popper... All over the map. No load, under load - no change. I thought I had it solved, but it is still there. The list of things I have done is as follows:
- replaced crank & cam position sensors, replaced fuel filter, checked MAF, pulling a rock-steady 20in of vac at idle, changed plugs, replaced coils, replaced O2 sensor, changed DME, changed chip, no oil in coolant or vice-versa, and I am sure I am forgetting some other things.

The DME is giving me the 1281 code but I suspect that is from the swapping of the ECU, and the emissions show a high HC.

The odd thing about this misfire, is that I once did the 'shogun reset' of the DME, and when I initially started it, the car ran beautifully. Nary a miss to be felt. I thought "Eureka!", only to be let down when the miss re-appeared when the car reached operating temp. WTF!!!!

I started to think of all the things that change in the car when it warms up, and I was wondering if a bad injector would do this. Does the ECU change the mix when the car is cold? If so - would it be possible that it does fine shooting in the richer/colder mix, then starts screwing up when warm? Also - would the injector cause a high HC in emissions? If it's missing due to an injector (or injectors), does the injector simply not fire (causing a miss), or would it dump a ton in there and cause that cyl. to 'flood', thereby causing a miss and the high HC?

I am completely and utterly stumped here....

[White94RX]

so, you said rich/lean condition, well which is it? it can only be one or the other. that's probably what's causing your problem.

[TouringDan]

so, you said rich/lean condition, well which is it? it can only be one or the other. that's probably what's causing your problem.

Sorry - misquoted on the 1281 code. It is running rich.

[Rebel635csi]

I dont know if this might help...but i was reading a BMW UK Magazine a few weeks ago and they guy swapped an S52 into his E30 Touring and was getting missfiring...

turned out hes o2 sensor plugs were on the wrong O2 Sensors...one o2 sensor feeds info for 3 cyl, the other o2 sensor to the other 3 cyl....so u might wanna check that....

i was gonna tell u earlier through PM but u said u figured it out...

about the injectors...they are nothing more than glorified relays....so if u had a bad injector it would lean out the mixture or leak and richen the mixture all the time...it wouldnt happen only when the car warmed up.

Seeing as the ECU ignores O2 sensor readings untill its warmed up that also kinda points to what i stated earlier...

[TouringDan]

I dont know if this might help...but i was reading a BMW UK Magazine a few weeks ago and they guy swapped an S52 into his E30 Touring and was getting missfiring...

turned out hes o2 sensor plugs were on the wrong O2 Sensors...one o2 sensor feeds info for 3 cyl, the other o2 sensor to the other 3 cyl....so u might wanna check that....

i was gonna tell u earlier through PM but u said u figured it out...

Thanks for the idea - but my car was converted to OBD1, and I only have one O2 sensor now....

[Rebel635csi]

^^ sorry...but u're up a shit creek without a paddle..

i know i'd be pissed off too....

[fc3stech]

I am deep into deciphering the cause of my misfire. It is completely random - and does not seem to hit on the same cyl. Sometimes it'll go for a few seconds without a miss, and others - it's like a popcorn popper... All over the map. No load, under load - no change. I thought I had it solved, but it is still there. The list of things I have done is as follows:
- replaced crank & cam position sensors, replaced fuel filter, checked MAF, pulling a rock-steady 20in of vac at idle, changed plugs, replaced coils, replaced O2 sensor, changed DME, changed chip, no oil in coolant or vice-versa, and I am sure I am forgetting some other things.

The DME is giving me the 1281 code but I suspect that is from the swapping of the ECU, and the emissions show a high HC.

The odd thing about this misfire, is that I once did the 'shogun reset' of the DME, and when I initially started it, the car ran beautifully. Nary a miss to be felt. I thought "Eureka!", only to be let down when the miss re-appeared when the car reached operating temp. WTF!!!!

I started to think of all the things that change in the car when it warms up, and I was wondering if a bad injector would do this. Does the ECU change the mix when the car is cold? If so - would it be possible that it does fine shooting in the richer/colder mix, then starts screwing up when warm? Also - would the injector cause a high HC in emissions? If it's missing due to an injector (or injectors), does the injector simply not fire (causing a miss), or would it dump a ton in there and cause that cyl. to 'flood', thereby causing a miss and the high HC?

I am completely and utterly stumped here....

Yes the ecu does change the injector duty cycle when the car is cold, it will run richer to bring the car up to operating temp as well as to help with the cold start cause the vehicle is inefficient at cold temps, and yes a injector could cause High HC's because if its clogged or starting to fail and staying open to long it will start spraying to much fuel or to little both will cause excessive HC's to little fuel will cause a lean condition which can the ignition system cannot ignite and when it missfires the air and fuel that didnt ignite go through the exhaust and that reads as high HC's, to much fuel can be to hard to ignite as well causing a misfire, so yes injectors can cause a lot of problems if there faulty, another thing could be your engine coolant temp sensor, have you also did a compression test, low compression will diefenitaly cause a misfire as well, its worth checking

[bandit7784]

yeah so what year make and modle is it i have been gettin alot of the 98-04 bmws in latley that i have been reflashing the control modules on adn have ran beautifly and now if i get a rough idle or a miss thats the safe place to start

[Grim Reaper]

Just another idea on where you might want to look... ground straps, and since it appears to be when O2 grabs control.... do you have steady voltage?

[TouringDan]

Just another idea on where you might want to look... ground straps, and since it appears to be when O2 grabs control.... do you have steady voltage?

Interesting suggestions, and I'll look into both tomorrow.
Thx