Author Topic: Poor running/20mpg SOLVED! (Read 3557 times)

///m42 sport · « **on:** November 22, 2009, 02:35:53 PM »

Ok heres a quick breakdown of what happened. (no pun intended)

About 2months ago pulling into parking lot to get sushi, car suddenly idles roughly and dies. I hear a distinct metallic sound inside the intake manifold for a couple secs. I was able to restart it and keep it running only by giving it gas. Towed home that night. Got 1444 on stomp test. Eventually after giving gas and riding idle for couple mins, got car running. Rough idle improved over time till it was pretty stable. but still was getting 20mpg and loss of power!

Vids here.
http://www.youtube.com/watch?v=zXSTeOm2uZE

Asked on forums what most likely happened and what to check.
TPS=replaced
ICV=replaced
vacuum leak=all air hoses 2yrs old. no leaks
02 sensor=couple months old
clogged cat= replaced with newer cat
check AFM, MAF=checked, were freely movable

camshaft sensor= pending
crankshaft sensor=pending
plug wires=pending

coolant sensor= on order
fuel filter=on order
fuel pressure regulator= on order

Then today was listening to cartalk on npr. someone called in about a spark plug blowing out b/c wasn't torqued correctly. I decided to check it mine out since it was easy and I replaced them myself about 4yrs ago and it sounded like something I could've done. haha. Guess what... it was loose! What was weird was the center elctrode piece had fallen out!!! Not sure if its still in the cylinder or not, but Ive been driving it around like that for 2m's. Think it wouldve worked itself out by now?

I took pics of spark plugs, will upload tonight. They were NGK's. not sure if this kind of failure is common or not, but I might switch back to bosch

///m42 sport · « **Reply #1 on:** November 22, 2009, 05:02:50 PM »

this what I found. NKG, spark plug was loose

the male end of the spark plug came loose and was attached to the plug wire

tip of the spark plug was gone

WTF!

I just drove around a little bit more and its back to its original poor running condition! Could it be plug wires?

KenC · « **Reply #2 on:** November 22, 2009, 06:46:23 PM »

You've been dumping fuel into the cylinder for a while without spark. You probably don't have a piston ring left.

1991 E30 M42 · « **Reply #3 on:** November 22, 2009, 07:12:06 PM »

it is possible but i doubt it unless he is running fuel that is high in alcohol content like e85

///m42 sport · « **Reply #4 on:** November 22, 2009, 07:22:09 PM »

Well immediately after I put the spare plug in I saw a immediate improvement in throttle response and fuel economy. It was like a brand new car. I parked the car for a couple hours and it started running poorly again. It felt like the poor response would cut in and out. Not sure what it is but I have a spare set of plugs coming in, will swap out

Also wondering why the spark plug got trashed like that. And the tip falling out couldn't have been good either. Could it still be in the cylinder?

DesktopDave · « **Reply #5 on:** November 23, 2009, 08:41:42 AM »

Run a compression check. That'll give you a baseline on engine condition. If you have a bent valve or worn rings the engine will never be right, but you could likely drive it for a while until you locate a decent used cyl head.

bmwman91 · « **Reply #6 on:** November 23, 2009, 06:15:27 PM »

You might have a coil pack going south. When those start to go, the thing will intermittently pull really poorly at lower RPM's, and eventually start misfiring.

///m42 sport · « **Reply #7 on:** November 23, 2009, 06:58:15 PM »

^^ I think that might be the case. It runs well above 3k.