Jim Levie

[E30_fiend]

You're the god of all things relating to motor problems. So I have a quick and hopefully easy question. I am still having problems running a bit rich and having a choppy idle on a cold motor. Heres what Ive replaced:

Temp Sensor
O2 Sensor
Injectors
Valve cover gasket
Replaced both supply and return fuel lines from the fire wall to fuel rail and fpr
Spark plugs
Cap and rotor
Swapped ignition coil with working one.

The symptoms include a choppy idle on a cold motor. After about 30-45 seconds it smooths out and then its fairly stable. Also I went from getting about 320 miles on a tank and now its hard for me to get even close to 300. I think Im averaging like 275 on a tank which is pretty shitty. There are really no driveability problems with the exception of a small surge every once in a while when Im cruising. It basically just cuts for a second moving the car back a bit. I DO HAVE A LAMBDA CODE 1 pulled. Thats why I replaced all the things I did.

Car is a 90 325iS 5 speed

The only thing I havent done is a smoke test. Is there a redneck approach to doing a smoke test? The smoke test would help me locate an intake leak which MAY be my problem.

any help would be greatly appreciated from anyone not JUST Jim hahaha.





Taylor

[jlevie]

You really need to do a smoke test. Unfortunately I know of know way to do that without a real smoke machine. There are other possible causes, but until the possibility of intake leaks are ruled out there's no point in considering the alternatives.

The only alternative to a smoke test is to replace every seal, gasket, and hose that could result in an intake leak.

[E30_fiend]

damn, alright then where the hell can I find a smoke machine? I have a shop I work at and we can possibly buy one if I support the case well enough that we need one.

Or if that doesnt work out, where is a good place to check it out? I have worked at 3 different shops and none of them have had a smoke tester.

Also, what are the other causes if there actually aren't intake leaks?


thanks Jim




Taylor

[Sagaris]

I have never done a smoke test , I am sure Jim would have some great insight on it but as I have thought about it, I would think that you would need to do it when the car is cold so the fan isnt spinning and blowing the smoke around. I was guessing that running a stick of incense around the engine bay near suspect problem areas might work. Who knows, the religious value of the incense might cure it :P

[erik325i]

I have never done a smoke test , I am sure Jim would have some great insight on it but as I have thought about it, I would think that you would need to do it when the car is cold so the fan isnt spinning and blowing the smoke around. I was guessing that running a stick of incense around the engine bay near suspect problem areas might work. Who knows, the religious value of the incense might cure it :P

Haha, a stick of incense isn't going to help you find anything.
You use the smoke machine to pump smoke into the intake. When you see smoke coming out of any area, you probably have a leak.

Erik

[Sagaris]

Picture quasi-related, but awesome nonetheless

[E30Nova]

damn, alright then where the hell can I find a smoke machine? I have a shop I work at and we can possibly buy one if I support the case well enough that we need one.

Or if that doesnt work out, where is a good place to check it out? I have worked at 3 different shops and none of them have had a smoke tester.

Also, what are the other causes if there actually aren't intake leaks?


thanks Jim




Taylor

Where you at in socal? I used to work at Firestone in Riverside and they had a smoke machine. I used it on my E30 to check for any vacuum leaks. I'm sure other Firestones will have it, along with other shops. Just try a big chain shop.

Matt

[Farbin Kaiber]

PepBoys sells them for about $600.00 last I bought one. (2008)

[E30_fiend]

Im about an hour and a half to two hours away deom riverside so thats a no go. I just wish there was a redneck way of rigging something up that would work.

Hey Brandon, how did the machine work that you bought? I figure its very simple how it actually works. Maybe a few different fittings for different sized intake hoses and a machine that obviously makes smoke, turn it on and see where the smoke comes from.



Jim, what is the most suspect hose on the m20? Isnt it one of the hoses running to the bottom side of the TB? Anyone can chime in on this. I have checked most of the easy to get to hoses and squeezed them to check for cracking and all visible ones check out. I have also used the carb cleaner trick on both a cold and warm engine with no results but Im thinking if it is in fact a bad hose somewhere, that it is out of reach of the carb cleaner.





Taylor

[Farbin Kaiber]

Hey Brandon, how did the machine work that you bought? I figure its very simple how it actually works. Maybe a few different fittings for different sized intake hoses and a machine that obviously makes smoke, turn it on and see where the smoke comes from.

Amazing, makes a 2 hour hunt for a manifold leak take 20 min. Pull a vac line, or TB boot, put in special plugs(plastic discs), put hoes into adapter, turn it on, and wait. Make sure not to be smoking around workspace... It's sooo great.

[E30_fiend]

feck I need one

[jlevie]

Jim, what is the most suspect hose on the m20? Isnt it one of the hoses running to the bottom side of the TB? Anyone can chime in on this. I have checked most of the easy to get to hoses and squeezed them to check for cracking and all visible ones check out. I have also used the carb cleaner trick on both a cold and warm engine with no results but Im thinking if it is in fact a bad hose somewhere, that it is out of reach of the carb cleaner.

The most common suspect is the intake boot. But there are quite a few possible leak locations and several small leaks that are hard to find visually or with carb cleaner and add up to a major leak. The complete list of possible causes of an intake leak is:

Intake boot
Throttle body gasket
ICV hoses & connections
Brake booster, hoses, and connections
Crank case breather hose
Evaporative control hoses, valve, and expansion tank
Fuel pressure regulator & hose
Injector seals
Valve cover gaskets & bungs
Oil filler cap
Dip stick o-rings
Oil return tube o-rings

Because there are so many possibilities the best diagnostic is a smoke test.

[E30_fiend]

Throttle body gasket
Brake booster and connections
Evaporative control hoses, valve, and expansion tank

I removed the things Ive checked. Also what Im wondering is why I have a rich condition when an intake leak would cause a lean condition. i.e. unmetered air entering the system. Is it because my O2 sensor is telling the computer to run more rich to fix the lean condition?

I think I may have answered my own question there...

thanks Jim

[agent]

I had a warm idle issue which was caused by a breather hose being split - the one that runs from the valve cover to the intake just ahead of (and under) the TB. It did not reveal itself as the culprit with a carb cleaner spraydown. It was only suspected after firm pressure was applied to it by a friend while trying to start the engine warm and it held idle until pressure was released. Turned out to be split on the underside where it makes a right angle turn after the TB-side connection. Pelican has it for $3.

[jlevie]

I removed the things Ive checked. Also what Im wondering is why I have a rich condition when an intake leak would cause a lean condition. i.e. unmetered air entering the system. Is it because my O2 sensor is telling the computer to run more rich to fix the lean condition?

I think I may have answered my own question there...

Re-read what I said about adaption. If the DME is seeing a lean condition in part of the engine regime it will increase fuel trim to eliminate that. Since fuel trim is applied throughout the range of engine operation you can wind up with an average condition of a rich mixture. An aged O2 sensor simply compounds the problem since with age the sensor reports a leaner condition than actually exists.