Is this just the nature of the vane style AFM?

[Sagaris]

My worst tank was 22 my best tank was 31, I dont have the self control to do any better than that. My commute is >95% freeway, Work and home are 1/2 mile from the freeway ramps and any around town/errand running is done in the Toyota ultimate driving appliance.

[ChaseN]

I get 26 highway in my iX...26-29 in an i seems doable

[Schniddy]

hehe

ok so now the real question..26-29mpg what the hell!?

[Schniddy]

hehe

ok so now the real question..26-29mpg what the hell!?

[Sagaris]

Timing isnt adjustable though

[Sagaris]

OP are you driving an ETA?

No, I adhere to the "i before e" rule.

[Schniddy]

OP are you driving an ETA?

[nando]

they are relevant because both affect vacuum. a misadjusted valve (too tight) can leak, and timing affects vacuum as well.

[Sagaris]

I picked up a vacuum gauge and connected it to the vac. line on the FPR.
The gauge moved between 15.0-15.5 inHg every 2-3 seconds.

The Bently has a decent diagnostic chart for vac. at idle

According to the Bently, my readings indicate:
15-22 inHg:
Normal performance Engine in good condition

10-15 inHg:
a) incorrect ignition timing
b)incorrect valve timing
c)low compression
d)Leaking intake manifold gasket or fuel injector seals


since mine is 15 I am on the fence.
I do not see how a and b are relevant unless engine parts are mechanically damaged but c is possible (190k miles) and d is likely as well. The slight fluctuation throws me off. when the engine is revved the reading stays steady and doesnt jump around.

For anyone else that want to look into vac. gauge readings I came across these sites that may or may not be helpful.

http://autospeed.com/cms/A_2393/article.html

http://www.classic-car-magazine.co.uk/articles/fault-diagnostics-vacuum-gauge.html

just an update for anyone following or interested until I can do further testing

[jlevie]

The use of carb cleaner doesn't mean that you don't have intake leaks. It only means that any leaks that are present didn't respond to to that test or you din't hit the leak with the spray. Find a shop that can smoke test the intake. That is the only sure way of finding any and all intake leaks.

[Sagaris]

I blasted through a full can of carb cleaner while checking for vac. leaks

I had no real revelations except for a popping sound when I sprayed it down around the intake manifold, which was difficult to do even with the straw. The idle did not change when I heard the popping sound though.
A few months ago when I replaced my injectors, I noted that one of the bolts on the intake manifold was loose enough to turn with my fingers so I wouldnt be suprised if more intake manifold nuts were a bit loose so I took a look at that today. I took the airbox and intake boot off and tried to snug all the intake manifold nuts down, put it back together, and took it for a drive. The hesitation during sudden throttle blips off idle is somewhat improved and what I assumed was valve tick, is now reduced.

I know that when exhaust manifold gaskets are bad, you can hear the distinct ticking coming from them (See also: any early 90's Nissan V6)
but do bad intake manifold gaskets tick too???

Unless the evap. canister has some sort of leak in it, I am pretty sure my intake manifold gaskets need replacment. I think I will wait on it until I do a head rebuild.

[LowR3V'in]

It shouldn't bog, but if you floor the thing as fast as you can
it's normal for there to be nothing going on for 1/2 a sec.

no acceleration enrichment.

The 1980s was a high tech era for bmw.

[jlevie]

Could injectors be a slight cause of this? gunked up not being able to respond to quick inputs?

No.

[AnimalE30]

Could injectors be a slight cause of this? gunked up not being able to respond to quick inputs?

[Sagaris]

I checked my AFM resistor track and it has some pretty deep grooves. I attempted to move the wiper to an ungrooved part of the track but it didnt move hardly at all so I am not going to mess with it anymore.

I guess I will bust out the carb cleaner tomorrow until I can come up with a way to do a smoke test. Those intake manifold gaskets are going to be hard to spray.