running rich when warm?

[onion456]

hey all, got a '76 sage green westy, 2.0L FI...

last night i FINALLY got rid of my LAST exhaust leak. the leak was at the manifold on the #3 cylinder. i drilled out the stud bosses of the manifold, ground them down to give me more reach to the head, and flattened the flanges with a bastard file via ratwell. leak is gone, dead quiet on that side now =)

drove it to work this morning (20+ miles via freeway) bus fired right up and drove like a top when it was cold. beautifully smooth, i was stoked. ran on the freeway for 30 mins, CHT gauge read cooler than usual. after i got off the freeway, the engine was acting tired. oil pressure was really low cause it was hot. (5-7psi-ish) idle was low. noticed occasional misses. once i got to work, i let it idle for a while longer while i walked around to listen, and ive got this popping at the muffler, like a mild backfire. the muffler is a POS extractor type, im sure too cheap to be any good.

the engine seems like it is running rich, with the backfiring and all, although i recently looked at one of my plugs and it was tan/white.

one other thing i can think of, is ive been thinking it might be related to my aux air valve, which happens to be not mounted to anything, just floating in space. altho according to L-jet manuals, it should close when the engine is warm, which would mean less air. if it is not working cause it is not mounted, it would be giving me too much air, which is the opposite of running rich.

i guess i cant really say anything for sure unless i look at some LM-1 readings or something; i know it is easy to misdiagnose stuff like this.

any comments or suggestions appreciated; im gonna check my timing after work, and see how she performs on the way home...

[Amskeptic]

hey all, got a '76 sage green westy, 2.0L FI...

last night i FINALLY got rid of my LAST exhaust leak. the leak was at the manifold on the #3 cylinder. i drilled out the stud bosses of the manifold, ground them down to give me more reach to the head, and flattened the flanges with a bastard file via ratwell. leak is gone, dead quiet on that side now =)

drove it to work this morning (20+ miles via freeway) bus fired right up and drove like a top when it was cold. beautifully smooth, i was stoked. ran on the freeway for 30 mins, CHT gauge read cooler than usual. after i got off the freeway, the engine was acting tired. oil pressure was really low cause it was hot. (5-7psi-ish) idle was low. noticed occasional misses. once i got to work, i let it idle for a while longer while i walked around to listen, and ive got this popping at the muffler, like a mild backfire. the muffler is a POS extractor type, im sure too cheap to be any good.

the engine seems like it is running rich, with the backfiring and all, although i recently looked at one of my plugs and it was tan/white.

one other thing i can think of, is ive been thinking it might be related to my aux air valve, which happens to be not mounted to anything, just floating in space. altho according to L-jet manuals, it should close when the engine is warm, which would mean less air. if it is not working cause it is not mounted, it would be giving me too much air, which is the opposite of running rich.

i guess i cant really say anything for sure unless i look at some LM-1 readings or something; i know it is easy to misdiagnose stuff like this.

any comments or suggestions appreciated; im gonna check my timing after work, and see how she performs on the way home...

Yes it is easy to misdiagnose. So far, sounds lean when warm. Very lean, as a matter of fact.

The auxiliary air valve does not change the mixture. It is downstream of the AFM and merely allows air to bypass the throttle plate, so if more air goes in, the AFM already knows this.

Please check like your exhaust valves depend upon it, for any vacuum leaks, this includes the oil filler and dipstick and breather box + hose, the s-boot for cracks (that always occur where you can't see them), and run a little WD40 around the intake manifold-to-head joint + injector seals on a warm but not hot engine. A lean engine will have a slight increase in idle speed when you find leaks, a rich engine will bog down even worse, but too bad, leaks must be eradicated.
Colin

[onion456]

looked for vac leaks before i left work- squirted around with WD-40, couldnt find anything. took the alternate route home to stay off the freeway & keep head temps down.

got home and checked my timing, it was pretty far off, like 8* ATDC. spun her back around to 7.5 BTDC and she seems to like it. idle is back up (a little too fast), no backfiring or other problems. this is where i really need the help- i got the fire started but need a clue with the fine tuning stuff. i guess i will look forward to Colins visit! i may take her back on the freeway tomorrow morn to see what my temps are like now.

[airkooledchris]

7.5 BTDC is a nice guide, but be sure to check where your at at 3500 rpm's, as it's more important to make your max advance 28* than it is to stick to the 7.5 BTDC at idle figure.

as others have said, forget the idle, set it where it needs to be when it's at speed.

[onion456]

i will do that- thanks

drove on the freeway again this morning, no problems, head temps were way down, stayed under 400 the whole time. 60-65mph. this actually scares me a bit, because my temps were so high before, i was suspecting my new gauge was at fault.

it still seems to be idling poorly when warm- may be time for a tune up- new plugs, check valve adjustment... i have not looked at the valves since i first dicovered i had hydros, like a year ago.

thanks all for the help

[onion456]

well this weekend has been quite a reminder course in tuning/timing. ive been working on such neanderthal jobs as chasing exhaust leaks and banging out dented panels that i forgot i have points and what they do. finally remembered them tho, and when i did the lightbulb went off. i had an issue not too long ago that the bus would die when it got warm, and it turned out to be my points had walked on me. turns out they were doing it again, which explained the crappy running when hot.

i played a lot this weekend with getting my dwell just right, then balancing timing vs idle speed. i just put in a new set of points (with some grease on the diz lobes) and my dwell is set to about 27. (which i cannot get with a .016 feeler gauge- i have to use a .008) with vac diconnected and plugged, timing is set to 26-28 BTDC at 3200 RPMs. comes back down to around 7 BTDC at 850 RPMs. happy happy.

poor running is gone, idle is pretty smooth. i have acceptable power... however in 4th gear, my temps are high (425) according to my VDO gauge, which i dont wholly trust because it is a replacement for one that i accidentally fried, and has been reading high since the day i got it. whether the high readings are real or not is the question. perhaps its time to think about getting a DD gauge.