FI - idle changing with temp

[onion456]

trying to dial in new camper special engine, running a crappy FI setup from a '75 auto bus. the plenum and throttle switch have 'extra' vaccuum ports on them, which i have plugged. all parts look hammered to crap and my wiring harness aint much better... everything seems to work tho.

symptoms:

cold start; starts fine, idle around 1k. Air/fuel is 13.5 - 14

warm-up; idle drops to 700-600, occasionally stalls. at this RPM, air/fuel leans out to 16, 17, 18, sometimes higher. feathering the throttle brings RPMS and air/fuel back to normal ranges (13.5 - 14)

once hot, the idle climbs to 1700 RPMs. air/fuel around 13.5 - 14

adjusting the idle to be correct when hot will make it stall tons when cold/warm- undrivable till totally warmed up.


verified the throttle is closing all the way, no mechanical reason for the high idle. i dont want to dink with the AFM until i can solve why its so high once the engine is hot. i want to think vaccuum leak, buuuut idunno. wouldnt expect A/F to be correct if it were.

any idears?

[Amskeptic]

trying to dial in new camper special engine, running a crappy FI setup from a '75 auto bus. the plenum and throttle switch have 'extra' vaccuum ports on them, which i have plugged. all parts look hammered to crap and my wiring harness aint much better... everything seems to work tho.

symptoms:

cold start; starts fine, idle around 1k. Air/fuel is 13.5 - 14

warm-up; idle drops to 700-600, occasionally stalls. at this RPM, air/fuel leans out to 16, 17, 18, sometimes higher. feathering the throttle brings RPMS and air/fuel back to normal ranges (13.5 - 14)

once hot, the idle climbs to 1700 RPMs. air/fuel around 13.5 - 14

adjusting the idle to be correct when hot will make it stall tons when cold/warm- undrivable till totally warmed up.


verified the throttle is closing all the way, no mechanical reason for the high idle. i dont want to dink with the AFM until i can solve why its so high once the engine is hot. i want to think vaccuum leak, buuuut idunno. wouldnt expect A/F to be correct if it were.

any idears?

All fuel injection adjustments, mixture and idle speed, must be done warm. That is where your engine lives.

If you have cold running issues, then you must look at cold running items.
You have:
Temp sensor I in the AFM
Temp Sensor II in the #3 head area
Auxiliary Air Regulator.

If idle speed is lousy during warm-up and good when fully warm, vacuum leaks are unlikely to be an issue, right? With a Camper Special being focused on breathing at speed, you may have cam overlap that is just blowing the airflow reading at idle. If mixture is good when warm and lean when cold, then sensors become more important.

Don't even bother the cold start circuit. It has nothing to do with warm up.
Colin inyourareaApril20-24

[onion456]

argh, save me from myself willya? :diabloanifire:

so i decided to set idle when hot, do a dynamic lean adjustment and a static rich adjustment, to bring my idle richer and my high rpms to stay put...

starting out cold, i see 12.5 A/F idle at about 900rpms. then the dreaded mid-range temps come, again idle drops too low and i see very lean readings. then i warm up, 12.5-13 idles at 1600rpm, 11.5-12 under way.

my idle is still way too high... or is it?! when warmed up, it will suddenly and unexplainably drop to 1000, with a/f around 14. give it some gas and it will usually come back to idle around 1600.

concerning the AAR- this only affects idle speed during warm-up, correct? im trying to get it as high as i can to get rid of this mid-warm symptom, so ive adjusted it wayyyy open. it does close fully eventually. i dont have a thermostat installed yet (gasp!) cause i cant find a #)(@*$ pulley anywhere. anyone got one to spare, please pm me.

more problems; intermittent bucking! hooray. my AFM does have some small white spots on the wiper contact, but the bucking does not seem to be in any one RPM area. im giving the evil eye to my wiring harness, which is crispy as hell; im wondering if im getting voltage dropouts at the coil.

my 3 options: fix this turd of an FI system, get a better FI system, or give dual carbs a try. hey i love the FI and all, but i'd like a running bus too.

[midatlanticys]

argh, save me from myself willya? . . . . my 3 options: fix this turd of an FI system, get a better FI system, or give dual carbs a try. hey i love the FI and all, but i'd like a running bus too.

Onion, welcome aboard!! and pls don't get frustrated with your f/i - it's a great system, but requires a clear/sharp focus and intense *listening* to bring back to full funtion. There are capable people here to help, but it is not done with magic powder!

have you wandered down through the flow chart here looking for glitches: http://www.vaglinks.com/Docs/VW/Misc/VW ... Manual.pdf

there is a t'stat pulley here http://www.evwparts.com/Merchant2/merch ... Thermostat

ref: bucking - how clean/shiney are ALL your grounds to the body/chassis? old shagged/stiff wire or supple fresh copper?

[. . . . . Colin inyourareaApril20-24

you did catch this subtle hint, right!!?

Good luck!

[chitwnvw]

...concerning the AAR- this only affects idle speed during warm-up, correct?

You can check the aar for correct operation. Stick it in the freezer, then stick it in a really mild oven, like 200 degrees. IIRC it should be open in the freezer and close in the oven.

If it is not opening and closing as it should, you will have problems. It's easy to check.

[onion456]

thanks guys for the replies

yes i did catch the subtle hint =) pretty much a done deal, i just need to request the time off.

AAR works correctly using the 12v supplied at the connector. right now it is hanging in free air- i have new AAR mounts but ive yet to install them. my other bus works correctly and it too is hanging in air.

my case FI ground is clean and fresh- i brightened it up good before i installed it. the ground at the dual relay is bright as well.

like i said before, my wiring harness is crispy crunchy. insulation cracking and bare in places. i dont like it.

part of the reason i bought this particular bus is that its the same year as my other one- i wanted to have interchangable parts between busses. and then i went and bought an FI system that is different than my other, didnt realize it at the time. AFM has a diff number of pins. else i'd swap the thing out and see what happens. im currently looking into a replacement system.

i take back what i said before about carbs =P im definitely an FI guy. some parts about going to carbs sounds appealing... but im already ahead of the learning curve on FI, i'd have to start from scratch on carbs.

whats bothering me is every day is different- today the bucking was bad, but the idle behaved itself, aside from the mid-warm part, which is still too low. when hot, idle wanted to be around 1000. i notice too that the bucking doesnt seem to be an issue when im fully warmed up.

thanks for the links and stuff- i appreciate it

[onion456]

i feel like i should add;

when the engine is warming up, the idle starts out fair and begins to worsen as the engine warms up. if i am not at the wheel to supply some extra gas to keep the idle up, the idle will drop and i will occasionally hear a sound that i think is 'pinging'. it does not sound like a 'ping', but rather a fairly loud knock, 'feels' to me like the mixture predetonated and tried to run that cylinder backwards.

=/

[vwlover77]

I think the FI has a "natural tendency" to go through a low-idle situation during warm up, particularly without a thermostat. Enough time passes for the AAR to close and the Temp Sensor II to start warming, but the engine isn't really warm enough yet for the engine to idle where it ought to.

I think this problem is amplified on Camper Special engines due to the performance camshaft. (Where's Wayne? I seem to remember him having these issues.)

Randy in Maine would chime in with his standard good advice at this point: Make sure your Temp Sensor II is in good shape, especially the wire coming out of it. Maybe just replace it if it's not nearly new.

[Amskeptic]

i feel like i should add;

when the engine is warming up, the idle starts out fair and begins to worsen as the engine warms up. if i am not at the wheel to supply some extra gas to keep the idle up, the idle will drop and i will occasionally hear a sound that i think is 'pinging'. it does not sound like a 'ping', but rather a fairly loud knock, 'feels' to me like the mixture predetonated and tried to run that cylinder backwards.

=/

As per vwlover77's post + the following:

When the idle is doing the 1600 rpm deal when warm, check to see if the timing is up near 12-16-20* . If the idle speed is adjusted to close to 1,000+, the centrifugal advance will kick in.

Bentley has a warm up resistance value map for the temp sensors. See if your sensors are changing values at the correct rate, CHT is easy, but the afm temp sensor is tricky. They should be starting at 2800 ohms at 68* IIRC.

The electrical part of the Auxiliary Air Regulator is just a heater. The actual airflow boost when cold comes from a strictly mechanical device, a disk with a hole attached to a coiled bimetal.
Colin

[onion456]

thanks all

the AAR is hanging in air, so the closing of the aperture is functioning solely from the 12v heater. i've verified it, at least, is functioning correctly.

im not sure i understand this:

When the idle is doing the 1600 rpm deal when warm, check to see if the timing is up near 12-16-20* . If the idle speed is adjusted to close to 1,000+, the centrifugal advance will kick in.

but i will check when i am experiencing that symptom and report back...

one thing i did do yesterday when warming up is put a timing light on it during warm-up; when the idle begins to drop, my timing is hovering around 0* and threatening to go ATDC. my timing is set to 28* BTDC @ 3500rpms. i have a 231 168 005 distributor, which, according to Old Volks Home:

Bus & Pickup Late 1976-1978 All States, 1979 Federal * 2000

Note: This Distributor also fits Type 4 (412) 1974
Distributor: VW 021-905-205P, Bosch 0231 168 005 > 022-905-205S, 0231 170 093
Note: 0231 170 093 dist primarily used on California Late 1976-1978 and all Federal 1979 Models
Can Use:
Points: 01 011
Condensor: 02 074
Rotor: 04 033
Note: 0231 168 005 dist originally equipped with Speed Limiting Rotor 04 016 (5400rpm)
Dust Cover: 039-905-241, Bosch 1230 500 139 > 1230 500 147
Cap: 03 010
Distributor Cap Clip: 034-905-265, Bosch 1231 251 033
Parts Kit (Shims, Washers & Hardware): 059-998-211, Bosch 1237 010 007
Coil: 00 012
Vacuum Can: 07 060
Ignition Wires: 09 171
Spark Plug: W8CC
Timing Set At:: 7.5deg BTDC @ 850-950 rpm (Man Trans), 900-1000 rpm (Auto Trans) w/strobe, vacuum hose connected
Advance/Retard Range: Vacuum: 8.5-11deg Adv @ 7.9 In. Hg; Centrifugal: 8-13deg @ 1600 rpm, 20.5-24.5 @ 3400 rpm

according to this, i am not timing it correctly, should i set timing at idle? which is contrary to what most folks preach...

cant believe i just spent $50 on a pulley and a bolt, i must be insane...

[chitwnvw]

AAR should close based on ambient temps.

Set timing at idle, then adjust for max advance and let idle rest where it will.

[onion456]

AAR should close based on ambient temps.

so i should unplug the 12v heater connection? why did they put it there to begin with?

Set timing at idle, then adjust for max advance and let idle rest where it will.

sooo... time it at max advance....?

[dtrumbo]

AAR should close based on ambient temps.

so i should unplug the 12v heater connection? why did they put it there to begin with?

The AAR closes when the 12 volts makes the heater heat. I suppose one could argue that the time required to do so will vary with ambient temperature. I don't know if this is what chitwnvw was implying, but you need the 12v connector connected.

Set timing at idle, then adjust for max advance and let idle rest where it will.

sooo... time it at max advance....?

Yes. As you've figured out, you can skip the first step. Time it as you have been doing which is 28 degrees BTDC at 3000+ RPM and let it fall where it may at idle. At that point, if it drastically differs from 7.5 BTDC at idle, you might investigate the general health of your distributor (is the advance plate sticking, etc.).

[midatlanticys]

this keeps jumpin' out at me . . . .

. . . . my wiring harness is crispy crunchy. insulation cracking and bare in places. i dont like it.

. . you mean the insulation is cracked and/or gone and you are looking at bare wire . . . in places? If the bare wire is black (vs. shineyish copper) it has oxidized from ambient moisture and the conductivity of such wire is, at least, questionable.

[Amskeptic]

The AAR closes when the 12 volts makes the heater heat. I suppose one could argue that the time required to do so will vary with ambient temperature. I don't know if this is what chitwnvw was implying, but you need the 12v connector connected.

The heater times the fast-idle step down very specifically. Without a functioning heater, the AAR will eventually bring the idle down from ambient engine conduction, e-v-e-n-t-u-a-l-l-y . . .
Colin