sag off idle, idle problems

[chachi]

months old RJE 2.3. lots of of new parts on this thing so surprised when it came back from the builder with a sag in the acceleration. talked to rocky, he said it may need to be timed. local shop said it was at 0*, they went to +7. afterwards it seemed to lose a lot of its sag, but the first time around the block after picking it up i swung around and mid-180 it died. shut it off and it started right up but after that it has always wanted to die when first starting up in the morning. when warmed up it doesn't want to die when coming to a stop, like it does at first, but the idle is still really uneven and seeming like it might die. also, sometimes when coming off idle you will get a massive sag that bogs to about 1.5 or 2k rpms when it roars to life and takes off, possibly heat related. same shop advanced the timing even a little farther but now it feels a little too far and only sort of masks the larger problem.

- van has a brand new tank, pump and filter. waiting on a fuel gauge to test directly at the rail to rule out fuel pressure
- new rotor and cap installed by shop. they recommended plugs too but i think all three are a red herring
- AFM has writing on it consistent with a van cafe rebuild in 2015 and checks out with the tencentlife AFM voltage test
- RJE rebuilt throttle body
- injectors not rebuilt by RJE like we'd discussed but rocky says it's probably because they tested them and they passed
- pressure control valve hums, has continuity and accelerates its hum when the AFM is advanced
- new coolant temp sensor

untested:
- computer
- idle control unit

i'm just about to start the tests on 24.61 and 62 and would love any other ideas anyone has.
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'74 transporter panel
'91 vanagon carat NAHT

[jberger]

This is all about tuning.

Time that engine to 40° BTDC at 3000rpm.. Check the CO% at idle by either a sniffer or reading the voltage off the o2 (while unplugged).. Adjust AFM wiper as well. Check the throttle switch adjustment. Check for vacuum leaks. Every time I build a new engine there is a test and tune period where wrinkles are ironed out.

[chachi]

thanks for the response. i'll see what i can do.
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'74 transporter panel
'91 vanagon carat NAHT

[Ahwahnee]

[chachi]

yeah, the timing, what does that mean? they said it was advanced but i know there's the two different places you can measure the advance from, so it kinda means nothing for diagnostic. gonna try the tencent timing, his AFM writeup was great.
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'74 transporter panel
'91 vanagon carat NAHT

[ohhorob]

[chachi]

[chachi]

[ohhorob]

[wareiter]

not revving up smoothly might be the distributor advance. Bogging down at mid RPM's? might want to check if advance is coming in too quickly. maybe one of the springs on the advance weights wiggled loose? Pull the cap and twist the rotor by hand. Is there decent resistance and does rotor snap back? Maybe also look at vacuum advance/retard and make sure vac lines are hooked up correctly. This might explain the idle problems.
Good luck and keep us posted.
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1985 weekender
1989 560 SL
1995 RR Classic
http://waterboxer.blogspot.com

[jberger]

[Howesight]

[Howesight]

A few other comments:

1. After getting the idle CO adjustment done, if the engine still bogs, it may be time to check the operation of the AFM. You need an analog "sweep dial" VOM for this to check for drop outs in the traces inside the AFM. Someone posted a youtube video showing the procedure.

2. Have you checked everywhere for vacuum leaks? Don't forget the crankcase ventilation tower - - the diaphragms in these parts do fail. Block the hose from intake manifold (on the intake manifold side - - leave the vent tower side open) to the tower to check whether this affects your symptoms.

3. The boot connecting the AFM to the throttle body often develops unseen cracks that open with engine movement. Remove the boot and visually inspect it.

Hang in there! Like J.Berger says, this is a shake-down period. Even seasoned techs often find a hose clamp not tightened, etc. Rocky sold you a long block, not a whole new engine.

When adjusting ignition spark timing, be very careful to use the correct pulley mark. If using the Tencent method, you need to make your own pulley mark.
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'86 Syncro Westy SVX

[chachi]

...
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'74 transporter panel
'91 vanagon carat NAHT

[chachi]

also expensive shop says said CO "normal." hydrocarbons ~600+. don't know what that tells me.
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'74 transporter panel
'91 vanagon carat NAHT

[chachi]

finally got this problem on the mend thanks to dave at d and m. as you all correctly stated, it was tuning, plain and simple. dave removed the O2 sensor and measured oxygen at 9% when he was expecting more like 1.1. jberger, you mentioned a mixture sensor in another thread that you were mounting in the O2 position, if i'd popped for that i might have got there. but i was happy to have dave figure it out when no other shop could.

i fully admit to losing my cool on this. as you guys pointed out, rocky sells engines. this was not the engine. the miserable state of tune that this car left his shop makes me wonder, but basically this is a tuner motor and i didn't know to expect to have to have it tuned. rocky's initial ambivalence about my mechanic choice was also unhelpful; if i'd know to take the van to dave, who rocky knows, likes and approves of, i could have saved myself a TON of stress and frustration. but i guess that's the game. i'm not driving a $200 craigslist bus anymore.

my recommendation to anyone in portland with one of these engines is get to know dave. he's the only one that can help you.
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'74 transporter panel
'91 vanagon carat NAHT