Viprklr

iTrader: (5)

$8D
Saujpv3
730

383 TPI
224/230 cam

This phantom idle surge is driving me up the wall. This is what i've done so far to combat the surge. Nothing has helped at all yet.
Can't set minimum air yet due to the surge.
Have not been able to locate any vacuum leaks. Interestingly enough though the surge didn't start until I installed my AS&M runners. Coincidence?

Tightened up the O2 thresholds and rich/lean error tables
Flattened the spark advance on the main table
Flattened the spark advance on idle closed throttle table
Added startup spark
Dizzy set at 2 deg and prom changed to agree (didn't like 8, 6 or even 4)
Removed fuel in the idle cells
Adjusted idle speeds to 1000 in prom. Can't get mechanicals to agree.
Tightened up idle SA and retard tables.
Locked in open loop

First starting of the car nets RPM's of around 1300. As the car warms, within 45 seconds, it drops to 1200 rpms and starts to surge. It only surges in park and stopped in gear. I have about a 300 or so rpm surge.

Idle kpa is in the mid to upper 30's.
IAC has gotten down to as low as 22 steps. Will not run at all if the iac is fully closed and disconnected even with idle screw all the way open.
IAC does not really seem to follow the surge more than 3 steps.
Spark was jumping with surge which is why I tightened up the error correction.
WBO2 has idle around mid to upper 13's.
SA relative to TDC is around 26.

I'm sure i've forgotten some pertinent information. Please help. It's disheartening to see that the 17K that I just put into the car nets me an embarassing surge.

YenkoST

iTrader: (5)

With my engine, it idles at a steady 750 rpms with 24.26* of timing. Min. air is set to 700 rpms and tps to .56.

Have you checked your plugs gap and the overall condition of the plugs. I have the Jacob's ignition system/ultra coil and .045 works great for me.

My IAC steps are usually around 8.

zipfast

iTrader: (2)

Try setting all the cells around the idle cell to the same number, (fuel and timing). Like 30 and 40 kpa 800 rpm - 1200 rpm

Viprklr

iTrader: (5)

I ultimately want an idle of ~900. Right now everything including the hex cells are set for 1000. Just can't get there.
I have an accel coil, new 8mm wires, all new plugs gapped at 35.
Can't get my TPS to .56 (non adjustable) and due to having the idle screw fully open. I consequently have a TPS voltage value of .73.
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Done this. Hasn't helped.

86Z

iTrader: (4)

this is typical with an SD setup, mine is around the same voltage, there is no adjustment on those only the older maf ones, after installing the runners did you readjust the iac and min idle?

Viprklr

iTrader: (5)

Can't. The car won't run with the IAC fully closed and disconnected. I have to physically hold the throttle open more.
The surge stalls the car. Minimum idle at this point is the idle screw fully screwed in which nets me an idle of 1300. It still surges at this point. The surge is gone if I hold the throttle around 1350 to 1400.
Whenever I reset the IAC, reconnect it, then start the engine I have IAC steps as high as 220. It ever so slowly drops from there and the surge is present the whole time.

1tpi

Sounds like it didn't do this with
the old runners, have you tried putting them
back on and seeing if that stops it

YenkoST

iTrader: (5)

Sounds like maybe a vacuum leak perhaps?


Have you did a vacuum test on the engine?

vernw

iTrader: (2)

One other thing to consider is a bad IAC. I had one that was not moving, but the computer thought it was. The IAC counts displayed in the data stream are only what the ECM told the IAC to do, not what it actually did. There is no feedback from the IAC to the ECM as to where it is positioned. So the IAC can be stuck and not moving and the computer will never know it. Mine surged terribly back whn I had this happen when using my Super Ram and S_AUJP.

You could also have a vac leak, but the kpa values you are getting sound pretty good, so I actually doubt that is te problem. Try a different IAC if you have one available.

Viprklr

iTrader: (5)

I sold my stock runners to another member so swapping those back on isn't an option.
I did find 1 vacuum leak but fixing it did nothing to correct the problem.

The IAC is 200 miles new. Is there a way of testing it's movement without using Vader's method with a baggie? What I found a bit interesting while datalogging the IAC is:
Resetting the IAC produces counts in the 200's. It slowly drops and I mean SLOWLY.
Shutting the car off and then restarting produces IAC values in the 40's. Why such a jump? Could it actually be bad? IAC counts of 200+ and counts in the 40's produce no difference in idle speed or characteristics.

My P/U coil has a resistance value of 934. Upon flexing the leads it does change value slightly. It goes up about 10. Doesn't seem to me that it is the problem but why would the resistance of a wire rise when flexing unless there's something wrong?

YenkoST

iTrader: (5)

Pickup coil sounds like its close.....I think its supposed to read 900 so that's not much off.

I would say the IAC is the culprit then....like I said....when I'm warmed up...I'm running 8 steps.

Viprklr

iTrader: (5)

Sorry, I neglected to mention that 934 is a hot number.
742 is cold.

I talked to my local NAPA where i got my IAC. They seem to think they can warranty it. I'm just debating on going GM though. I broke my original. The first one I bought from NAPA was broken. Now this one doesn't seem to be working.
Can I test this thing by putting it in a baggie, starting the engine, and watch the pintle?

1991CamaroRslow

iTrader: (3)

I had a new IAC from Auto Zone and would get a crazy idle and a weird stumble whem decelerating. I swapped that one out for an ancient one that was in a stock TB I got, problem solved.

Viprklr

iTrader: (5)

I guess i'll go that route. Hopefully they'll warranty it.
Maybe it is just that the IAC is not opening enough. Since nobody is suggesting anything prom related I guess it must be mechanical.

What idle do you guys think I should be able to get this 383 TPI with a 224/230 .565/.570 112 cam down to? I'd like to see 900 or even 800. The current 1300 is just not acceptable.

YenkoST

iTrader: (5)

I have a bigger cam idling at 750 rpms...so yea I think you can.

Viprklr

iTrader: (5)

Good news Yenko.

I ended up changing the p/u coil since it was original and I had to wait for a replacement IAC. The p/u coil didn't fix the surge but I was able to drop the idle screw and get a TPS value of .56.
I just put the new IAC in today. Preliminary results are excellent news. Surging gone. I'll test more tomorrow to be sure. Too many monsters running around on the streets and ringing my doorbell tonight for me to really get much done.

randy4762

Just my 2 cents. How many miles did you say were on that dizzy? I once had a truck with over 150,000 miles that ran super, just not under 1200 rpm. It was a totally stock truck. Severe surge. Every couple months the idle would creep higher. Eventually,You actually had to keep the rpm's over 2000 for it to even run! It ended up being a bad distributor. The reluctor had started to lose it's magnetism and wasn't firing the p/u coil very well. When I built my new motor last fall, I remembered this (my dizzy had over 160,000 miles). I just bought a reman (A1 Cardone) for $70. If you ever have had a new dizzy in your hands, spin it and you can feel a very sharp magnetic kinda pulse as the reluctor passes the coil points. I spun the old one and it had no noticable "pulses" at all! The magnetic field on a new one is so strong that I thought it was built wrong and was binding. So in hindsight, installing a new module or coil may improve the condition, But the shaft has to be replaced to fix the reluctor and it is much easier and cheaper to replace the whole thing. This part is actually discontinued.


Randy

Viprklr

iTrader: (5)

The prelims were premature. Still surges. Takes a bit longer for it to start now though. The car will not run with the IAC fully closed (for the reset) unless the idle screw is fully open. There is slight surge with the idle screw fully open and the IAC reconnected. As soon as I drop the idle screw just a little bit the surge comes back with a vengeance.
Are the BLM cells supposed to move around when the car is locked in open loop via minimum CL temps?

I have 92K miles on the dizzy.

YenkoST

iTrader: (5)

Vacuum test the engine with a guage.

Your welcome to PM me and try my tune if you would like.

Viprklr

iTrader: (5)

13 inHg at 1100 idle. It goes up to 16 with the surges.
I just swapped in stock AUJP main timing tables. Same problem.
It almost seems like the surging becomes a major problem when the car gets to a certain temp or even trying to go into CL.
Upon warmup today it was surging about 50-75rpm until it warmed up. Then it became a 400rpm surge.

PM sent.

YenkoST

iTrader: (5)

Have you tried raising the temp?

I had a surging problem on my last 383....just started one day.....and come to find out my aluminium heads had a Proxy holes in them causing them to put the fire out. Now, that not be the case so is your valve adjusted correctly?

Viprklr

iTrader: (5)

Raising the temp? I've raised the minimum coolant temp for closed loop to 255 if that's what you mean.

I adjusted my valves according to comp cams website. I did it on the stand. Last time I tried adjusting the valves with the car running ended up being a mistake. Couldn't hear the individual valves. Also the rockers were slinging so much oil that I actually started a fire on my header collector.

vernw

iTrader: (2)

So you're running open loop intentionally? Then I'd definitely get a data log to see what is going on. Not much of a way to tell other wise. Open loop is a lot harder to set up initially for an idle, definitley needs to be "tuned in". No other way to go about it unless you have a good O2 sensor and run closed loop.

YenkoST

iTrader: (5)

You can set them with the engine off which I do.....just warm it up and I go to town....makes the lifters be pumped up.

Yea, you are running in open loop. My tune was setup mostly in open loop but I set it back to closed loop for ya. In closed loop, I would surge a little bit about 50 rpms worth sometimes but never 400.

I'll go today and see if I can get a vacuum reading on my engine. High 30 kpa just sounds low to me....that's like a stock engine almost. I've gotten many people that with that cam in a 383 idle about 50-55 kpa.

vernw

iTrader: (2)

Or cut the top out of a cheap old valve cover like I do and adjust them running. A lot more sure that way IMO.

89RsPower!

just saw you stated this problem occured after installing as&m runners, another member had a problem with them sealing at the plenium causing the same problem you are having, turned out they didnt seal properly.. heres a link to his thread https://www.thirdgen.org/forums/afte...long-tube.html

Viprklr

iTrader: (5)

Vern - Yep, open loop intentionally. I was planning on tuning my VE tables via the WB02 in open before allowing closed loop. Adjusting these rockers with the engine running is a bit of a problem. The exhaust is so loud that last time I had to use an engine stethoscope on the rocker stud to hear it. Didn't work too well. I ended up overtightening. I'll play with Yenko's burn and see what happens. If the idle issue is still there......I'll post a small datalog.

Yenko - I'll give your tune a shot. Thanks! I would really like to know what your kpa readings are.

89 - I initially had 2 sealing issues with the runners. Both on the DS. I've since corrected them. I had to drill out my Bigmouth for a larger hole to repair the rear seal and re-tap and get shorter bolts for the front seal. Carb cleaner did what propane couldn't do for me in finding these leaks. Both of my leaks were at the intake manifold and not the plenum. BTW - fixing them didn't fix my surge. Bummer huh.

The cam is Comp cams XFI 224/230 .566 .570 112lsa - this is WITH the 1.6 rocker math. Can't seem to find my original cam card.

Viprklr

iTrader: (5)

Now we're getting somewhere! Thanks Yenko for your tune. I taylored it to fit mine and now get an idle of 750-800. Much better in that department.
I still have a surge though. It does, however, settle down to a steady idle after anywhere from 30sec to 1 minute. The kpa's are also up into the mid 50's now at idle.
I'm currently playing around with it a bit more. If I can't get it to fully settle down i'll post a datalog for whoever would be so kind. I've got to get this thing straightened out before tomorrow. The car's going in for some welding.

YenkoST

iTrader: (5)

No problem man....glad I could help. What's your A/F look like at idle? You will probably need to lean it out just a tad more then me b/c of the 36 lb/hr injectors more than likely....you have a wideband to look at the A/F ratio I am assuming.....

One thing...you have set the min. air correct and correct the dist. setting for your setting?

JP86SS

iTrader: (1)

The only thing I can think you haven't tried is the PCV valve.
It can act like a vacuum leak. I imagine you've tried blocking it but maybe not.
The other thing for finding out if there is a leak is a piece of wood/metal to slide in place to cover the TB. Can show you if you have air getting in elsewhere if your IAC counts are low.

Viprklr

iTrader: (5)

Yep. I have the ZT-2. My AF's are hanging around mid 14's at idle.
The distributor setting is the same (2 btdc) mechanically and in the prom.
Still can't set minium air. The only way I can start the car with the IAC fully closed and disconnected is with my foot on the gas.
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I pulled the PCV yesterday with the engine running and stuck my finger over it. It was sucking pretty good. This I did while the engine was surging. Didn't correct the surge.
My IAC counts do eventually get to 0 now at idle. I guess i'd have to be quick if i'm going to cover the throttle body.

YenkoST

iTrader: (5)

I know you said you checked the vacuum lines....that might be worth checking again.

Still seems like you have a vacuum leak. I run about 6-8 counts of IAC.

That's about the way I have to start mine when I do new engines to set the min air. I give it a little throttle and then blip it or have an extra hand to hold the throttle until you get up there. I have my min. air set to around 700rpms.

Now, my engine does surge on occasion but usually when I just load a new tune to it and its adjusting everything around.

Viprklr

iTrader: (5)

I keep re-visiting the vacuum leak deal. I guess it's possible to have an internal leak. This time I used starting fluid (and a fire extinguisher) to try and find one but to no avail.

I'm attaching a small datalog of what the engine JUST did. It's the surge that eventually settles down. If I shut it off and then re-start the car....the surge is back until it settles down again.

ramiles

Any chance the Throttle body isn't compatible with the Plenum and Runners? The early models have a different IAC airflow passage through the TB, Plenum and runners than the later years (89). In the early years there is a separate passage underneath the regular pelnum. The later year TB has a different recess in the back that dumps the IAC airflow right into the main plenum.

Viprklr

iTrader: (5)

Interesting thought but not a possibility for me. I'm running the stock TB with the stock plenum. The plenum has been seriously ported, gasket matched, and the throttle ports were opened up to 58mm. Still running the 48mm TB though.
I've also picked up a very light throttle surge along with a coastdown surge. I see why lots of people go carb.