jbrob007

I have surging on an 86.5 with Porken 3.5 chips set to run on 89 Octane (with "lean mode" plugged in), stock cats & dual exhaust. I also have some ignition "knocking" at WOT... not good.
Step 1: I'm thinking its a lean mixture issue so first thing was to disconnect the lean mode connectors on the LH. That helped immensely!!! But surging is still there, only lighter, and the ignition knocking is also there, only lighter... Step 2: In the process of replacing the O2 Sensor. The old Sensor looks brand-freakin-new when I replaced it so I'm guessing thats NOT the issue. Havent tested it yet since the weather has gone to pot in Ohio

Ken, Mr. Porken to me, suggests its most likely a MAF issue and may need to adjust the MAF or have it rebuilt... Does anyone on here know how to adjust the MAF (without hooking up a bunch of tech stuff). I'm tech stuff deficient in both possession (dont own any) and knowledge (how to use said tech stuff)

Any suggestions, comments or advice greatly appreciated.

Randy V

Surging is often due to a vacuum leak and/or failing idle stabilizer valve (ISV).

Try the ISV cleaning procedure as a first step.

Also, have you tried disconnecting the battery for a few hours to reset the brains?

Mike Frye

The information you're looking for is in the LH/EZK test plan

I'm afraid I don't have it all memorized, but basically you have to meter the MAF itself in your hand and preset it.

Then you should meter for the same reading back at the harness to confirm that the wiring is good.

Finally, you will need a blink'r or a wideband O2 sensor in order to dial it in with the car warmed up and running. This will require a long allen wrench so you can adjust the MAF in situ.

Sorry I don't have any more specifics but it's a pretty detailed plan that you'll probably have to look up.

Also, just because the MAF reads good in your hand doesn't mean it's working properly, I think they degrade slowly over time so that you need to get them rebuilt after so many miles or years.

Swapping it out with a known good one is probably the best and easiest option.

I agree with Randy, surging is often not a MAF thing but an O2 or a vacuum leak thing. If it wasn't surging before though, Ken probably knows something we don't know about the interaction of all of the moving parts.

Randy: The brains in an S3 aren't smart enough to be reset.

jbrob007

Guess I'm gonna have to find the ISV cleaning procedure. I just replaced it, along with all the vac lines, etc, during the intake refresh, but you never know... I'll start there.

Thanks!

John Speake

The nominal setting of the MAF pot is 386 ohms, a used MAF will need to be higher than that dependant on the degree of ageing. You could try setting it to 600 ohms to see if that improves things.

I suggest you also disconnect the O2 sensor for a while, the LH ECU will revert automatically to the middle of its control range (open loop), which eliminates one complication.

I am concerned about the knock you are getting. The mixture would have to be very weak, or ignition far too advanced to get that. Maybe your EZ-F has a faulty MAP sensor ? Have you checked you are getting full engine vacuum (about 21"Hg when at idle, engine warm) at the vac port on the EZ-F ?

jbrob007

The problem is I wouldnt know where to start... I'm gonna need to get hooked up with someone who knows how to test this equipment

jbrob007

Although, I can disconnect the O2 Sensor - no problem.

Question: If the car runs well with the O2 Sensor unplugged, why would anyone plug the thing back in IF you dont have to submit to the idiotic EPA smog tests??? Which I dont...

Thanks!

jcorenman

Joel,

If you are getting audible knocking/pinging/detotation, then check with Ken but my advice would be to go back to stock chips (at least for the EZF), then sort out the fuel mixture. The 85/86 cars don't have knock sensors, and detonation can do a lot of damage.

Good hunting!

rexpontius

if I remember correctly the Porken chips also use the CO pot setting with WOT.
My 86.5 ran worse initially after installing the porken chips, but with help of Ken I discovered the CO pot was WAY to far adjusted, resulting in too rich running.
I adjusted it to 390 Ohms and the car runs fantastic.

adjusting the CO pot is very easy, all you need is the correct allen head and a multimeter.

John Speake

Judging by the colour of the OP plugs, he is running too rich which suggests the O2 loop is not in control because either the O2 sensor has a problem, the MAF mixture setting is too "rich" (too high resistance) or the LH has a problem.

If he is runing that rich and still has detonation, then there is a serious risk of engine damage.

How was the car running before you fitted the chips ? It's hard to believe it was 100%

jbrob007

I'll check with Ken to see if switching out just the EZF is an option (for now). Thanks

jbrob007

Is there a thread on here with directions on how to adjust the CO pot? I wish Dewayne had an 86.5... his write-ups are PHENOMINAL!!! I'll do a search for CO pot adjustment and see what I can find. If anyone knows of an existing thread, please post a link. Thanks!

PorKen

Plugging the EZ 'octane loop' plugs together will make the timing near stock.

Otherwise:
- Make sure the air temp sensor is connected.
- Verify that the WOT switch is working.
- Have the MAF tested/rebuilt.
- Adjust MAF CO to ≥382.

jbrob007

John, Not sure who's plugs your refering to? I'm the OP and havent commented on the plugs. Heres some history: When we did my intake refresh we changed the plugs and the original plug's color was perfect - definitely not rich - nice light tan. It didnt surge and dont know if the pinging was an issue prior to the chip install as this was my first drive in a 928 in over 35 years. It was probably there, but may be more prounounced with the higher performance. Currently, it starts right up without any issues, idles very smoothly at 750 or so, doesnt stall, doesnt backfire, no black exhaust... but has the minor surging at light throttle and pings ONLY at WOT. We changed every vac line, breather hose, o-ring, etc but there are so many places for a vac leak its tough to readdress... I'm gonna pull the plugs to check for rich/lean coloration and consult with some of my local club guys as far as testing the MAF.

Thanks!

jcorenman

Adjusting the CO-pot is covered in the WSM. The problem is that to do it properly, you need access to a gas analyzer or a wideband O2 sensor. The purpose of the CO pot is to adjust the fuel mixture for an individual car. With a wideband O2 sensor, adjust the CO-pot for an air-fuel mixture of 14.7 at idle, with the O2-sensor disconnected.

The alternatives are to either get the MAF tested and/or rebuilt, or set the CO pot to the default value of 386 ohms (as John described above), or do a "guestimate" for an aging MAF of maybe 600 ohms. All of these are only approximations, see above.

Another option is to use Ken's "Blinker" to set toe CO-pot using the factory O2-sensor as the reference. This works if the O2-sensor is working correctly (which it may not be, given the symptoms).

To check the CO-pot resistance, remove the MAF and check the resistance with an ohmmeter, between terminals 3 & 6-- see WSM pg. 24-113 for the pin numbering.

I hope this helps.