[Addlight]

I am having an issue that I hope someone here can help diagnose. I have an idle drop when I put the car into neutral, for example, as I approach a stop sign. It normally drops to about 500, but occasionally will drop lower, to the point that my dash will light up before the car catches itself.

By deduction, I think it's the idle stabilizer valve, but want to get other thoughts.

The car idles perfectly on start up and when sitting, and does not fluctuate. Car runs very smooth, without hesitation all the way to redline. As routine maintenance for our five year emissions, I have done recently:

- checked all vacuum hoses and they are tight all the way around the engine and under the airbox.
- cleaned and calibrated the MAF. It tests fine.
- installed new O2, temp II, and spark plugs
- checked plenum boots (no cracks) and retightened the clamps
- replaced fuel vapor hoses and Y connector.

So, do I have to wrestle in a new idle stabilizer valve, or is there something else to check first?

Thanks,
Matt

[worf]

Your symptoms are consistent with an out-of-spec Mass-Air Sensor.

- cleaned and calibrated the MAF. It tests fine.

How did you clean, calibrate and test it?

Do you have Porken’s Blink’r to adjust it?

[Addlight]

Thanks. I do have a Blink'r but did not break it out yet. I have used it before, several years ago.

I cleaned the MAF with CRC's cleaner and reset it to 382 ohms. I tested it using John Speake's testing procedure for voltage and resistance. It was rebuilt by Injection Labs a decade or so ago and 10k miles ago. I did not adjust idle or the resistance using the Blink'r. Sounds like that's my next step.

Matt

[Crumpler]

Hey Matt,
Several thoughts.
You could be right to suspect the ISV if it is not “catching “ the rev drop. Or ECU is catching it and preventing an engine kill each time.
But as Worf says, many other factors to look at, and he’s usually right.
Just because the ohms are in spec on the MAF (or even the isv) doesn’t mean it’s optimal unfortunately.
The 86 has a bi directional ISV which I dislike, and the door movement sucks, IMO. But the 86 also has a throttle bypass screw which you can use to your advantage.
If you haven’t, jump the idle control and see what your idle speed really is. Obviously adjust if lower then 680-700 rpm.
WSM has a good section on that.
The CO tubes are usually long gone, and I’ve never actually seen a factory tester. IMO a wideband is the cat’s pajamas, if you want to go there. Makes it pretty easy to tune maf and idle speed to optimal.
But if you own a blinkr already, that’s the move.

[worf]

Thanks. I do have a Blink'r but did not break it out yet. I have used it before, several years ago.

I cleaned the MAF with CRC's cleaner and reset it to 382 ohms. I tested it using John Speake's testing procedure for voltage and resistance. It was rebuilt by Injection Labs a decade or so ago and 10k miles ago. I did not adjust idle or the resistance using the Blink'r. Sounds like that's my next step.

Hmmm…. ok. Then the mass-air sensor goes to the bottom of the list.

Before digging into the ISV…

tell us about your WOT/idle switch and its little “accessory” harness than connects it to the LH/EZF/engine harness.

[Addlight]

Hmmm…. ok. Then the mass-air sensor goes to the bottom of the list.

I can still run the Blink'r. Won't hurt. I was a little lazy when I reset the MAF because I needed to get the smog cert done and don't have a digital timing light. Now, I have more time so can get my hands on one.

Before digging into the ISV…

tell us about your WOT/idle switch and its little “accessory” harness than connects it to the LH/EZF/engine harness.

I did not look at my TPS, and have not in quite a while. It was good when I did my full intake refresh (ten years ago - fuel lines, regulators, injectors, hoses, vacuum, ISV, etc) so it's about the only thing I didn't replace. But, I have not messed with it. I can check the TPS when I do the Blink'r, right? I believe the testing procedure includes verifying it's working.

Thank you, I appreciate the help.
Matt

[Mrmerlin]

NOTE you setting the MAF to 382 is your starting point for mixture.

You need to set up the idle circuit by disabling the idle circuit,
then setting the idle speed via that brass screw at the front of the intake .

Once this is done then set the mixture with the MAF, use an O2 sensor OR
you can use your nose smelling for a not too rich or lean exhaust then recheck the idle.
NOTE the MAF may need to be sent off to be tested.
NOTE the TPS short harness is also a problem if its old as the connector can crumble.
Roger sells new short harnesses
NOTE check for vacuum leaks before you do any settings changes

[worf]

NOTE the TPS short harness is also a problem if its old as the connector can crumble.
Roger sells new short harnesses

What I mentioned above too.

The first thing to do when looking at idle issues is to make sure the ECUs “know” that they should be idling.

Before digging into the ISV…

tell us about your WOT/idle switch and its little “accessory” harness than connects it to the LH/EZF/engine harness.

But, I have not messed with it. I can check the TPS when I do the Blink'r, right? I believe the testing procedure includes verifying it's working.

You check the idle/WOT switch at the ECU (both) pins. Details are in the LH/EZF troubleshooting guide on the WSM CD-Roms. If you don’t have it, let me know.

But, first, as MrMerlin posts above: visually check the ‘stub’ harness from the LH harness to the switch *at* the connector to the LH harness. It’s the 3-pin connector on the right-side (passenger-side) of the water bridge. It should be retained by a little bracket.

[Addlight]

Thanks guys,

Stan, you were there and in the lead when we did my intake.

I am aware 382 ohms is the starting point for calibrating the MAF, but without the ability to calibrate it, I thought that would the best place to set it. As discussed above, I will get my hands on a digital tach and set idle and MAF with the Blink'r.

MAFs can always fail, but I doubt this one has at 10k miles on a robust rebuild. So, shipping it out for rebuild or swap is a last resort. Also, I was not having the idle drop before I did the routine maintenance for emissions testing, which leads me to believe it is related to something I did and not the sudden failure of the MAF. My gut instinct is that Worf has it right, and it was me who put my MAF out of spec by resetting it without calibration.

I have the WSM and know where the TPS harness connects, so I will do these tests /inspecitons as well. But, like above, the idle drop seems more likely to be because of what I did than the sudden failure of a component. I'm not ruling anything out, but that is why I think my best first step is calibrate the MAF with the Blink'r.

The Blink'r manual states "Rotate throttle linkage at engine. Just before the throttle stop is reached, the yellow LED
should go out. If it does not, then the TPS or extension wiring/connector is suspect." That is what I was referring to in using the Blink'r to test the WOT switch. I assume since the blink'r connects to the test port that it is communicating through the computer and back out to the port. But I will also visually inspect the harness and connector.

[worf]

I assume since the blink'r …

Yeah. I dunno. ‘bin a decade since I used mine.

The diag plug is probably routed to junctions in the LH harness that therefore are ‘downstream’ of the stub harness.

But, check the wiring diagrams to be sure.

[Mrmerlin]

Dave do you have a Blinkr ?
do you wanna sell it?
I had one but it disappeared.

OP,

Take the MAF to Kevin at Injection labs and let him test it he is in Boulder

[Addlight]

OP,

Take the MAF to Kevin at Injection labs and let him test it he is in Boulder

Oh, man, Stan, you hurt my feelings. Is that all I am to you now, just "OP"? This is Matt, the guy you hit 120 on I-70 with coming back from a show at the airfield, the guy whose car you redid the A/C and installed the new shocks and motor mounts.

I know Kevin at Injection Labs. He used to hang out with us quite a bit, and came to Emanuel's parties. He rebuilt my MAF. He also gave me a terrifying ride on the backroads of Boulder County in his 930 where I wasn't even sure we were connected to the road some of the time.

Anyway, I will reach out to him if I can't get the MAF calibrated. But I want to check everything on my own first.

Matt

[Mrmerlin]

Hi Matt I didnt recognize your screen name nor the car color,
does your wife still make excellent chocolate chip cookies?

[SeanR]

I stopped using MAF's rebuilt by injection labs about a decade ago because they were improperly calibrated and could never get them to work as well as a JDS unit. Greg also experienced the same issues. I'd toss a JDS on and see if that is the issue.

[worf]

I stopped using MAF's rebuilt by injection labs about a decade ago because they were improperly calibrated and could never get them to work as well as a JDS unit.

After sending them several units per year, every year for many years, I stopped using Injection Labs because, about 10 years ago, Kevin stopped returning my calls and emails for no particular reason that I know.

<shrug>

[Addlight]

Hi Matt I didnt recognize your screen name nor the car color,
does your wife still make excellent chocolate chip cookies?

Hi Stan,
I figured and was just busting your chops. The car is black again. That copper color was just a Plastidip I did for fun.

If possible, my wife's chocolate chip cookies are even better. We've got about a dozen different types of cookies sitting here that she made for Christmas.

I am geting a digital timing gun later today and will be back in the garage tomorrow. I'll calibrate the MAF (or fail to), check the idle/WOT switch and connector, and report back.

Thank you again to everyone who has chimed in.

[Addlight]

For all following along:

I checked my TPS harness. The harness looked good. Not brittle, no exposed wires, connectors solid. I tested it at the ECUs per the WSM and it checked out.

Short story: the car was running rich and I had to back out the MAF pot adjustment to lean it out, but I did.

Long story: I spent more time than I'd like aligning my MAF so I could get the pot adjustment tool in and rotate it. While the MAF was out, I checked the resistance and it was at 382 ohms still. I got the car up to temp and then installed the MAF adjuster, idle adjuster 7mm socket and the Blink'r.

Following the Blink'r instructions, I checked the WOT switch again and it passed. The car idled right at 699 RPM, so I didn't make any idle adjustment. However, once I switched the Blink'r to test mode, the red light was solid, meaning the car was running rich. I had to back the MAF pot out about 2.5 turns before I got a slow blinking light. Flipped the switch to the right and the red light was out for a moment and then went to rapid blinking red light. That meant it was now set where it was supposed to be.

So, I am at 0.5% CO according to the Blink'r, but was definitely was out of spec before testing. The real proof will be getting it out on the road for a hard drive with plenty of starts and stops to make sure the idle holds.

First, though, I have to get the 3mm head out of the MAF pot. When I tried to work the adjustment tool out, the 3MM head stayed behind. I'll try some long pliers first. Otherwise, I will have to pull the airbox and lift the MAF again to get to it.

Matt

[Addlight]

Stan,
Are you looking for a Blink'r? I'm not selling mine, but hopefully won't need it again for a while so would be happy to loan it to you.

Matt

[Mrmerlin]

I would like to buy one,
I dont need it now however

[worf]

Dave do you have a Blinkr ?
do you wanna sell it?
I had one but it disappeared.

I do. But I will need it soon.

Why don’t you get another one from Ken?

[Addlight]

Final update:
I took the car out for a spirited drive and a few miles of stoplight to stoplight: It idled perfectly and no rev drops. Smooth as a timeshare salesman.

Lesson learned: Don't mess with the MAF unless you need to and can calibrate it. If you do mess with it, measure and record the resistance before you start so you can return it to that if you need to (I didn't).

Big thanks to everyone, with a special thanks to Worf for calling it. I would not have suspected the MAF, and I truly struggle to understand the interactions of some of the electronic engine controls on this car. I appreciate being able to call on people smarter than me.

Matt

[linderpat]

ok guys, I give up - what is a blink'r? I looked and found Seth's old thread, but that just looked like a testing light.

[Addlight]

ok guys, I give up - what is a blink'r? I looked and found Seth's old thread, but that just looked like a testing light.

It's another of Porken's very clever inventions. Basically, it plugs into the diagnostic port at the front of 85-86 cars (maybe also ROW 16Vs that had MAFs?) and reports whether your car is running rich, lean, or in a stoichimetric state. In other words, it's a simple device to help you adjust your fuel/air ratio. It's only for the cars with a MAF where adjusting the resistance using the MAF's pot makes a difference (not 87 and up).

Porken doesn't sell them anymore, but there are guides on TOS of how to make your own. Here is the manual for it: https://liftbars.com/docs/Blinkr.pdf.

Matt

[linderpat]

Interesting. Thanks Matt. I've had an 86.5 and 2 85's, but hadn't heard of this process before.

[Mrmerlin]

Matt after resetting the MAF I would be interested to know what the ohms setting is on your car.
I was finding that with the 84 / 85 Euros and a fresh MAF the setting would be about 170 to 178 Ohms for a good mixture and good running.

Dave I would buy a Blinkr but Porken doesnt make them anymore,
and I have not spent the time to make one.

[Addlight]

Matt after resetting the MAF I would be interested to know what the ohms setting is on your car.
I was finding that with the 84 / 85 Euros and a fresh MAF the setting would be about 170 to 178 Ohms for a good mixture and good running.

H Stan,
Sorry, it took me a couple days to get back out to the garage. I just measured 156 Ohms at the LH.

Matt

[FLInstigator]

I have a similar issue with my 82 dropping below idle when going into neutral after coming off throttle. What is the best way to test the CO level for an earlier 16v model? WSM calls for a special tool to test it but I have no idea where to get one and I'm pretty sure it's not available. Tried using a wideband O2 but that doesn't give me CO and no blinkr for the 16V.

[worf]

I have a similar issue with my 82 dropping below idle when going into neutral after coming off throttle. What is the best way to test the CO level for an earlier 16v model? WSM calls for a special tool to test it but I have no idea where to get one and I'm pretty sure it's not available. Tried using a wideband O2 but that doesn't give me CO and no blinkr for the 16V.

I am far from a expert on 16Vs - Stan’s (@Mrmerlin) the man for that - but …

… there are at least two idle-air bypass valves on the 16Vs. They are easy to bench test and still available (at least one is) if indeed they can’t be rebuilt.

[Mrmerlin]

Flint if your engine is dropping idle you should first check for vacuum leaks , put a vacuum gauge on one of the damper lines and monitor you should see 18 IN.
Next tighten all the hose clamps for every connection look for cracked hoses.

Next have a look at the idle control units and spray some cleaner into them , blow dry
then some long term oil spray so it wont rust.
Check the timing belt timing as well as the distributor timing.
Finally turn up the idle a bit. RPMs to 875 /925
NOTE if none of this fixes things then you will have to get into the barn door wiper .
I use my nose to set mixture thats about the only way besides having an O2 reader.

NOTE make sure the sample tubes are not broken off the ex manifolds and if so plug the ports.
Make sure the O2 sensor is the factory part not the generic version as the connector is not the best.
Check the temp sensor for the injection and its connector.
make sure the green wire is in good condition and it is a Bosch part.

Clean the 2 injection ground wires on the RT cam tower. spray with Deoxit 100
Mixture can be adjusted by fixing vacuum leaks or readjusting the barn door wiper spring.
Dont touch this part till absolutely last.

[FLInstigator]

I didn't mean to hijack the thread. Just wanted to know if there was a way to measure the CO for a 16V car to check what my AFM is doing. I will message you separately Stan and thanks.

[Addlight]

I didn't mean to hijack the thread. Just wanted to know if there was a way to measure the CO for a 16V car to check what my AFM is doing. I will message you separately Stan and thanks.

You aren't hijacking anything. I got my resolution, so go for it. Although, I would say keep the discussion public--either here or in a new thread--for posterity and to get as many educated suggestions as possible.

I don't know anything about the 16V, but I know from enough experience that my first step with erratic idle is checking vacuum. Even when I think I've got it all, there is something loose or leaking.

Matt

[FLInstigator]

Probably should go to its own thread but here goes.....

Flint if your engine is dropping idle you should first check for vacuum leaks , put a vacuum gauge on one of the damper lines and monitor you should see 18 IN.

Getting about 16 steady. If I increase idle to 950 I get 18.

Next tighten all the hose clamps for every connection look for cracked hoses.

Have been through all of the hoses and clamps. All hoses have been replaced.

Next have a look at the idle control units and spray some cleaner into them , blow dry
then some long term oil spray so it wont rust.

Idle control units? 82 LJet has AAV which has been opened cleaned tested and AFM. Got a replacement AFM from 928 Intl in 2022 (I have been in this one but have it back to where it started trying to solve this) Intake has been apart, intake tubes replaced, injectors replaced, injector seals replaced, all hoses and clamps replaced. What other idle control units are there?

Check the timing belt timing as well as the distributor timing.

Timing belt has been replaced and checked. Distributer set correctly with timing light. Actually have 2 distributors.

Finally turn up the idle a bit. RPMs to 875 /925

Tried bringing up the idle and down. Still does the same thing.

NOTE if none of this fixes things then you will have to get into the barn door wiper .
I use my nose to set mixture thats about the only way besides having an O2 reader.

I have been in here and messed with the wiper, dial, bypass screw. Have it all back to where it was. Don't have a way to measure the CO which is why I asked in this thred. Have a wideband O2 sensor but have my original cat feeding to a Borla only one O2 port. How else can I measure CO?

NOTE make sure the sample tubes are not broken off the ex manifolds and if so plug the ports.

Sample tubes?

Make sure the O2 sensor is the factory part not the generic version as the connector is not the best.

Factory Oxygen Sensor installed

Check the temp sensor for the injection and its connector.

Have original temp sensor and replacement. Both do the same thing. Connector is good. Replaced front harness and have replaced all injector connectors as well still same.

make sure the green wire is in good condition and it is a Bosch part.

It is a bosch green wire

Clean the 2 injection ground wires on the RT cam tower. spray with Deoxit 100

Connections have been cleaned and Deoxitized.

Mixture can be adjusted by fixing vacuum leaks or readjusting the barn door wiper spring.
Dont touch this part till absolutely last.

Like I stated earlier I have already been inside the barn door. I took pictures of it in 2022 where things were and have it back to those settings. It hasn't really run right and I thought another AFM would have solved it but it didn't.

Have original injectors as well as Rogers newer 4 port injectors. Same result. The car starts up fine. Idles around 1000 or so then drops to about 800 after a few minutes. If I hit the gas and release idle drops below 800... close to zero and immediately bounces back up. Once warm the car will sometimes hunt idle surges from 800 to 1500 or so. This will go away after a bit. After a really good drive the car will still drop idle but then when I'm at a light or stop idle can drop way down to 200-300 or so almost stalling staying there no surging. If I disconnect idle microswitch there is no more idle drop or hunting idle. Instead the idle will hover at around 1600-1800 then slowly drop down. so no idle drop below idle or hunting but rpms hang and slowly drop.

Other things I've done...

Sent my computer to Airtek and it works in his 82. Tried two spares he had in mine and they both do the same thing.
Sent my TSZ switch unit to him and it worked in his car plus tried a spare in mine same result.
Vacuum limiter (UFO) hoses replaced and good. Tested the unit and it holds vacuum. Have a spare. Both do the same thing.
Original regulators and damper. They all hold vacuum and no leaking fuel.
Replaced fuel pump check valve.

I've been fighting this for a while. I know I'm probably missing something simple but it continues to evade me. With that being said I can still drive the car but just don't want to take it too far until I get this figured out.