High idle after throttle blip 84 533; wall of text; videos; SOLVED!

E28 technical advice asked and given! Troubleshooting, modifications and more.
Mike W.
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Re: High idle after throttle blip 84 533; wall of text; videos

Post by Mike W. »

willyv124 wrote: Dec 20, 2021 9:47 AM
Mike W. wrote: Dec 20, 2021 12:08 AM One more observation, FWIW. At .8V off the O2 sensor you're running very rich. I'm not sure of the significance of it, but you should be ~.45, while it's not a linear thing, you're definitely rich.
I guess the question then is
  • Is my sensor good and I'm actually running rich
  • Is my sensor bad and this is a whack reading
May or may not be related, but I do feel like there is a "heavy" gasoline smell while its running. I always chalked it up to be an old car, but maybe it is running rich?
Yes, O2 sensors tend to die by either being slow to respond or failing to put out any voltage. The early single wire ones like you would have on a 533 don't seem to be as long lasting, but I think it's reporting correctly. Now if they're hooked up they can be dead and still have a reading of around .4V because of a reference voltage being put out by the ECU, but not .8, that's definitely high. Like I said, the reading should bounce around, up and down, up and down. Yours is very steady. What are the readings with it hooked up?
demetk
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Re: High idle after throttle blip 84 533; wall of text; videos

Post by demetk »

Since you're not electrically challenged :) suggest you retrofit a 3 or 4 wire O2 sensor, if you're keeping this version of motronic. If you are going to ditch it then the e28 535 motronic 1.1 or the e34 535 motronic 1.3 have the wiring built in.
willyv124
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Re: High idle after throttle blip 84 533; wall of text; videos

Post by willyv124 »

Mike W. wrote: Dec 20, 2021 12:35 PM
Yes, O2 sensors tend to die by either being slow to respond or failing to put out any voltage. The early single wire ones like you would have on a 533 don't seem to be as long lasting, but I think it's reporting correctly. Now if they're hooked up they can be dead and still have a reading of around .4V because of a reference voltage being put out by the ECU, but not .8, that's definitely high. Like I said, the reading should bounce around, up and down, up and down. Yours is very steady. What are the readings with it hooked up?
Seems like its definitely dithering when its hooked up. See the video here. Also new issue, is random surging of idles which you can hear/see in these videos.
The surging is not consistent. I'll come to a red light, it'll idle fine for a bit, then surge, then be fine. Sometimes I come to a stop light and no surge.
This is happening with both icm's btw. If anyone is willing to let me borrow a known good 2 wire icv to just rule that out. That would be amazing. My

demetk wrote: Dec 20, 2021 12:39 PM Since you're not electrically challenged :) suggest you retrofit a 3 or 4 wire O2 sensor, if you're keeping this version of motronic. If you are going to ditch it then the e28 535 motronic 1.1 or the e34 535 motronic 1.3 have the wiring built in.
I'm not opposed to going to 1.3 at some point, but was really hoping to solve this as is :lol: I have some other things I want to take care of before considering motronic 1.3 (replace this hacky e39 fan with a spal electric fan wired to the regular inputs, brakes, suspension). Also I don't want to let this 37 year old car beat me!
willyv124
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Re: High idle after throttle blip 84 533; wall of text; videos

Post by willyv124 »

Hmm. My fuse #5 has gone out 2 days in a row now and fuse #6 has gone out once in the past couple weeks. Coincidence? I also have a random 1 pin brown wire not connected where the ecu/icm is. It's coming off the same loom that goes to the glove box light bulb. I assumed it went to the dash lightbulb, but theres only one connector on that that is already connected.
Mike W.
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Re: High idle after throttle blip 84 533; wall of text; videos

Post by Mike W. »

willyv124 wrote: Dec 20, 2021 4:30 PM
Seems like its definitely dithering when its hooked up. See the video here. Also new issue, is random surging of idles which you can hear/see in these videos.
That looks good. Someone might have tweaked the AFM slightly richer, but the O2 corrects it once it comes into play.
The surging is not consistent. I'll come to a red light, it'll idle fine for a bit, then surge, then be fine. Sometimes I come to a stop light and no surge.
This is happening with both icm's btw. If anyone is willing to let me borrow a known good 2 wire icv to just rule that out. That would be amazing. My
From my experience, that's almost standard. Actually I had 2, 733s and one was pretty good, not great, but the other was much like yours is.

demetk wrote: Dec 20, 2021 12:39 PM Since you're not electrically challenged :) suggest you retrofit a 3 or 4 wire O2 sensor, if you're keeping this version of motronic. If you are going to ditch it then the e28 535 motronic 1.1 or the e34 535 motronic 1.3 have the wiring built in.
I'm not opposed to going to 1.3 at some point, but was really hoping to solve this as is :lol: I have some other things I want to take care of before considering motronic 1.3 (replace this hacky e39 fan with a spal electric fan wired to the regular inputs, brakes, suspension). Also I don't want to let this 37 year old car beat me!
demetk
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Re: High idle after throttle blip 84 533; wall of text; videos

Post by demetk »

willyv124 wrote: Dec 20, 2021 4:30 PM
The surging is not consistent. I'll come to a red light, it'll idle fine for a bit, then surge, then be fine. Sometimes I come to a stop light and no surge.
ICV on its way out. Try this. Install a 1/2" water valve before the ICV and open it up about 1/3 of the way. Disconnect the ICV and start the car. Adjust the bypass air through the valve so you get about 1100 rpm idle. Connect the ICV back again and report if the surging has disappeared and what your idle is now. Who knows maybe it will work for you too.

I'd also do a smoke test to see where you may have any leaks. A simple DIY smoke machine is a google away that has a soldering iron, a sock and some baby oil as the key ingredients. :)

Oh and a single wire O2 sensor is not very good as a diagnostic tool since it's not heated and it will cool down fast at engine idle rendering it useless.
willyv124
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Re: High idle after throttle blip 84 533; wall of text; videos

Post by willyv124 »

Fuse 5 popped again and i’m also getting no current from the icm to the icv anymore. Fun times. Going to need to check all the harness pins again
Mike W.
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Re: High idle after throttle blip 84 533; wall of text; videos

Post by Mike W. »

demetk wrote: Dec 20, 2021 8:00 PM
Oh and a single wire O2 sensor is not very good as a diagnostic tool since it's not heated and it will cool down fast at engine idle rendering it useless.
I've never had that problem. As a matter of fact, in even moderate weather, ie not freezing, I get an output just after start. Keep in mind -33s had the O2 sensor mounted much closer to the exhaust manifolds than 535s did.
willyv124
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Re: High idle after throttle blip 84 533; wall of text; videos

Post by willyv124 »

My floating ground wire on the glovebox was shorting on the glove box bulb, this was causing the fuse 5 short. I wrapped the floating ground with electrical tape, still not sure where that ground goes.

Decided to recheck some pins on the harness. Car cold, around 55 degrees F.
  • Resistance measured at the coolant temp sensor itself ~2.5k ohms
  • Resistance measured on icm harness pins 11 and 4 when ecu is connected ~1k ohms :x
  • Resistance measured on icm harness pins 11 and 4 when ecu is disconnected ~2.5k ohms
  • Resistance measured on ecu harness pins 13 and 5 ~2.5k ohms
See below for details. Looking at the etm ICM harness pin 11 is piggybacked off of pin 11 of the ecu harness.
Image

So I decide to unplug my ecu and see if I can find any wiring issues. Well the harness is heavily wrapped with what looks like the oem wrapping and seems like nothing is worn anything down. So looking at the bentley/etm pin 13 on the ecu harness is the cts, so i check the resistance on pin 13 and pin 5 of the ecu harness and it matches the raw CTS reading... and then i recheck pin 11 and 4 on the icm harness and it also matches the raw CTS reading...

I plug the ECU back in and recheck pin 11 and 4 on the icm, same bogus reading near 1k ohms. (battery has been disconnected this whole time btw). This can't be right? Is there a short in my ecu. Its a rebuilt ecu doctors unit.
willyv124
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Re: High idle after throttle blip 84 533; wall of text; videos

Post by willyv124 »

Even weirder actually
  • cts disconnected, ecu connected. icm harness 11 and 4 show same ~1k resistance
  • cts disconnected, ecu disconnected. icm harness 11 and 4 show correct infinite resistance.
  • cts disconnected, ecu harness 5 and 13, show correct infinite resistance
willyv124
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Re: High idle after throttle blip 84 533; wall of text; videos

Post by willyv124 »

demetk wrote: Dec 17, 2021 7:02 PM So did you keep the fuel injection system from the 533? Because the ICM and ICV are so bloody expensive it may have been cheaper to convert to M1.3.
Mike W. wrote: Dec 18, 2021 6:26 PM Which brings me to another question, were the 533 fuel injectors retained? This is probably a non issue as 533 injectors were much higher flow than 535s and I doubt the problem, but just something to keep in mind. Also you can use 535 injectors (probably) as they're high impedance/resistance with 533 engine management, but not the other way round. Oh, you can for a while, but you'll burn out the driver in the 535 ECU if you use it with 533 low impedance injectors.
Well, you know what they say about assumptions. I had assumed the shop that did this swap had done it right, but they definitely did not. More details in this thread https://www.mye28.com/viewtopic.php?f=3&t=157556 I actually have a 3.0 bar FPR instead of the 2.5 bar I should have and I suspect my injectors are incorrect as well, I will check its impedance tomorrow. So going to resolve this FPR issue first and I also have a smoke machine tester coming to confirm no vacuum leaks. No point in diving any deeper until I can confirm spec fuel pressure and no vacuum leaks. Thanks again for your help
willyv124
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Re: High idle after throttle blip 84 533; wall of text; videos

Post by willyv124 »

Big day today installing new parts
  • 6 new SMP FJ11 low impedance injectors from partsgeek which also have the Lucas D1540BA part number on them from five o motorsports. (previously was incorrect high impedance injectors)
  • New coolant temperature sensor
  • New 2.5 bar fuel pressure regulator (previously was incorrect 3.0 bar)
  • New icv hose to intake manifold replacing previously cracked one (crack didn't go all the way through though)
  • Unrelate, but did the blade fuse retrofit kit
Additionally I did a smoke test with this https://www.amazon.com/AutoLine-Pro-Aut ... B07JVT1NG2 and found no leaks, granted I was using a bike pump but i confirmed multiple times smoke was coming out and when I made my own vacuum leaks, smoke did appear.

With all the above new parts, same symptoms as before, still a idle above 1000 rpm, when blipping at warm, it will drop below idle sounding like its going to stall for a split second. I'm at a loss, at this point everything seems to test correctly. I've been using the original icm, but I guess I can try the new one again.

Could a bad TPS cause that dip when transition from off idle to on idle or is this just a works or doesn't work situation? At this point, it sounds like even though my ICV tests correctly, could it be bad and not reacting quickly enough?

Pictures of the new hardware
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DJM1986-5
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Re: High idle after throttle blip 84 533; wall of text; videos

Post by DJM1986-5 »

Given the engine swap and the fact they left the 3.0 FPR on the engine...do you have the correct TPS for the 533? It's the same as a 535...but...ruling out the absurd.
willyv124
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Re: High idle after throttle blip 84 533; wall of text; videos

Post by willyv124 »

Yes it is the correct tps. I also tested shorting pins 1 and 2 of the tps harness to rule out a bad tps (even though it tested fine).
willyv124
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Re: High idle after throttle blip 84 533; wall of text; videos

Post by willyv124 »

DJM1986-5 wrote: Jan 07, 2022 9:10 PM Given the engine swap and the fact they left the 3.0 FPR on the engine...do you have the correct TPS for the 533? It's the same as a 535...but...ruling out the absurd.
I tried a $260 used ICV on ebay. Seemed better but still not completely impproved, so I returned it.

I then bought a spare ICV from DJM1986-5 and the idle is definitely improved. Pretty much at 1k or right below and the drop after the blip is much less noticeable/not as severe.

Going to keep working on this, I still have the o2 sensor to replace
willyv124
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Re: High idle after throttle blip 84 533; wall of text; videos

Post by willyv124 »

Well. I've replaced the o2 sensor and still have the same idle. DJM1986-5 has been graciously helping me troubleshoot on and off the past few weeks. I've started sourcing a motronic 1.3 kit as well as being in the middle of getting e34 calipers vapor honed / cerakoted for the big brake kit upgrade.

David asked me to double check that I didn't have any resistors. Confirmed no resistors on the CTS or the AFM connector
Image
Image

Also double checked the resistance readings of the new CTS. I was seeing 200 ohms engine warm, which is below the bentley range of 270 to 400. 2400 ohms cold at 65 degrees f which is in spec. I realized I hadn't bled the cooling system after I had replaced the CTS, so I did that per the bentley, made sure it was a solid stream of coolant from the bleed screw, open and closed a few times, did another reading, 240 ohms, better but still out of spec. Makes me wonder if I should add my own resistor like BMW and also get a 350 ohm resistor to take the place of the CTS to just rule it out.

Additionally I also tested a cold start with the CTS unplugged. The idle was better than normal, (see the video), after revving, the idle again went back to 1000. Unplugging the CTS while the engine is warm causes the engine to stumble and the idle to drop. David had mentioned this should cause the idle to rise, possible clue of root cause? Also when trying to do a warm start with the CTS unplugged, it will not start at all.
cold start CTS unplugged video

Anyone have a 008 ecu that I could borrow (with a deposit of course) to rule that out. At this point, long term I'll be going motronic 1.3, but I really want to find the root cause of this issue. :D
willyv124
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Re: High idle after throttle blip 84 533; wall of text; videos

Post by willyv124 »

SOLVED.

Image

Felt like searching mye28 again and looking at search results on the later pages that I hadn't looked at before. I came across this reply from wkohler about how his new violet coolant temperatures switch didn't work out of the box and the op of the thread had the same issue. Also came across another similar reply.

So yesterday I decide to try my luck and short the terminals while the engine was warm and what do you know.. I'm pretty sure its idling perfectly now. I did a continuity test of the switch while the engine was warm... no continuity, looks like i have the same issue with DOA switch. Even beyond the issue of the switch not working, I should have suspected that this switch would not be a replacement, because its a 0 cel switch (p/n 12631279719) vs the original 45 cel (p/n 12631279716). Which if i'm not mistaken would mean that the switch has continuity when above freezing. I still have my old crusty switch so I'll bench test that to see if its working. But i'd like to try to source an alternative switch so I found the following options
  1. DIY example 1, example 2
  2. ebay poland reproduction
  3. 17 cel p/n 61311364437 with matching spade connectors
  4. 35 cel p/n 12521741900 with ev1 connector
  5. 44 cel p/n 12521741900 with ev1 connector
I'm leaning strongly towards the 44 cel ev1 connector and then changing the harness connector to match with an ev1 connector.

It's funny a few of you had suggested I try shorting those connectors before and either I did it wrong or I had other issues that needed to be resolved first for this to be the final one. Long term i'll be going motronic 1.3, but I'm happy to have resolved this and now have a much better understanding of all the components at play.

Here's a video of the idle, it seems right on spec but I'll let you be the judge. Seems to also have the characteristic wander of motronic 1.0. It's so quiet at idle now, like a modern car where I question if its even on.

Will update on what I end up doing for a new coolant temperature switch.
demetk
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Re: High idle after throttle blip 84 533; wall of text; videos; SOLVED!

Post by demetk »

Thanks for documenting all of the different switch options.
Mike W.
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Re: High idle after throttle blip 84 533; wall of text; videos; SOLVED!

Post by Mike W. »

Wow, nice work. You did so much chasing it down I'm worn out just reading about it again, briefly in a summary. Tip of my hat to your perseverance.
Tiit
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Re: High idle after throttle blip 84 533; wall of text; videos; SOLVED!

Post by Tiit »

Thanks for documenting and sharing. Well done.
willyv124
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Re: High idle after throttle blip 84 533; wall of text; videos; SOLVED!

Post by willyv124 »

I wanted to follow up and say I did order the 44 cel ev1 temp sensor and it works as a replacement. I did a quick bench test to confirm that it was open at room temp and then with a hair dryer i was able to get the circuit to close and after installing it works as expected as well.

Image

Some links to things you might find useful.
1. ev1 connectors here and here
2. ev1 2 way boot here or here
3. wire splices like this or this
4. tutorial on splicing https://www.youtube.com/watch?v=pVG1hi3yTJ8
Joey28
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Contact:

Re: High idle after throttle blip 84 533; wall of text; videos; SOLVED!

Post by Joey28 »

Thanks a lot for documenting this. This is the sort of thing these forums are for, and helps keep these great cars on the road when they might otherwise be hobbled by some stupid little sensor that's NLA.
TexasZinno
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Re: High idle after throttle blip 84 533; wall of text; videos; SOLVED!

Post by TexasZinno »

Fantastic write-up! Great visuals and happy to see a thread this in-depth get resolved.
richardb
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Re: High idle after throttle blip 84 533; wall of text; videos; SOLVED!

Post by richardb »

I wanted to jump in here and comment, as I had a high idle issue with my 84 533i as well. I installed the updated coolant temp sensor as shown in this thread, which made zero change vs. the purple top sensor.

The factory idle valve (early style) is black plastic; it tested fine at 9.5 ohms and clicked on/off with 12v power applied. So, it seemed to test fine. As a last resort I upgraded and replaced it with a 325e/528e metal valve, which also tested at 9.5 ohms and clicked on/off with 12v power applied.

Started it up and... the idle is as smooth as butter. Runs perfect.

In summary, if you're having a problem with your idle in an early car, dump the black plastic ICV ASAP.
richardb
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Re: High idle after throttle blip 84 533; wall of text; videos; SOLVED!

Post by richardb »

Video update: resolved high idle by replacing the plastic valve!

https://youtu.be/g7kLaxX5T8E
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