Intake Manifold Air Sensor for 5 cylinder

[smores]

Have you tried replacing the MAP sensor in the ECU? I just went through replacing literally every sensor on my 93, and it turns out it was the MAP sensor.

[postjosh]

TheOneTrueQuux - i couldn't find my multimeter but i just ordered one. my mechanic did run a scan on the ecu that's how he determined that there was no signal from the sensor. he warned me that it could be the ecu that was faulty but that we should try replacing the sensor first. i don't think he pulled the sensor to test it but he tested the wiring to the ecu and said it was okay. i will test the old and new sensors' resistance with the multimeter the next time i have access to the van.

smores - no, i haven't replaced the map sensor. i will ask about that, if the air temp sensor replacement doesn't fix the problem. the van was scanned by my mechanic and the only code was that it didn't see the air intake temp sensor.

thanks all!
_________________
'93 EV Wkndr – 5 cylinder – 5 speed - 280k+ miles

[TheOneTrueQuux]

[postjosh]

[postjosh]

[Abscate]

[postjosh]

[postjosh]

so, i installed the adapter and new sensor today. it does seem to be working but i won't know for sure until i drive it for awhile and have my mechanic scan the ecu.

here's the details:

the old sensor was reading 3.1 KΩ on the thermistor the potentiometer was running at .5KΩ when i pulled it. the van has been running incredibly rich. smoky exhaust, rough idle and occasionally stalling.

i installed the new sensor and adapter. the hardest part was getting the new sensor in the old hole. i came very close to breaking the air intake hose even after putting a little grease on the lip. if i were to do it again, i would probably have used a dremel to shave down the size of the lip on the new sensor. it was pretty easy to figure out the pins because they are actually labeled on the original sensor. the color coding of the wires is

pin 1 = blue/white (potentiometer)
pin 2 = blue/yellow (themistor)
pin 3 = brown/white ground

there wasn't obvious change as i adjusted the pot. so i just opened it all the way up to lower the resistance. it seems that lower resistance makes the ecu run things leaner. i noticed that it wasn't missing on idle. when i looked at the exhaust it was still dirty, literally dripping carbon on the ground. i revved the engine and let it idle for about five minutes. the exhaust was cleaner and it was dripping less. i took it for a ten mile test drive. it ran much better than it has recently. when i came back, the exhaust smelled much cleaner. it was no longer dripping but there was a little smoke visible.

i will post anything that i notice as i drive the van more. i obviously have a lot of carbon buildup that will need to be burned off. i probably still have other issues (map sensor?) but the main thing is that i feel much more confident driving it now.

an additional thought for anyone else who has the same problem... first off, test the resistance of your old sensor. if it's too high, and you can't source a new 3 pin one, you might try the following before you build one of these adapters for the two pin sensor. disconnect the three pin cable from you sensor but leave the sensor installed in the air intake hose. install a 2 or 2.2 KΩ resistor between pins 2 and 3 on the connector. my guess is that the van will run better like that than it will with a bad sensor and this will help you troubleshoot the problem and buy some time to figure out a permanent fix.

i hope all this will be of some help to other ev owners
_________________
'93 EV Wkndr – 5 cylinder – 5 speed - 280k+ miles

[edavid]

Sorry, I am late to this thread, but I have a 1993 eurovan MV with the three prong G42 air intake temp sensor, and I think it's bad. I have measured the resistance across the outer prongs on the sensor and used a hair dryer to heat the sensor, expecting that the resistance would change, but it does not. Did you do any testing of the sensor yourself, or rely on the codes as you mentioned in your post. I assume you were never able to source a replacement part?

What were the symptoms you experienced? My van starts fine and runs well for about 5 or 10 minutes and then suffers from a catastrophic loss of power. It only lets you drive about 10 mph and bucks back and forth, which seems to coincide with whenever the transition between "cold operation" and "normal operation" is supposed to happen. Would you think the G42 air temp sensor could have something to do with this?

Eric in Fredericksburg, VA

[rocknroj]

This is in response to Eric.

I have a 93 and have done a fair share of tinkering with it.

Do you have access to the wiring diagram?

What is the manufacture date on the door sticker?

Do you have access tot he Vag COM?

i find them both invaluable..

Spendy indeed but cheaper than a couple hours of shop time with most likely no results... No I am not selling the stuff.

Your symptoms could be caused by many issues like 02 sensor wiring or grounds. Perhaps once getting off warm up phase the 02 sensor not fluctuating. Getting those readings displayed will tell you what the ECU sees as far as intake air temp, coolant temp, timing interpretation, 02 sensor fluctation, injector pulse duration... etc....

There is hidden ground below the exhaust manifold on the passenger side that is used by the sensors. It is hard to get too and often overlooked.. Requires some special tools like a short handle wrench to tighten it. Perhaps a fine tooth ratchet would work.. Its below the intake air heat generator and goes into the harness going to the o2 sensor.

I doubt that the intake air temp would make your car run as bad as you say.

On my car i went thru the wiring checking all the grounds, all the wires between the sensors and the pins on the ECU (Both for resistance and short to ground)..

Of course All the vacuum hoses should be checked/replaced... Even the tiniest crack in an old hose will cause operational issues. They fail where they connect to the manifold, fuel pressure regulator, the T's , the one way valve going to the interior flaps, and of course the connection to the ECU. Its a routine maintenance item, pretty much annually. Recently I installed silicon vaccum lines to avoid that annual procedure and they seem to be holding up well.

I think those are basic tests to perform on these cars when things are not correct.

I run with a vacuum gauge zip tied to my dash and usb power plug with voltage display in the lighter outlet.. Both of these provide basic information regarding the health of the engine as well as warning of time to do some maintenance.

The manifold vacuum readings tell al ot and the fuel injection system is highly dependent on the manifold vacuum readings, hence the need to keep those lines in good order..

One other odd thing that happened to me was the ignition switch failure. The electrical part has some contacts that wear over time and can leave one stranded in a bad place... Its a cheap part and cheap insurance to not get stranded without the right tools.

[edavid]

Rocknroj,

Thanks very much for the fast response! I do have all the Bentley
manuals for the eurovan, and we have used the Vag COM to pull the
codes from those two connectors under the dashboard left of steering
wheel. The only codes were for the engine coolant temp sensor and
the throttle position sensor. Over the last year or two, here is
what I've done:

1. fuel pump replaced
2. fuel filter replaced
3. oxygen sensor replaced
4. spark plugs replaced
5. spark plug wires replaced
6. coil replaced (and coil wire to distributor)
7. both coolant temp sensors replaced
8. throttle position sensor replaced
9. air temp switch (controls the intake air snorkel flap via vacuum) replaced
10. ignition switch relay replaced
11. ignition switch key cylinder replaced
12. wires from throttle position sensor to ECU checked for continuity
13. wires from engine coolant temp sensor to ECU checked for continuity
14. verified that there is vacuum going to the air temp switch

I have checked some of the vacuum lines, as many as I can easily
see, and found no issues, as well as the big rubber corrugated
intake hose that connects to the throttle body, and found no
holes there either.

As I mentioned in my first post on this thread, the symptom is
always the same: drives perfectly fine until it "warms up" and
then suddenly loses power and I have to limp back home going no
more than 10 or 15 mph with lots of back and forth bucking. If
I stop the vehicle and shut the engine off for 10 minutes, I can
usually start driving again with no malfunctions. Do you happen
to have any experience with an ECU going bad? I read that there
is a guy in Florida who specializes in Eurovan ECU diagnosis and
repair, or he has rebuilt ones he would sell.

Thanks very much,
Eric

[rocknroj]

Sounds like you did a lot already.

The vacuum leaks are mostly imperceptible to the eye, sometimes they can be felt. It is a pain. I bought some continental brand silicon.. So far so good. The slip on easier than the rubber with the fabric. The one thing to watch out for on the silicon is that it is more flexible so care must be taken not to introduce kinks.. The slight cracking on the edges where the old style hose connects is enough to induce leaks. I believe that any leaks make the car run too rich.

My most recent parts swap resulted in a better running machine, it was the TPS. Even though all tests indicated the old one was good, a new one made the car run much better.. It was about 7 years old as I had installed it when I first purchased the vehicle...

It did make me think about re-seating all the plugs and perhaps thats what made the difference. Even a very slight amount of corrosion on a connector can increase the resistance significantly.

I have had the spark plug wires go bad. It could be heat induced. They do sit at an odd angle and bounce around a lot. I did the in the dark test with a spray bottle and long handle insulated screwdriver. Wiggle the connectors around or the wire above the connectors and look for arcing to the case... That can be an intermittent problem.. The center hi tension lead failed on me in the past also.. That one I found with a resistance test.

Recently on mine I checked continuity to the 02 sensor from the fuse box, specifically the heater circuit. After pulling up the o2 harness into the engine bay to make repairs, I found the signal wire also about to break (both were at the o2 sensor plug. Thats when I discovered the hidden ground I mentioned before (never knew it was there).. It was definitely loose, and after studying the wiring diagram found that it provides ground to the ect, o2 sensor and perhaps more (cannot remember).

Since you have the vac com, why not read the measuring blocks?

You can set it to record and drive the thing. There is also a mark button so you can indicate in the log the point of engine malfunction.. Need a wife or buddy to ride with you and push the button to be safe..

I am guessing you will see something change dramatically on one of the sensor inputs, or more accurately the vag com interpretation of the ECU data.

Just scroll thru the measuring blocks 1-5 I think tell most of what you need to know. The response frequency is a bit slow so its hard to see if the o2 sensor is swinging as it should sometimes. Made me think about getting an analog multiimeter..

All that said your condition is odd indeed.

Somewhere I saw a post regarding good vs flaky rebuilders.. Might have been here but not 100% on that. Indeed a risky proposition. My spare 'f' code I picked up from a guy in ukraine. I also bought parts from latvia.. The EV was a lot more popular in other parts of the world, and still is..

A wrecked car is often a good risk eh,, must have been moving.

I guess that's about all I can suggest this rainy day..

[edavid]

Rocknroj,
Thanks very much for your response, all excellent suggestions. My brother has the vag COM software on his laptop so I will ask him about doing the driving test and recording values as you suggest.
I have never tried the route of putting in a request for these sensors through junkyards but maybe I should do that and try to snag one if they get a wrecked Eurovan. Interesting that you mention Latvia, I at one point ordered a side view mirror for the EV from Latvia.
Your time and thoroughness are much appreciated,
Eric

[rocknroj]

my pleasure.. I have received some good advice here so giving back is good. that and exercising my brain on a sunday when I rest my body is ok too.

Did you mentionion if this is a 'new to you' machine, or one that you have had for a while and used to run good?

I picked up an ecu a while back. The wrecker insisted that his database was correct and it was not.. So a wrong ecu i purchased and later sold on ebay, so do diligence is required.

That ground I mentioned, no one ever mentioned it before and I discovered by feel was loose on my car causing intermittent gremlins..

One other thing I ended up doing was to replace the connectors as the insulation had been stripped back to back probe and eventually without the insulation the wires become weak and corroded. A safety pin soldered to a test lead works well for probing the wires by poking a pin hole thru the insulation without destroying it.

The throttle position sensor comes to mind as thats the acceleration input. Some models have a closed throttle switch and some dont. Its a mid year change.

Take note of your ECU model when you hook it up to vag com. I have looked many times at compatibility info, often to misled.. Mine is an 'm' code. Installed an 'f' code and it works good but has a deceleration stumble when I take my foot off the pedal on the highway. More study indicates the 'f' code is for models with the closed throttle switch which my vehicle does not have. So check out the door sticker for the manufacture date.

Engine load, coolant temp, ecu supply voltage, calculated timing and o2 sensor fluctuating from .1 to .7 are things that I would look for first. Fuel injector duration should increase under load. Throttle position should increase smoothly with no gaps. That one you can check first with ignition on, engine off..

I will be interested in your findings..

[postjosh]

sorry for the late response. i haven't been on the forums for awhile. i replaced the sensor because my mechanic said it was most likely bad because he wasn't getting a reading from it from the ecu.

this all happened after the ignition coil failed. i'm wondering if there was some kind of electrical short or surge the messed up my sensor and who knows what else. the engine was really fine before this whole mess.

the main symptom was that the engine was running very rich. it always ran rich but it was much worse after the ignition coil replacement. there was smoke from the tailpipe and you could smell the gas. it also ran like crap and stalled frequently. i tried disconnecting the sensor and it made no difference.

the replacement i came up with definitely had an effect. it was no longer running obviously rich. it still stalled frequently and tended to hesitate/lug down at certain speeds. adjusting the potentiometer only changed the rpm range where the hesitation/lugging occurred. at least the van was drive-able. i put about 200 miles on it before it crapped out from some other cause and i had it towed to my mechanic.

he cleared the engine ecu by disconnecting the battery and it seemed to be running about the same as before it crapped out. i asked him to figure out what was happening and he blamed it on the sensor i built. i think he was looking for an excuse to walk away from the problem. he suggested that i get the ecu "tuned" for the new sensor as the diagnostic software still wasn't reading it.

to answer your question, i do think my hack sensor works. i also think that i have other problems that are stopping me from getting the van running properly.i really haven't had time to look into this any further. when i have time, my next step will be trouble-shooting my ecu but for now the van is put away for winter. there was a suggestion earlier in this thread about an atmospheric pressure sensor in the ecu that fails. i really don't know.
_________________
'93 EV Wkndr – 5 cylinder – 5 speed - 280k+ miles

[BatesEV]

Ok since the coil was changed was the ground that is right there broken? It’s under the abs and next to the coil.

Also when you disconnect the blue coolant sensor does the idle speed increase?

When all the sensors are working the ecu adjust the idle speed based on the core setting done during the “chicken dance” to account for the load by regulating the ICV. When I’m learn mode the idle speed is set by an air bypass screw in the TB to 900rpm.

There is a procedure to clear the ecu memory by having the engine fully warmed up(one fan cycle) and with the sensor disconnected you slowly rev the engine above 3k 4 times. You do this dance to set the timing then the idle.

The o2 sensor readings would happen after about 90secs when it goes closed loop and actually starts to read the sensor.

Also an overly rich is a default of one of the sensors including the PS sensor goes bad. It’s a default of the ECU. Germans I feel make these tricks and games to keep inferior minds from working on their stuff. I know these games rattled my mind

[TheOneTrueQuux]

[postjosh]

thank you. i will definitely do that at the next opportunity. as i've mentioned before, i'm not in a situation where i can't do any work to speak of myself. the next time i bring it in, or i have a place i can work on it, i will check that. unfortunately, this year is rough financially and i have to prioritize getting it painted before i sort out the mechanicals. i don't want to get into politics but let's just say it's not easy to survive in the northeast at the moment.
_________________
'93 EV Wkndr – 5 cylinder – 5 speed - 280k+ miles

[TheSaw]

Hi, I'm from Spain and I have a '94 AAF, have you tried relay number 30? often fails and causes rough idling and jerks

[bjanaszek]

Resurrecting this thread to ask: what is the trick to installing a new manifold air sensor in a 1995 5 cylinder? I got my old one out with a bit of difficulty, but I cannot manage to get the new one installed, even with lubricant on the body of sensor. I don't have a Bentley manual, so I am assuming I am missing some sort of trickery.
_________________
1995 EVC - 5 cylinder manual