3.2 stalls when it gets warm

[Hugh R]

I don't drive it as much as I should and that may be part of the problem.

Lately, its been stalling as soon as it gets warm (a mile or two of driving). It will stutter and stall and won't want to restart, sometimes it does, but it smells gassy. When its cooled down it will start up and do the same thing.

Battery is newer and charged, the alternator light is not on. I tried changing out the DME relay and got nothing. It has fresh gas and a new fuel filter about 3 months ago.
Also a new O2 sensor to help pass SMOG last year.


Any thoughts would be greatly appreciated.

[rick-l]

Down the DME troubleshooting highway we go.

Now you need to find out if spark or fuel is missing, tach bounce while cranking, IAC valve vibrating etc.

If it is intermittent I'm sure it will get worse before it gets better to aid troubleshooting.

[Hugh R]

I can hear the IAC vibrating, didn't notice any tach bounce when cranking, but I'll look again. The car is currently sitting under a tree down the street where it died. In seeing if the problem was chronic I drove it a 1/2 mile up and down the street so I didn't have so far to walk home.

My adult son drove it to Ventura and back a few weeks ago (80 miles R/T) and he said it ran just fine.

[DanielDudley]

Doesn't the cylinder head temp sensor determine the richness of the mixture ?

There have been some good guides to reference sensor replacement lately, and there are some good you tube videos on how to test them out, but pulling the driver's side rear wheel and looking at the insulation on the leads will be a good first step. You will also see the lead for the temp sensor in there.

I'm sorry to say that I had some good links to some informative threads, but I lost a lot of good stuff when my wife uploaded Windows 10 into my computer.

[Hugh R]

I start it up and let it idle and after 5-10 minutes it starts surging from idle to about 2K for a second or two and does this a dozen times until it just quits, smells very gassy.

[Lyle O]

I recently had the opposite problem (wouldn't idle when cold). It turned out to be my idle control valve., but I learned a lot from the team here in the process. My $.02...

ICV only effects cold idle really, so chances are this is not your problem.
Check your cylinder head temp sensor. This tells the DME when operating temp is reached, and since your problem starts when warm, this would seem a logical place to start. There are some good threads that tell you how to test it (you just need a digital multimeter). The other sensors could also be an issue, but check CHTS first.
The DME is pretty durable, but could have issues. If you can try your DME in a buddy's car, you can quickly see if it is at fault.

Good luck, and keep us posted.

Lyle

[Hugh R]

Lyle. doing a search now. Thanks

[Hugh R]

So I unplugged the CHTS plug and put my Fluke on the one (not two) pins on the bracket side and got essentially 2,100 ohms, when cold, its supposed to be 4.4-6.8K Ohms 1.0-1.3K Ohms when hot. I started it and uplugged the CHTS plug when running and it immediately ran rich, so the DME seems to be seeing the sensor and its not a broken wire, ran it up to warm with the CHTS plugged in and then unplugged again while running, it immediately ran rich again. I ran it until hot and check the CHTS and got an open circuit (it didn't read any ohms).

So I'm thinking I need a new CHTS, about $100 from PP for a Bosch Original. However, the new one is two wire (a ground is added) so do I need another female plug end to add an additional ground?

This item here. Pelican Parts - European Automotive Parts and Accessories - Porsche • BMW • Mercedes • Volkswagen • Audi • Saab • Volvo • MINI

Any thoughts would be greatly appreciated.

[brianlay]

Sounds like you weren't measuring correctly. You should measure the sensor not the bracket side, that's the input to the DME.
OTOH, those one wire sensors tended to fail and you probably should have changed it long ago.

[Hugh R]

Not so sure, the left (female) one is connected to a wire bundle that has a bunch of other wires that disappear into the left side of the engine compartment, but the side to the right of the bracket seems to only have one white wire. "White (yellowish) male plug just barely sticking out.



White wire just barely sticking out to the right of the heater blower duct thing.

Not disagreeing with you, this is totally foreign stuff to me and I appreciate all the input I can get. BTW, I stuck the Fluke probes in the left (female side and still got 0-1 ohm resistance as well.

[rick-l]

Have you checked for spark when it won't restart?

Gassy smell, stumbling, IAC wide open = Intermittent spark????

Ingo has a test stand he could put your DME on or you could put your DME into another car.

[jlex]

The sensor wire that goes directly to the CHT sensor is the one to the right of the bracket. It goes thru the tin & emerges at the LR fender area. That's the wire you want to test. If your has only one wire, it the earlier, ungrounded version that's been supplanted by the more reliable 2 wire system that has a ground wire.

[Hugh R]

Sometimes when it stumbles and stalls it will sort of start and stumble again, many times not. I'll run it tonight until it stalls and then check for spark.

[kyngfish]

Just a few tips. The side in the picture is the harness side, the sensor side is the side actually stuck in the bracket, and the wire goes off into the middle left of the engine bay. Is that harness side plug cracked? IF so, there's a place in Lauderdale, Eagle Day, that sells just the plastic plug online. Wouldn't have the foggiest about how to replace it, but it's a 20 dollar part and the entire harness is a few grand.

The other side is the CHT, bear in mind that the ohms change relative to your ambient temp, so if it's 80-90 degrees F right now, because it's summer, I believe you can be at around 1400 ohms and it's working. The Bentley manual has the exact measurements. I think the ohms are actually in the hundreds when the engine is actually hot.

I don't think you need to create a ground wire, I think the harness side already has a ground.

To replace the CHT:

• Some threads here will tell you to get a sensor wrench or cut a slit up the side of a deep socket. For my CHT at least, this didn't work. There's a stiff plastic insulation that goes up the wire a few inches and a normal deep socket isn't deep enough. I think you're better off getting a 14mm flare nut wrench. Once you thread the sensor, you can tighten with that wrench from the left side where the cutaway portion for the sensor sits flush to the engine.
  
• Another option, and what I did, is cut a half inch slit into the ring side of a box wrench, basically turning it into a light flare nut wrench, which worked fine for me and took 5 minutes with a dremel
  
• There are two grommets on the CHT, one to protect the sensor in the engine, and the other to seal up the hole to the engine compartment. The upper one is for the engine compartment and has has a hole for the CHT wire, but also two holes for the Ref and Speed sensors. If you want it to go in right, you'll have to cut slits into the grommet so you can put the wires through, recommend doing this BEFORE the install.
  
• Now that you're prepped, put the car on stands and remove the driver's side rear
  wheel (right side). To the right of the damper, you'll see a black oval shaped grommet protecting the CHT. Use silicon spray and pry that off.
  
• You should see the CHT and wire directly in the engine. Cut the wire, and let that wire dangle there, you'll use it later.
  
• Use a regular 13mm socket to get the old CHT out. Be gentle, and you may need an extension and swivel socket. I have a short handled socket wrench that works well to get into these tight spaces. Remove the CHT.
  
• Thread in the new CHT by hand until you feel it threading in smoothly, you really don't want to cross-thread it. Once it's hand tight, use your flare nut or cut box wrench on the left side to tighten. Remember the old ones are usually 13mm and the new ones are 14mm. You may want to look up torque specs, but, not having a torque wrench or a deep socket that fit in there, I just tightened it reasonably tight, but not too tight and left off.
  
• Spray the lower rubber grommet liberally with silicon spray and it should pop in easily.
  
• Next I removed the rubber grommet from the engine compartment using silicone spray. I believe I pushed it inwards, and then pulled it back out sideways, sliding the ref and speed sensor wires out.
  
• Then I tied the OLD wire to the new sensor plug and used that wire to thread the new wire through to the engine bay. Damn near impossible to do it by hand.
  
• Slide the ref and speed sensor wires into the slits you cut into the new grommet and using silicone spray on the rubber, again just push it into the hole in the engine compartment
  
• In the engine bay, to remove the old plug from the bracket, you can spray down the bracket with kroil and just pull on the little lip on the rear facing side of it, it should slide out and then you can pull the old CHT plug out. My new plug didn't fit into the bracket so I had to sand it down a little, but you can do whatever you want.

Honestly this whole thing took me 4 hours, but 2.5 of those hours were spent trying to make the whole deep socket slit thing work. Just use the wrench and you're better off. Feel free to send me a PM if you need specific help. It was a fun job and I did it with a lot of help from people on this forum.

Cheers.

[Hugh R]

KY

Thanks so much, that is very helpful.

[DRACO A5OG]

I have the SST you can borrow, but lets confirm it is your CHTS or DME.

See you soon,

J

Nice write up Brother M

[Hugh R]

CHTS was exactly what it needed from our host. $125 with tax and shipping and 1.5 hours of work. Not as difficult as I was fearing.

Thank you to everyone who offered suggestions. I know without this forum I'd be taking it to someone.

[DRACO A5OG]

Outstanding!