Need some input -> Problem with 3.2 transplant going lean and misfiring after two min

[victorymracing]

Have the chassis and fuel injection ground points been checked?

[jrenfrew]

Read a few pages and thought I might have one way to narrow your search...

Have you got an IR thermometer gun?

I know you've measured the mixture leaving the engine, but that's the "raw" output form the engine. The computer might not be dropping the mixture and it's something else causing the mixture level to decrease.

Measure the exhaust temperatures on each cylinder at idle when the fault is occurring.
If all ports are consistent in temp then you know the issue is system wide. If one or more ports are much lower than the others, then you can focus on those cylinders specifically. Like what could be common to them, fuel rail/ground/???.

That $19 tool has helped me solve lots of rough running engine problems before!

Works the same for an engine that's off idle too. Run the engine at speed "lumpy" for a while, so the exhaust temperatures can adjust. Kill the engine, pull over and read the exhaust port temps and look again for one really high or really low.

Hope that helps Wayne!
You're WAY farther ahead on your 914-6 than me. Still have to get my 3.6 mounted and 915 flipped.
-JR-

[Mixed76]

Triple-valve constapulator bonding nipple is either blocked or invariable, consider re-regulating both sides.

Sent from my Nokia 7.1 using Tapatalk

[proporsche]

Originally Posted by wjdunham

Any more detail on the parts shown in this pic? Specifically the adapter that bolts to the AFM? Wayne's build has something similar.
Thanks,
Bill

i got mine from Performance Products -later Automotion-no longer in biss.But i have seen this flange on BMW`s used quite often .Maybe some BMW web site or forum would know the location of it?
Ivan

[piledriver]

Its an OXYGEN sensor...
An O2 sensor measures residual O2, not fuel mix, the correlation is only valid with no misfires.

An ignition misfire shows up as a lean mix.

Fix your ignition?

Small exhaust leaks can also provide interesting 02 readings.

Also... fuel going super rich and causing misfires will also read super lean on the o2...
if it doesn't burn it isn't using oxygen, so it reads lean even with fuel pouring out the tailpipe.

check your injection pw and flows. check fuel pressure.

What else changes at same time and what drives the change in behavior? temp sensors bad?

[Curt Morgan]

You could also confirm this by the following as well.

Look up the resistance spec for the temp sensor when the engine is warm.

Run the engine until it gets warm (when it starts to act up). Check the resistance on the sensor.

To confirm this is the issue, unplug the temp sensor and put equivalent resistors between the two slots in the wiring harness. Start it up. If it runs well when warm, you have your solution.

Curt Morgan

[vip]

Dr. Bartlett can tell you ,the distributor will cause problems as the clearance of the rotor to cap . this is caused by ware in the shaft because of the design .the ware
drops the cap to rotor clearance .As the spark can not flow
Undesired Operation will mask as fuel injection problem.
Frequency over load .
Had one 3.2 in VW. bus with this problem
Shaft on this had 7mm end play.
installed good used .05 clearance. engine ran perfect.
the 914 is hard to get to the distributor make a hole in fire wall for service.

Dr bartlett sign off.

[ggraaf]

After going through all the posts here, including the beautiful description of Wayne's feelings for his 914 (post #254, yes some wine helps to write nice stories), which took me two full days and nights I became aware something has not been mentioned.

When I swapped my 914-1.8 LJet for a 3.0 911 SC engine, I took out the charcoal filter. When starting the 3.0L engine it ran quite well during a short while, but after that it ran very badly and often stopped running at all. After some days I had to take gas and a lot of air escaped from the tank when taking off the tap. At first I thought it was due to the warm weather here in Catalunya at that summerday but also wondered me if I had ever seen this before. After some searching I discovered that the breather hose to the (removed) charcoal filter was obstructed. The high pressure in the gas tank seemed to be the cause of this and of the erratic running of the engine disapeared instantaneously. So I suggest to have a look at this.

Now I am in the process of mounting an identic 3.2L engine my 914. Thanks to this thread I learned a lot. I like very much the elbow of the air filter and will have a look to order this. For the moment my K&N filter is mounted straightforward to the AFM. Therefore it slightly hits the trunk lid. I also came across the brake-out board which is very interesting for analyzing electrical problems on this engine.

Last thing: Unfortunately the shipping costs for orders at Pelicanparts to Europe are unforbiddingly high (apart from customs taxes). For any tiny thing the bill easely raises to $40 only for shipping. Isn't there a better, more economical way?

Greetings, Gerber

[easyed8]

Wayne,
If you will replace the cylinder head temp sensor , your problem may be solved.
This component fixed a similar problem that I encountered. i believe their was an
update for this sensor from two prong to three. Get the one that matches your
engine. If the three prong is the only one available , you will have to wire in the
three prong plug to your existing harness to match the three prong sensor .
Hope this info will bring you the solution you are after!

Easy Ed

[Wayne 962]

Thanks everyone for the input - I've been very busy with family / personal stuff, but I will post an update soon...

-Wayne

[wel999]

Hi Wayne,
If the fuel outlet fitting is too close to the return line fitting, it could cause a turbulence in your fuel supply. The 3.2L engine will need more fuel volume than the four cylinder engine.

Hope that helps.
Bill L.

[Wayne 962]

Originally Posted by allenone20

You may have already checked this but make sure the fuel line is not touching or near a heat source.
It may be that the fuel is being heated to causing vapor to form in the line.
As a precaution you should heat shield or insulate any exposed fuel lines.

I did check that, and I also just replaced all the fuel lines and have triple-checked that. Also, the car was running poorly after two min of idling, so that, while a good thought, doesn't really fit the fact pattern.

Originally Posted by FFOURIE

Hi Wayne,

I had a similar problem on my Boxster 2.5 flat six. It turned out to be a faulty vario cam solenoid on bank 1. I replaced the solenoid and the engine has since been performing perfectly

Thanks, and that is good advice for a Boxster, but these 3.2L engines don't have that advanced technology.

Originally Posted by petza914

Though my 914 is a 4 and has dual 45mm carbs, I had a problem where there was just enough kink in a fuel line where it would flow enough gas for low speed cruising, but when I'd try to accelerate hard, the kink would make the car run out gas. I would take a look at the location of the fuel pump, the lines going to it from the tank, including the return line, and make sure that fuel flow isn't being restricted. Also, is your pump mounted at the front near the tank or at the rear near the engine?
Enough fuel might be filling the lines to make the car run for 40 seconds before it essentially runs out of gas due to a pump issue or line restriction.

The fuel pressures look good while we're having this problem, so that eliminates that potential issue. Still, I have re-run all the lines and made sure there are no kinks. That also wouldn't explain why it seems to run fine for two minutes and then goes downhill from there?

Originally Posted by Donnoel

Sounds like thermo switch is bad . On cold start the valve doesn’t operate . After a minute or so it starts to operate. When in operation it induces vacuum flow . On the switch is a tiny cap, about 1/8 dia. If the cap is missing it wil cause a vacuum leak. Switch is located at the base of the throttle body . Good luck

The thermoswitch is indeed capped off, and I did smoke test the car when it was warm (no leaks showed). Even if the switch were bad, that wouldn't necessarily explain the left/right mixture problem that is showing up? A vacuum leak there would affect the entire motor, presumably?

Originally Posted by Craig_D

Great thread! I was wondering what happened after you recovered this one! Wayne, your perseverance is amazing, and it seems like you're so damn close!

That's indeed the story of this car! So dang close for so long of a time!

Originally Posted by rob911

Been several years since I laid hands on the 3.2 engine and have only skimmed a few pages.
Does your car have the WUR Warm up regulator?

That's a common problem on the CIS cars (the Motronic cars don't have a WUR), and a good guess if one has a CIS car (1973 1/2 through 1983)

Originally Posted by fehrpla

Chiming in here, and hoping this is wrong and not a head slap moment, but everything I've read here concerns either fuel supply or electronics. I've had numerous occasions on my '84 3.2 911 where it would hunt for idle and would be bad enough that the engine would die completely between shifts, but seemed to run fine at constant speed. I found the solution on another forum and it was simply to insure a good seal on the oil fill cap. I've seen other threads as well where someone went out and bought a replacement cap but it still didn't seal well enough causing the problem to continue. If it is that simple, the rest of the work done to date will make that beast run like new, and for a long time.

Good suggestion, but the oil venting system is not installed on this car. Normally, the oil tank is vented into the intake manifold, so when you lift the oil cap off, it creats a big vacuum leak. We don't have that on this car. That also woudln't explain the left/right issues?

Originally Posted by proporsche

Wayne, i was wondering? Do you have to have that bend flange on the afm? You could use simple one like i have on my 911?
ivan

Yes, that is needed in order to fit the air filter into the 914 engine compartment.

Originally Posted by Clay Perrine

Wayne,

Have you checked the oil vent lines between the oil tank and the engine? The tank is part of the intake system on a 3.2, and if there is an air leak anywhere in the tank, it will cause all sorts of lean running mischief. Kinda like a 1.8L 914 with bad oil cap seals. Also, the oil vent line between the tank and the intake should have a restrictor in it to make the engine idle with the oil cap off. Lots of 914-6 3.2 conversions forget to put it in. Without it, there is too much air bypassing the AFM and that could cause lean running at idle.

Good luck.

Clay Perrine

Indeed, a fine suggestion for a standard setup, but this oil tank is not vented through the intake. If there were a leak, it would be a crankcase leak, which *shouldn't* affect anything, although at this point, I'm ready to consider anything.

Originally Posted by SimpleAuto

I would bet money you have vacuum leaks at the insulators between the heads and the intake manifold. I also have seen some of the rubber boots on the intake halves joint leak. Reseal intake manifold, fuel injectors, upgrade to Griffiths hoses on all 3 fuel lines, and all vacuum lines and I bet it runs well. Just get it warm and misfiring and spray the bottom of each intake runner to find the worst offenders. You'll see the immediate improvement on the wide band or gas monitor.

Good Luck,
Chris

Simple Auto Solutions

Indeed, I thought that was the case - we've smoke tested all of the injectors, and I've now replaced all of the seals and the spacers. I've smoked it warm and cold as well. No leaks detected with the smoke machine.

Originally Posted by jim fling

I had a 3.2 and it ate up factory plug wires. Changed them twice in 25,000 miles.
The car had similar symptoms.. I don't know why but from new it always smelled like hot rubber after shutdown. Never could find out why. Most troublesome Porsche I ever owned worst of 5

Hmm, that's interesting. We have new BERU plug wires with the internal resistors. Maybe the ones you had didn't have those? My gut is that this is not an ignition problem here though...

Originally Posted by johnman001

Did you get this resolved? I know you have had lots of suggestions, and this may sound kinda rookie, but did you swap in a known good DME? That is one component that I didn't see you swap.

Yup, Steve W. lent me one of his loaner ECUs for testing (along with a host of other stuff to test with), and the two ECUs behaved exactly the same. That was a big help, as so many odd things can go wrong with an ECU.

[Wayne 962]

Originally Posted by Pete000

Wow, after all this trouble shooting and so many fancy electronics I would have thrown in the towel and gone ITB's or a nice set of proper Webers !

That's an option, but if the problem is mechanical, not fuel injection-related, then you will have problems with those too. With this latest round, I have a small sinking feeling that the problem is deeper inside the engine. More on that coming in the next post. Also, these low-lift cams are not ideal for carbs - in order to get the most performance and power out of a set of independent throttle body carbs, you want some higher (S-profile) cams. Of course, those typically require matching pistons. Slippery slope indeed. Who knows, maybe that's in the future (but I already have another 914-6 with a 2.8RSR high-lift cam motor in it).

Originally Posted by Mike Festa

Check your catalytic convertor or muffler for flow. I had a car with similar issues and the muffler had a baffle that when run for a few minutes would block the exhaust flow

No CAT on this car, and I swapped the muffler (thinking the same thing that you did). I swapped back the sport muffler last night with new gaskets.

Originally Posted by mca

I’m an SC guy so the 3.2 is a bit unfamiliar. But I wouldn’t say that ignition problems show up immediately. Specifically, I’ve had many issues with brand new coils once Bosch began manufacturing them in Mexico. As the coil warmed the issues surfaced. Had similar issues with braided plug wires. And the infamous decel valve on the SC - that one was fun to troubleshoot ??

Good suggestion - tested this with a new coil (swapped back the old black one after the new one made no difference)

Originally Posted by wjdunham

Any more detail on the parts shown in this pic? Specifically the adapter that bolts to the AFM? Wayne's build has something similar.
Thanks,
Bill

The stuff I bought to make the intake were from Spetre Performance on Amazon. Not big buck stuff, fairly inexpensive, but not super-cheap junk that seems like it will fall apart. The funny thing with all of these aftermarket parts is that they are almost all the same - made in the same Asian factories. I've seen stainless steel exhust systems purchased for literally $100 on eBay that are made in the same factories as the ones that cost $2,000. I'm not BSing or exaggerating - it's an odd business sometimes. Anyways, the Spectre Performance stuff is cheapish Asian stuff (the air filter adapter and the aluminum tube) but seems fairly well made.

Originally Posted by victorymracing

Have the chassis and fuel injection ground points been checked?

Yup, all three ground points are there, and the resistance has been checked and all of the contacts cleaned as well.

Originally Posted by jrenfrew

Have you got an IR thermometer gun?

I know you've measured the mixture leaving the engine, but that's the "raw" output form the engine. The computer might not be dropping the mixture and it's something else causing the mixture level to decrease.

Measure the exhaust temperatures on each cylinder at idle when the fault is occurring.
If all ports are consistent in temp then you know the issue is system wide. If one or more ports are much lower than the others, then you can focus on those cylinders specifically. Like what could be common to them, fuel rail/ground/???.

I agree, this is a very useful tool. I have a few of these including the FLIR camera. The tool is extremely useful for finding dead cylinders. Less useful for finding intermittant issues. The problem is that the exhaust doesn't dissipate head uniformly across all cylinders, so you might find one cylinder exhaust pipe temp that is 20-degress less than another. If you don't have a baseline (measurements of the temps when the car is running perfectly), then you don't know if it's related to an engine issue, or it's just the way the exhaust is bent and interacts. BIG differences in temperature (like 300 degrees on one cylinder and 90 degrees on another) point to dead cylinders, but that's not what we have here as a diagnosis.

Originally Posted by Mixed76

Triple-valve constapulator bonding nipple is either blocked or invariable, consider re-regulating both sides.

Huh?

Originally Posted by piledriver

Its an OXYGEN sensor...
An O2 sensor measures residual O2, not fuel mix, the correlation is only valid with no misfires.

An ignition misfire shows up as a lean mix.

Fix your ignition?

Small exhaust leaks can also provide interesting 02 readings.

Also... fuel going super rich and causing misfires will also read super lean on the o2...
if it doesn't burn it isn't using oxygen, so it reads lean even with fuel pouring out the tailpipe.

check your injection pw and flows. check fuel pressure.

What else changes at same time and what drives the change in behavior? temp sensors bad?

Car has issues with the O2 sensor unplugged as well, but worse with the O2 sensor plugged in. The left/right mixture difference seems to be the real problem. I smoked the exhaust (several times) so I doubt there is an issue with exhaust leaks. Plus there are none to be heard either.

You hinted at something there, I think the O2 sensor is correctly reading, which means that there's something wrong with the engine left/right. More on that soon.

The fuel pressures, injectors, etc. have all been checked.

Originally Posted by Curt Morgan

You could also confirm this by the following as well.

Look up the resistance spec for the temp sensor when the engine is warm. Run the engine until it gets warm (when it starts to act up). Check the resistance on the sensor.

Temp sensor was checked and was a bit out of spec, so we replaced it. Didn't make a difference unfortunately.

Originally Posted by vip

Dr. Bartlett can tell you ,the distributor will cause problems as the clearance of the rotor to cap . this is caused by ware in the shaft because of the design .the ware
drops the cap to rotor clearance .As the spark can not flow
Undesired Operation will mask as fuel injection problem.
Frequency over load .
Had one 3.2 in VW. bus with this problem
Shaft on this had 7mm end play.
installed good used .05 clearance. engine ran perfect.
the 914 is hard to get to the distributor make a hole in fire wall for service.

Dr bartlett sign off.

We thought this too - although it wouldn't necessarily explain a left/right variance in the mixture. Wear on the shaft should show up uniformly? I also checked the distributor with a scope over a long period of time and visually checked the sparks with a camera - no ignition problems detected...

Originally Posted by ggraaf

When I swapped my 914-1.8 LJet for a 3.0 911 SC engine, I took out the charcoal filter. When starting the 3.0L engine it ran quite well during a short while, but after that it ran very badly and often stopped running at all. After some days I had to take gas and a lot of air escaped from the tank when taking off the tap. At first I thought it was due to the warm weather here in Catalunya at that summerday but also wondered me if I had ever seen this before. After some searching I discovered that the breather hose to the (removed) charcoal filter was obstructed. The high pressure in the gas tank seemed to be the cause of this and of the erratic running of the engine disapeared instantaneously. So I suggest to have a look at this.

That is a great suggestion, and that is indeed an issue with the tank setup on this car - the expansion tank was disconnected and the vapor hose wasn't plumbed correctly. But issues like this typicaly happen after driving a lot with vacuum building up in the tank. The Boxster has this problem when the electronic relief valve is broken. I will replumb my expansion tank in the near future - for now it's venting to the atmosphere through the small hose...

Originally Posted by easyed8

Wayne,
If you will replace the cylinder head temp sensor , your problem may be solved.
This component fixed a similar problem that I encountered. i believe their was an
update for this sensor from two prong to three. Get the one that matches your
engine. If the three prong is the only one available , you will have to wire in the
three prong plug to your existing harness to match the three prong sensor .
Hope this info will bring you the solution you are after!

Easy Ed

The cylinder head temp sensor was indeed out of spec, so we replaced it, but it didn't fix the issue, unfortunately.

Originally Posted by wel999

Hi Wayne,
If the fuel outlet fitting is too close to the return line fitting, it could cause a turbulence in your fuel supply. The 3.2L engine will need more fuel volume than the four cylinder engine.

Hope that helps.
Bill L.

Interesting thought. I haven't heard of this being an issue for other people on other conversions though. Plus the fuel pressures look good. The fuel lines for the 3.2 were expanded for the conversion, so that was indeed done correctly. Also, fuel flow wouldn't be an issue at idle, presumably?

-Wayne

[Wayne 962]

Okay, Sunday May 31 update. Did the following:

- Replaced all fuel lines with new ones (except for the center tunnel).
- Installed new fuel tank
- New spark plugs (third set - they are only $1.50 each my cost, so why not?)
- Cleaned up the engine compartment
- Installed new air flow meter from the 964 Singer take off
- Re-plumbed the air filter and pipe
- Cleaned up the battery terminals
- Cleaned up the intake and some of the carbon build-up in the cylinders
- Changed out the oil filter (added some anti-friction zinc additives)
- Had the injectors cleaned and tested (again) - one came back as "CLOSED", but now are functional

Started the car up. Conclusion - it runs better, but still has issues. It's not misfiring per se, but the idle is lopey and not smooth. Same as before, where it starts and runs fine at 1,200 for about two minutes and then settles down into an irregular idle. Also, plugging in the O2 sensor makes the mixture go lean (again) - this has not changed. If you read the previous posts, I determined that the engine was seeing 1-3 run rich, which was then (presumably) resulting in it leaning out the whole motor. This behavior does not seem to have changed.

Exhaust temps seem to have improved and are uniform. I have measurements and photos of these.

My thoughts at this point? I think there is some type of underlying issue with the engine. Indeed, all of this crap running at idle has gummed up the cylinders with carbon (one can see it with the intake off), and I will be runing a bunch of Techron and Seafoam through the system as I take it out for an "Italian Tuneup". Perhaps that will assist. It's possible that there were previous problems (documented on the previous threads and fixed, things like ignition wires, cylinder head temp sensors, and AFM issues) that caused a rich running condition that gummed up the cylinders. No engine likes to really just idle for long periods of time, which is what this has been doing as I've been working on it. So, I plan to take it out on the highway to beat the snot out of it and get it proper and warm (with the Techron running through it too). We'll have to see how that works. In general, at this point, it's easy to over think things...

-Wayne

New setup installed with the new pipe and air filter:


Front fuel tank compartment with the tank removed:


Cylinders 1-3, pretty much cleaned up nicely:


Another shot of the air cleaner setup now:


New fuel tank!


Tank with all of the stuff that needs to bolt on to it:


Looking fairly torn apart:


WTF?!? This fell out of the bottom of the bag that the tank came in. It looked like a brochure for some new tanks, and I was tossing it out when I actually decided to read it. So, then I had to don my "Chernobyl" suit and go buy some carb cleaner (Berryman 12 Chemtool), and spend a few hours cleaning out the inside of a "new" tank! I called my supplier on this, as I had never heard of this, and he had never heard of it either! Go figure. Just keep that in mind in case you buy a new tank!


Good stuff, Warren loved this stuff:


Cleaning in the inside of the tank. Gloves, mask, goggles, etc - it's like I'm going to the grocery store!

[Wayne 962]

More photos:

Here's what the Air Flow Meter mixture screw looks like when you drill out the plug:


Another shot of the air cleaner setup:


New gaskets and spacers. They are relatively cheap, so one should probably replace them if they are old:


Cleaning up the engine bay:


Remember to remove the paper towels!


Installed the new lines and the wire harnesses:


Cripes, I forgot to label the speed / rpm sensor and they are both 3-prong plugs, so one can mix them up. The wires will hint to you at which one goes where, but I had to double-check with the ECU connector just to make sure:


Smoke tested the whole thing when reinstalled - found a few spots that I quickly tightened up:


Another photo of the smoke test. I put a screwdriver inside the air flow meter to prop the flapper valve open. Important to put a reminder note on the top so you don't forget!

[Wayne 962]

Even more photos:

This boot is $10 or so to replace. Make sure that you leave one side loose, then mount down the intake and then tighten, otherwise you'll pre-stress the boot.


Ignition wires are now properly sorted:


Filter inside the injectors - they all looked fairly okay:


More ignition wire routing:


Injectors were re-tested and came back with one "CLOSED". That seems bad, and may be a sign that all need to be replaced with new injectors. I think if my problem persists, then I will replace all the injectors. Having one completely closed is odd / bad.


I came up with a clever idea to attach different colored zip ties to each one to keep track of them:


I made sure to label that in the sheet:


Here's what the AFM plug looks like when you remove it:


Newish 964 AFM. Doesn't look "messed with":


Other side of the AFM plug:

[Wayne 962]

More:

Engine bay, jumper the DME relay to power the pump and check for leaks:


Fuel lines underneath, temporarily zip tied for now (I use red zip ties to indicate things that are "temporary only".



Front fuel pump setup:


IR temps:, cylinders 1-6:

[Wayne 962]

Videos:

First startup. Running better, but not perfect. With the O2 sensor plugged in it doesn't run as well as without it plugged in. I think there's still something off left/right on the engine:


Again, same thing but car is warm and I hooked up the LM-1 O2 measurement tool:


-Wayne

[manbridge 74]

One thing I recall from Bosch training.... if you mount the AFM in any other position but dead straight horizontal there will be running issues that are hard to solve. Not saying that’s wholly your issue here but I’d mount it correctly to rule out variables.

[manbridge 74]

Clarification: the one pictured above is inverted and needs to be flipped....