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

[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.

[FFOURIE]

I had a similar problem with my Boxster 2.5 The misfire and leaning out was caused by a faulty vario cam solenoid { in my case on bank 1} I replaced the solenoid and the engine is running smoothly with no problems

[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

[famoroso]

Boy, this thread reads like an enthralling murder mystery! I find myself creeping up on the edge of my seat in anticipation that each new post will drop the smoking gun big reveal. Like Tiger King, I don't think this thread could have been better timed.

Kudos to Wayne for the perseverance and to all the contributors, including many of the forum's top dogs. I love seeing both Steve W. and Sal chiming in as 3.2 Carrera whisperer brothers from other mothers and opposite coasts, especially as Sal is advising on my 3.4 '87 build and Steve tuned my '88 on the dyno.

Steve tuned my '88 on the chassis dyno at Gameface Motorsports. While I was there, I noticed their engine test stand. Several times during this thread I've thought that I would have given up on trying to diagnose this with the motor in-situ, pulled it and have Sergio run it on the test stand.

Anxiously awaiting the next installment of this serial.

[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!

Can't wait to see what solves the problem, and with everything that's been changed I hope it runs like a top.

Cheers,

- Craig_D

[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?

[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.

[ggraaf]

Hi,
I just came across this thread due to the email 'Help Wayne Dempsey with his Latest DIY Puzzle' I received. Currently I am in the process of converting my 914 with the identic 3.2 motor. Previously it had a 3.0 from a 911 SC. So conversion is, apart from the electronics and electric connections, relatively straightforward. As I own a 911 3.2 as well I already came across some issues of this motor and maybe my hint can help you. I did not go through all the messages here so I am unaware if the Lambda sensor has already been excluded as cause of the problem. But to me it might be a problem that the sensor is at the exhaust and therefore it receives cold exhaust gasses. At the 911 the sensor is nearby the headers (downstream of the catalytic converter) and therefore receives hot gas. I intend to weld a nut on top of the (original replica 914-6) heat exchanger where the three tubes from cylinders #1, #2 and #3 come together. This point is the nearest where the sensor can be put and hopefully the gasses will still be hot enough.

Hopefully this helps a bit.

BTW excellent and interesting thread!

[proporsche]

Originally Posted by Wayne 962

That is pretty neat. No, mine is not as Gucci as those, but this time I did size everything correctly and I fabricated some nice custom brackets to hold / suspend the filter using the stock mounts - used an old muffler clamp that I found - drilled a hole in it, and mounted it using a rubber grommet and an existing S-shaped bracket. I also tied the AFM into an existing boss on the manifold. I was surprised that this seemed to work fairly well on the first try, but of course, it's not in the car quite yet!

-Wayne

(VEX Robotics table in the background, if anyone is trying to figure that out...)

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

[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

[proporsche]

here
many bmw places have this
ivan

[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

[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

[johnman001]

I'm late to the party, and I haven't read through all your posts. I did try to read quite a few. It looked like you did swap many parts.

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.

I saw you did injectors, crank sensors, O2, AFM, and Temp sensors (which is what I thought it might be until you tested them). I wish your thread had a bit of a recap with things that were already tried.

In my time with 3.2 engines, I have found them to be reliable and fairly simple to troubleshoot, but as everything else, they are getting older.

You seem to have a wealth of knowledge in this thread, and I wish you the best of luck in getting this resolved.

[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 !

[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

[mca]

Originally Posted by Wayne 962

I have not done the ignition cables yet. I did replace the plugs, the cap and the rotor because I have been burned so many times in the past on these. I had a jet ski that I spent hours trying to track down a problem - it would cut in and out almost randomly from 4 to 3 cylinders. I thought it was the fuel supply - had the pump cleaned and rebuilt. No dice - turned out a new set of plugs did the trick. That's happened at least 3 times in recent history to make me try them regardless (besides plugs are cheap). I didn't think that would work in this case, and it didn't.

The reason why I don't think the plug wires are the culprit (or anything part of the ignition) is that the car runs fine for the first two min or so, and then starts to miss. It also goes lean at that point. Ignition problems would show up at the first moment, and they wouldn't necessarily cause a lean mixture to occur immediately following a normal warm-up period. Still, the wires could be suspect, but my gut tells me (at this moment) that the problem lies elsewhere?

-Wayne

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 🙄

[uwanna]

Man, there's now an over abundance of "cooks in the kitchen" and many are suggesting
things that have already been tried. Suggestion, before posting ideas, go to page 15
of the thread Post 283 and you will find Wayne's synopsis of the many things he has tried. Kinda will get you somewhat up to speed.

[proporsche]

yes, guys as said above... do some reading before comments.....
Ivan

[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

Originally Posted by proporsche

here
many bmw places have this
ivan