3.6 not running... help!

911teo · 08-12-2005, 02:45 PM

Yesterday I finally (after 5 months) picked up the car to take it to VIR for a full 3 day weekend on the race track....

But things are not going according to plans...

The engine is not running particularry well...
It stumbles, burps regularry at 2.5k and 3.8k rpm in acceleration and everytime I lift the throttle.

It happens at WOT or if I gently let it rev. No matter what I do. It is so frustrating...

It sounds as if it is backfiring and it feels like the power drops dramatically for a fraction of a second. Once past those 2 points it goes smoothly... But as soon as I lift it starts burping and stumbling again...

I am no expert here but I checked all the electrical connections, changed the distributor caps. The car is running a little rich... but not too much.

It has a Cyntex chip. It's a 97 V-ram with Euro brain and harness.

Needless to say that my 1st day at VIR was not fun. So now I am stuck at home...

PLEASE HELP!

Bill Verburg · Bill Verburg's Garage

Assuming you used his kit, have you talked to Steve? He pinponted a potential issue on mine in 30sec, A poor connection made good transformed the engines performance and cured a raft of issues, none like yours fortunately.

911teo · 08-12-2005, 03:01 PM

I purchased EVERYTHING from Steve Timmins... engine, chip, kit, clutch, exhaust, brain, harness.... u name it... it came form Steve.

Friday is Steve's day off... So I will have to wait until tomorrow.

I am sooo frustrated right now...

Steve assured me the engine was running perfectly when in his car.

I don't know...

Bill Verburg · Bill Verburg's Garage

Believe him, something was probably miswired or a connection is not as solid as it could be.

I'm sure that Steve will be able to give you some direction.

I know it's frustrating

Jack Olsen · 08-12-2005, 03:23 PM

Is the distributor belt working? Have you tried swapping out the DME relay and the Cyntex chip?

911teo · 08-12-2005, 03:35 PM

If it was a distributor belt problem wouldn't it be impossible for it to run at all? Again not an expert here...

I do not have but the Cyntex chip and the DME that came with the motor... If it is chip related my weekend is over... Am I doing any harm to the engine? Should I just drop it and not drive it anymore?

Jack Olsen · 08-12-2005, 03:43 PM

The car will run with only one distributor functioning, but not well. Verify that both distributor arms are moving, or try disconnecting each coil lead while the car is running, and see if there's a difference.

The DME relay is near the DME box, but it is not inside it. It's a black cube about 1-inch square. It controls the fuel pump, and can have quirky behavior as it fails.

911teo · 08-12-2005, 03:59 PM

The car runs, albeit at lower RPMs, with only one distributon connected.
The DME relay looks like is connected properly...
I disconnected it and connected it back... same results.

Jack Olsen · 08-12-2005, 04:18 PM

Do you have access to a spare DME relay? It's a good idea to carry one with you. (The Timmins kit also puts an inline fuse for the fuel pump in the same area -- this is another good spare item to have on hand.)

Five months in the shop and one day for shake-down is pretty gutsy behavior. Vacuum leaks and wiring gremlins are common issues after a rebuild or a swap. How did the shop doing the work describe the engine's behavior?

911teo · 08-12-2005, 04:29 PM

It's Friday 8:30pm now here. Porsche parts are now sut for the weekend. So no spare DME.
As per my shop...they checked all the vacuum leaks. They think it's a chip issue. Otherwise they don't have a clue... They said they could run a diagnostic next week.

As per the 1 day... You know how it goes... I had booked this event 2 months ago... when I had been told the car would be ready in 1 week...

We went down to the wire... and obviously the car was not ready yet!

Jack Olsen · 08-12-2005, 04:41 PM

I've been there myself.

I doubt it's the chip, though.

CBRacerX · CBRacerX's Garage

Remove the DME from the harness, or disconnect the battery (your choice). Wait 5 minutes. reconnect. Fire up.

Are you Sure that the engine runs with either coil wire connected? Make sure your check _both_ of them.

Trying to help.

Chris

911teo · 08-12-2005, 05:19 PM

Chris tried both the battery and the DME.

And the engine fires up with either coil connected.

And do not worry... I know u guys are trying to help! I'll retry everything again... You never know...

CBRacerX · CBRacerX's Garage

Sounds like your cylinder head temp sensor is going south. Since the car is running rich (but not too bad as you note) this is a likely culprit. It will get worse and then fail. Can be annoying to change with engine in the car but perfectly do-able (ask me how I know).

Chris

Kevin Stewart · 08-12-2005, 05:24 PM

what about the ground straop on the ground for the dme, Kevin

CBRacerX · CBRacerX's Garage

FYI - the only known chip issue with Cyntex v-ram software is a drop in the redline after significant use. A DME reset will resolve it.

Chris

V-ram 3.6 in '87 911 and lots of Timmins parts on the car

CBRacerX · CBRacerX's Garage

Kevin also makes a good point, but that will not usually make the car rich.

911teo · 08-12-2005, 05:31 PM

DME Ground checked...
I just went for a quick spin again... It's getting worse... especially as I lift the throttle... It reminds me of the sound F1 cars used to make when the anti-spin was active (out of a slow turn). It's almost like it's backfiring all the time on release and stumbling on acceleration precisely at 2.5k and 3.8k... I am lost.

911teo · 08-12-2005, 05:35 PM

Quote:

Originally posted by CBRacerX
Sounds like your cylinder head temp sensor is going south. Since the car is running rich (but not too bad as you note) this is a likely culprit. It will get worse and then fail. Can be annoying to change with engine in the car but perfectly do-able (ask me how I know).

Chris

That happened when I had still the 3.2 engine. It never behaved like this...

As per the 3.6 running rich it was done to pass emission tests... It is rich as in NOT lean... It's really not too rich...

einreb · 08-12-2005, 05:42 PM

Did you do the DME reset yet? its easy. disconnect the battery for a while (10 minutes?)and then connect it back up.

There are lots of 'shot in the dark' suggestions... vacuum leak, MAF sensor dirty, bad CHT, bad o2 sensor, bad ground, loose electrical connection, et cetera.

I just did a swap and it took a while to shake out the bugs. Had a bad electrical connection AND a vacuum leak.

The pisser is that this will be a little tough to diagnose and fix by guessing. The upside is that its VERY doubtful that anything is seriously wrong with the engine.