This is back to the problem in right hand turns and at high rpm. We get a studder until we either turn right to clear it or upshift and hit a lower rpm. We have replaced almost everything. Let me explain what we have done (doesn't mean that a "new" item we have replaced is not bad as well). By the way, the engine has been rebuilt several times over this past 7 years..

Timeline:

Problem started about 7 years ago. Had bucking at freeway speeds.
Took to Reitmeir's and they replaced the FI trigger points- problem went away.
Problem came back again.
We "hardwired" the coil to see if it was iginition- was not
We rebuilt our FI wire harness and installed new TPS- problem went away for a while
Problem came back again. This time also with LEFT hand turns.
Replaced the MPS with a rebuilt one- problem went away for a while
Problem came back again.
Replaced the relay board- no change
Installed Pertronix ignitor- no change
Moved the fuel pump to front and replaced fuel pump and filter- no change
Replaced the FI brain- problem went away for a while
Problem came back again. Still left hand turns, but also noticed an RPM sensitivity.
Replaced FI trigger points again- problem went away for a while
Problem came back again.
Replaced the coil and plug wires (but used the same ends)- no change
Rented the FI tester from PP and found a suspect wire in our FI harness- problem went away for a while.
Problem came back again.
Figured our wires in our harness were brittle so we bought a Bowlsby harness- problem went away for a while.
Problem came back again.
Installed a MSD- don't get me started here but it ruined 4 pistons individually shearing off the ring lans and causing multiple engine rebuilds- removed MSD.
Replaced the MPS with a new unit- no change
Cleaned up what we think were all the grounds again (firewall by relay board, on the engine for FI, Transmission ground, Battery to chassis ground- that's all, if there are others let me know)- no change
Fuel injectors were flowed- engine felt more balanced at idle, but problem not fixed
Finally we did this-
Connected a long hose to the FI port and attached the pressure gauge so we could see it while running. Used a 2 channel battery powered O-scope and connected to FI#3 and the coil. We ran the car until the problem occurred (just down the street). We saw pressure was steady, coil voltage was steady, FI#3 pulses went to hell- went from nice pulses to noise).
We replaced the FI trigger points and re-ran with same setup- problem not seen
Problem came back.
Latest rebuild of the engine-problem no happens in RIGHT hand turns and with high rpm
Decided it must be the distributor as with shaft wobble that would explain the noisy signal on the FI#3 injector (just the only one we wired up not specifically #3, assume them all) , the rpm sensitivity and the turning sensitivity (but no the movement from LEFT to RIGHT this year)
Guy at distributor rebuild place said our distibutor was shot with lots of wobble and off about 12 degrees at high rpm.
Put in new distributor and it idled better (no hunting) figured we had it licked.
First turn at Butonwillow- the problem was back
We swapped out with a known good other distributor (thinking maybe the rebuild was bad) and the problem was still there (still in RIGHT hand turns and rpm).
Borrowed another MPS from Kevin and Greg- problem was still there.
Put in another coil-problem was still there.

SO, that brings us to today- I don't get it....
Here is our list of items that could be rpm and/or g related and some notes:

FI trigger points- replaced with new distributor, no change- NOT it
Distributor- replaced with new distributor, no change- NOT it
FI brain- replaced once , but still suspect it there a test for high rpm signal integrity?
Rotor cap- replaced, no change
Pertronix- replaced with new distributor with point, no change- NOT it
Spark plug, coil wires- replaced, no change, but could be possible since old connectors used
Relay board- replaced with no change, what really goes bad on these
Are there other ground points we are missing?
Main wiring harness issue- but doesn't explain the rpm related issue
MPS- replaced with working one, no change- NOT it
FI harness issues- we have had connector issue with the Bowlsby harness and had to replace one wire going to Trigger points
Coil- replaced with another one. One thing I noticed is there is .8v at the negative (#1) terminal and 11.4 volts across #1 and #15. Is this normal, or is there a ground we are missing?- however, hardwiring this in the past had no effect... of course we did not hardwire the ground..., but problem on Oscope showed issue at injectors and coil voltage was constant
Fuel pressure- verified with pressure meter during issue, not movement constant 29.5 psi
TPS- problem is not full throttle related, but rpm related and it is basically new


PLEASE HELP ME!!!!
Thanks for all your stabs at this in advance, I will try anything.

Chris Kolstad
1973 914 2.0L BP

The head temp sensor could have an intermintant falt or threds could be stripped. This would cause the sensor to get an incorrect reading once in a while after the car was warmed up.

Just my two $ worth!

Jeff

Thanks. I did replace the head temp sensor during one of the rebuilds. I have installed the 270 ohm resistor setup on that in line. I can try to remove it and make a direct connection. However, I don't think that could cause cutout at high rpm. Doesn't it only effect the richness?

Chris

Hows the main harness look to the column/ignition switch ??

Hows the relay board look ??

Relay boards cause some weird ass issues over time.

What is the battery voltage ?? ARe you overcharging the battery at high RPM ?


B

Main harness looks OK- have checked it out before nad did again recently--this shuld not be rpm related (could be g related though)
Relay board is new (well 2 years old now)- still where is the rpm related piece here?
How would overcharging the battery at high rpm matter? how would that be g related?

Thanks,
Chris

Do you have a big heavy key ring hanging off the ignition key? Goes with Brad's item #1.

Bare with me. I want to think about everything you listed.

Charging would be RPM related... and charging would be relay board relsted (that is why I went down that path)

Coil voltage sounds low to me unless you meaured at full load.

What type of battery do you have in the car and how long has it been there ?

B

Standard type battery. Been there for 8 months. Battery voltage looks fine.
Yes, coil voltage seemed low to me as well which is why I pointed it out. Thsi was measured at key-on, not at full load.
As for the key thing, nope, just the ignition key and a light plastic key fob. This is purely a race car, so no house keys.... I did replace teh ignition switch BTW. Forgot to list that...
Back to the alternator, it is old, but it seems to be charging fine...
Like i said in my timeline, I hooked the coil up to the oscope and it did not vary in voltage (up or down) when the problem occurred.

chris

BTW Brad...thanks for the offer, but I'd rathre not "Bare with you"....;-)

Yes, the sensor only adjusts the fuel/air mixture.

How about something simple like someone dropped a bunch of washers in the gas tank and when you turn they clog the fuel line! lol


Jeff

try a different engine.
put your engine in a different car.

that way you can eliminate some (IMG:style_emoticons/default/smile.gif)

Yeah, uh thanks Andy. If you have a donor car, we can talk...
Anyway, on the overcharging note. I did try out a different regulator (metal can protruding from relay board) and it made no difference. Are you talking about the alternator directly or something messed up with the regulator?

Chris

Alternator at 6Krpm (which is where you would entering some of the corners)

I just need to come by and spend more than 15 minutes going over this with you. I'll print off the list and head down. I'm really concerned about things moving around in the car under high G. Things on the fuse panel... things behind the gauges..

The TACH. I have seen TACHS cause all kinds of weird runnings issues.

You owe me a beer anyway...LOL


B

Yep, I do still owe you a beer. Maybe two by now with interest and all.
As for the tach thing, I did try removing the tach connection at the coil and it had no effect.
I think the thing that is the most telling in this is the rpm sensitivity. That tends to rule out lots of the items that are only G caused like wires by the fuse box, etc.
As for the alternator, is it the alternator that spits out too high a voltage or the regulator that is supposed to clip it?
The reason I come back to this is the fact that we did blow up a battery a while back if you recall and borrowed one from Kevin whose car was dead at that event. Kevin's battery set the track record that day....;-)
Maybe I should check into an alternator or at least a test of ours...

Chris

OK.

The tube frame race car was having a cutout problem that wouldnt show its ugly head until you where into the run by 8 corners or so. I changed everything. It ended up being the Alternator was putting out too much voltage and causing the injection system to shut down as everything overheated. Testing at idle and under small load.. everything looked fine.

I do beleive this is electrical. I have also seen batteries with loose internal plates cause this issue under high G loads.

B

So, does anyone have a good used alternator they wouldn't mind parting with?

Chris

I can bring 1-2 of them down with me. The problem is: I dont know when I'll be down next.

How I'm thinking on this:

You and dad have a bad habit of reusing old parts during the rebuild. I'm betting that Alt has gone through all the different engines.. and its probably the one that came with the car.

Before I changed it out.. I would: unplug it completely from the car and drive the car around on the battery. In other words isolate the alternator from the system. This is easy and doesnt require getting under the car.

B

uhh...since your engine is having problems....what a perfect excuse to tell wifey that you are putting 2.7 six in the car (IMG:style_emoticons/default/laugh.gif)

They are building a 911. No need for a conversion.

Chris and his father Chuck can outdrive just about all 914 2.0 4cyl cars in the state of Cal. They will be the last people to convert their 914 when they beat most of the sixes...LOL


B

Chris.....you want an alt?

Email me tommorow in the AM to see if I remembered to bring one in for you.

Yep, same alternator. All we do is unplug the cable to the relay board, right?

Yeah we already have a 3.2 in my dad's Carrera. Don't think he would mind the swap....

Chris