injector wires shorted, what could it damage? - Page 2

blown 944 · 08-27-2007, 02:31 PM

It sounds like aslightly lean condition to me.

I am thinking that it is not giving a long enough duty cycle to the injectors.

To try something different lets try to richen it up a little through the DME.

There is a FQS switch on the side that is adjustable and if you go to position 3 it will richen it up 6%.

From what I have read most chip manufactures use the std FQS percentages even though they are new burns.

I think your DME is under the dash below steering wheel similiar to the early 944's.
There is a little plug that you can remove and stick a 6 penny nail in there to turn the little switch

the settings go as follows

all the way counter clockwise is 0

1 is +3% fuel
2is -3% fuel
3 is +6% fuel
4 is 0 fuel change and -3 degrees timing
5 is +3 fuel and -3 timing
6 is -3 fuel and -3 timing
7 is +6 fuel and -3 timing

I was going to send you to wilks site but it is down.

soxnail · 08-29-2007, 06:12 AM

If you did the ISV test then the DME no longer had any control over idle (other then timing which is a small amount), as the car was still surging the dme's only contribution to the problem (if any) would be a fluctuation in the fuel injection cycle.
My next likely suspect would be the airflow meter. Do you have an oscilloscope or access to one. If you do then we can dynamically test the AFM. If not at least test the afm by taking of the afm connector and test the voltage between pin 7 and gnd. I think for your car (as opposed to the 951) the reading should be 100 to 250 mv at flap closed and as you push the flap open slowly it should rise to 8V. There should be no drop outs or jumps in the voltage as it goes up. If you have a scope hook it up to the dme connector pin 7 and do the above test (BTW it is done with ignition on but car not running). You should see something like this picture, with no jumps or drop outs.
SOX

blown 944 · 08-29-2007, 06:27 AM

Sox are you sure he should see 8v? Are you supplying a specific voltage or using the DME voltage into the AFM?

I have only seen 5v on the late systems, and actually up to 12+ on the early

I also suspected the AFM to a degree, but the surge just seems like a lack of fuel across the board. That's why I thought in a different direction not to mention the afm is virtually non existant at idle.

I don't want to confuse the guy, but trying different things may get the job done anyway

soxnail · 08-29-2007, 06:36 AM

It is 5V for the 951 as far as I know. My knowledge of the 924's is limited but the book on the 944 says 8V. Lean all across the board would cause an rough idle problem too imo. Any way I am just trying to eliminate he problem by testing one system at a time.
1) ISV
2) AFM
next would be the injection system, but by all means I will move to side line and you can continue to help him

I will keep monitoring good luck.
Sox

soxnail · 08-29-2007, 06:36 AM

It is 5V for the 951 as far as I know. My knowledge of the 924's is limited but the book on the 944 says 8V. Lean all across the board would cause an rough idle problem too imo. Any way I am just trying to eliminate the problem by testing one system at a time.
1) ISV
2) AFM
next would be the injection system, but by all means I will move to side line and you can continue to help him

I will keep monitoring good luck.
Sox

soxnail · 08-29-2007, 06:37 AM

sorry double post

blown 944 · 08-29-2007, 06:42 AM

Together, it will get solved.

It's probably some silly little vacuum leak hiding anyway, he he

924sownerga · 08-29-2007, 01:35 PM

At start the FQS switch was set to 3. At 2 it seemed very hard to start. All the rest of the positions it seemed about the same. Maybe slightly easier to start at 7 which is where I left it for now. All of the positions had a surge.

I will try to borrow an oscilloscope

Any chance that the DME relay could be turning on and off in cycles

Thanks for the help again

soxnail · 08-29-2007, 01:39 PM

Brad if you can get a scope good if not try to measure the voltages at the points indicated in my post, and post the results. This will serve to either confirm its the AFM or take it off the list of suspects.
Sid you are probably right on the vacuum but he seems to have chased it (leaks) down pretty well.
If the AFM passes then I want to look at the injectors. One or more may sticking or damaged. Or the short may have damaged the injector drivers( not likely).
Lets do this one step at a time.

Sox

soxnail · 08-29-2007, 01:52 PM

I take that back I just read the thread again. What was the result of trying to chase the vacuum leaks.
SOx

soxnail · 08-29-2007, 01:57 PM

One more thing, in testing the afm one thing you can do. With the car idling (and surging) try to manually open the afm vane a little bit and see what happens. If you open it too much the car will die.

blown 944 · 08-29-2007, 02:37 PM

Sox sounds good

To answer the question Brad I don't think the relay will do anything remotly close to that it seems it works or not

It is strange it was set to 3 in the beginning I wonder if there has been some trouble with a lean condition before.

To reiterate what all have you done to check for vacuum leaks?

924sownerga · 08-29-2007, 05:10 PM

I performed the voltage test on the car as described on Clark's Garage. The voltage was smooth up to 5 volts and starting at 250mv. The temperature sensor read slightly low 1.2k-ohms but the temperature is 92 degrees F, which is outside the testing range listed. If I know how to read the ohm meter. (an electrician I am not). I think we can check the AFM off the list. If you push the AFM flap open while the car is running, it dies or slows almost immediately.
Note: my Haynes manual (944 1983-1989) says the voltage should go to 8 volts but Clark's Garage says 5 Volts. It responded just as it should according to Clark's Garage)

I replaced almost all the vacuum lines. I ran them over the top of the engine. I sprayed starter fluid at connections, but hard to tell with the inconsistent running to judge anything concretely. What I can say is that there was no major leaks. I have not tested the vacuum pressure. I did listen with a stethoscope at all joints for leaks and did not detect any. I plugged the ISV joint with my finger and the car seems to pull a very good vacuum. Hopefully the ISV valve is supposed to be pulling a vacuum at about 2000 rpms. There still is almost no change in function if it is connected, plugged, or unplugged.

I once again listened to the injectors, With a stethoscope they sound like a plastic"y" very rapid clicking. I could hear them best on the fuel rail directly over each injector and could hear the same on the side of each injector. I believe that all injectors are firing at the same rate. Therefore they may be plugged but they are cycling. How rapid is the firing cycle? They are firing at a rate that would be way to great to count. I am afraid that I may be hearing the valves and I can not hear the injectors. It is only a small doubt.

soxnail · 08-29-2007, 08:13 PM

"I plugged the ISV joint with my finger and the car seems to pull a very good vacuum. Hopefully the ISV valve is supposed to be pulling a vacuum at about 2000 rpms. There still is almost no change in function if it is connected, plugged, or unplugged."

That does not sound right. What do you mean "ISV joint" ? No change is not good.
Look at the pic below and tell me what you are doing when you do the above test. Ignore the fact that it is a 951 lay out, the ISV and its connection should be the same. Also I will have some time tomorrow Thursday to do live trouble shooting. We can use the chat function on this board.
Sox

924sownerga · 08-30-2007, 02:16 PM

I will send you a PM. Thanks, Brad

924sownerga · 08-30-2007, 02:56 PM

The hose that goes to the control valve that comes off the oil separator does not seem to pull much vacuum at all. It is also allowing very small amounts of oil into the air box, almost negligible but there. I don't know that I have ever seen oil in the air box. Should I be getting a good vacuum from this source?

soxnail · 09-08-2007, 06:30 AM

updates ??
Sox

924sownerga · 09-13-2007, 11:10 AM

I know without a doubt that I have no vacuum leaks. The intake manifold held positive pressure well.
I checked all the wires and found a few cracked wire insulations but no shorts. My next planned step is to replace the DME. I found one at a salvage yard close by for not too much. I will try to replace mine to see if this is the cause.
The car does not seem to have much power. Then again it is running like *&^(.
Could a bad coil cause a surge and rough start?
If I replace the DME with a stock DME without an oxygen sensor the car should run but just run rich. (Correct?)

Thanks for the help,
Brad

soxnail · 09-13-2007, 11:15 AM

Stock DME without O2 sensor will make it go to a default mixture map. The control over mixture will be lost but if the idle mixture is set right then it should run pretty much as normal. At WOT it should not matter at all as the O2 map is bypassed.
Coil can do it but...not rev up and down.
Sox

924sownerga · 09-17-2007, 01:48 PM

I put in the new computer today and the car started right up. Idled great. I was happy.
I took the car for a test drive and got maybe three blocks and the car died. It would not restart when I let the clutch out in second gear as I was rolling to a stop. I turned off the ignition and it immediately restarted, idled fine. When I took off again it died. Repeated the process three times on the way home and as I was pulling into the driveway the surge started back up. It is idling but with a significantly less surge.

Is something telling the computer to do this??? That is what it sounds like to me. I think it may be God telling me to scrap the car.

My plan is to test the AFM input into the computer while it is running, change the DME relay, possibly look at the ignition switch???

Anything else....