Compression Results

[EyExR]

One thing I don't think I mentioned is that my brakes feel hard. I know this could be the brake booster... How do I test?

When I put my foot on the brake pedal and start the car it moves down to the floor so it 'seems' ok. But when I'm driving it's definitely a bit hard.

I ask because when I had my smoke test done we found a couple of small leaks at the cam plugs but that was it. From my understanding, you can still have a vac leak at the booster that will NOT show up from a smoke test. Correct?

Need a little advice here fellas...

[EyExR]

Well... got the injectors back. After I installed them in the rail I did a quick test and one of them had around 5 or 6 drops of gas come out past the pintle cap then it stopped. I'm assuming this is ok? It wasn't leaking at all after that... jeez. It's always SOMETHING.

I went for a drive. I thought everything was good! but after about 20 minutes. CEL comes back on.

I guess I'll suspect the O2 sensor and cat next...

What a fiasco.. :???:

[EyExR]

Well, I'll hold off on buying another CPS for now...

I've sent my injectors out to MEPEH to be cleaned. We'll see how refreshed stock M20 injectors do...

[Lugnuts]

when i swapped mine to the plastic version due to the old original one becoming suspect there was zero difference

I'd be interested to know if the resistance was the same for both units.

[digger]

when i swapped mine to the plastic version due to the old original one becoming suspect there was zero difference

[Lugnuts]

Yes, I was thinking about this last night and was reading up on how the CPS sends signals to the ECU.

I didn't realize there were two types. I will try to track one down with the metal housing... Anyone have a part number handy?

The CPS is a passive (unpowered) inductive pickup. Frequency and amplitude of the generated voltage sine wave increase as engine RPMs increase. I don't know enough about electromagnetism to understand what problems would occur (if any), by using a part with a higher resistance.

The part numbers are the same for plastic vs metal housings - seems some manufacturers have started producing units with plastic housings, perhaps for durability/cost reasons. My initial part was Vemo (FAE?), the replacement (metal housing) was German made SWAG. Either I got a bad batch, someone can't read a spec sheet or it doesn't make a damned bit of difference. My engine certainly seems happier with the replacement unit installed.

Running both units via an oscilloscope and revving the engine would be an interesting exercise to see if there's any appreciable difference in output.

Part number I used is 12141720852. I'd be real interested to hear if swapping yours made any difference.

[EyExR]

No, drive it with fresh spark plugs and the o2 unplugged. Ignore the CEL while doing it.

Oh okay. Gotcha! So I'm looking for fouled plugs, right? About how long should I drive the car for?

[ForcedFirebird]

And then plug it back in, correct?

I tried this. CEL came on again...

No, drive it with fresh spark plugs and the o2 unplugged. Ignore the CEL while doing it.

[EyExR]

Try replacing your crank position sensor. I had the same resistance reading on mine and I strongly suspect it was the cause of detonation in my engine (plastic housing, made by Vemo?). Replacement unit with a metal housing reads the expected 540 ohms and things are better. Not perfect, but I think what's left can be resolved with a decent tune.

Yes, I was thinking about this last night and was reading up on how the CPS sends signals to the ECU.

I didn't realize there were two types. I will try to track one down with the metal housing... Anyone have a part number handy?

[EyExR]

Yes, oil can skew 02 readings, but if you unplug the o2 sensor and reset your ECU, it will default to a stock table. If the car runs cleaner after that, the o2 is suspect.

And then plug it back in, correct?

I tried this. CEL came on again...

[Lugnuts]

Try replacing your crank position sensor. I had the same resistance reading on mine and I strongly suspect it was the cause of detonation in my engine (plastic housing, made by Vemo?). Replacement unit with a metal housing reads the expected 540 ohms and things are better. Not perfect, but I think what's left can be resolved with a decent tune.

[ForcedFirebird]

Yes, oil can skew 02 readings, but if you unplug the o2 sensor and reset your ECU, it will default to a stock table. If the car runs cleaner after that, the o2 is suspect.

[EyExR]

when i last had an AFM and was doing some diagnoisis i found this site helpful http://www.the944.com/afm.htm

Thanks Digger! Yeah, the guys at OMG sent me the same link. I did all the tests and it came back perfect. The hunt continues.....

I'm getting my old M20 blue top injectors rebuilt and will try that next. If that doesn't do anything I'm going to put in a Magnaflow Cat and replace my O2 sensor again. Then that would be everything.

The only other thing I can think of is an intake leak at the break booster. I'm not sure how to test that and will do some research....

OMG smoke tested and I only had a couple of small leaks which I believe I've taken care of. I will get it smoke tested again before all is said and done. And I'll have the exhaust smoke tested as well.

I'm also thinking that the bad cylinder rings could now be adding to the air/fuel mixture problem. Is that possible?

[digger]

when i last had an AFM and was doing some diagnoisis i found this site helpful http://www.the944.com/afm.htm

[EyExR]

Doing electrical tests the Bentley says to move the sensor flap on the AFM and the resistance should fluctuate. But by what values???

As I move the flap resistance increases but then seems to decrease the farther I push it. Does this make any sense?