windydog

I thought i would create a new thread to document my diagnostic of the 993.

1) 996 brought over the PWIS to see whats going on. When we tried to data log, it keep saying "start engine." The car is an early model 993 with OBD1.
I always thought that OBD1 didn't have this feature, but I maybe wrong. I know it works on OBD2 cars.

2) After much frustration, and constant low vacuum readings I pulled off the supercharger and said "get running in stock configuration" and go back and tackle supercharger.
I started the car this morning with the highest hopes of 11 in of hg. I got the exact same vacuum condition. My heart dropped and just could do nothing but feel defeated....

So, i know we go back to basics.

* I was thinking that my ECU might have issues. I originally thought that i had DME relay issues and I jumped it using a paper jumper harness. Shortly after, the car went dead. But somehow it started up again. I am wondering if i blew my ECU at that point. From what others said, most likely not.

* I was reading that the ECU has little to do with the vacuum, but if i am not firing then i got a problem.

* Could bad coils cause all this, which would equate to bad spark?

* I was thinking i probably still have a vacuum leak somewhere??

This morning i realized that the supercharger is not the issue, so the plan is to reinstall once i figure this problem out.

I know that I have a bad cylinder head temp sensor, code 1114. I used a 300 ohm resistor to fool the car its warm.
I am checking the wiring harness to see if i have any issues.

I am stumped, so any advice is greatly appreciated.

wallra

to start with make sure your running on all 12 plugs. to check this start the car and then disconnect 1 ignition control module and see If it will run the do the same with the other. your distributor belt is ok right. low vacuum could be from not running on all cylinders or maybe jumped cam timing. remember an engine is a big air pump.

Steve Weiner-Rennsport Systems

JMHO,.....

You need a systematic approach to troubleshooting that prioritizes your symptoms so you can concentrate your efforts where it yields constructive results.

Ignition & fueling issues do not affect low vacuum: cylinder pressure and camshaft timing have the greatest impact.

The VERY first thing to do is a leakdown test since low compression (for any reason) directly affects vacuum. These engines do not 'jump time' without a lot of mechanical racket and its something you WILL notice.

Follow that with an intake system smoke test once the supercharger is reinstalled. Vacuum leaks of any size will cause you major grief. This means a VERY careful & detailed examination of every component in the intake.

Please note that I've only addressed your complaint about low vacuum. I didn't discuss running problems which is a different subject altogether.

windydog

Thats a good point.

Right now, I verified that the chip/GIAC chip was not the culprit.

* I did check the car F/I by disconnecting the the connectors to the F/I.
Passenger side: I noticed a huge difference
Drivers side: I noticed almost not change. This leads me to believe that maybe I am getting incomplete spark.

I am going to try your advice wallra.

Steve,
I am going to do a compression check as well, if the above turns out to be fine. If the compression check turns out good, then i will do the leakdown.

More to come.

windydog

Results:
Performed compression check on the passenger side, which I suspected was good. I got 180 psi and stopped. This confirmed that my process for checking was good.
Performed compression check on driver side and got 0 psi on 1, 2. I stopped because I will assume i will get 0 on 3.

The plugs seem wet, which means that they are getting fuel on the drivers. The passenger side is getting black carbon, which i would expect.

Seems like i have bigger problems then supercharger not functioning.

WD

Steve Weiner-Rennsport Systems

Leakdown testing will allow you to pinpoint the source of the problem, something that compression tests do not do.

windydog

I will be performing a leakdown test next week when i have time.

windydog

One thing to note:

After I would let the car cool down, i would smell burnt off oil. I would even see it coming from the heater box into the engine bay. I disconnected the heater hose for the time being. You could see smoke coming out of the opening which the heater tube attaches to.

I also looked under the car and there is lots of crap near the oil return tubes.

I am still planning to do the leakdown test. I am going to buy the equipment tonight. Funny 70 to buy the equipement, 200 to perform the test.

I am hoping its the oil return tubes, as they have already been replaced, they are the collapsible types.

Again, more to come...

Jack Esposito

What should the normal vacuum reading be for a 993 at idle?

windydog

11 in of hg

windydog

While waiting for my leakdown kit to arrive i checked the compression on the Driver SIde bank.

1: 0
2: 0
3: 180

The leakdown should reveal more. I am hoping its something simple.

nine9six

Consider this... at zero pressure on cylinders 1 & 2, you might want to purchase an endoscope on eBay for about 12 bucks and check to see that you have not holed a piston, prior to the more labor-intensive leak down test.

Additionally, since the car is running like it's out of time, check all of your plug wires for proper placement and seating.
Also check the distributor belt is still intact, and not broken.

nine9six

Duplicate post

wallra

leak down test is going to tell you where the leak is. hopefully it's just a tight valve. If you compression gauge has a hose the comes off you could hook it up to a compressor and here the leak. I went to the start of your post to see If you did any thing to the engine before the charger install. just for the hell of it are all the spark plugs tight upper and lower. I forgot you don't have adjustable valves. but It still could be a lifter holding the valve open.

nine9six

wallra,
All hydraulic lifters were replaced, so you may have something there.