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Hey Guys,

I have 1994 Trans Am bone stock. I've been trying to diagnose why I am not passing smog, so I figured I would do a compression test to see the state of the engine and making sure everything is ok. I managed to get 7 cylinders tested (Cylinder 4 has 135 PSI which makes me a little nervous) but I cannot for the life of me get to Cylinder 2. Is there an easy way to do so? I managed to get the connector right on top of the spark plug hole, but there is no room to twist it on. The connector is at a 90 degree angle facing up and the friction of it hitting the car is making it almost impossible to turn at all. Am I missing something? Or do I need to remove something? Any help would be appreciated
 

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What were the pressures of the other 6 cylinders you tested? Sorry, can't help you with cyl # 2.

After posting the psi results for other cylinders, you next tesxt should be a code scan and a running sensor scan with an obd 1 scanner.

The code test is important because there are codes that don't light the check engine light. These include DTC 16, 36- both opti codes, & DTC 41 , 42- both icm codes. There are other codes that don't light the cel.

A running sensor scan is important as it can show sensors not performing at normal readings. This can help point you in the right direction for troubleshooting.

Next, you should own a PC based oscilloscope, if your going to live with a car that has an optispark distributor. The scope is omly 100% way of testing the low & high resolution 5 volt square waves that opti sends out. Also good for testing 50 hertz fuel enable signal.

You can buy a pc based scope on ebay, amazon, etc for around $70. I use the Hantek 6022. It works well, once you learn how to use it.

Vacuum & exhaust leaks before the cat, are a major source of running problems. To help you, go to following link and download the 94 service manual. www.mediafire.com/?40mfgeoe4ctti
 

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I figured it out. I ended up taking a drill and opening the mouth all the way and managed to fit the compressor tip of the hose into it and lock it down and lower the hose down and into place and use the drill to slowly turn the hose while guiding with my hand into spark plug threads. You might be able to do it alone, but I had my dad help.

Cylinder 1 150 PSI
Cylinder 2 140 PSI
Cylinder 3 145 PSI
Cylinder 4 150 PSI
Cylinder 5 152 PSI
Cylinder 6 135 PSI
Cylinder 7 145 PSI
Cylinder 8 149 PSI

I've ran a scan and no codes. I have the 94/95 program and didn't see anything troubling. At least I don't think,.I uploaded a brief test file. This was after the engine was warm.

I had a cheap chinese knock off optispark replaced about 4 years ago. Thing is practically new since I have been trying to get trans am to pass smog for quite some time and hardly use it. Had an epiphany that maybe the OEM original may still be good and feared the newer opti was inferior/broken. Replaced the opti with OEM and still runs the same. Possible but doubt there is an issue with optispark, but I suppose I can check.

No vacuum leaks that I can see. Exhuast leak is the next thing on the docket to test out
 

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Since lowest to highest compression only varies by about 11%, there's nothing to worry about there.

Vacuum leaks can be hard to find. Best way to find them is with a smoke machine. But starting fluid works good if you follow safety procedures and have fire extinguisher at hand. You spray starting fluid around all vacuum sources, while engine is running.

If engine speeds up, at that place you have a vacuum leak. rubber intake boot at throttle body is a common place for leaks.
 

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Hey Guys,

I have 1994 Trans Am bone stock. I've been trying to diagnose why I am not passing smog, so I figured I would do a compression test to see the state of the engine and making sure everything is ok. I managed to get 7 cylinders tested (Cylinder 4 has 135 PSI which makes me a little nervous) but I cannot for the life of me get to Cylinder 2. Is there an easy way to do so? I managed to get the connector right on top of the spark plug hole, but there is no room to twist it on. The connector is at a 90 degree angle facing up and the friction of it hitting the car is making it almost impossible to turn at all. Am I missing something? Or do I need to remove something? Any help would be appreciated
Try using an oscilloscope measuring the current draw on the starter motor will show you a weak cylinder. 135 is pretty little low for a 10.2 to 1 compression motor.
 
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