Hi everyone, I recently bought a 94 Camaro 3.4 L auto and I have been having issues with power. When I bought the car it did not run and it was initially due to a dead battery. I charged the battery and had it load tested and then also had the altenator tested just to be safe. Initilally the car would not idle due to vacuum leaks, but I since then have fixed the major one which was in the map/fuel pressure sensor hoses, so it now idles around 1K rpm and responds extremely well to throttle response all the way up to the redline, however when I put the car in gear,, a small amount of shudder is seen in reverse, and when I put it in drive/2/1 I get a ton of shaking and the car will not even move under its own power unless its in 1. I limped this turd home about 5 miles home from where I live and It eventually would get up to speeds that allowed me to stay in drive. I changed plugs and wires just to see if that was the problem.

Could bad gas cause this? the car has sat up since may/june. I'm kind of lost for a direction. Should I be looking to check compression/leakdown or fuel pressure/clogged fuel filter next?

I'm not getting any white smoke in the exhaust after warmup so Im not sure it has a head gasket issue.

Thanks,

Bret

 

change fuel filter, dump contents of filter into clear container, dump from the tank side so to see what has been collected. could be plugged or have water in it. also check fuel pressure. fuel pump could be failing.

 

Ok so I changed the fuel filter. It had some black junk in it but it did not have a ton of restriction when I blew through it. I decided to go ahead and compression test the engine and all cylinders read between 145-150 when allowed to rotate 1-2 seconds so I'm even less likely to believe head gasket as no water has collected in the oil. I had a friend help me while I listened to the engine and under load I can hear a loud vacuum type leak sound that was not present while in idle. The sound doesn't seem to be coming from any of the places where a vacuum line is present, so I'm not sure what to think about it. What fuel pressure should I be looking for and is there a shrader valve somewhere on the fuel rail that I can use to test?


Thanks,

Bret

 

Just some random thoughts.

With a head gasket you would have had one clean plug with maybe a tint of green or brown depending on the coolant you have.

There are PDF shop manuals in the Manual folder at the bottom of the main page. Also I am sure a "Fuel pressure for XXX" in a google search would yield you answer on fuel pressure.

Any codes? Even if the light is not on you may want check for codes to see if you have any pending or any PCM codes. I don't know the 3.4 are they MAF or speed density? If it has a MAF sensor try tapping it.

Assuming you do not have a sensor/injector/ignition issue.

Fuel pressure
1. Fuel pressure test
Timing chain stretched
2. vacuum reading under load
Plugged Cat
3. Exhaust back pressure test.

To check your ignition you can buy a spark tester for cheap and check each plug circuit one at a time. If you have access to a infrared thermometer you can check the temp of the exhaust manifolds right at the exhaust valve. If a cylinder is missing it will be cooler then the rest. If some are hotter they could be showing vacuum leak or bad injector

Non-Contact Infrared Thermometer With Laser Targeting

90° Inline Ignition Spark Checker

There are still a lot of other things that can be going one.

 

yes there is a shrader valve to test fuel pressure. follow your fuel lines and you will find. here is link to factory service/shop manual. click link with your year or closest year. there is one for 94. https://www.mediafire.com/?40mfgeoe4ctti

 

Alright so I rented a fuel pressure Guage from the auto parts store and here's what I found. 39psi with car off, 36 at idle, 42 with regulator hose removed and a constant 40 while at Wot. From what I can tell these are all within spec. I just dug out an inline spark tester and all 6 cylinders are getting spark so I'm guessing the coil packs are ok.(correct me if I'm wrong lol) I read that you could test if the cat is plugged by putting the car in park and then neutral whike in idle and if there is no change in rpm I should be fine? I would drive to the auto parts store and get the codes read( no loght on dash)but it's quite a ways away and I'm not pushing this turd through traffic with no throttle response. When i drove the car home it was midnight so no one was around.Thanks for the help so far guys.

 

I see no logic in that test what so ever. The ONLY difference between Neutral and Park is that the parking paw locks the drive shaft in place so the car will not roll freely. Everything else about the transmission is the same. There is NOTHING that should ever cause a change in the way the engine runs switch from park to neutral except maybe you shift linkage pinching a vacuum hose or some odd event like that.

The ONLY way to test for a plugged cat is a back pressure test. On a vacuum gage a plugged cat can look like a jump timing chain so I normally do back pressure first then check vacuum. Plugged Cat is also a lot more common then timing issue.

 

I thought the whole notion was insane lol. I just had the ignition control module checked out just to make sure it wasn't somehow cutting out under load. I'll get on the back pressure test and see what happens.

Bret

 

Ok so I tested the backpressure and there were close to 10 pounds so I dropped the cat and found that the element in the cat was crunched up and had stuffed itself to the back of the cat. Just to test to see if the issue was fixed I hung up the exhaust and took it for a spin . There definitely is an improvement but it still 0-60 in 30 or more seconds. It still acts like the nissan I used to have and the timing was way off on it. Anything else I can check? I figure vacuum will be next on the list


Bret

 

check plugs and 02 sensors for fouling. if they is all black, replace.