I am stumped on this one. I hope somebody can help.

1995 Monte Carlo Z34 3.4L DOHC V6

On Saturday I stopped for gas at Shell and filled the tank with 89 octane. Got about 3 miles up the road and the sound of the engine began to change. It got really deep and loud, sounded like the exhaust loosed up (but it didn't), a mile further up the road the car began losing power, felt like it was being held back. I was cruising/struggling along at about 60MPH, which took about 65% throttle to achieve. I thought i got bad gas so I ran it out, and replaced it with 93 octane sunoco, a can of octane boost, and a can of fuel injector cleaner. The car still has no power. Bogs if you give it any gas from a dead stop, and continues to bog and struggle all the way up to 4000RPM. Then around 4000RPM at WOT it feels like its beginning to struggle less and it picks up some speed. At 5000k at WOT it feels like it did before the problem began, it has power, sounds healthy.... then it shifts, bogs like crazy, and struggles all through the next gear until 4000RPM.

I did a vacuum test to check the cat, vacuum is good at idle and excellent at 2500RPM.

I unplugged the MAF an TPS, no change

I used my GM Spark Plug tool to check spark (coil packs). Spark is bright blue, looks healthy.

Check engine light is on, but I never bought the ridiculously expensive scan tool for the vehicle so I cannot check it (OBD 1.5).

Gas was removed and replaced with 93 octane Sunoco

Wires and plugs have 8K on them....

What the heck would cause this?

Dan

You need to have that code pulled. It'll tell you exactly what the issue is, and it could be something as simple as a speed sensor or something.

I know,... this is crazy though.. I ruled out alot of stuff and I am not sure what the heck is wrong. I may have to pull the trigger on that scan tool. I just hate to buy something I know I am never going to use.


Just did a fuel pressure test, and its within spec

DG

Quote:


Just so you're aware, places like Autozone rent hose scanners for free. You do have to put down the deposit which is considerable, but you get all that back when you return the tool.

Trust me, for something you may only use once or twice it's easier to rent it and return it.

You can check ODB1.5 as ODBI with a different pin out.

I wish I had that pin out.

I have the "super rare" two pin obd1 port. It takes an extra special scan tool.

Went to autozone, advance auto, midas, firestone, sears, nobody has this scan tool.

I have been doing alot of reading online...

These are the things I don't think it could be

Fuel Pump or Filter (the fuel pressure was good)
MAF, TPS, EGR, Coolant Temp Sensor (didn't act any different when unpluged)
O2 sensor (still runs like crap in open loop, and 02 sensors don't work until closed loop)
Spark Plugs and Wires (look good and are new)
Clogged Cat (I have really good vacuum)
Bad Gas (Replaced the gas new gas)


These are the items I feel are of concern....

1. I am thinking it could be the Knock Sensor. Can these cause this type of disturbance at a low rpm, yet smooth out issues at a high rpm?

2. Injectors leaking when the vehicle is running?

3. Crank position sensor... just because I am not sure how it works or what it does, and what the symptoms are....

Anybody care to clarify?

Dan

Yes, please don't bug this guy about shorting pins or plugging an OBD2 scantool into it. It's a bastard-child GM obd2 computer with an obd1 connector. Probably the only one that could scan the code is a GM dealer and it'd probably take them a few tries to figure it out.

just a thought but aren't the DOHC's driven by a belt? I would check that out sounds like a timing thing to me