Newbie here too.. Sorry for the long post...

I have a 2000 GMC Jimmy, 4.3 4WD, 135k

About 3 weeks ago, I noticed that I had no power on the throttle (like to pass somebody). Then after paying more attention to the vehicle, I realized that the motor had a light shake, more than normal. It would shake more vigorously when throttle was applied.

I am a college student and didn't have any time to work on her for about 2 weeks.

During the 2 weeks, she began to idle rougher.

In the process of doing an oil change, after filling her up with oil, went to start her, to (get a more accurate) check on the oil lvl and she didn't start. She turned over but wouldn't start.

I went back to the basics: Air, Spark and Fuel.
Fuel Pressure: 62psi
Abundant Air
Spark from Magnito to wires was there
Pulled codes: P300

So I thought it was the plugs, next day replaced plugs...
She didnt want to start, took many tries to get her started.
In trying she would stumble, shake, and backfire... when I finally got her started, she shook on idle - when throttle applied she shook worse...

over the next few days, starting her varied from starting right up to not starting at all. During this time, sometimes she would idle OK, and sometimes she would shake on idle... when given gas the intensity of the shaking varied, sometimes very rough at 2k RPM or sometimes smooth... when smooth at 2k she was rough at 4k, when rough at 2k she was extremely violent at 4k.

I have been searching for an answer for a couple days and cant find a solution.

Here is a list of what i have done:
New PCV valve
Replaced sections of vacuum lines
Cleaned EGR valve
Put heat and seafoam into gas tank

After ^ she wont start at all. When trying to start her; If i left go of the starter , when she would start to tremble , she would spin her self around for a few seconds, it was very rough and violent, never enough to get her over 200 RPM

 

when she'd stop, she end with a gentle backfire.
If I didn't let go of the starter she would just turn round and round.

Some background information:
About a year ago new plugs, cap, rotor, wires and fuel filter
About 3 months ago installed cold air intake

Finals are this week, and i want to go home relatively soon, so I need her fixed ASAP!

 

The fuel pressure. Did it ping to 62 and hold? or did it fall rapidly. Id look at fuel filter again. Just take it off blow in it. if its really hard to get air through it replace it. Unplug the egr and try to start it. Also get some maf cleaner and clean the maf sensor. Dont use brake cleaner.

 

P0300 is almost always caused by a fault in secondary ignition, (Spark plugs, distributor cap, rotor, plug wires, ignition coil). It can also be caused by low fuel pressure, but it looks like your pressure is acceptable, provided it doesn't leak down excessively. Sounds like it needs an AC Delco distributor cap & rotor. Don't waste your time or money on an aftermarket cap & rotor. Put a dab of silicone dielectric grease on each terminal, inside and out, of the cap.

 

P0300 is a random cylinder misfire. Check your firing order first, then plug gap and go from the plugs back to the cap and rotor. I believe the gap on the plugs should be 0.060 inch and the firing order on the 4.3 is 1-6-5-4-3-2. Its best to use AC ignition parts like captain hook suggested.

 

Thank you all for a speedy reply, new ideas are always appreciated,

Unfortunately, i am a dink and lost the needle in my fuel pressure gauge.... so I cant re-test her until i get another, I have AC delco cap and rotor with bocsh platinums (which I have in my 88 GMC s15, and she hasn't had any problems with them - that's why I got them for my 2000...), I will try cleaning the MAF and Ill inspect the fuel filter...

 

We're working on a 2000 1988 is totally different. Bosch plugs in the 2000 have been known to cause problems... it really should have AC Delco 41-993 plugs with a gap of .060"
Did you put dielectric grease on the terminals of the cap?
When were the plug wires last replaced?
Have you had the distributor out?
Have you checked camshaft retard?

 

Iv come to realize that I will no longer use anything other than AC Delco plugs, due to so many people saying that there are difficulties with anything other....

Yes, I put dielectric grease on the terminals of the cap.
The plug wires were replaced about a year ago.
I have not had the distributor out yet.
I also have not checked the camshaft retard.

Thank you for responding so quickly, Im sorry that I havent had the time to advance on this situation to give you better updates.

 

Don't buy a new fuel pressure gauge. Most parts stores in my area will loan you one. These things are frustrating at times, but when they are running good, it's great.

 

sorry its a been awhile - but here is an update:
Iv replaced the following:
Spider injector
MAP sensor
the upper and lower intake gaskets
valve cover gaskets

I also cleaned the MAF sensor...

I have attempted to re-install the distributor (using a Haynes manual) - did everything the book says and now she is backfiring through the intake and wont start at all...
Any ideas? please help