I have a 2001 GMC Jimmy that has 143,000 miles on it. I am currently experiencing hesitation and slipping either from take off or when I am on the highway going 70MPH, and around 2000-2400 RPMs. It feels like it slips and hesitates sometimes when taking off and moving between 1st and 2nd gear.

So far I have done the following:

Cleaned MAF sensor
Cleaned carburetor
Cleaned EGR valve and replaced gasket
Changed type of fuel (now using Mobil)
Used Cevron Techron Concentrate Plus fuel system cleaner (2 cycles)

The next thing I will be looking to do is to check the intake setup for any cracks and whatnot. I am not sure if it makes a difference, but a corner piece on the air filter cover is broken off, but not big enough for air to get through.

Plus, my fuel filter was last changed at the 108,000 mile mark.

Also, another thing that I noticed before, but went away since then, was that my exhaust smelled of rotten eggs, and the exhaust fumes has discoloration. From what I have researched, it may be due to a bad catalytic converter. I'll have to check it to see if there is a rattling noise.

Now, by the details that I have given, is there anything else that I should be looking for? I have done a lot of research on these forums, and have followed many steps, as shown with what I have done so far listed above.

Any help would be greatly appreciated!

 

Stale air freshener?

Get scanned for DTC codes. Rotten eggs is sulphur dioxide - fouled cat from too long in default max fuel delivery mode.

How many miles have you done with SES light on?

 

When my SES light was on before, I had 2 codes. One was P0101 (MAF), and I believe the second was P0446. For the P0446, I replaced the gas cap, because I had a old locking gas cap that I have had for 4 years, and it had a crack and was a bit broken.

Also, I have had issues trying to pump gas into my tank at times, where it always backs up and the gas doesn't want to flow naturally into the tank. This has been happening ever since I had my fuel pump replaced, so I am unsure if there was a kink or something. Not sure if this issue is related to the P0446.

Right now, I have no codes stored in the car, not just because I reset them after doing the mentioned jobs above, but because I had the battery disconnected while working on the EGR unit.

EDIT: Also, I forgot to mention that I have a K&N filter. I cleaned it and oiled it up. Made sure that there wasn't too much oil on it.

 

I was about to BINGO when you said K&N. Pull the MAF and clean the element wire CAREFULLY, like maybe with a model paintbrush. Remember, it's sensitive to the AIR MASS, so it's sensitive.

Open loop idle quality means nothing. It has to warm up before you know stuff.

 

lol, MAF has already been cleaned. And I made sure to be careful with the wires, lol.

Anything else?

 

Has it gone closed loop? FULLY warmed up? If so, and no SES light, then go basics: air, fuel, fire.

Air: Air filter clean?
Fuel: Static and Dynamic pressure tests. See youtube for FP test vids, see FORUM HERE for CORRECT procedure. You HAVE TO know these pressures to diagnose a car with NO SES light. It ain't hard NOPE.
Fire: Wires, plugs, timing, static timing first, then dynamic timing. Again, not hard, and NECESSARY if no codes.

Post questions. Plug and Pray replace-a-part Fully Automatic Assault Wallet Select-Fire don't NEVER work NOPE nOPe NEEOOOp. Nuh uh.

 

Everything is now taken care of. Turns out it was the fuel filter, which was plugged up big time. Put a new one on, and the truck drives like a dream.