Hello, New to the forum & getting really discouraged. I love the Chevy * series & transfered to a sonoma 2 years ago, with a few issues previously but nothing big. WIth-in the past week I've had to have the heater core replaced, got it back from the shop, the next morning I got on the interstate & at 30 to 40 mph my engine is reving up but the truck wont go any faster, foot to the floor doing 35 (truck will do over 100mph when running correctly) CEL came on, it produced 3 codes 1 of which was for MAF, dont remember the others. Replaced the MAF & air filter, cleared codes, too for a test drive CEL came on again codes indicated MAF rechecked all connections made to correct it & reconnected the electrical connector to the sensor(must not have gotten it on all the way. reset codes, took it for another test drive & the CEL began to flash, still cant get over 35mph. New codes are P0102 MAF, P0101 MAF performance issue, P0300 misfire detected. Obviously I can do a full tune up on it, but do not want to spend any more $ until i know it will be fixed, does anyone here have any ideas as to what the real issue could be, is it really just lack of spark? or a bad replacement MAF? or could the shop have done something while replacing my heater core (full dash, cluster removal)? any help would be appreciated.

they also would have had to drain the coolant and possibly remove some things for clearance under the hood. i would look for some pinched wires or something unplugged from the maf to the computer.

im sure its not terminal just have to figure out what happend, that have the 4.3 or the 4cyl?

You might want to look at the possibility of a plugged exhaust system. If the exhaust system is plugged the pressure will cause the symptoms you describe. One way to verify this without a vacuum gauge would be to disconnect the catalytic converter and test drive the truck to see if the symptoms go away.

it has the 4.3, the shop has assured me they did not disconnect the computer, just moved it out of the way, but ive looked at all of the connectors i can find & they all feel & look correct, as far a pinched wires, all of the wiring has the plastic wire loom covering which all appears to be undisturbed (dusty) but i think i may start pulling the cover off to check.

one person mentioned the cat converter before but that i would also get a sulfur smell, the smell is not present which is the only reason i have not entertained this, is it possible to be plugged without the smell?

i dont think the cat would give you maf and misfire codes, it would be o2 codes

I have had many of the same symptoms on cars in the shop, and that was the issue.

Your misfire is the problem. Can you scan live data? Finding the correct p030x code will help. However, seeing work was done on the truck I would start by checking wires. Make sure they are plugged in. Test the resistance on the plug wires. Test the coils. Pull the plugs and inspect. A bad misfire will show up on the plug. Also check and make sure none of the plug wires are near or touching the O2 sensor wire. Look for a vacuum leak, that can also cause problems like this.

Well I ended up replacing the Cap, rotor & plugs, all were original (plugs had the factory paint on the ends) not bad for 127000 miles. This cleared the misfire code however it appears the cat is plugged 99% positive which explains the odd smell that I equated to electrical but is apparently what a cat smells like now. why do they think it needs to cost sooo much? I am told that taking the dual (inline) cats off would actually make the truck run worse, although i cant imagine how as it feels like its going to die & not restart one of these times, If i take the cats off how bad will it be, or can i do something like drilling some hole in the bottom of the front one to relieve the back pressure until i can affoud to replace? are there any tricks I am unaware of for this?

The best to do is take them out and replace them with a TEST pipe for a temp check to confirm if its the issue then if so replace immediatley do not drive with the test pipes on...You can replace it with a High flow cat for cheaper than a stock replacement

are we talking engine damage on the test pipe or not exactly legal as to the reason to not drive it that way?