Ok, long story….. Sorry for the rant but want to make sure I have everything that has been done included……… I am writing from memory so some specifics are not in my limited memory capacity …….

2001 Trail Blazer (mid-year name change, same as Blazer but changes were cosmetic), 4.3L Vortec “W”, 4X4, 230,000 miles and have owned since 2002, <10,000 miles. Well maintained.

Trouble started several months ago, more than likely many more (wife’s truck). She came home complaining that acceleration was poor and gas mileage was decreased. “How long has it been this way?” “Quite some time now.” “Why haven’t you said anything before this?” “Well, …….”. “Never mind!”

I put the OBD II reader on it, came back as O2 sensor (Pre CAT), that explains both poor gas mileage and lack of power (too much fuel being injected). At that point I figured just change both, no big deal, off to NAPA. Returned, replaced same and cleared the codes. Started truck, went for a ride, nothing had changed. OBD II reader had pending codes, multiple misfires but O2 sensor codes didn’t return.

After careful (or not) thought, it had been quite some time since the plugs, wires, cap and rotor had been changed. Off to the auto parts store, returned with same. Installed them, cleared the codes,went for a test drive and it operated the same. More thought, Ding, Ding, Ding, must be fuel related. Out comes the pressure gauge, key on, engine off, 60 PSI, key off, bled down rather quickly…….. Off to the internet……..

Spider assembly or Fuel Pressure regulator….. Simple, if it was the regulator then it made perfect sense to change the spider also (based on the known poppet failures), if I am in there why not. Ordered the MPFI replacement unit (found the GM Bulletin detailing their hidden knowledge of the poor design of the poppet units), GM Parts Direct, good price and free shipping. Assembly arrived; tools collected and place on a table with plenty of room for removed parts (Sharpie & plastic bags), beer in the cooler, nice music in the background……. In I go (the failure was 2 of the hoses feeding the poppets), whole process took about 4 hours, not bad considering I had limited instructions (I carefully marked all removed parts, bolts, sensors, etc., etc. , etc., …… so the reassembly would go without a hitch (in the past, if I don’t have the time to reassemble immediately it is best to have everything marked, see above, bad \ limited memory, I wasn’t sure I could get it all done in the same day).

All back together, cleared codes and started it up, appeared to run much better at idle, went to back out the driveway and it stalled. Bummer, attempted restart to no avail. Opened another beer to ponder what could be going on ?????? Seemed to be a fuel issue, back to the garage, fuel pressure gauge, key on, 0 PSI………

We have had an issue with the fuel gauge for several years, it worked, it didn’t, internet said it is \ was related to the unit in the tank (sender), fuel pump failure is also a known issue…… So, no big deal, on the net, ordered it. It arrived within a couple of days, at that point I asked wifey how much gas was in the truck……. “I really don’t remember.” Wasn’t a good answer as far as I was concerned, being that the tank had to be removed. Key on, gauge says empty, but it would also say empty when it was full, so no help there.

Jack it up, 4 jack stands elevated on top of 2 wood blocks each (8” additional height) to ensure enough room. I was quite surprised and pleased that the straps and their brackets were rust free and in great shape. I used the floor jack with a piece of plywood to support the tank once the brackets were removed. Hoses were a bitch but eventually got the tank removed, the PO issue, pump fine…… tank empty……. No fuel, can’t imagine the lack of pressure, last I saw wifey she was heading for the lower 40 at a rapid pace….. No big deal, tank out anyway so the gauge would be working again, some good news. Pump installed, tank re-installed, fuel filter replaced, off to 7/11 for a five gallon can of gas, premium. Gas in the tank along with the recommended amount of Seafoam additive. Fuel pressure @ 60+ LBS and no bleed back. Cleared the codes, truck starts, idles fine, but the same issue, multiple misfire. Back to the net……….

Next replacement part, new distributor, existing one seemed to have excessive play in the rotor, thinking it was the bushing or the gear. No big deal, ordered one with an aluminum body, came with cap, rotor & wires. Arrived in 2 days from NJ, set the engine on top dead center via harmonic balancer & on compression stroke (so I thought) and installed same using marks on body of distributor (I now have a spare set of wires). Cleared codes, started engine, runs very rough so I shut it down immediately. Pulled cap off distributor, lined it up on top dead center via balancer, not even close. Reinstall it using the mark on the housing, put cap back on and installed wires. Cleared codes, started it and it ran even rougher. Shut it down, more thought.

There was a strong smell of gasoline under the hood, more thought, pressure gauge reattached, 60+ Lbs with key on, bled down rapidly with key off. At this point my thoughts turned to the spider. Tools out, plenum off, there had been a minor fire within the intake plenum and one of the injector hoses had a hole created by the fire, hence the fuel bleed down & odor. Off to the net, ordered a replacement injector and did some additional research.

Came across a piece about the harmonic balancer rubber drying out and allowing the outer piece to slip, therefore TDC mark no longer accurate. After more reading and research I determined the best way to find true top dead center without removing timing chain cover was to use a piston stop on the number one cylinder. Using a compression gauge I found the compression stroke (for sure this time), inserted the stop and located the true TDC. The mark on the balancer was 90°off; therefore distributor was also 90° off, out comes the distributor, reinstalled in the correct position using the mark on the housing. The injector arrived in a couple of days, installed it and put everything back together. Cleared codes, checked fuel pressure, all is good.

Engine ran well, a little misfire but really not that bad. I contacted a friend of mine whose son – in – law owns a high end used car dealership (he works there a couple of days a week for beer money, he is retired) and he hooked me up with their best mechanic. I had read that the PCM may need to be flashed due to the new distributor and it would require a much better scaner then I have.

I had wifey take it to the dealership (I was out of town on business), the mechanic looked at it while it was running and concurred there were misfires. He connected his scanner and just picked up the misfires, nothing else. While he was under the hood he came in contact with the coil wire and shocked the crap out of himself. He shut the engine down, rerouted the coil wire, started the engine, misfires gone. She operated the truck for several weeks, ran even better then when it was new.

She came home one day and reported that she was unable to get the truck to accelerate beyond 20 MPH or so. I took it for a little drive within the neighborhood and confirmed the truck would not accelerate beyond that. Back to the driveway and the scanner. Multiple misfires, no other codes. Engine ran \ runs smoothly from idle to around 1500 RPMs then starts to break down, no power and will stall at times. Thoughts returned to a fuel issue, gauge attached, and placed on windshield where it could be read from within, accelerated engine and fuel pressure appears to increase when accelerating, so that seems fine.

At that point I called the mechanic and he asked that I bring it over so he could scan it. Not possible, we live in a hilly area and I was afraid it would get stuck at the bottom of the hill on the way there. He asked if my scanner had a live data feed and asked me to let him know what the MAF sensor was reading, it was .02. He said that was way low and asked if I had cleaned it. I told him no but would do that and get back to him. Cleaned it and the reading remained the same. I then replaced the MAF Sensor, reading remained the same.

I decided the best course was to use the record feature on the live data readings; I recorded all 40 sets, accelerating at different levels throughout the recordings. I printed out the recordings and delivered them to the mechanic. In looking over the recordings he said that the only thing he was able to gain out of them was the best possible explanation was the timing chain either slipped or there was a broken tooth but that he couldn’t be sure unless I was able to get it to him so he could scan it.

What’s a couple of more parts, I figured with 200,000+ miles might as well do that too. I ordered a performance chain, performance cam & crank sprockets, new tensioner, new cover, water pump gaskets and a new harmonic balancer. I opened it up and inspected it, no broken teeth, I manually turned the engine to top dead center via marks on cam & crank sprockets and all seemed ok except for some slack in the chain. I found it strange that there was no tensioner though, took a trip to the dealer and found that it didn’t require one. Needless to say, I have installed all of the replacement parts and reassembled it.

I started it up and the same condition exists, will accelerate perfectly from idle to 1500 RPMs but not beyond. I am stumped! Any and all suggestions \ help would be greatly appreciated.

 

Did the mechanic check the cam retard? It is a requirement after removing/replacing the distributor. I would also check for a restricted exhaust.

Any codes?

 

I was thinking clogged cat also

 

Thanks for your help....


First, the only code is P0300. Cam retard, is that the spark advance? That reading is between 14.5 + 32.0 .


What is troubling is it ran perfect for several weeks then this problem appeared.


The scanner I have has the ability to read live data and also record. I am going to post the data below. I warmed it up prior to recording, there are 46 different data recordings. For the first 10 or so I left it at idle and then gradually accelerated the engine for the remaining, you will see the increase in RPMs.


I will be leaving for work, a 3 hour drive and will not be returning until Saturday night. I will have access via the net to answer any questions but will not be able to perform any tests or be around to beat it with a hammer......


Scanner Recordings, I attempted to copy and paste, no go, to much data. I have attached a PDF file with the data:




Thanks again for your assistance:


Kevin

 

Greetings all......


After reading some other threads I figured it best to check the output of the fuel pump prior to the regulator, although it is an aftermarket pump the pressure is 100 + Lbs, so all is good there.......


Has anybody had a chance to look at the OBD II recordings?


Thanks again for the assistance.....


Kevin

 

this might be something to look at.....a collapsed cat and pre cat if you have a new york or cali blazer.......i had one that collapsed in both and gave me performance issues, shifting issues and bad mileage.... easy way to check is to remove the pre cat o2 sensor and take it for a ride and look for improvement and or hit the cat a few times and listen for a rattle..... a temp sensor would work too looking for hot spots on the cat

 

If the coil spark plug wire could shock him, the wires need to be replaced, not re-routed. (BTW, the coil wire should have corrugated tubing over it to protect it) You may not believe the ignition system is the culprit, but spend the money to change every thing with AC Delco parts as a troubleshooting tool. Plugs, wires, cap, and rotor.




You may find that some previous person got lazy and did not change one or two of the difficult to get to spark plugs.
Also double check the spark plug wires to the numbers on the cap.

 

Thanks Again to all for your assistance.......


This afternoon I did a few things to troubleshoot my issues based on your replies, 1st, removed coil wire and installed new tubing around it, securing both ends with cable ties. No change.


Next, removed both Pre-Cat O2 sensors, wrapped aluminum foil loosely around openings, started it up. It was loud but accelerated as it should, diagnosis....... bad cat.


I have ordered the assembly from RockAuto and it should arrive just in time for Thanksgiving, I figure Turkey on the grill (Weber Grill , indirect method, I have done it that way for more then forty years (if you have never tasted it or tried it that way, go for it, you will never go back to doing it any other way......)) and then under the TrailBlazer. I figure its only 8 nuts (nine including the guy underneath), couldn't take more then a couple of hours........


I will keep you all posted as to my progress........


Happy Turkey Day........


Thanks again for all that have assisted........


Kevin

 

Greeting all, thanks again for all the assistance.......

Long story (boy has it been), problem was the CAT, clogged and in pieces. The assembly, both down pipes and the CAT assembly arrived on Tuesday.

I started by removing \ snapping off the bolts \ studs on the muffler flange and cutting the pipe just in front of the old CAT to remove that part of the assembly. I attempted, for more then 3 hours to get the studs out of the muffler flange to no avail. I had sprayed them with PB Blaster on multiple occasions, no help there. I attempted a punch & hammer, a pneumatic hammer and a torch to heat the flange but there was nothing I could do to get them out. I ended up cutting the ears off both sides of the muffler flange using a Dremel Cutting Disk, took some time but was successful (I left enough of the holes to ensure it would be secure).

Next was a shot and a beer to facilitate my thinking, what came upon me was the possibility that I may break off the studs in the exhaust manifolds (not good, I assumed I would need to remove the manifolds in order to replace the studs). Both down pipes and the pipe between the resonator (if that is what it is) and the old CAT were in good shape so I elected to just use the replacement CAT and make the connection.

Off to the parts store, I found a piece of pipe sized correctly for the job, inserted same, two clamps, two flange bolts & the gasket. I started it up, burned the CAT in, let it cool down. Another beer and then off for the test drive. The Vortec is back, although it now has quite a few new parts it runs quite well.

If there is anyone interested, I have the down pipe \ resonator assembly available (has gaskets for the exhaust manifolds) for sale, will give a good price as I am sure RockAuto will not want it back, send me a PM and I will come up with a good price (located in MD).

Thanks again to all that assisted………..

Kevin

 

Glad you got it all figured out