Hello everyone,
i have been browsing the forums here for days but I'm at a loss. Last Friday afternoon I was driving somewhere going up some big hills and my blazer started misfiring. Car is shaking pretty bad, no power, almost feels like it's gonna die at times. Eventually it came up with cylinder 6 misfire. Before this happened a few months ago I had replaced spark plugs, wires, rotor/cap, and fuel filter. Fuel pump is new, reads 80 psi from the pump when I isolate it for a leakdown. I was thinking it's probably the spider injector because I know they go bad. I didn't want to spend $300 on a new MPFI unit so I went to the wrecking yard and found one. Ordered new pintle caps and tested it out. All 6 look like they spray fine. I found the issue on my old spider, the poppet for cylinder 6 had a bunch of crap fouling it up. So I cleaned that one and the junkyard one up. My old unit looks like it sprays good as well. Tried my luck with both, same multiple misfire issue, seems to be cylinders 6 and 2. Tomorrow I'm going to do a compression test but when I pulled the spark plugs and put my thumb against the hole while cranking I can feel pretty good pressure. I have read other forums where the issue was a worn distributor gear or even a bad crankshaft positioning sensor. I am really at a loss guys, any help would be appreciated. Vehicle has 205k Miles, ran just fine before these issues. I just don't want to keep throwing money at it. I may even pop the valve covers to make sure the valves are working as they should.
Any advice is appreciated

 

I would also like to add some random info, so my old spider injector regulator passes the leak down test no problem. The mpfi unit regulator from the wrecking yard passes as well, but I bought 2 borg Warner fuel regulators from Oreilllys Abe both fail the leak down. The design is slightly different, silver in color. I thought that was very weird

 

No problem. Begin by posting the results of all four tests performed exactly as decribed in the the fuel pressure sticky at the top of the 2nd gen forum. Want very recent test values, not a pass/fail or a guess or old readings from some test in the past. Also please inform if you have the upgraded MPFI injector spider (do you have wires out to the end of the spider legs?) Next please inform if your scanner will read and display CMP retard. If not, get Car Gauge Pro for Android from Google Play and the BAFX Bluetooth OBD2 adapter as sold on Amazon. Total is about $30. We will go from there.

 

have you checked the ignition coil yet?

 

Hi guys, thank you for your replies and sorry for the late reply. Looks like I figured out the issue, bent exhaust valve. Now I need to figure out if anything else in the motor was damaged like a lifter or cam.

 

sorry to hear that Jlp06 any idea how that happened?

 

Brian,
i am not entirely sure to be honest with you. But it looks like the valve barely nicked the piston. The lifter looks fine, as far as I can tell the cam doesn't look damaged either. From reading online there is a TSB out reguarding the exhaust valves on these motors. Apparently they like to "hang up". A user suggested honing out the valve guide another 0.0005"-0.001" to give it that extra clearance. Good news is my cylinder head looks fine, not warped and the rest of the valves look fine. I need to pull the driver side head to look at it as well. I am not a mechanic by any means but I am a machinist and I can read and measure tolerances, I am considering pulling the motor and doing a rebuild. My blazer ran completely fine before this valve issue but when I was compression checking the motor I only got 30 in some of the cylinders. Which is very weird. So I'm debating if I should even try rebuilding my cylinder heads and throwing it back on or if it would be a waste of time. It's possibly the head gaskets could have been going bad and causing it to lose compression maybe? They looked pretty rough

 

Why not just swap the heads, and while your at it port and polish those bad boys. This is just me but if the lower end is fine why mess with it?

 

I am dealing with a similar issue and a wet compression test showed no change so I am assuming I have leaking head gasket or valve train issues so to be sure both are covered I ordered new gaskets bolts and freshly rebuilt heads and I'm only in it for a mere $340 is all. To me it was a no brainer to just buy the new heads that way I can break exhaust bolts without worry as well as know that once I have it apart I can go ahead and put it right back together. I also couldn't get my current heads rebuilt for what I paid for new heads ($239 shipped to my door) so that helped in my decision.

 

Actually I was considering that.
so far my heads look good, not warped at all. I'm gonna test the valve seats for leakage, i guess it really depends I kind of want to rebuild the whole motor. Has over 200k and I have a lot of oil leaks. Might be good for a refresh. But yeah I will definitely do some port work, unshroud the heads a bit