Maybe this will help:

https://blazerforum.com/forum/2nd-ge...lazers-103424/

The VIdent 400 seems pretty powerful but I cannot confirm if it can command an EGR valve since my 2002 does not have to test it on. Thats a standalone unit. HP tuners is PC software.

George.

 

Drove the Blazer yesterday morning about six miles, ran great, no SES light. About two hours later started it up and rpm’s rolled to about 2k and stayed there an SES light stayed on, fought it for six miles back to the house, the usual bucking an chucking, delayed shift time from first to second, uncontrolled rpm swings. Code was the one for crankcase position sensor signal A loss. Any idea, no misfire codes, just the CPS one.

 

Tell me about these rpm swings, do they happen:

• While driving and the transmission is shifting up and down
• While driving in a stable gear and a steady throttle position
• In park at idle

Did you ever get the capability to graph the pre cat O2 sensors like this:




What is the history on the crank sensor (replacement, wiring, relearn)?


George

 

The rpm swings don’t happen all the time but when it does it pretty much during all three of the conditions you listed. That is a replacement crank sensor from 4 years ago when all this mess started. The wire connection is pitiful, wire covering is cracked and missing, plan on hitting the local pull a part to find a better connection plug. Will a relearn be required if I don’t actually remove the sensor? My present scanner can do graphs so I’ll get you that data, I’m going to order the Viadant 400 this week

 

This started before or after the new crank sensor?

I would like to see the O2 sensors graphed in park at idle and 2500. Then again when the truck runs like crap holding the speed as steady as possible. Same with all 4 fuel trims. The trick is to be in park or a steady speed and load. After rereading this story and thinking about this, I think that either:

A sensor, its voltage/ground/wiring goes wonky, or
Unmetered air thats unstable gets going, or
Fuel delivery goes haywire

I dont think that ignition would cause all this surging. stumbling and lack of power but not a 2000 increase in rpm. That said, we should get that crank sensor straightened out. If the signal is corrupted enough from wiring a relearn may help some but again probably not this whole mess.

After all the above we also need to try and catch any sensors that drop out when the poop hits the fan.


George

 

I’ve not been able to fool with the Blazer lately, wife finally had enough of me delaying a bathroom overhaul for two years so that’s what I’m doing now. I’ll catch the O2 data graph’s hopefully this weekend. I have wasted so much money an time on this thing that it’s become extremely personal to find the fix. I’m grateful to you for your helping me along this journey.

 

Hello All, have not touched the Blazer in months, last work was new timing chain and gears, CMP is now -1.65. Did notice the Crank Position Sensoe connection was trash, cracked wire covering and loose pins. Spliced in a new connector today and adjusted CPS distance to the relucter wheel. Cranked right up and had perfect idle. Test drive was great, smooth power, perfect transmission shifts….. but at about 10 minutes I get the SES light flashing for about 10 seconds 🤬😩😡, SES flashed twice more before I got home. Scanner showed the good old P0300.

 

You... have done a LOT fighting this old truck! I don't see that you've changed the spark plugs though, only pulled #5 at one point. I also don't see any results on checking the plug wires either (they can be finicky unless you use the AC Delco's as well). At a minimum, I think you're past due to read the plugs themselves to see if they can provide any insight on rich/lean, possibly damaged ceramics or bad gap at this point. If you haven't pulled the rotor itself off and looked at the underside, I'd do that as well. I had a rotor look perfect on top but had a hole almost blown through the bottom of it cause me no end of problems. As far as the replacement distributor goes, there are divided camps on sticking with an AC Delco or replacing with an aluminum bottomed one. I'll be replacing mine with one of the higher quality (I hope at least) aluminum ones since I have a cam retard issue with my original one. I wouldn't rule out the coil itself either since the problem seems to get worse at higher rpms, especially if it's still the original coil (it will be riveted in and not bolted) and it would have gotten bounced around when you replaced the fuel injection spider previously. No matter what though, I'd give everything a good hard look one more time before going to the parts store (or preferably rockauto for anything AC Delco for the price alone) and read the plugs and rotor.

 

Finally received the ilink 400 with GM data. Guessing I had missed this during all the past scans but the IAT was stuck at 42 degrees but outside temp was in the 80s. Quick R2 of this sensor and test drive around town had my fingers crossed, good idle, good running but my street has a steep hill to climb, got the SES light at about 30 mph 😡🤬🤬. I grab some O2 data and noticed Bank 1 sensor was different from Bank 2 sensor voltage readings.

 

Also when cranking this thing it fires off violently, meaning it starts immediately in like 2/3 seconds.