My Jimmy has a relay on the evaporator box under the hood, on the side towards the fender. My '72 has it under the glove box. I have no idea where a '73 would possibly have it, but @kennyw probably would know.
CK5
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My 73 blazer has the relay on the evap box as well
I’m of no real help but I did put one from rock auto in my k5 without any thought, and it broke the squirrel cage. That truck did have ac though so maybe as mentioned above, that’s what Nuked it.
The PF4 has started doing the erratic TPS thing again. It's not as regular as it was before, like maybe once a week. When it does it, it's always starting the truck after it has been parked all day at work. Hasn't done it in the morning. That's the only common trait I've noticed so far. It jumps up before I even touch the throttle. What I end up doing to fix it is turn the truck off and wait for the ECU to click off and restart. Usually have to do that 2 or 3 times to get the TPS to hold at 0. It will drop down a couple percent every time I restart.
For now I'll just live with it. Doesn't affect drivability other than making the idle annoyingly high.
And the idle isn't high because the throttle is physically open, but because the IAC will park at a high value so when you come to a stop it might be open as much as 50%. Since the TPS is reading over 2%, the IAC stays parked at that high value. As I've mentioned before when this happened, I wish the PF4 was setup to park the IAC at 20% like the Holley stuff I've run. The PF4 seems to park the IAC at whatever position it was in before the TPS goes over 2%. So if the engine is cold, it might be open quite a bit when it parks.
For now I'll just live with it. Doesn't affect drivability other than making the idle annoyingly high.
And the idle isn't high because the throttle is physically open, but because the IAC will park at a high value so when you come to a stop it might be open as much as 50%. Since the TPS is reading over 2%, the IAC stays parked at that high value. As I've mentioned before when this happened, I wish the PF4 was setup to park the IAC at 20% like the Holley stuff I've run. The PF4 seems to park the IAC at whatever position it was in before the TPS goes over 2%. So if the engine is cold, it might be open quite a bit when it parks.
Ugh, the PF4 is giving me fits again; not TPS related. I'm wondering if the O2 sensor is failing. I did a visual inspection looking for anything like a burnt plug wire or the like, but didn't find anything amiss. No detectable exhaust leaks. I have all green lights on the diagnostic screen.
These are screen recordings.
View attachment Saturday screen recording.mp4
View attachment Monday screen recording.mp4
These are screen recordings.
View attachment Saturday screen recording.mp4
View attachment Monday screen recording.mp4
So the TPS issue was never solved?
Are you running a 43 or 58 psi fuel map? Your pressure seems to be in between those settings. Not that I would expect such erratic AFR and fuel trim numbers from that fuel pressure.
Are you sitting in park applying throttle?
I assume that the engine is stumbling, but a misfire should show more oxygen and add more fuel, correct? It's going rich and trying to pull fuel.
Are you running a 43 or 58 psi fuel map? Your pressure seems to be in between those settings. Not that I would expect such erratic AFR and fuel trim numbers from that fuel pressure.
Are you sitting in park applying throttle?
I assume that the engine is stumbling, but a misfire should show more oxygen and add more fuel, correct? It's going rich and trying to pull fuel.
I'm guessing its 58psi, should pull down to 50 or so under vacuum and increase as throttle opens
the massive fuel cut makes me wonder about the spark quality, unless the timing moved and it doesn't see that
O2 is always possible.
I should have been clear, those videos were taken while driving.
@Bent77 is correct, 58psi. I was thinking about the distributor moving also.
The TPS was acting normal, reading 0 at idle. It's still a mystery once a week occurrence that I've yet to link to a common trigger point other than it's always right after startup (before even putting the transmission in gear) for the commute home. I just wanted to be clear it wasn't a compounding issue to what I have now.
I started to write a long rambling post, but let me sit and organize my observations better so it's easier to follow. I'll post more later.
@Bent77 is correct, 58psi. I was thinking about the distributor moving also.
The TPS was acting normal, reading 0 at idle. It's still a mystery once a week occurrence that I've yet to link to a common trigger point other than it's always right after startup (before even putting the transmission in gear) for the commute home. I just wanted to be clear it wasn't a compounding issue to what I have now.
I started to write a long rambling post, but let me sit and organize my observations better so it's easier to follow. I'll post more later.
Exhaust leak near the O2 sensor?
Not yet but I will.
That's possible the sensor is near the collector flange. I can't hear one, but that's obviously anecdotal.
Here's my attempt to better collect my thoughts.
- Past several months it has been sputtering during moderate acceleration particularly at the bottom end of 2nd gear. Clears up as rpm rises.
- Changed fuel filter over a month ago because of above issue.
- Saturday it starts surging idle in gear at stoplights. The RPM swings up and down and the difference continues to increase to the point it will drop low enough to stall. I can hold the idle over 1000 RPM and the idle will still oscillate a couple hundred RPM.
- I did not try putting it in neutral to see how it idled. To be honest, I was afraid it would die when I shifted back into gear. Of course this is going on in heavy traffic so I can't mess around too much I'm just hoping it doesn't completely die on me.
- Also starting Saturday, it accelerates like I'm running out of gas. It sputters and hesitates, basically falling on its face so you have to just creep up to speed. It's so similar to running out of gas that every time I instinctively look at the fuel level without thinking (tank is over half full BTW).
- Once up to speed, 65mph, it seems to run fine.
- At lower speed, 35mph, it doesn't run well. However if I run a lower gear/higher RPM, it runs better.
Usually exhaust leaks cause extra air in the pipe, and then the computer puts extra fuel in. You seem to be having the opposite problem.
Suspect the feeling of it running out of fuel is probably in fact that, and it’s not pushing enough fuel in because it’s cutting it
Suspect the feeling of it running out of fuel is probably in fact that, and it’s not pushing enough fuel in because it’s cutting it
Don't overlook the basics and also don't assume a part is good because it was recently replaced.
IAC?
I agree with what everyone said, it seems to be cutting fuel and we don't know why.
Fuel pressure seems stable with MAP so I don't think it's your filter or pump.
How do your plugs look?
Fuel pressure seems stable with MAP so I don't think it's your filter or pump.
How do your plugs look?
Found the static timing was at 16 so I dropped it back to 12 like it wants. We'll see his it runs tomorrow. Seems okay parked in the driveway, but that was not really a problem.
I did reset the learning.
Pulled a plug on each side.
Passenger:
Driver:
I did reset the learning.
Pulled a plug on each side.
Passenger:
Driver:
Looks like some crappy gas. As Mark said, they need changed. Round electrodes are inefficient.
I am reading tour post as 1 plug from each side. Pull the rest.
The bar is showing that it could use more timing at running driving rpm.
I am reading tour post as 1 plug from each side. Pull the rest.
The bar is showing that it could use more timing at running driving rpm.
I didn't pick up on any green looking at them in person. I did pull a 3rd plug Sunday but it didn't look any different. (pics below)
I agree about the bit of oil burn. It does use about a quart in 6000 miles. Unfortunately it has all the timing the ProFlo4 will allow at cruise, 40°. This is something Heath and I discussed at one point that it was too bad Edelbrock didn't allow for more.
I will replace the spark plugs. I do have 28k miles on the engine now. Driving home yesterday it ran fine except for still having an issue with missing/hesitating on acceleration. I noticed you can see the misses watching the ShortFT. When it's jumping around rapidly, that's the problem spot.
View attachment Screen_Recording_20240930_180028.mp4
I agree about the bit of oil burn. It does use about a quart in 6000 miles. Unfortunately it has all the timing the ProFlo4 will allow at cruise, 40°. This is something Heath and I discussed at one point that it was too bad Edelbrock didn't allow for more.
I will replace the spark plugs. I do have 28k miles on the engine now. Driving home yesterday it ran fine except for still having an issue with missing/hesitating on acceleration. I noticed you can see the misses watching the ShortFT. When it's jumping around rapidly, that's the problem spot.
View attachment Screen_Recording_20240930_180028.mp4
