A.I.R system?? -have loss of power… code 43 for knock, and 44 for lean condition????

[scouthead]

As says the title… 1988 TBI 350- manual transmission means it got the AIR /smog pump stuff here in CA.

I drove the truck HARD earlier this week. Rocky trails/sandhills… in and out of low range… revved the motor good quite a bit. Things were running fine… we stopped for a beer.

When starting the engine 30min later -rough idle. Drove away in 4-low and left the play area. Get to open road and shift into 2high- immediately I notice how bad the power loss is- I’m working the throttle and slipping the clutch just to pull away in first gear on flat ground… then check engine light came on and ran even rougher. Then the light went away and it ran a little better again.

The Lights on the dash cluster went out… (there may be something up with the combo switch) lights came back on -repeated a couple times.
I made it home.

Visual inspection and everything looks in place. pulled codes
43-knock sensor
44 - lean condition

 

[scouthead]

I was surprised to see a code 44 lean condition- if anything there’s been a hint of rich exhaust smell for a while.

I’ve been checking things-
-good spark at all 8 plugs
-hooked up smoke machine and looked for vacuum leaks- couldn’t find any with that route.
-EGR is fairly New and seems to open and close correctly with a vacuum pump
-O2 sensor is fairly new and the truck idles bad and runs bad before it’s warmed up, so I’m not suspicious of the O2 sensor right now.
-coolant temp sensor was tested a few years ago and was in spec and functioning… there is still a defined difference between open/closed loop so I’m not suspicious of temp sensor
-there’s no water in oil/oil in coolant that I can detect
-no new noises from engine

 

[scouthead]

After pulling the codes and disconnecting battery to clear them, the truck ran WORSE. Checked timing- seems good. When I disconnect the advance wire it barely runs, but it appears to still be set at 0 base timing.

Suspicious of Idle air control valve- did the reset procedure with no real difference to how things are running.

Got to thinking that the smog pump/ air injection system might have issues and pumping air into the exhaust at all times? Causing the lean condition and if bad enough tripping the knock sensor??

 

[scouthead]

I found that the AIR diverter valve doesn’t hold vacuum. Is it supposed to?? When I connect a vacuum pump, the valve doesn’t hold vacuum. It does redirect air a bit bit, but just for a second before the vacuum bleeds away. This seems like it would have been BOTH:
-a small constant vacuum leak at the throttle body
-continuously pumping air into the exhaust.

I’ve got the diverter hoses off and plugged the engine side/capped the vacuum port on throttle body.

Initially it seemed to idle MUCH better, and I had high hopes. That slight rich exhaust smell is immediately gone. I let the engine fully warm up.

Took it for a test drive =low power, and immediately threw a check engine light. Both codes 43 and 44 again.

Parked it. The EXAUST is REAL hot now. I mean - cats are hot to begin with, but after a trip around the block, my skid plate is so hot I can’t touch it. Got about 3 inches of air gap there- Never been that hot before!

Yes fuel seems to be spraying from the injectors well. I haven’t checked fuel pressure yet, but it was good 4-5000 miles ago when this engine went back in

 

[scouthead]

The Cat is new- less than 2000 miles on it.

I’m going to pull the spark plugs and attempt a compression test just for the hell of it. Anything else I should be looking real hard at?