91 Pickup 3.0 - Code 25
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91 Pickup 3.0 - Code 25 (Lean) On Hard Acceleration Only
I need some suggestions. Finally got the engine back in the truck after fixing all the firewall rust. I rebuilt the top end of the motor due to a burnt exhaust valve on #4. Turned out that all 6 exhaust valves were too tight.
I made all the connections and started the engine up. It started first try but I had to adjust the timing back to 10 degrees. It runs great. At idle there are no CELs. I can smoothly move the throttle and there are no codes. If I blip the throttle a few times it will throw code 25. I've checked the following:
1. TPS - before I installed the throttle body I tested it and it seemed fine.
2. AIC - When I cleaned out the throttle body and readjusted the AIC by blowing air through it and pouring hot water in the coolant lines. When its running you can hear the RPMs drop when it closes so I believe it is operational.
3. O2 - O2 wiring was bad but the broken wire was replaced and the O2 sensor is new. I checked the diagnostic port with the analog meter and the O2 output swings as it should, and the ECM also swings as it should.
4. I've checked for vacuum leaks but have found none.
5. I installed a wide band O2 in the exhaust and the AFR is right as 14.6. It stays right there if I smoothly accelerate. It drops to 8-10 if I hit it hard.
6. Coolant temp sensor is within spec.
7. Checked compression - Gauge says all are around 130 psi (it is a cheap kit). Engine has 308k on it.
I did remove the EGR, PAIR and CAT. All vac lines to the EGR and PAIR are capped at the intake and throttle body. I plan on checking fuel pressure and VAFM. What else should I do?
I appreciate any suggestions.
I made all the connections and started the engine up. It started first try but I had to adjust the timing back to 10 degrees. It runs great. At idle there are no CELs. I can smoothly move the throttle and there are no codes. If I blip the throttle a few times it will throw code 25. I've checked the following:
1. TPS - before I installed the throttle body I tested it and it seemed fine.
2. AIC - When I cleaned out the throttle body and readjusted the AIC by blowing air through it and pouring hot water in the coolant lines. When its running you can hear the RPMs drop when it closes so I believe it is operational.
3. O2 - O2 wiring was bad but the broken wire was replaced and the O2 sensor is new. I checked the diagnostic port with the analog meter and the O2 output swings as it should, and the ECM also swings as it should.
4. I've checked for vacuum leaks but have found none.
5. I installed a wide band O2 in the exhaust and the AFR is right as 14.6. It stays right there if I smoothly accelerate. It drops to 8-10 if I hit it hard.
6. Coolant temp sensor is within spec.
7. Checked compression - Gauge says all are around 130 psi (it is a cheap kit). Engine has 308k on it.
I did remove the EGR, PAIR and CAT. All vac lines to the EGR and PAIR are capped at the intake and throttle body. I plan on checking fuel pressure and VAFM. What else should I do?
I appreciate any suggestions.
Last edited by Soren; 06-22-2018 at 04:38 AM.
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