Need help p0300 and slight backfire
#11
Downstream sensor(s) do not affect engine performance. All they do is monitor the converter(s).
Fuel pressure and leakdown needs to be checked at the fuel filter outlet.
Distributor: no check engine light with P1345 in memory means the distributor is meshed correctly with the cam gear. It also means camshaft retard is within ~13 degrees, it needs to be 0 degrees +or- 2 degrees. Best to have it checked and adjusted if necessary to eliminate crossfire in the cap.
Fuel pressure and leakdown needs to be checked at the fuel filter outlet.
Distributor: no check engine light with P1345 in memory means the distributor is meshed correctly with the cam gear. It also means camshaft retard is within ~13 degrees, it needs to be 0 degrees +or- 2 degrees. Best to have it checked and adjusted if necessary to eliminate crossfire in the cap.
Last edited by Captain Hook; 02-20-2016 at 09:07 PM.
#12
ok sounds good i ordered 2 denso 234-4012 o2 sensors today but they will not be here for about a week i will try to do the max pressure test this weekend
the cam adjustment should be able to wait until after i get the misfire fixed since it ran fine before?
i was planning on getting an alignment before this happened so i would rather get both done while i'm there.
the cam adjustment should be able to wait until after i get the misfire fixed since it ran fine before?
i was planning on getting an alignment before this happened so i would rather get both done while i'm there.
#13
Camshaft retard can be off ~13 degrees, which is huge, and not set P1345, but you will have misfires, guaranteed.
#15
Ok I know it's been awhile but a I got stuff done today
Rechecked vacuum lines broke a rubber elbow replaced it everything else looked good
Max psi test hit 80psi held pretty good
Replaced fuel filter while I was there
Replaced both upstream 02 sensors
Ran new fuel trims
At idle. At 2k rpm
B1
Stft 0. 50
Ltft 6.2 21
B2
Stft. 0. 1.5
Ltft. 5.4. 1.5
Map 12.9. 10.3
Spk adv 20. 36
Iat. 80. 80
Maf. .77. 2.2
02 b1s1
V. .2. .5
%. 50. 50
B2s2
V. .2_.8. .4_.7
%. 0_-1. 0
Also I put in a bottle of chevron techron like you said
Rechecked vacuum lines broke a rubber elbow replaced it everything else looked good
Max psi test hit 80psi held pretty good
Replaced fuel filter while I was there
Replaced both upstream 02 sensors
Ran new fuel trims
At idle. At 2k rpm
B1
Stft 0. 50
Ltft 6.2 21
B2
Stft. 0. 1.5
Ltft. 5.4. 1.5
Map 12.9. 10.3
Spk adv 20. 36
Iat. 80. 80
Maf. .77. 2.2
02 b1s1
V. .2. .5
%. 50. 50
B2s2
V. .2_.8. .4_.7
%. 0_-1. 0
Also I put in a bottle of chevron techron like you said
#18
She's running lean.
1. Inject propane or carb cleaner spray directly into the MAF at the air box connection and see if the oxygen sensors respond, (voltage must increase).
2. Prop the throttle open at ~1500 rpm, (couple of business cards or so) between the throttle linkage and the stop screw. Then disconnect the IAC, (idle air controller) so the PCM can't control idle speed. Using propane, look for vacuum leak(s). Idle speed will increase if/when you hit a vacuum leak. Check along the intake gaskets where they meet the heads. Pull the PCV valve out and inject some into the valve cover. Check the PCV valve itself, might be broken or stuck open. Kink off the power brake booster line and see if idle speed decreases. Also, really need to get all four numbers on the fuel delivery system and post them: https://blazerforum.com/forum/2nd-ge...eakdown-88305/
1. Inject propane or carb cleaner spray directly into the MAF at the air box connection and see if the oxygen sensors respond, (voltage must increase).
2. Prop the throttle open at ~1500 rpm, (couple of business cards or so) between the throttle linkage and the stop screw. Then disconnect the IAC, (idle air controller) so the PCM can't control idle speed. Using propane, look for vacuum leak(s). Idle speed will increase if/when you hit a vacuum leak. Check along the intake gaskets where they meet the heads. Pull the PCV valve out and inject some into the valve cover. Check the PCV valve itself, might be broken or stuck open. Kink off the power brake booster line and see if idle speed decreases. Also, really need to get all four numbers on the fuel delivery system and post them: https://blazerforum.com/forum/2nd-ge...eakdown-88305/
#19
Ok ran the tests you told me to
Fuel psi
At service port
Key on engine off 62 psi
Dropped to 55 psi held for 10+ min
At fuel filter
Key on engine off 80 psi
Dropped to 73 psi held for 10+ min
Propane at maf 02 sensors value changed
Iac unplugged engine ran at 1600 rpm by itself
Tried propane all around intake and in pcv port on valve cover no change at all
Tried pinching brake booster line no change at all (iac was still unplugged )
Fuel psi
At service port
Key on engine off 62 psi
Dropped to 55 psi held for 10+ min
At fuel filter
Key on engine off 80 psi
Dropped to 73 psi held for 10+ min
Propane at maf 02 sensors value changed
Iac unplugged engine ran at 1600 rpm by itself
Tried propane all around intake and in pcv port on valve cover no change at all
Tried pinching brake booster line no change at all (iac was still unplugged )
#20
Connect the scan tool and display live data. With the engine idling at normal operating temp, (200F), trans in park or neutral, all accessories turned off, PCM in closed loop operation: Post all values, (idle speed, fuel trim, fuel cell number, ignition advance, MAP, MAF, TPS, BARO, ECT, IAT, etc, etc, and camshaft retard if the scanner will access it). Anything it shows, post it