89 5.0L Code 33 Stumbles when warm
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From: Sacramento, CA
89 5.0L Code 33 Stumbles when warm
1989 Bronco 5.0L auto
Had codes 31 and 33; replaced the EVR, EVP, and EGR Valve.
Still have code 33 (no signal that EGR valve is opening) . Checked vacuum line to EGR from EVR- holds vacuum. EVP voltage check seems good.
Runs fine when cold, but when it gets warm (10 mins driving, and the temp needle just off of the peg), it sputters/stumbles under moderate acceleration. WOT and it is OK, seems to be normal.
Question:
1) what changes in the EEC-IV system at warm-up?
What "turns on" that may be causing the problem?
2) Does the TFI ever go out partially when warm? (replaced TFI ign module six mo. ago)
Thanks, Chris
Had codes 31 and 33; replaced the EVR, EVP, and EGR Valve.
Still have code 33 (no signal that EGR valve is opening) . Checked vacuum line to EGR from EVR- holds vacuum. EVP voltage check seems good.
Runs fine when cold, but when it gets warm (10 mins driving, and the temp needle just off of the peg), it sputters/stumbles under moderate acceleration. WOT and it is OK, seems to be normal.
Question:
1) what changes in the EEC-IV system at warm-up?
What "turns on" that may be causing the problem?
2) Does the TFI ever go out partially when warm? (replaced TFI ign module six mo. ago)
Thanks, Chris
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Have you checked the resistance of the EVP? I got one at the junk yard, thought it was good after checking it, low resistance was only 50 ohms, put it in, got code 33 from it, and my check engine light came on. Put my old one back in and returned 31, but at least the check engine light went off. So I guess I need a new EGR, doesn't appear to be opening.
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The resistance will not change if the EGR doesn't open, but doesn't mean the EVP is bad. To test that you have to remove the EVP from the EGR and test it. Be careful when removing it, spray it with some PB Blaster first and let it soak, those tiny bolts will twist right off.
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Before I started this thread I installed new EVP, then EVR then EGR valve. Did checks today and all seem to be operating OK. Zeroed out codes and will check and see what shows up next.
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From: Sacramento, CA
Checked good voltage to the EVP and variable resistance from the EVP when vacuum applied to the EGR valve - all OK.
Changed O2 sensor a few months back, have good input volts to the TPS.
???
Changed O2 sensor a few months back, have good input volts to the TPS.
???
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