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Car Forum / Pontiac / Pontiac Fiero / August 200785 2m4 engine problem
85 2m4 180K miles runs good cold after it warms up it looses power on low rpms. The car when i say it looses power it like stumbles or bucks mainly noticable uhen the rpm's are low like running on the highway climbing a hill at 60 65 mph it will buck if I down shift to 4th getting rpms up it will climb the hill easier Also when I am first getting onto the highway it will start to buck if I try to accelerate to quickly. I replaced the O2 sensor as it had a code and I replaced the plugs, cap & rotor and one plug wire as it was 18K ohms the rest are around 2K. swaped the MAP sensor and replaced the TPS as well. I replaced some of the more older looking airline tubes as well. There are no codes at this point. Any help would be great as its driving me crazy. Hank > 85 2m4 180K miles runs good cold after it warms up it looses power on > low rpms. The car when i say it looses power it like stumbles or bucks [quoted text clipped - 11 lines] > Any help would be great as its driving me crazy. > Hank Hank have you changed the fuel filter? >> 85 2m4 180K miles runs good cold after it warms up it looses power on >> low rpms. The car when i say it looses power it like stumbles or bucks [quoted text clipped - 12 lines] >> Hank >Hank have you changed the fuel filter? Yes fuel filter replaced and checked EGR as well ran it tonight it runs good when cold but as soon as it get near operating temperature it runs crapy again ?? Thanks Hank >>> 85 2m4 180K miles runs good cold after it warms up it looses power on >>> low rpms. The car when i say it looses power it like stumbles or bucks [quoted text clipped - 18 lines] > Thanks > Hank Is it just at operating temp or when you are driving down the road and it reaches operating temp? What about a vacuum leak? Have you done any checks to see if you have cracked vacuum lines? >>>> 85 2m4 180K miles runs good cold after it warms up it looses power on >>>> low rpms. The car when i say it looses power it like stumbles or bucks [quoted text clipped - 21 lines] >reaches operating temp? What about a vacuum leak? Have you done any checks >to see if you have cracked vacuum lines? Yes runs fine at cold which only lasts a few minutes. At operating temp it runs crappy. I replaced a couple of vacuum lines that did not look good. I do not have a vacuum gage its missing I will pick one up but never really used it so not sure what to look for. Hank >>>>> 85 2m4 180K miles runs good cold after it warms up it looses power on >>>>> low rpms. The car when i say it looses power it like stumbles or bucks [quoted text clipped - 28 lines] > really used it so not sure what to look for. > Hank A good vacuum gauge is soapy water look for bubbles >>>>>> 85 2m4 180K miles runs good cold after it warms up it looses power on >>>>>> low rpms. The car when i say it looses power it like stumbles or bucks [quoted text clipped - 29 lines] >> Hank >A good vacuum gauge is soapy water look for bubbles I put a vacuum gage on it tonight the vacuum presure held stable just like the book said I also checked the coolent sensor the resistance at cold and at hot measures fine like the repair guide says. Still no stored codes in the ECM. Have you checked the exhaust backpressure yet? You could have a clogged catalytic converter, muffler or collapsed pipe. You can check it at the O2 sensor location. The book mentions that it should be no more than 1-1/4 psi. That may cause the idle problem as well as loss of power after building up pressure..unrelated to the temp. It would also cause the temp to increase faster than usual as the pressure builds. Might be worth investigating. My first guess would be clogged cat since that is common on older vehicles. >Have you checked the exhaust backpressure yet? You could have a clogged >catalytic converter, muffler or collapsed pipe. You can check it at the O2 [quoted text clipped - 3 lines] >faster than usual as the pressure builds. Might be worth investigating. My >first guess would be clogged cat since that is common on older vehicles. Not sure how I can check that out ? Hank remove O2 sensor and attach a guage there? get you an oem vac, that is the problem had it for years before I figured it out. replaced with junk copy it ran for a while then problem came back, thought that couldnt be it just replaced it. got oem and sure enough. oh and it was heat related and will never ever give you a message! cost like $40 but i would bet my $40 on it! >remove O2 sensor and attach a guage there? |
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