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Re: Vacuum pressure on '86 2.8L --- TOTALLY STUMPED
In message <JxX2tWiP5BNp-pn2-NnDw1Qd4X29K@anon.none.net>, "Will Honea" wrote:
>On Tue, 16 Dec 2003 04:29:09 UTC bllsht <nospam@invaliddot.net> wrote: > >> In message <151220030900494970%RhmpL33@nospam.net>, "Rich Hampel" wrote: >> >> > >> >Its a @ 2SE (non-Kalyfornia) >> >> Good, that eliminates a problem with electronic controls. >> > >> >Cam timing is Correct >> >> If you say so.... >> >> > >> >Yup, I know (now) that changing/replacing intake gaskets has been a >> >waste of time. >> >With low vac the engine runs retarded hence rich at normal highway rpm, >> >at low vac all the dampers in the air cleaner close ... also make it >> >run rich (but I have them locked out at the moment). >> >> Two or three posts have mentioned restricted exhaust now, and you haven't >> responded to them. Have you checked this? A *symptom* of plugged exhaust would >> be low vacuum. This would cause a couple of problems. >> >> 1) If you can't get the all of the burned gas out, you can't get a full charge >> of fuel/air in for the next cycle. >> >> 2) That vehicle is equipped with a back pressure EGR valve. Too much back >> pressure could cause too much EGR action. Too much exhaust gas in the >> combustion chamber displaces too much of the air and fuel needed for decent >> combustion. >> >> Once again, have you checked for restricted exhaust? > >Can you put a number on the expected or acceptable back pressure >(pressure ahead of the cat) for the 4.0 and/or the 2.5? I've seen >lots of talk about excessive back pressure, but just what constitutes >excessive?? I don't have a number for it. I don't know if there is one. Most that I see are pretty obvious just by the symptoms. The marginal ones can be picked up using a vacuum gauge. |
Re: Vacuum pressure on '86 2.8L --- TOTALLY STUMPED
In message <JxX2tWiP5BNp-pn2-NnDw1Qd4X29K@anon.none.net>, "Will Honea" wrote:
>On Tue, 16 Dec 2003 04:29:09 UTC bllsht <nospam@invaliddot.net> wrote: > >> In message <151220030900494970%RhmpL33@nospam.net>, "Rich Hampel" wrote: >> >> > >> >Its a @ 2SE (non-Kalyfornia) >> >> Good, that eliminates a problem with electronic controls. >> > >> >Cam timing is Correct >> >> If you say so.... >> >> > >> >Yup, I know (now) that changing/replacing intake gaskets has been a >> >waste of time. >> >With low vac the engine runs retarded hence rich at normal highway rpm, >> >at low vac all the dampers in the air cleaner close ... also make it >> >run rich (but I have them locked out at the moment). >> >> Two or three posts have mentioned restricted exhaust now, and you haven't >> responded to them. Have you checked this? A *symptom* of plugged exhaust would >> be low vacuum. This would cause a couple of problems. >> >> 1) If you can't get the all of the burned gas out, you can't get a full charge >> of fuel/air in for the next cycle. >> >> 2) That vehicle is equipped with a back pressure EGR valve. Too much back >> pressure could cause too much EGR action. Too much exhaust gas in the >> combustion chamber displaces too much of the air and fuel needed for decent >> combustion. >> >> Once again, have you checked for restricted exhaust? > >Can you put a number on the expected or acceptable back pressure >(pressure ahead of the cat) for the 4.0 and/or the 2.5? I've seen >lots of talk about excessive back pressure, but just what constitutes >excessive?? I don't have a number for it. I don't know if there is one. Most that I see are pretty obvious just by the symptoms. The marginal ones can be picked up using a vacuum gauge. |
Re: Vacuum pressure on '86 2.8L --- TOTALLY STUMPED
In message <JxX2tWiP5BNp-pn2-NnDw1Qd4X29K@anon.none.net>, "Will Honea" wrote:
>On Tue, 16 Dec 2003 04:29:09 UTC bllsht <nospam@invaliddot.net> wrote: > >> In message <151220030900494970%RhmpL33@nospam.net>, "Rich Hampel" wrote: >> >> > >> >Its a @ 2SE (non-Kalyfornia) >> >> Good, that eliminates a problem with electronic controls. >> > >> >Cam timing is Correct >> >> If you say so.... >> >> > >> >Yup, I know (now) that changing/replacing intake gaskets has been a >> >waste of time. >> >With low vac the engine runs retarded hence rich at normal highway rpm, >> >at low vac all the dampers in the air cleaner close ... also make it >> >run rich (but I have them locked out at the moment). >> >> Two or three posts have mentioned restricted exhaust now, and you haven't >> responded to them. Have you checked this? A *symptom* of plugged exhaust would >> be low vacuum. This would cause a couple of problems. >> >> 1) If you can't get the all of the burned gas out, you can't get a full charge >> of fuel/air in for the next cycle. >> >> 2) That vehicle is equipped with a back pressure EGR valve. Too much back >> pressure could cause too much EGR action. Too much exhaust gas in the >> combustion chamber displaces too much of the air and fuel needed for decent >> combustion. >> >> Once again, have you checked for restricted exhaust? > >Can you put a number on the expected or acceptable back pressure >(pressure ahead of the cat) for the 4.0 and/or the 2.5? I've seen >lots of talk about excessive back pressure, but just what constitutes >excessive?? I don't have a number for it. I don't know if there is one. Most that I see are pretty obvious just by the symptoms. The marginal ones can be picked up using a vacuum gauge. |
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