02-27-2021, 02:14 AM
basics means one of 3 failed paths. (with odd exceptions , one being A/T with wrecked TC torque converter clutch inside) and melted cat, or stuck open EGR
seen EGR do this.
casing cracked, what this crack does is , not known as it can crack in so many ways inside and out. I block off the port to prove it is not bad. using solid gasket at base, no holes.
EGR sticks every mile driving or random, block it.
hoses hooked up wrong to EGR and gets vacuum when never it must. for sure at idle. no vacuum to EGR allowed, I block the EGR base with sold gasket to prove it is bad.
base gasket missing or cracked sucking air, but engine races super fast will fill power so is not your cause.
1:bad engine or with good compression cam lobes a wreck (they open sure but not by much) very rare this lobe deal. You cam is not timed wrong.
2: bad spark weak, intermittent or timing bad or the mech, advance is wreck, looking at it works best no springs missing there or fly weights rusted. !!!
on gen 1, 89/90 I take the distributor fully part to prove the mech advance is not a wreck and the vacuum adv too not sticking. and leakdown test pass on its diaphram.
3: bad fueling vast ways to fail. (ECU does all fueling and never does it do spark here)
best I can tell it is #3 . clogged injector (even 75% clogged is possible) see it. one guy here found that and the FPR was jerry rigged to higher fuel pressure. WOW hard to find.
sensors read wrong makes fuel inject wrong.
map if first , check keyon, idle voltage. (both must be near my page data )
O2 sensor stuck high, forcing lean condition. the 1989/90 ecu gives O2 more control that should be allowed, cured in 1996, unplug it gets you 0.45vdc and can hide the too lean or to rich conditions. (as test)
ECT reading hot for cold. (wrong ECT or bad)
one more trick
run with ECT unplugged, see if more power happens? this will force rich. (but sadly retards spark) so.... not definitive by much.
test all sensors carefully here.
for sure hot and cold. even use a heat gun, to me sure they do not fail hot, and go open ,dead or shorted.
one other test only shops can do is scope the injector wire pair, and is tricky one 8v. scope must not be grounded and both scope probes across the injector wire pair.
the Plus width correct tells you injector is clogged, or have low fuel pressure (yours is good PSI)
if Pulse width it too low, the ECU sensors are telling lies. same with too long pulse too rich.
seen EGR do this.
casing cracked, what this crack does is , not known as it can crack in so many ways inside and out. I block off the port to prove it is not bad. using solid gasket at base, no holes.
EGR sticks every mile driving or random, block it.
hoses hooked up wrong to EGR and gets vacuum when never it must. for sure at idle. no vacuum to EGR allowed, I block the EGR base with sold gasket to prove it is bad.
base gasket missing or cracked sucking air, but engine races super fast will fill power so is not your cause.
1:bad engine or with good compression cam lobes a wreck (they open sure but not by much) very rare this lobe deal. You cam is not timed wrong.
2: bad spark weak, intermittent or timing bad or the mech, advance is wreck, looking at it works best no springs missing there or fly weights rusted. !!!
on gen 1, 89/90 I take the distributor fully part to prove the mech advance is not a wreck and the vacuum adv too not sticking. and leakdown test pass on its diaphram.
3: bad fueling vast ways to fail. (ECU does all fueling and never does it do spark here)
best I can tell it is #3 . clogged injector (even 75% clogged is possible) see it. one guy here found that and the FPR was jerry rigged to higher fuel pressure. WOW hard to find.
sensors read wrong makes fuel inject wrong.
map if first , check keyon, idle voltage. (both must be near my page data )
O2 sensor stuck high, forcing lean condition. the 1989/90 ecu gives O2 more control that should be allowed, cured in 1996, unplug it gets you 0.45vdc and can hide the too lean or to rich conditions. (as test)
ECT reading hot for cold. (wrong ECT or bad)
one more trick
run with ECT unplugged, see if more power happens? this will force rich. (but sadly retards spark) so.... not definitive by much.
test all sensors carefully here.
for sure hot and cold. even use a heat gun, to me sure they do not fail hot, and go open ,dead or shorted.
one other test only shops can do is scope the injector wire pair, and is tricky one 8v. scope must not be grounded and both scope probes across the injector wire pair.
the Plus width correct tells you injector is clogged, or have low fuel pressure (yours is good PSI)
if Pulse width it too low, the ECU sensors are telling lies. same with too long pulse too rich.
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