odyssey
Active Member
- Posts
- 364
- Location
- Derbyshire
'93 LSE 4.2. Recent top end rebuild, runs well apart from erratic hot idle/bog down. Starts and idles well from cold, once up to temp can surge, or bog down.
Replaced blocked rad which has solved various temp/cooling probs.
Everything is sparkly clean, heads, plenum, rams etc, were acid dipped. Retimed static ign, checked airgap; vac advance and weights both work. Stepper works (I have 2 and test them by leaving one screwed in and connect the other, switch on & start and the plunger moves in and out no probs). AFM hotwire is cleaned, and all connections seem clean tight and dry. No vac leaks that I can find. TPI, MAF and CTS show resistances within the recommended ranges. Have re-set base idle. Plugs are sooty.
Some times it can be idling quite happily, switch it off, then try and restart, it'll fire once then just crank. Have to crank it for a couple of secs with the fuel pump fuse removed, replace the fuse and it starts and surges up to 2000+ revs for 5 - 10 secs, then settles down again.
Sometimes when driving, if I drop into neutral it will surge between 1000 & 2000 revs with no throttle.
Wondering about the O2 sensors now, given that they don't start working till it's hot, I've found the details on testing and will do that later today, as looking at the fuelling feedback status below there is a discrepancy between the banks. What should these values be? and what sort of leeway is there from the recommended percentages?
Recent diagnostic test (before rad replacement and other tweaks such as base idle re-set) showed trouble codes:-
DTC - 0021 / Status - Present / description - ECM tune selection resistor.
DTC - 0048 / Status - Present / description - Stepper motor/air idle valve.
(@1100 rpm):-
Coolant temp ---- 72.42C
Calculated position of air idle control valve , (nominal 15 - 25) .. 171 steps.
Bank A fuelling feedback status ...... +17.37%
Bank B fuelling feedback status ...... -1.01%
Av injector opening banks A & B ....... 3.14ms
(@1947 rpm):-
Coolant temp ---- 74.58C
Calculated position of air idle control valve , (nominal 15 - 25) .. 154 steps.
Bank A fuelling feedback status ...... +19.6%
Bank B fuelling feedback status ...... +11.55%
Av injector opening banks A & B ....... 3.38ms
Any suggestions would be very welcome as I'm getting huge grief from the other half who's car it is and she's not driven for months as she doesn't trust it.
TIA - Alastair
Replaced blocked rad which has solved various temp/cooling probs.
Everything is sparkly clean, heads, plenum, rams etc, were acid dipped. Retimed static ign, checked airgap; vac advance and weights both work. Stepper works (I have 2 and test them by leaving one screwed in and connect the other, switch on & start and the plunger moves in and out no probs). AFM hotwire is cleaned, and all connections seem clean tight and dry. No vac leaks that I can find. TPI, MAF and CTS show resistances within the recommended ranges. Have re-set base idle. Plugs are sooty.
Some times it can be idling quite happily, switch it off, then try and restart, it'll fire once then just crank. Have to crank it for a couple of secs with the fuel pump fuse removed, replace the fuse and it starts and surges up to 2000+ revs for 5 - 10 secs, then settles down again.
Sometimes when driving, if I drop into neutral it will surge between 1000 & 2000 revs with no throttle.
Wondering about the O2 sensors now, given that they don't start working till it's hot, I've found the details on testing and will do that later today, as looking at the fuelling feedback status below there is a discrepancy between the banks. What should these values be? and what sort of leeway is there from the recommended percentages?
Recent diagnostic test (before rad replacement and other tweaks such as base idle re-set) showed trouble codes:-
DTC - 0021 / Status - Present / description - ECM tune selection resistor.
DTC - 0048 / Status - Present / description - Stepper motor/air idle valve.
(@1100 rpm):-
Coolant temp ---- 72.42C
Calculated position of air idle control valve , (nominal 15 - 25) .. 171 steps.
Bank A fuelling feedback status ...... +17.37%
Bank B fuelling feedback status ...... -1.01%
Av injector opening banks A & B ....... 3.14ms
(@1947 rpm):-
Coolant temp ---- 74.58C
Calculated position of air idle control valve , (nominal 15 - 25) .. 154 steps.
Bank A fuelling feedback status ...... +19.6%
Bank B fuelling feedback status ...... +11.55%
Av injector opening banks A & B ....... 3.38ms
Any suggestions would be very welcome as I'm getting huge grief from the other half who's car it is and she's not driven for months as she doesn't trust it.
TIA - Alastair
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