Read reference to this but not sure if it applies to my car. Chasing bad idle and would like to do this if I can. Otherwise, I guess I would have to take it to the dealer/shop to get the codes?
Don
Self Diagnostic - what, where, how is it?? 94Q
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Q45tech
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- Posts: 14296
- Joined: Tue Apr 30, 2002 3:19 am
- Car: 1990 Q45 342,400 miles 22 years ownership with original engine
1995 G20t 5 speed 334,000 miles 16" 2002 wheels - 205/50/16 Sr20ve vvl
Re: Self Diagnostic - what, where, how is it?? 94Q (daegrigg)
The check engine codes on pre OBD2 ecu [before 1996] are not very helpful unless some monitored system is grossly grossly out of spec or failed entirely.
Even with a Consult you must know normal conditions for temperature and altitude............mileage etc.........then be prepared to conduct some test and become a detective.
Most tests just look for a signal [right or wrong just some signal not a zero or not 5 volts] anything in between is listed as ok.
You have to have tested similar aged Q and be able to mentally extrapolate the Consult readings to what might be appropriate for conditions...........why techs who don't work on Q very much have such a hard time trouble shooting......EVEN THOSE OF US who own and drive one everyday are often stumped at least for a while........because we don't have enough very specialized test equipment [dealers don't have it either] or cannot spend the time testing everything.
An area we constantly discuss is the difficulty in testing the coil on plug ignition system........need to create plug wires to clamp test equipment on an the time to pull the coil covers off and on .........easier to just replace the plugs than to test them.
Hard to trace an idle misfire compared to OBD2 systems which have individual codes for each cylinder [they use the O2 signal sync time delayed from firing to exhaust]...........hey that O2 pulse shouldn't be oxygenated [lean] calculating back to the exact cylinder that misfired.
Trying to do it with a Consult is a nightmare of mental calculations even for me much less a tech..[not that I am smarter just I've spent the time thinking thru/developing a proceedure]..........you can often guess which bank with careful analysis.........but those roving misfires caused from slight MAF error [voltages].......just on ragged edge because the system idle is 5% too lean [in ultra hot conditions] [or low compression from age] are another case entirely.
Why you use BG44k [as the first step] to see if things improve then you have a clue.
Even with a Consult you must know normal conditions for temperature and altitude............mileage etc.........then be prepared to conduct some test and become a detective.
Most tests just look for a signal [right or wrong just some signal not a zero or not 5 volts] anything in between is listed as ok.
You have to have tested similar aged Q and be able to mentally extrapolate the Consult readings to what might be appropriate for conditions...........why techs who don't work on Q very much have such a hard time trouble shooting......EVEN THOSE OF US who own and drive one everyday are often stumped at least for a while........because we don't have enough very specialized test equipment [dealers don't have it either] or cannot spend the time testing everything.
An area we constantly discuss is the difficulty in testing the coil on plug ignition system........need to create plug wires to clamp test equipment on an the time to pull the coil covers off and on .........easier to just replace the plugs than to test them.
Hard to trace an idle misfire compared to OBD2 systems which have individual codes for each cylinder [they use the O2 signal sync time delayed from firing to exhaust]...........hey that O2 pulse shouldn't be oxygenated [lean] calculating back to the exact cylinder that misfired.
Trying to do it with a Consult is a nightmare of mental calculations even for me much less a tech..[not that I am smarter just I've spent the time thinking thru/developing a proceedure]..........you can often guess which bank with careful analysis.........but those roving misfires caused from slight MAF error [voltages].......just on ragged edge because the system idle is 5% too lean [in ultra hot conditions] [or low compression from age] are another case entirely.
Why you use BG44k [as the first step] to see if things improve then you have a clue.
Thanks Q45Tech. Very information. Seems that Self Diagnostic does not hold much promise in my case.
I've done the BG44kCleaned MAFClean Throttle place/bodyConfirmed that injectors at all but 5 and 7 are workingChecked EGR valve (not sure what I found)Wiggled bunch of wires
The bad running always occurs below 2000 rpm regardless of the gear
Next, I guess I will check the injector s resistance
Thanks, Don
Sleepless in Maryland
I've done the BG44kCleaned MAFClean Throttle place/bodyConfirmed that injectors at all but 5 and 7 are workingChecked EGR valve (not sure what I found)Wiggled bunch of wires
The bad running always occurs below 2000 rpm regardless of the gear
Next, I guess I will check the injector s resistance
Thanks, Don
Sleepless in Maryland