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o matter, code 51 is what it is, the EGR is bad. you can take that to the bank.
the ECU dont lie.
now we get to the area of great complexity, (but mine ran ok with it cut off)
The ECU on many years, is programmed to drop to LIMPHOME, if certain things go bad.
If the ECU sees too many failures.
or if it sees that it has no control of fuel mix. ? and IT dont know way?
it then drops to limphome, (no codes stored ! see? no DTC's stored)
the results are that it goes very rich and spark advance is greatly retarded and a huge power loss and missing.....
All this was improved in 1996 in the usa or 1998 in canada ..

rule 3 , if the ECU dont flash codes, it dont mean all is well
that is correct these old and stupid ECU's do not have a full set of diagnostics
so when things go wrong (terribly) they cant report.
welcome back to the 1990's

"My Cat was cut off years ago and I never had any problems because if it. "
you assume your ecu works like other years. this is incorrect. (and diffr,. in canada too)
There are 4 generations of ECU. 89 (no EGR 51 at all)
then pre 94, uses MAP sensor and will fail 51 for any bad egr, modulator or missing cat.
post 94 (diffr, year in calif,) the EGR thermoprope sensor, this device. sees the valve open
'and go from cold to hot and , passes diagnostic 51
then in 1996 we get the OBD2 and then a new EGR pressure sensor, (top rear of intake)
so if your car has code 51, tell the helper if the EGR mAIN has 2 wires going to it.
also some kicks have the wrong ECU, so the ECU number then is very important.

also the 8v and 16v have different introductions (changes) by year.
end part 1.
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