4kq hard starting-stumbling

William Perron w_perron at yahoo.com
Wed Jun 22 17:13:49 EDT 2005

I've been having a problem w/ my '85 4kq lately that I
can't seem to figure out.

Problem:  Hard starting when "cold"-- cold varying
from 50F to 95F.  Car will sometimes catch when key is
first turned, but then stalls.  After a few attempts
the car will eventually start, but will have trouble
idling for about 30 seconds- usually need to keep the
revs above 1500RPM during this time - then the idle
evens out and I can drive away.  Once car is warm, I
can turn off and restart easily.  AFter it sits for a
few hours, the hard starting begins again.

Diagnostics/Changes so far:
-Checked Idle switch- it is working properly
-Swapped ECU temp sensor with known good--no change
-Cleaned all grounds, connections including intake
manifold grounds for ECU
-Swapped in known good plugs/wires distributor cap -
no change
-Swapped large intake manifold boot - no change
-Attached hose clamps to all ISV hoses - no change
-Swapped ISVs - no change
-Checked all hoses for vacuum leaks - nothing found
-Re-did all small vacuum hoses in engine compartment
w/ new ones- no change
- Installed new injector seals - no change
-Centered air plate in fuel dist. - no change
-Checked that Cold start valve is receiving voltage
when cranking - it does receive voltage
-Checked after start enrichment function--ECU does
enrich mixture after starting
-adjusted idle speed (w/ duty cycle meter), mixture
and timing- no change
- installed known good fuel pump relay no change
-installed a normal relay so fuel pump runs whenever
ignition is on--waited at least 30 sec to "prime
system" ---no change

I'm really not sure what else to check at this point. 
ONe interesting thing I noticed is that the car seems
to start pretty well if I leave the ISV unplugged??  I
though the ISV might be a problem so I swapped in a
differnt one--no change...

Any thoughts or comments appreciated 

Burlington CT
'85 4kq

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