Dennis or Scott - Need help!!!

[AZhitman]

Still dealing with weirdness with my car.

Symptom: Rough, loping idle at cold start, improving somewhat once operating temp is reached but still not as smooth as before. Problem surfaced immediately after a plenum pull with #4 and #8 injectors and all underplenum coolant and fuel hoses replaced.

#5 cylinder is showing problematic, so we switched coil pack, plug and injector with other cylinders, #5 remained the problem. Tech states he did compression test on all cylinders and #5 is showing low compression. Can't figure out where to go from here, and tech is eager to hear input from other professionals.

[NISTECH]

have him do a leak down test(more accurate) but since he did the comp test I assume he did it both ways. once with out oil to seal the rings and once with a small amount of oil. did both readings reveal it was low. What was their final conclusion on the high resistance thing?

[AZhitman]

The high resistance thing appears to have straigtened out (I guess). Could the 2 be related?

I'll ask if he did a leakdown test dry or wet.

Any other ideas? I'm getting really nervous about this one, especially since it turned out NOT to be a pinched/cracked injector o-ring...

[NISTECH]

well you said he did a compression test not a leak down test. these are 2 different tests. leak down measures % of air loss from a completely closed off cyl. anything over 10% not good. and you can isolate where your air loss is by listening in different areas. pull the oil cap if you hear a high volume of air running out its rings. if you open the throttle and hear air its the intake valve, if you go to the exhuast pipe and hear it its exhaust valve. Fun little prank here to pull on the novice tech. hook up one of those shop exhaust systems with a pump out. and you can here air leaking out of other spark plug holes and intake. I'm a a-hole sometimes he he he. the resistance thing has always been in the back of my mind but if they tell you it has resolved it self perhaps they just tested it wrong intially and there was never a problem to begin with. but I was baffled when you said nothing more about it and they were going down other avenues. cause a high resistance in the circuit , as with any basic electrical circuit, would use up some of the supplied voltage and not allow it to be used in the device intended or the device would not have enough to perform its task completely. I dont know if the q uses it or not dont get alot of Q's in the shop but does it have a trig unit like the J-30 and the Z car? maybe its gummed up on the connections or a pin backed out?

[Q45tech]

With leak down test you have to be prepared to test at TDC and half and full stroke..........incase of bore taper.

My Q fails the compression test dry [no added oil] and cold [room temperature]...............but a pressure monitor fitted under the spark plug shows it quickly get above minimum when the rings heat up and is fine by the time the coolant gets to normal.

A running compression test at idle will show around 55-60-70 psi due to the miniscule amount of air in the cylinder and the long time interval of the cycle at 675 rpm.

What is idle vacuum as measured with a tee on the fuel pressure regulator vacuum line? 18.0" HG?