90 Q coil
-
Q45tech
- Moderator
- 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: 90 Q coil (MR.Q)
I could but in 7 years of servicing over 1,000 Q we have only found 2 bad coils.
Oil leaking into plug well or just old plugs........usual cause is dirty or failed injectors.
Oil leaking into plug well or just old plugs........usual cause is dirty or failed injectors.
Certainly. There aren't all that many (common) things that can cause a single cylinder to not fire. And for each possiblility there are ways to diagnose. Use an infrared thermometer on the exhaust manifolds to figure out which cylinder isn't firing.Look at the plugs for clues. Look for signs of arcing or corrosion. Once you know which cylinder isn't firing you can try to swap the coil with a known good one or with one from the same engine. You can do a fuel pressure leak down to check for a leaky injector/seal, an ohm test to look for a bad injector or listen with a stethoscope to hear if the injector is firing. Clogs might be hard to pinpoint.
Re: 90 Q coil (Q45tech)
I did have a coil go bad last year on my '90. No oil, but a big carbon streak on the plug, which was really corroded, even though it was pretty new. Maybe it wasn't the coil itself, but I had an extra set so I just swapped it (and the plug) and the problem disappeared.Q45tech wrote:I could but in 7 years of servicing over 1,000 Q we have only found 2 bad coils.
Oil leaking into plug well or just old plugs........usual cause is dirty or failed injectors.
Re: 90 Q coil (Q45tech)
My dad di tell me that I neede to replace my valve cover gasket because I did find oil on my spark plugs. I believe it was on the left side. When my engine was put in I saw the guy screwing my A.A.C valve, should I take it to the dealer and get it screwed the right way?
Re: (DAEDALUS)
I got my car towed to a japanese shop and the manager told me that I had bad harnesses and too many splices to even get the Q diagnosed. The cars diagnostic bar said Low Charge and the car would just cut off on me. I did a tune-up and that wasn't the problem. What may be the problem?
Re: (DAEDALUS)
The battery is an INTERSTATE about 4-5 months old. The A.A.C valve is on right but there's an adjustment screw and the mechanic who put the engine in adjusted it. What is the importance of the A.A.C valve?
The AAC is an ECU-controlled throttle. It keeps the RPMs up when the car's cold so it warms up faster. Assuming everything else is good, the AAC needs to be adjusted right so your idle is good when the car's warmed up. If you're idling around 650 warmed up then it's probably good. Either way, it won't cause a miss.
Re: (DAEDALUS)
Thank you!
-
Q45tech
- Moderator
- 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: (MR.Q)
"It keeps the RPMs up when the car's cold so it warms up faster."
No, that is the PRIMARY job of the throttle body mounted wax/spring [coolant controlled] thermo ---- throttle valve cracker opener [warm up idle cam]..........why the two coolant line go to throttle body.The IAC is limited in the amount of air it can flow.
The AAC/IAC along with variable ecu ignition advance attempts to keep HOT idle speed at 650-675 rpm under the varying load of alternator, power steering, AC compressor. Also at cruise it acts like a sudden throttle close dampener to progressively let the rpms fall [in steps] when you suddenly let off throttle.
You set the IAC screw by turning it all the way in, then back out 2.5 to 3 turns............if the idle is not at the correct HOT rpm either the IAC is dirty inside or the throttle body is dirty or something else is misadjusted.
Ideally one would use a Consult to see that the ecu is pulsing the IAC solenoid at 10% duty cycle [no lights, no AC on] at HOT idle.
All about dynamic range: an IAC with 10% allows a significant range of upward additional air to compensate for loads [AC on say 25-30%] [all electrical drain worst case adds another 10%] turning the steering wheel fully adds 10%. At 70-80 mph the IAC reads like 60%-80%........setting a floor on engine rpm.
80% IAC pulse duty should raise the unloaded idle to like 1100-1300 rpms.....what happens during a power balance test.
No, that is the PRIMARY job of the throttle body mounted wax/spring [coolant controlled] thermo ---- throttle valve cracker opener [warm up idle cam]..........why the two coolant line go to throttle body.The IAC is limited in the amount of air it can flow.
The AAC/IAC along with variable ecu ignition advance attempts to keep HOT idle speed at 650-675 rpm under the varying load of alternator, power steering, AC compressor. Also at cruise it acts like a sudden throttle close dampener to progressively let the rpms fall [in steps] when you suddenly let off throttle.
You set the IAC screw by turning it all the way in, then back out 2.5 to 3 turns............if the idle is not at the correct HOT rpm either the IAC is dirty inside or the throttle body is dirty or something else is misadjusted.
Ideally one would use a Consult to see that the ecu is pulsing the IAC solenoid at 10% duty cycle [no lights, no AC on] at HOT idle.
All about dynamic range: an IAC with 10% allows a significant range of upward additional air to compensate for loads [AC on say 25-30%] [all electrical drain worst case adds another 10%] turning the steering wheel fully adds 10%. At 70-80 mph the IAC reads like 60%-80%........setting a floor on engine rpm.
80% IAC pulse duty should raise the unloaded idle to like 1100-1300 rpms.....what happens during a power balance test.
Re: (Q45tech)
That's alot of knowledge I appreciate it.