My 2018 Infiniti qx60 has an intermittent starting issue. It just cranks longer than normal before firing. This has been very gradually getting worse for many months. Yesterday, for the first time, it cranked until it timed out. But later in the day it was okay. Most of the time it’s okay. No codes or pending codes ever. Shop found nothing and couldn’t replicate problem. I want to be proactive and address it before I get stranded, but how? I have an antique OBDII scanner, but I haven’t been able to record anything useful. Maybe a more modern gizmo that I can leave plugged in and check with my phone? What is my move?
1st guess being a Nissan/Infinity product, I would say it is probably the cam & crank sensor(s), Nissans/Infinity’s are known for their cam and crank sensors failing… Again just a quick guess…
Make sure your battery is in good working order, never mind the age, it could be 3 months old or 3 years old…
Make sure the engine oil is full, proper viscosity and not dirty…
Does it do the long cranking after sitting overnight or for many hours like sitting all day at work??? But once started, it then starts OK until it sits for long periods of time again???
Or does it start great when the engine is cold (overnight or sitting long hours) but once warmed up is when you have the long cranking???
You can use a scanner with Live Data to read the engine RPM’s while cranking, check the fuel rail pressure, and check for Cam/Crank Alignment (or CKP/CMP Sync Status)…
My scanner has live data, but different modules are giving different rpms and it only refreshes every 0.5 seconds or do. And their is no fuel pressure.
Shop said battery tested good. Just did oil change with SYN 0w20.
Engine never seems to have a problem when it is hot, but freezing cold isn’t necessarily worse than room temperature. And it can be fine after sitting for days.
This could be a fuel pressure issue or a weak fuel pump. Try turning the ignition on for a few seconds before cranking and see if it starts faster. If it does, have the shop check whether fuel pressure is bleeding off. A scanner may help but catching the problem when it happens is key.
That’s not how to test for a bad fuel pump.
You turn the ignition switch on for a second or two, and then turn it off. Repeat this a half dozen times,.This operates the fuel pump enough times to prime the fuel system and to build enough fuel pressure. Then try starting the engine.
Tester
hsn_19’s post is almost certainly generated by AI. No surprise that it doesn’t get the procedure right.
A long crank that never sets a code, creeps worse over months, and once ran until it timed out is a fuel delivery or a signal problem. The shop not being able to reproduce it tells you it is a bleed-down, not a hard failure.
Test it before buying any sensor. Engine cold, overnight: key on, count to five, key off, three times, then crank. If it fires fast on the third prime, the rail is losing pressure while it sits. The usual suspect on these is the check valve in the pump module, not the pump itself. If priming changes nothing, look at the crank signal: your scanner will show cranking rpm even at a half-second refresh, and 150 to 200 rpm steady while cranking means the sensor and its wiring are fine.
Second free check, on a cold morning before you start it: read coolant temp in live data and compare it to the outside thermometer. They should be within a few degrees. If coolant reads 40 when it is 20 out, the engine is fuelling for the wrong temperature and that is your long crank with no code.
One thing specific to these: the fuel pump relay lives in the IPDM box under the hood, and when those contacts go bad the pump runs sometimes and not others. If the prime test points hard at fuel and a hot-wired pump runs fine, that relay is the part.
Since the shop could not reproduce it, keeping a short note each time it happens would help a lot: how long the car sat, whether the engine was cold or warm, and how long it cranked. If the long cranking mainly follows a long sit, that points more towards fuel pressure dropping off while parked. Also check the battery terminals are clean and tight, as a poor connection can look fine on a test yet still cause slow cranking.
A dirty throttle body can cause rough idling.
You could try cleaning it using this.
Also, don’t open the throttle plate by hand to clean the throttle body. It can be damaged doing so and you could end up buying a new one.
Have a helper get in the vehicle, turn the ignition on and step on accelerator pedal to open the throttle plate so throttle body can be cleaned.
Tester
I don’t think stepping on the pedal does anything when the engine is off. And I don’t have a good way to reprogram it if I do clean it. I did my wife’s car and it drove crazy and threw MIL’s. If you think it’s worthwhile, I’ll pay to get it cleaned. That might be worthwhile even if it isn’t the problem, right? It has never been cleaned in 90,000 miles. I’m going to try recording tps and throttle command data with my scanner. If I am lucky enough to catch another bad start, it might be telling?
You should probably pay some one to clean the throttle body.
Since you’re unable to follow simple instructions.
Tester
I’ve been a member of this site for almost 20 years. When I have a question about a car, I jump on here and hope Tester answers. You are usually the most helpful dude on here.
When I said engine off did people think I meant ignition off?
Life Advice ? That means questions about finances , health and personal relationships. Not whether a vehicle will start.
Life advice as in I don’t strictly want DIY repair advice. Should I go to dealer because dealer tools would really help here? Should I sign up for roadside assistance and wait until it needs a tow? Some AI tool I never knew existed? I dunno. It really does complicate your life if your car is not dependable.
For a car this old a dealer is not necessary. You’d probably be better off (and more cost effective) with an independent mechanic who knows the brand.
Since you’re trying to avoid getting stranded, here are a couple of cheap steps while you track it down. Try hsn_19’s test every time for a week: key on for a few seconds, then crank. If it starts normally after priming, that points toward fuel pressure bleeding off, and a shop can put a gauge on the rail overnight to confirm. For logging, a Bluetooth OBD dongle with an app that records sessions can work, but many can’t read fuel rail pressure on every car, so check the app’s supported data for your model before buying. Recording RPM during a long crank would at least show whether the cam or crank signal is dropping out. Last thing: look up what your insurance or roadside plan covers for towing, including distance, so a no-start away from home is an annoyance and not a scramble.
That doesn’t work. The fuel pump only runs for a second or two and then shuts off, And if the anti drain-back valve is bad. turning the ignition on for a few seconds isn’t enough to reprime the fuel rails and injectors and build the proper fuel pressure.
That’s why you turn the ignition on for a second or two, then shut if off and repeat a half dozen times to reprime the fuel system and build the proper fuel pressure before trying to starting the engine.
Tester