Long crank, no faults

[Jimmy Brooks]

Yeah - I don’t think battery would cause this issue, but it is maybe something to keep an eye on.

Thinking about the high RPMs at start, I wonder if you could have a vacuum leak. What are your RPMs at idle after it warms up? I would expect a lean code to show up, but you could check your fuel trims after the car is warmed up (so it’s in closed-loop fuel control). Check short term and long term fuel trims and see how they look.

The other thing that comes to mind is the throttle body plate and the throttle position sensor. A little gum in that throttle body can cause the butterfly to stick just a bit and throw things off. You could try cleaning it good with some carb cleaner if you haven‘t already. The TPS (integrated into the throttle body) also can cause these issues if it starts to go bad, but I’m not sure how to test it.

It’s only on initial crank where it’ll spike to 2000 like in the video I posted of the regular crank. The high idle sits at I think 1300-1400 (right where the tachometer pin covers the “auto” part of the auto high beam lamp) idle stays pretty stable on that for about 20 seconds then will drop to 800 (when it’s cold) then will drop to 600 and stay there. No rough idle and the rpms don’t wonder. What do you think I should start with

Also what should I be seeing on fuel trims, what’s normal?

 

[jlglr4]

At idle, short and long term fuel trims added together should be within +/-10%. 0% is perfect. Those idle numbers seem okay - so not sure what’s causing that spike to 2000.

In case you are interested in how the system works: When warm and in closed-loop fuel control, the ECM calculates the amount of fuel needed based on the various sensors telling it how much air (and the density of the air) is coming into the cylinders. The o2 sensors then analyze the exhaust to see if the amount calculated at the front end is correct. The o2 sensors then tell the ECM whether the mixture is too rich or too lean, and the ECM corrects the mixture by adding or subtracting a certain % of fuel from the calculated amount, i.e., fuel trim. It does this by pulse width modulation of the fuel injectors, keeping them open for slightly longer or shorter time frames. If you have the V8 engine, I think you can actually see the pulse width modulation per cylinder with the GAP tool, which can sometimes identify a fuel injector that is not functioning properly. On the v6, we can’t see this. But, it won’t tell you if an injector is leaking down after the car is shut off.

Short term fuel trim is the near-instantaneous changes based on real-time feedback from the o2 sensors. Long term fuel trim is basically the amount of trim that the ECM is detecting on a longer time frame - maybe on the order of several minutes. Different manufactures use different strategies as I understand it - not sure what LR uses specifically. But the take home here is that the fuel trims are additive, so if you see long term -5% and short term +3 at idle, you have -2% total fuel trim at idle.

 

[Jimmy Brooks]

At idle, short and long term fuel trims added together should be within +/-10%. 0% is perfect. Those idle numbers seem okay - so not sure what’s causing that spike to 2000.

In case you are interested in how the system works: When warm and in closed-loop fuel control, the ECM calculates the amount of fuel needed based on the various sensors telling it how much air (and the density of the air) is coming into the cylinders. The o2 sensors then analyze the exhaust to see if the amount calculated at the front end is correct. The o2 sensors then tell the ECM whether the mixture is too rich or too lean, and the ECM corrects the mixture by adding or subtracting a certain % of fuel from the calculated amount, i.e., fuel trim. It does this by pulse width modulation of the fuel injectors, keeping them open for slightly longer or shorter time frames. If you have the V8 engine, I think you can actually see the pulse width modulation per cylinder with the GAP tool, which can sometimes identify a fuel injector that is not functioning properly. On the v6, we can’t see this. But, it won’t tell you if an injector is leaking down after the car is shut off.

Short term fuel trim is the near-instantaneous changes based on real-time feedback from the o2 sensors. Long term fuel trim is basically the amount of trim that the ECM is detecting on a longer time frame - maybe on the order of several minutes. Different manufactures use different strategies as I understand it - not sure what LR uses specifically. But the take home here is that the fuel trims are additive, so if you see long term -5% and short term +3 at idle, you have -2% total fuel trim at idle.

Is it not normal for these trucks to jump 1800-2000 rpm for a quick second on initial turn over? I’m asking this because for as long as I can remember even when the car was starting normal it always did this.

 

[jlglr4]

Mine does not ever rev that high, but I live in Northern CA and keep it garaged, so it’s never very cold at startup. My v6 revs at 1200 for about 30 seconds, then drops to 800 for just a couple seconds, then down to 600. Temperature might affect it, but if you are still in Pasadena, I don’t imagine it gets too much colder outside in Pasadena than in my garage. Not sure though.

I’ve heard plenty of other people say on this forum that their car revs up a little higher - maybe like yours. And, maybe the v8 revs higher at startup to get to temp a little faster (can’t remember if you have the v8 or v6). So, I don’t know what’s normal. Maybe others will chime in.

 

[ftillier]

Mine sometimes goes up to 2k, but only very briefly. Usually it just goes to 1300-ish, then down to 800, and then 600.

 

[Jimmy Brooks]

Mine does not ever rev that high, but I live in Northern CA and keep it garaged, so it’s never very cold at startup. My v6 revs at 1200 for about 30 seconds, then drops to 800 for just a couple seconds, then down to 600. Temperature might affect it, but if you are still in Pasadena, I don’t imagine it gets too much colder outside in Pasadena than in my garage. Not sure though.

I’ve heard plenty of other people say on this forum that their car revs up a little higher - maybe like yours. And, maybe the v8 revs higher at startup to get to temp a little faster (can’t remember if you have the v8 or v6). So, I don’t know what’s normal. Maybe others will chime in.

Just to clear things up when I say jump to 1700-2000 for a second I mean like this

Also all fuel trims look normal.

Wouldn’t a leaky injector cause the car to run poorly?

 

[jlglr4]

That idle looks pretty normal to me. And fuel trims look good. I think an injector could leak enough to lose fuel in the rail while sitting for a few hours, but not affect drivability. I would have maybe expected to see more in the fuel trim, but maybe not. Just takes one injector to drain the lines of pressure. Wish I had a diagnostic for the throttle body/tps, but I don’t.

 

[Jimmy Brooks]

That idle looks pretty normal to me. And fuel trims look good. I think an injector could leak enough to lose fuel in the rail while sitting for a few hours, but not affect drivability. I would have maybe expected to see more in the fuel trim, but maybe not. Just takes one injector to drain the lines of pressure. Wish I had a diagnostic for the throttle body/tps, but I don’t.

Hypothetically wouldn’t I be able to sort of tell if one was slowly leaking out fuel by seeing how fast the pressure diminishes from the fuel rail after pressure reaches its peak after shut off?

Would one injector flooding one cylinder be enough to make the whole engine not able to turn over and fire. I would think all the other cylinders would be able to fire and then I would get some sort of misfire code.

Also if it’s a stuck injector do you think it would be enough to do damage to the engine? (Gas getting into the oil or possibly even hydro locking it?)

 

[Jimmy Brooks]

That idle looks pretty normal to me. And fuel trims look good. I think an injector could leak enough to lose fuel in the rail while sitting for a few hours, but not affect drivability. I would have maybe expected to see more in the fuel trim, but maybe not. Just takes one injector to drain the lines of pressure. Wish I had a diagnostic for the throttle body/tps, but I don’t.

I’m thinking injectors too now, I just tried to start it and it sputtered 4 times getting the rpms to about 400 then finally turned over. Ran fine after though, no codes. Won’t be driving it until I looked at, don’t want to hydro lock the engine or throw a rod due to oil thinning. It seems as if the problem got significantly worse today because the car was only sitting for 2 hours.

 

[f1racer328]

I’m thinking injectors too now, I just tried to start it and it sputtered 4 times getting the rpms to about 400 then finally turned over. Ran fine after though, no codes. Won’t be driving it until I looked at, don’t want to hydro lock the engine or throw a rod due to oil thinning. It seems as if the problem got significantly worse today because the car was only sitting for 2 hours.

If you have an excuse to do an oil change, you could do an oil analysis and see if fuel is in your oil.

Won’t be quick though.