Starting Hesitation - Cranks fine

[flooredrunner]

Hello all,

I've recently started to experience a weird starting issue/hesitation on my rig.

It will crank just fine right up to when the cylinders are going to be fired off and then feels like it wants to die out or not fire the cylinders correctly. It will do this for a second or two and then start normally fine and the RPM will rise normally.

Just started noticing this a couple of days ago and would be good to catch it earlier rather than later. Hoping it isn't a stuck fuel injector.

Anyone have any ideas? Any input is appreciated.

 

[flooredrunner]

bump

 

[Ehahn84]

Could be a leaky injector. I had the same issue and thought that. Ended up being a bad IAC and throttle position sensor and needed a really good MAF cleaning.

 

[flooredrunner]

Could be a leaky injector. I had the same issue and thought that. Ended up being a bad IAC and throttle position sensor and needed a really good MAF cleaning.

Thanks for the reply! I have cleaned my MAF and replaced my TPS about 2 months ago due to check engine light with an aftermarket part. I will try to clean the throttle body and IAC.

Thanks for the suggestion

Edit: good looking rig btw

 

[4runnerfiend]

Thanks for the reply! I have cleaned my MAF and replaced my TPS about 2 months ago due to check engine light with an aftermarket part. I will try to clean the throttle body and IAC.

Thanks for the suggestion

Edit: good looking rig btw

Check all you vacuum lines are connected well and not cracked breaking on the ends. I was having funny starting issues and turned out to be a vacuum hose that was running the the... I believe the charcoal canister. 5 minute 0 $ fix

 

[BrianSD_42]

I have a similar issue. In my case sometimes I go to crank it and there feel like a 1 to 1.5 second delay before it starts up. Usually it starts up in < 1 second so going the extra 1.5 feels long to me. I've own my truck for 18 years now and this is a relatively new and sporadic issue. The truck has always started up though.
.

 

[gamefreakgc]

Pull the EFI fuse in the engine bay, then replace and see if it cranks up fine or not. If it does start fine, you've got a sensor out of whack that's changing the amount of fuel at startup, most likely the MAF since pulling the EFI fuse resets the learned fuel trims.

If it makes no difference, it's something more mechanical, like a leaky fuel injector or vacuum leak. Vacuum leaks are sneaky and can happen slowly over time or only during certain engine bay temperatures.

 

[flooredrunner]

Pull the EFI fuse in the engine bay, then replace and see if it cranks up fine or not. If it does start fine, you've got a sensor out of whack that's changing the amount of fuel at startup, most likely the MAF since pulling the EFI fuse resets the learned fuel trims.

If it makes no difference, it's something more mechanical, like a leaky fuel injector or vacuum leak. Vacuum leaks are sneaky and can happen slowly over time or only during certain engine bay temperatures.

This sounds very logical. Will try this tonight. Thanks

 

[DaMonkey]

Old timers will tell us: you need 3 things. Spark fuel and compression.

Since it runs normal and only happening during cranking, check your cranking voltage. Might be as simple as your battery. Normal is prob around 10.5. It drops from all the hard work and low revs on alt.

If you have an oscilloscope check during cranking the return signal from igniter to ECM. You should see a 0-5v square wave. First check at ECM then at igniter will confirm that circuit is solid or not. Then check square wave between igniters and coils. Could be a bad igniter at low cranking voltages. If you don’t have a scope, FSM says you can check voltage on these wires should be between 0.5 and 4.5v. But a scope is like X-ray vision and a great tool to have for issues like this. PC based 2 channel scope can be had <$100.

If that’s good, you can check signal into injectors at cranking. You’ll see the logic square wave from ECM for opening cycle. A current clamp and scope will also give you X-ray vision into the current sink into injectors. I think my current clamp to plug into scope was only $50 for a cheap Chinese unit but it works. Can see the signal and current on same time series with 2 channel.

I’d love to see more people diagnose injectors before R&R. It’s a big job and loads of threads that say: well I changed injectors and problem is still there.

If it’s of interest, and helpful to you, let me know - next few days maybe I’ll do a video how it’s done. Mine works well but wouldn’t mind seeing how consistent the pintles on my injectors are.