Start-Up Stumbling

[Offroader Member Find all posts View Profile Close Offroader]

I'm experiencing this intermittent engine stumble during the cranking/start phase. Can't predict when it will happen but just doesn't seem to fire up smoothly. Happens about once out of every 10 starts or so. Engine runs perfectly at all other times - no abnormal symptoms. No Check Engine Light or other such codes. Don't want to just replace suspect parts in an effort to pin the tail on the donkey. Any thoughts appreciated.
Also when starting, I tend to just blip the key to start and let it return to the On position as opposed to holding in the start position until the engine fires up. Haven't given it much thought until now. Is this the correct procedure?

[grizzly63 Junior Member Find all posts View Profile Close grizzly63]

Just experiencing what sounds exactly the same in our 06 Grande, what did you find?. Would be great to hear!,, Cheers! Grizz

[Bear63 Senior Member Find all posts View Profile Close Bear63]

Possibly dribbling injectors , is it only when its been sitting for a bit? hot or cold?

[Steve M Addicted PP Member Find all posts View Profile Close Steve M]

Yeah just flipping the key is fine. I do this to mine and the wifes Toyota, that's the idea of it anyway.........Could be as mentioned leaking injector/s so sort of like its flooded when first firing up. Any abnormal black smoke out back on start up ?? after its been standing (cold) or is it once the engine is warm ?? or both........ Cheers Steve

[grizzly63 Junior Member Find all posts View Profile Close grizzly63]

Sadly no pattern to it at all,hot/cold does,nt seem to care and like on previous post runs fine the rest of the time. Had electronics diagnosed as ok so maybe fuel is the issue. Thanks for the input I,ll chase it up with my local grease monkey!

[Offroader Member Find all posts View Profile Close Offroader]

I'm pretty sure this problem has something to do with fuel pressure bleeding off after the engine is stopped. Could be leaking injectors but there is no smoke on start-up. I'm thinking it might be a bad fuel pump as the fuel pressure regulator seems fine. Apparently there is a check valve in the fuel pump which keeps the line primed. If this is leaky then the fuel pressure might drop.

[Bear63 Senior Member Find all posts View Profile Close Bear63]

Leaky injectors will usually have no smoke on start up as the amounts they leak is very minor but enough to cause the rough running (had another one today)
You will need to do a pressure test and isolate each section to eliminate leaking pressure regulator which can give the same symptom as a leaking non return valve in the pump
Leaking injectors can only be checked by removal and pressurizing them so you can visually check for leaks , they will not dribble they will just get a dampness appear on the tips

[Offroader Member Find all posts View Profile Close Offroader]

Hi Bear, thanks for the info, I was thinking there would be smoke at the tailpipe from a rich condition. I'm hoping it isn't leaking injectors - expensive repair.
1. Would injectors bleed off pressure that quickly or take hours? If I start the car and stop it for 3-5 minutes I get the hard starting issue. If I restart under this time no problems. Want to do a pressure test but no shrader valve like some cars which makes it nice and easy. In the mean time turning the key on and off twice before starting seems to prime the line and resolve the problem.
2. How long do injectors last? Mine have done 250 000km. I know fuel pumps can tend to be on their last legs around this time as they head towards 300k.

[Bear63 Senior Member Find all posts View Profile Close Bear63]

That sounds like it is draining back , if buy cycling the fuel pump like that prevents it happening that is usually a sign that the rail pressure isn't holding , you will need to get a fuel pressure gauge in between the pump and the regulator , pressurize it and clamp the line just before the regulator so you can tell if its the non return valve in the pump
Injectors can bleed quickly or slowly there isn't any normal , but it doesnt sound like that now from what you are saying

[Offroader Member Find all posts View Profile Close Offroader]

Finally got this problem sorted. It was the fuel pump. Injectors and fuel regulator were ok. The check valve in the fuel pump is not serviceable but when faulty allows fuel to run back into the tank so I had to replace the whole unit. Better than breaking down on the side of the road. Won't have to worry for another 250 000km.

[grizzly63 Junior Member Find all posts View Profile Close grizzly63]

Hey all, I,m still battling this issue even after following what 'offroader' did, seems more prevelant when the weather is warmer tho!I,ve been chasing advise all over with no luck and wondered if anyone else was in the same boat?

[vlbaby Lurker Find all posts View Profile Close vlbaby]

Hi Grizzly,
I've just come from solving a similar problem on my my 03 grande petrol. Perhaps the only difference would be that mine was mainly hard to start when the engine was warm. I went through just about everything I could think off. I check temp sensors, cleaned the MAF sensor, checked fuel pressures, had the injectors cleaned and tested, but the thing that fixed it in the end was just replacing the injectors altogether. As I found out from someone else's post on another thread, the denso injectors tend to dribble or weep when they're hot. I ended up buying some cheap injectors from ebay, which are aisan brand instead of denso, but the injectors look identical to the originals. I ended paying $61 for a set of 6! You gotta love ebay! Maybe your problem might be a different cause to mine, but if you get your hands on the injectors cheap enough, it might be worth a punt.

[grizzly63 Junior Member Find all posts View Profile Close grizzly63]

Yeah Cheers, vibaby will look into it , how much would you normally pay for genuine plus labour?

[Hoody Junior Member Find all posts View Profile Close Hoody]

Yeah Cheers, vibaby will look into it , how much would you normally pay for genuine plus labour?

I have a moderate to strong vibration at low revs - Toyota checked and told me it's the injector blocked with crap. Suggested I run a couple of tanks of premium, otherwise $600 to clean.
Keen to find out what injectors and how much to install, or if easy to DIY