Hard start/ Cats/fuel pump/02 sensors/ (1 Viewer)

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Oct 3, 2019
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Salt lake city
so I’ve scoured different forums but having no luck solving a hard start issue. Bought a 99 lx470 about 2 months ago. Ran amazing for a couple weeks and still runs great once it’s running but after having it two weeks it would intermittently crank at start but not fire. Turn the key off and try again and it would fire. Sometimes it takes 2-3 tries. Sometimes it fires immediately. I did some regular tune up stuff when I first got it. Oil change/ new filters. Some things I’ve done since the issue started: new fuses at ecu and efi, new fuel pump relay, new fuel filter, cleaned the maf, checked charging system, new upstream 02 sensors. I have a new fuel pump but not installed, the heat shields on the cats are rusty rattling sob’s so it’s possible the cats could be trash and they could be causing the issue. I’ve got no cel though and almost wish I did so it might give an idea what else to check. Maybe I’m overlooking something simple? Any help would be greatly appreciated.
 
Sorry, vehicle has 152k miles, I’m the third owner, from what I can tell from a carfax the vehicle was maintained regularly till 138k, then was bought by a youngster in his 20’s and I think he realized he couldn’t afford to do much with it and sold it to me.
 
Many things can cause a hard start. One associated with long crank, is fuel injector leaking down. This is a little different then you describe. But I'd though I throw it out there. It's most common seen as long crank after sitting overnight.

Weak fuel pump on way out is certainly suspect.

R&R any vacuum lines that are hard and cracking when ends pinched closed. Just helps tuning, not likely your issue.

Watch the security light on center console. If it stay on once key in IG and during long crack. It's then likely the immobilize going out.

Clogged CAT can be problematic.

Read the codes, see if any pending.

Condition of old spark plugs can be revealing. As can watching fuel trims.
 
Last edited:
Appreciate that. Some things to look at. Plugs looked good. I’m certain it’s not an immobilizer issue. I’ve got both original keys and have checked that.
 

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