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-   -   Stuck injector = bent rod (?) (https://www.miataturbo.net/engine-performance-56/stuck-injector-%3D-bent-rod-110727/)

Bloopdog Oct 11, 2025 10:21 PM

Stuck injector = bent rod (?)
 
As the title suggests, did a small pull, injector 1 stuck open, afrs down to 10 with a misfire, coasted half mile and it shut off, wouldnt start again but would crank (i was in the turn lane midday traffic so i was worried about getting it moved)
pushed the car into a parking lot, where i tested some stuff assuming my afr gauge went bad or an injector had come undone. Smelt fuel while cranking and mid crank it stopped. I halfheartedly knew what this meant, but without thinking tried the starter again for a split second. Nothing. Knew it was locked up, took out plugs and it wouldnt move with a wrench, i didnt want to forcefully unstick it.
marvel mystery oil in it for a few hours drying the ethanol out and it was unstuck. Ethanol pools in the runners of the im, throttle body, literally everywhere. Threw stock injectors in, changed my oil - had a lot of ethanol in it, and it started and drove a block or two home on a basemap without getting into boost.

1.? rod bent or decent chance its fine
2.? Any good ways of checking for a slight bend or knowing a rod is very bent? Im assuming its not on the verge of just snapping given it drove home.

either i drive it for a long time when I get my new injectors in or I get a nicely ventilated block somewhere down the line. A rods only refresh was in the plans, but later down the line financially.

side note- just sourced a bp4w 110k mile bottom end for a set of large tupperware skirts spats and hardware, or i could just sell the kit for 500$ and it put towards a forged rods only build. Decisions decisions. 25e kit for 50$ from the junkyard to go with the 200$ junkyard hardtop, 150$ junkyard torsen i got under my belt

Reverant Oct 12, 2025 05:00 AM

My experience has been that the starter motor is not powerful enough to bend a rod and there is little inertia/energy in the crank/pistons/flywheel at that low of an RPM. It will absolutely happen at 2000rpm cruising down the highway, if you suck in water. Thankfully injectors are not large enough to be able to fill a cylinder within 2 engine rotations, so you can never hydrolock an engine with a stuck injector while the engine is running.

Bloopdog Oct 12, 2025 12:02 PM


Originally Posted by Reverant (Post 1670641)
My experience has been that the starter motor is not powerful enough to bend a rod and there is little inertia/energy in the crank/pistons/flywheel at that low of an RPM. It will absolutely happen at 2000rpm cruising down the highway, if you suck in water. Thankfully injectors are not large enough to be able to fill a cylinder within 2 engine rotations, so you can never hydrolock an engine with a stuck injector while the engine is running.

this is reassuring news. Its funny because I had known the second it stopped cranking what had happened, known not to try it again, but didnt stop myself from mindlessly trying to start it. I think im just going to start gathering parts for the rebuild. Shes tired and burning oil in boost anyway.

58nate Oct 21, 2025 09:07 PM

I bent the rods in a ford 302 and then a 351w before I found out the ECU was bad and kept one injector on constantly. The starter was enough to bend the rods on both engines. Depending how many CC volume your head is and how many CC's of fuel get in there can be catastrophic.

Reverant Oct 22, 2025 10:42 AM

I would assume the starter motor on a 302/352ci V8 is waaaay more powerful than the tiny Miata starter.

Bloopdog Oct 23, 2025 02:07 PM

To update this thread, put in some new kraken 700ccs and got them dialed in, in the process I turned boost control “off” to tune on wastegate pressure, somehow this made it keep the ebc closed instead of open, so I hit 16 pounds/boost cut before I could even realize. But so far a few tanks of e85 have lasted on full boost. Forged rods have been ordered though.


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