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Discussion Starter #1
So I developed a little problem that got so bad the car died and won't start today. The first symptom was I blipped the throttle to rev match and it just backfired super loud and when I would rev the engine hard it just bogged and popped. I thought it was the dizzy so I swapped in my extra and nothing changed. Just put in new spark plugs as well, seem to be getting spark at all 4 cylinders. Priming the pump makes pressure jump to 40psi and slowly taper off. TPS and MAP read correctly as seen in the log below.

All I can think of is a bad crank position sensor. I'll double check to make sure belt didn't slip but it got gradually worse so I doubt it's off. Could be a leaky injector but I pulled the rail last month and primed, not a drop came out. Putting new ones in anyway just because I want these flow tested and balanced. I've also not been able to go into boost lately, especially in lower gears or it would cut and backfire, and the tach would go crazy in this instance. Another thing leading me to crank position sensor. Not getting any codes which is very frustrating.

1997 Civic EX coupe - Stock Block - Ebay Turbo kit 7psi - Hondata S300 p28
Here's a video during the data log:
Change datalog extension to .s3d
 

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'91 CRX DX, D15B (D15Z7), DX L3
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The tach freaking out is typically an ignitor module issue. Was a big enough problem in ED's that they did a service bulletin.
 

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Discussion Starter #3
No voltage or continuity from harness connector for ckf sensor with key on.
 

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Discussion Starter #6
Cylinder 1 and 4 spark plugs are wet with fuel. 2 and 3 plugs are dry almost ashy. Uneven fuel or uneven spark? Hmmm... All 4 plugs are ~4.5 ohms. Plug wires are 3.6, 4.1, 5.2, 5.6. Seems all good there.

Months ago the car suddenly started running super rich. I tuned it out. Now I'm thinking injectors broke and I just ended up making cylinder 2/3 too lean.

New injectors tomorrow, we'll see. Any other ideas are welcome.
 

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93 Civic HB SI
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What kind of injectors do you have, and what are you replacing the current ones with?

I know it seems to run decent at idle based on the video, but just for giggles have you checked compression, especially now since you say it doesn't start anymore?

Low compression due to compromised valve sealing could allow for a backfire, especially if a burnt or bent valve was on the intake side. Honda's are two injector pulses per revolution, timed to inject during the intake and compression strokes. If liquid or vapor fuel is pooled at the back of the valve waiting to come into the cylinder under the compression injection pulse, but there is a leak and the flame front sneaks past the valve face, bang/pop/etc.

Sinilar symptom could technically happen if it was on an exhaust valve, leaking fuel/air mix past the valve into an already hot exhaust manifold, bang/pop/etc.

Typically when I see differences in spark plugs with a significant contrast like you describe above, some being wet with others being dry, I like to perform compression testing and leak down testing to verify basic cylinder sealing.

If you feel the injectors are leaking, this can skew compression testing. Make sure to pull the main relay connector, fuel pump connector or the fuse that feeds the fuel pump to prevent excess cylinder washout. Also disable spark. Spray some PB Blaster or WD40 in the cylinders then crank the engine over with the plugs out to relube the cylinder cross hatching. Then perform a few sets of compression tests per cylinder, and keep note of them. Your initial compression check might show good/ok after initially spraying the cylinder down, but after a few times, the excess lube will wash away and air will find it's way past things. Your looking for a large compression contrast as well as overall low numbers. For example, if you have 180 on 2 cylinders and only 110 or 120 on the others, sum ting wong!

On the other hand if your injectors were leaking, and lubing the cylinders bumped compression and it holds consistently after back to back tests, then it's a good bet you do have leaking injectors or similar.

If you see a large contrast even after back to back compression testing, perform a cylinder leak down check. Place each cylinder at TDC and air it up with a leak down tester. Look for significant leak down. If you see it, then add more air pressure and listen to see where your cylinder seal might be compromised. Listen to the intake/TB opening, the exhaust outlet and/or the crankcase through the oil cap hole for any significant leakn noise and air movement. It is normal to have some air leak past the pistons into the crankcase during leakdown testing, but you will just know when too much is too much. Serious leakage into the crankcase will almost always reflect the results of the compression test.
 

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Discussion Starter #8
What kind of injectors do you have, and what are you replacing the current ones with?

I know it seems to run decent at idle based on the video, but just for giggles have you checked compression, especially now since you say it doesn't start anymore?

Low compression due to compromised valve sealing could allow for a backfire, especially if a burnt or bent valve was on the intake side. Honda's are two injector pulses per revolution, timed to inject during the intake and compression strokes. If liquid or vapor fuel is pooled at the back of the valve waiting to come into the cylinder under the compression injection pulse, but there is a leak and the flame front sneaks past the valve face, bang/pop/etc.

Sinilar symptom could technically happen if it was on an exhaust valve, leaking fuel/air mix past the valve into an already hot exhaust manifold, bang/pop/etc.

Typically when I see differences in spark plugs with a significant contrast like you describe above, some being wet with others being dry, I like to perform compression testing and leak down testing to verify basic cylinder sealing.

If you feel the injectors are leaking, this can skew compression testing. Make sure to pull the main relay connector, fuel pump connector or the fuse that feeds the fuel pump to prevent excess cylinder washout. Also disable spark. Spray some PB Blaster or WD40 in the cylinders then crank the engine over with the plugs out to relube the cylinder cross hatching. Then perform a few sets of compression tests per cylinder, and keep note of them. Your initial compression check might show good/ok after initially spraying the cylinder down, but after a few times, the excess lube will wash away and air will find it's way past things. Your looking for a large compression contrast as well as overall low numbers. For example, if you have 180 on 2 cylinders and only 110 or 120 on the others, sum ting wong!

On the other hand if your injectors were leaking, and lubing the cylinders bumped compression and it holds consistently after back to back tests, then it's a good bet you do have leaking injectors or similar.

If you see a large contrast even after back to back compression testing, perform a cylinder leak down check. Place each cylinder at TDC and air it up with a leak down tester. Look for significant leak down. If you see it, then add more air pressure and listen to see where your cylinder seal might be compromised. Listen to the intake/TB opening, the exhaust outlet and/or the crankcase through the oil cap hole for any significant leakn noise and air movement. It is normal to have some air leak past the pistons into the crankcase during leakdown testing, but you will just know when too much is too much. Serious leakage into the crankcase will almost always reflect the results of the compression test.
I just don't see a loss of compression/valve sealing happening this suddenly with relatively soft driving and low abuse but it's certainly possible. After my battery is charged I'm testing voltage to each plug and injector to ensure that's even. I'll add compression testing to my list.

Injectors are rebuilt stock 240cc from eBay and ordered some not rebuilt one's. The car doesn't burn oil, just leaks it. Has piston slap on cylinder one cold start for a bit.
 

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93 Civic HB SI
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Take the injectors out of the equation, and see if you can run and start the car on brake clean through the throttle body.

If you are able, but were not able to get the car started with injectors in play, then fuelling is most likely the culprit.

There are both sides to fuelling though, electrical injection control and mechanical fuel pressure. I would check to make sure the ECU is physically able to pulse the injectors using a noid or test light. Like you said, also verify each one is receiving battery voltage when the key is on. The ECU pulses ground to the injectors.

Also check the injector coil resistance to make sure you have injectors that are still in spec from a resistance standpoint. I dont trust a lot of the injectors from ebay, electrically or mechanically, aside from the brands that have a known good reputation. Had a lot of bad ones come in the shop from customers over the years.
 
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