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injector drama

i've been helping my friend with his 85.5. thinking that a coolant leak was a bad head gasket, we started tearing it down. we found that the coolant neck at the back of the cylinder head was leaking coolant, so we repaired that and began reassembly.

some nonce had installed 928 injector o-rings at the injectors
(very large) and somehow managed to shove it together. thus, getting the injectors out of the intake manifold required a LOT of force. subsequently, two of the injectors were damaged.

being on a budget, my friend bought two used injectors from the local porsche shop. now the car idles like crap and will die when the A/C is engaged. we have checked everything we can think of, including vacuum, cleaning electrical connectors, replacing vacuum hoses and fittings, etc.

how likely is it that these injectors are just clogged and need a good cleaning?

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Old 06-23-2007, 02:49 PM
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Did he get the right injectors? What are the numbers stamped on the sides of them?
Should end with 150158

The last three numbers should match on all 4 injectors.
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Old 06-23-2007, 02:54 PM
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yeah, he got matched injectors. same numbers on all of them.
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Old 06-23-2007, 02:58 PM
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Was it an o-ring problem or were the injectors bad? When you put the ATF on the o-rings they swell up A LOT after you put them back together. I had to get all new o-rings for my new injectors because I had to take the rail off to replace the fuel line from the damper to the rail.

If you still have the old injectors and they are not damaged I would try replacing the o-rings. I paid $20 for 4 sets.

The 928 o-rings and injectors are different than the 944?
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Old 06-23-2007, 03:10 PM
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they definitely had the wrong o-rings. pulling the rail with both hands, i was unable to pull them out. the shop had both sizes and the 928 rings are definitely larger, probably close to twice as much rubber.

regardless, two of the injectors were ruined getting them out of the fuel rail/manifold and now the car runs really rough with the replacement injectors.
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Old 06-23-2007, 03:18 PM
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I would guess the two new injectors to be bad or dirty. The vac lines to the FPR and the damper don't make much of a difference in how smooth or rough it runs.

Did you get the spark plug wires back on tight? I know I take the last two wires off on mine when I take the fuel rail off because they run through the fuel hose from my damper to the rail. Maybe one of the wires is damaged.

Is it rough at all RPMs or more so just at idle? There is an idle speed adjuster, maybe it needs to be bumped up to 900 RPMs if you're lower than that.
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Old 06-23-2007, 04:41 PM
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it ran perfectly smooth prior to the recent surgery. wires have been checked. its mainly rough at idle.
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Old 06-23-2007, 05:15 PM
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What is the RPM at the rough idle? Below 900?
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Old 06-23-2007, 05:19 PM
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yeah, it staggers along at about 700
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Old 06-23-2007, 06:13 PM
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It think it would run much smoother if it were up to 900 or 950. I would try adjusting that idle speed adjuster. I think that at 700 RPM any additional stress to the engine like the AC would prob kill the engine.
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Old 06-23-2007, 06:21 PM
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turns out cylinder one is not firing. the injector is bad/clogged. total bummer.
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Old 06-24-2007, 09:05 AM
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Before tearing into it try a light tap on the injector with the engine running - sometimes the tiny little piston inside the injector gets stuck when it has sat for a long time. Once it breaks free it may work perfectly. I learned this on this websight and proved it true when putting a new/used engine in my wifes Honda. Different brand of injector but same construction. The tiny electrical pulse firing the injector is not quite enough to break thing free inside.

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Old 06-24-2007, 02:49 PM
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