Replaced injectors, occasional whistling noise

2000 XJ, 4.0, AW4, NP242.

I finally got around to doing the 0280155917 injector upgrade tonight after several months of procrastination. Everything seemed to go well until I got about four miles into the test drive.

What I have now is an occasional whistling sound - it's almost like the whistle of a boiling kettle only at lower volume. It only lasts for a few seconds, and the pitch remains constant regardless of road or engine speed. There are no other apparent symptoms related to it - just the sound. It doesn't seem to happen at idle, which is making it very difficult to track down.

There are no evident leaks at the injectors, either at the fuel rail or the head. Same goes for the fuel line connector at the fuel rail (which was not disconnected during the swap, FWIW), fuel damper, and fuel pressure test port. New O-rings were installed on the injectors. The throttle body was removed and does not show any evidence of having not properly reseated once reinstalled. CCV lines were not removed or damaged. Cruise control and cabin air vent selection work as expected, so I'm inclined to think it's not a vacuum leak from that system.

Any ideas? Apart from that noise, it's running great - much better than it has in a couple of years, in fact.

Does it do it only when you back off the throttle? Only when cold?

Saudade said:

Does it do it only when you back off the throttle? Only when cold?

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Good questions. It does it seemingly regardless of throttle position, though the whistle does go away again at idle. Didn't notice it happening when cold, and 4 miles of test-driving would've been enough to get it up to operating temperature. FWIW, the test drive ran for about 30 minutes, and the sound was fairly consistent during that timeframe.

I had the same "tea kettle" after doing an exh manifold swap. It happened when cold and after letting off the throttle. My guess was I had an intake leak big enough to cause a whistle but not big enough to cause a high idle. Don't know if it was the intake manifold, TB or EGR but I removed, RTV'd and reinstalled everything and whistle gone.

Saudade said:

I had the same "tea kettle" after doing an exh manifold swap. My guess was I had an intake leak big enough to cause a whistle but not big enough to cause a high idle. Don't know if it was the intake manifold, TB or EGR but I removed, RTV'd and reinstalled everything and whistle gone.

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Not ruling out the possibility of a manifold leak, but the timing on it would be very coincidental and I'd expect a more constant sound from it. No EGR valve on a 2000, so that's out.

Conceivably, the throttle body may not be quite seated properly (I'll re-check it in the morning when the engine's cold again), but I'd expect there to be performance issues and there just aren't any. The damn thing runs great.

It's almost like the noise is related to something that's cycling, but I couldn't establish a pattern. The IAC sprang to mind, but IIRC that shouldn't really be at play other than at idle. Air-conditioning use is not a factor here as it's turned off.

Couple of quick questions:

Did you clean the manifold and fuel rail so the new seals would seat properly?

Did you lubricate the new seals before installing the injectors?

joe_peters said:

Couple of quick questions:

Did you clean the manifold and fuel rail so the new seals would seat properly?

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Yes, and got what felt like positive engagement of the seals at both the fuel rail and manifold. Clips on the fuel rail end of the injectors are aligned and locked down properly.

Did you lubricate the new seals before installing the injectors?

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Yes - light coating of fresh motor oil on both rings.

almost sounds like a leak in the EVAP purge system, If you can't find any loose or unconected vacuum lines, you may have to have a reputable shop smoke while they cycle the purge valve with a scanner. I might add that spaying down the lines with brake cleaner & listening for Rpm change won't work, as the purge ops are a timed & condition event that the ECM decides when & If the conditions are right. Hence why you have to do it whith a scan tool.

nick86 said:

almost sounds like a leak in the EVAP purge system, If you can't find any loose or unconected vacuum lines, you may have to have a reputable shop smoke while they cycle the purge valve with a scanner. I might add that spaying down the lines with brake cleaner & listening for Rpm change won't work, as the purge ops are a timed & condition event that the ECM decides when & If the conditions are right. Hence why you have to do it whith a scan tool.

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This is a good call - but I think I may have found the problem.

Long story short: it looks as though there was some collateral damage to the intake tube under the top lip of the clamp retainer at the throttle body end. I finally got it to make the noise at idle, and some rocking and squeezing of the intake tube showed up a few hairline cracks I hadn't noticed before. The pitch of the whistling noise changed with movement of the tube, so it's looking like this is probably the culprit.

I'll go grab one out of the junkyard on Monday when they're open again, but on the off chance that I can't get a decent one does anyone have a part number for that tube (2000 XJ; 4.0)? I just need the rubber section that makes the 90-degree bend down to the throttle body from the airbox, and checking mine for a part number didn't yield any legible results.

Looks like the P/N is 53006275 Hose, Air Cleaner to T/Body

Sidewinder CC said:

Looks like the P/N is 53006275 Hose, Air Cleaner to T/Body

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Awesome, and it looks like '91-'01 are the same part number. Thank you!

I'm still looking for the whistling from my truck but I think mine is whistling a different tune. Checked my air cleaner gear but no luck there. Very elusive.

Man-up and use DUCT TAPE!

I've used liquid tape to seal up leaky vacuum hoses for years, so I think just I'll fill a garden sprayer with the stuff and douche down the entire engine bay with it. :laugh:

joe_peters said:

Man-up and use DUCT TAPE!

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Actually, that was my temporary fix

Gonna hit the junkyard later today and see what crops up. Having spent most of its life in a hot, dry climate, I'm finding that a lot of the rubber pieces on this XJ are rotting out sooner than most around here do so the hunting should be decent.

Grabbed a junkyard intake hose yesterday from a 2001 XJ. It got rid of about half the whistling noise, so I figured this was likely a compound issue.

Replaced the throttle body gasket that I had picked up at Autozone with one from the dealer and the whistle is 100% gone. The Mopar gasket is noticeably thicker and has a much larger surface area, and was only $3.50. I probably wasted more than that in gas in the roughly 100 miles that the Autozone item was in there due to the air leak.

casm,

Do you have the Mopar P/N for that TB gasket handy?

Thanks

Sidewinder CC said:

casm,

Do you have the Mopar P/N for that TB gasket handy?

Thanks

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The bag it came in says it's 53007543AB

Thanks casm.