Just joining the XR4Ti crowd hoping someone knows this car

XR4Ti / Sierra / Sierra Cosworth Discussions - Questions, problem resolution, general talk, technical tips and modifications.
99stockgt
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Re: Just joining the XR4Ti crowd hoping someone knows this c

Post by 99stockgt » Mon Jun 09, 2014 9:16 am

Alright so it's been a while since this beast has had any loving, so let's brush the dust off and see where we are. Car spent a while in a local garage getting some issues ironed out, removing the HVAC, A/C compressor, hiding the IC and building some new custom piping, replacing plugs/wires, etc etc.

As previously stated we are still fighting a cold idle problem. Generally speaking with the IAC attached it runs terrible so we are working with it disconnected. For some reason it seems whether connected or not she never realizes she's closed loop, so once warmed up she does idle much better. Idle is pretty solid around 1000 RPM. AFR is showing on the rich side.

As the engine temp improves so does the performance of the car, we see an occassional drop into lean when running mid range RPM 2500-3500 though only for a split second. As you move up through the revs is where we find the more concerning problem. Between 3500 and 5500 if under load and building boost she begins to "break up" losing power/boost and the AFR going all sorts of colors. Light accel into this range doesn't seem to cause the problem quite as much. There is also a bit of a smoke poof which escapes out the tail under higher boost and after shifts when under boost.

Plugs and wires are 300 or so miles old, brand new motorcraft.

My thinking at this point is, am I running out of fuel or air? I'm uploading a video to YouTube of the engine at warm temp so we can all make some educated guesses. Thanks in Advance!

http://youtu.be/2_ZfMVIw1gk
'71 LeMans Sport / '87 Merkur XR4Ti / '88 Merkur XR4Ti / '91 Syclone / '92 Stealth RT/TT / '97 4Runner SR5 / '99 Mustang GT

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tvissoc
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Re: Just joining the XR4Ti crowd hoping someone knows this c

Post by tvissoc » Tue Jun 10, 2014 10:21 pm

I've not read much of this thread, so you may have already been down the path of replacing these items:

1. TPS. XRs seem to be very picky about TPS quality and adjustment. If you're getting weird response at certain throttle positions, look to the TPS needing replaced.

2. Smoke? Could be turbo seals (usually shows up when accelerating away from a stop). Valve stem seals? Are you boosting into the crankcase? Check PCV. Make sure you can't blow through it.

3. Cold idle problems are often associated with the ECT sensor (the big one).

4. Missing under boost: Use standard copper plugs. Good plug wires. If you're feeling frisky, disconnect the knock sensor (after insuring ignition components are fresh and good). You might be amazed at the happy-happy feeling. Try at your own risk, and listen for detonation.

As I said, you may have already taken care of all this stuff, but thought I'd mention it. These are things I often ignored and sometimes the simple things are what fixes the issues.

Tony
Tony Vissoc
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tvissoc
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Re: Just joining the XR4Ti crowd hoping someone knows this c

Post by tvissoc » Tue Jun 10, 2014 10:24 pm

Oh, and make sure your ECU ground is good. You'll get all kinds of weirdness if that isn't grounded properly. Orange cable. Strapped on turbo somewhere.

Tony
Tony Vissoc
Nothing to see here. Move along.

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