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SC- warm hesitation & power loss

My í82 SC runs very well cold, but has issues when warmed up. It seems down on power & torque (a Carrera passed me today!? ) and hesitates under load (worse at lower rpmís). Iíve had a couple of small intake backfires over the past few weeks as well (it does have a popoff valve). This is all a new development (come to think of it, possibly coinciding with damp winter season). Plugs, cap & rotor are 2000 miles old, Fuel & air filters 1000 miles, plug wiresÖ. dunno- old? Fuel mixture & timing & valve adjustment by shop 2000 miles ago. My current thinking is the WUR may be out of spec & the mixture was set richer to accommodate this when cold? Iím looking for the JC Whitney tester, but it seems to be out-of-stock (can only find this one http://www.thetoolwarehouse.net/shop/TA-33865.html ). Would this be a good starting point, or does it sound more like an electrical issue?
Thanks!


Last edited by ubiquity0; 12-23-2003 at 02:13 PM..
Old 12-23-2003, 02:09 PM
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It's probably a good idea to check out the rest of the ignition system first...have you measured the resistance of the plug wires, checked that the wires securely fit on the plugs and rotor, checked that no sparks are "escaping" from the wires, and checked all your grounds? How do the spark plugs look? Your mention of the change in weather would make me suspect an intermittant electrical problem.

The WUR should act the same in all weather, assuming its heating element is hooked up...(you could test for 12V at the WUR electrical connection just to be sure about this).
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Old 12-23-2003, 03:02 PM
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Thanks for the ideas Colin,
I am not entirely convinced this is weather related- has been exhibiting the same symptoms lately when dry & wet, but the problem did seem to start around the same time as the rainy seasion.

I do get some occasional shorting from a couple of the plug wires- not a spectacular light show, but visible & night & audible nonetheless. Magnecores are on my wish list, but could it be possible that the stock wires function fine with a cold engine, but go to hell when hot causing this problem??

What effect would not having the WUR heating element hooked up have? I have 12V @ the connection but the plastic plug itself is brittle & I could imagine *might* not keep a continuous circuit. I would guess if the heating element were not functioning the WUR would continue to enrich the mixture w/ the engine warm?
Old 12-23-2003, 03:15 PM
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I'm not sure about your question about temp. related wire issues, but it does sound like they are worn out and worth replacing before you go too much further with other checks.

The WUR heater will keep the warm control pressure steady at a level higher than cold control pressure. So if it's not heated, warm control pressure may be too low, causing rich warm running.

The heat of the engine itself will also affect the WUR, but it really should have a functioning heater for better control. The colder weather would probably accentuate the problem - the WUR might not ever get hot enough.

Hope this helps!
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Last edited by cowtown; 12-24-2003 at 07:23 AM..
Old 12-23-2003, 04:20 PM
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I'm going to make sure that WUR elec connector is firmly attached with a zip tie for now- does anyone know what type of connector it is, & where I can get a replacement? (I'm an electrical dummy)
Have magnecores on order as well, so we'll see what happens.
Thanks
Old 12-24-2003, 07:13 AM
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Even when everything is right the WUR will take longer to warm up...it's just cold....

Or are you having problems after a good warm up? The WUR has internal heating and heater from the engine, but give it a chance. The heating element doesn't put out that much heat.

I know you're in Cali, but every year this time, folks post threads that there car is acting up...the CIS is good and weas designed to adjust to temp and air pressure, but it has limited range of self adjustability. esp, after 20+ years of age.
Old 12-24-2003, 07:22 AM
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The warm-up period is actually ok- always starts right up, idles ok (but not @ 1200 even though the AAR is open) & has good power, runs smooth. Its after the first 5 minutes when the problems start- rough running, hesitation. Lately engine temps haven't been going much above 180 though no matter how long the engine runs.

Last edited by ubiquity0; 12-24-2003 at 07:41 AM..
Old 12-24-2003, 07:34 AM
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In a perfect work, the CIS should adjust for changing amb. temps, but I bet your A/F was adjusted when it was nice and warm out. Now that is cooler, the A/F may need to be looked at again. I'm guessing it's running lean. The air is cooler and more dense. So if your car was adjusted toward the leaner side of things when it was say..July! It is now too lean for December! Just a guess from 3000 miles away.

If it were my car, I would turn the A/F mixture screw an 1/8 or 1/4 turn clockwise and see how the engine behaves after that.

When I am not on my way tot he EPA test station, my car is always on the rich end of things...
Old 12-24-2003, 07:48 AM
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So I pulled a couple plugs today. Its running rich!

Very rich. I leaned it out about 1/4 turn. Going to pickup new plugs & see how things go. Not sure how it got to be so rich?
Old 12-26-2003, 01:03 PM
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could be that the frequency valve isn't working due to a bad control unit relay, or the relay may have lost it's power source, which is the dome light fuse. when the engine is warmed up, pull the plug off the relay and see if the idle drops off and the engine sounds worse. if so, it was working ok, if not, check the fuse, or replace the relay. the relay and computer are under the passenger seat. the relay is in front, near the tunnel.
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Old 12-26-2003, 01:19 PM
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Ill tell ya what I think I know..the only way to do a plug check is to run at the speed and load for a time....at least 30 sec and shut her dwn quick cause the color changes so fast as you go into diff a/f/ aeras. Now after all said my vote is you have a lean cond. from??(on top of that its hard to get a correct reading like in the old days.
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Old 12-26-2003, 01:22 PM
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Just did a quick run- it feels better after leaning the mixture out. Will do a longer run & see how things go / check that pesky relay.
Old 12-26-2003, 02:48 PM
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thanks everyone.
It seems my relay is fine- checked it today. I also pulled a plug after a 3000 rpm run & it was pretty white (with the new leaner mixture). Its running better than it was though. I got the idle to improve a little further by enrichining it a tad (1/16 turn) & unplugging the O2 sensor. The warm idle rose to 1150 as soon as I unplugged it- is this normal? I adjusted it back down & its now pretty steady.
After washing the car it ran like total crap- so moisture does seem to be largely responsible for all this. It never used to do this, but today it would barely run after washing it- terrible hesitation. All the connections seem secure & distributor cap dry so I would think the plug wires would be prime suspect #1?
thanks
Old 12-27-2003, 04:36 PM
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Just a thought, but if your WUR electrical connector is shot, and water is getting in there, your WUR may not be operating correctly. I have a disfunctional WUR right now myself, and the symptons are: perfect cold start, but poor running after warmed up. If the WUR isn't working, the system will be rich, which might explain why leaning it out improved your running condition slightly. Check that WUR again.

I've been a long time lurker, but I'm starting to understand this whole CIS thing. Good luck.
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Old 01-07-2004, 08:53 AM
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I had a similar problem that just got diagnosed - It was as simple as a ground wire being corroded - which I replaced.
Hope yours is that simple.
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Old 01-07-2004, 09:09 AM
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gcalac- Have you tested your fuel pressures? I started with the same hypothesis- rich running when warm. Its running ok now I have leaned the mixture out & secured the WUR elec connection, but still not great. Just doesn't seem to have alot of power when warm. Cold it feels great. I have a CIS tester on the way which will hopefully clear things up.
What year is your CIS?
Old 01-07-2004, 09:09 AM
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Brawlins- which ground wire was the problem?
thanks
Old 01-07-2004, 09:10 AM
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Yes, my pressure was tested. It was a bit low when cold (about 12 lbs), and it wasn't increasing as the engine warmed up, which is why we focused on the WUR. Turns out the WUR electrical connector was mangled and disconnected, AND the WUR unit was shot. I've got one on order, so I'll let you know how it works out.

Did you ever find a source for the electrical connector?

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Old 01-07-2004, 09:38 AM
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