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'95 SE hesitates/misfires low RPM @WoT

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danq989

New CEG'er
Joined
Apr 26, 2008
Messages
11
Hi guys,

I'm the original owner of my teal '95 SE V6, 135K miles, bone stock except for some Stillen brakes.

In the last couple of months I'd noticed some vibration at idle and some slight hesitation at low rpm (<2000) and wide-open-throttle, but lately (seemed to be after one particular fill-up) it's gotten much worse. Now it hesitates, misfires, and bucks at anything above part-throttle when rpm is less than about 2500. Now the CEL comes on intermittently after the car warms up. It tends to go off when accelerating up a hill, but on again after coasting or light throttle.

I bought an EEC-IV code scan tool and pulled these from the stored codes:
176: HO2S BANK 2 indicates lean
332: EGR valve malfunction

I bought and replaced the front bank O2 sensor, which I believe is bank 2 (Hanes guide says cylinders 456 are the ones closest to the radiator, and that's the sensor I replaced).

The O2 sensor replacement didn't cure things by itself, so I took apart the intake shroud and cleaned the MAF, then sprayed an entire can of carb cleaner into the throttle-body. The back of the throttle butterfly was definitely filthy and the carb-cleaner ran black for a while. I tried to clean all passages I could reach with Q-tips, and they came out pretty dirty too.

After I put things back together, I've still got no real improvement in driveability :(.

What's next? Did I replace the correct O2 sensor?

A lot of folks seem to recommend new plugs/wires for my symptoms, but given the codes thrown does that make sense?

Also let me know any other low-hanging fruit I should grab (e.g. my fuel-filter is pretty old...)

Thanks to everyone, and I really enjoy reading the CEG forums!

---DanQ
 
Contours are infamous for EGR issues.. The EGR valves usually open at cruising speeds which may explain it malfunctioning when you coast down a hill. I have a 95 se V6 and after removing the throttle body, I found that the EGR passages in the upper intake manifold were clogged and all full of carbon. You may want to do the same and dig the passages out with a screwdriver. If you are gentle with the throttle body, you could get away with not having to replace that gasket (although it would be a good idea).
 
misfires

misfires

Check the green vacuum line going to the EGR from the solenoid, tends to crack very easily. If you have carbon tracking on any plugs, you will get a medium surging/buck at 2300 RPM or so (3rd,4th gear 35-40 mph), if you try to accelerate. New Motorcraft/Autolite double plats and Motorcraft/Autolite wires are best to use. I had carbon tracking occur with new parts, because of a small amount of dirt that got on the plug body (white part). Installed new plugs again, after cleaning the socket wrench really well, and using silicone grease in the boots, fixed it.
 
I have a '95 v6 mystique running fine; it gets similar codes now and then and a not infrequent CEL. I get 172 and 332 I think, for the bank 1 sensor and the egr. It does not affect running or gas miliage it runs very well.

You might replace the wires and plugs. I used iridium from autozone.

Mike
 
if the plugs and wires have any sort of miles on them I would consider replacing them. Motorcraft parts are best, but you can also use autolite plugs.


THe 172 was definately the O2 sensor. Also as suggested check the vacuum sorce for the EGR valve. apply a vacuum at idle and if the cars stumbles and dies then the valve is working. I would then replace teh dpfe sesnor as its metal and can corrode and fail. this could be causing the egr to stay open when it shouldn't be causing a poor idle. finally you need to remove the tb and clean the egr passages behind the tb. also checking for vacuum leaks and that the secondaries are closing when you start the car is also a very good idea.
 
Hi again,

Thanks for the tips, I'll definitely start by thoroughly cleaning the EGR passages, then move on to plugs & wires if that fails.

Now, sorry for the n00b question, but can someone very specifically describe the procedure to get at those passages most easily? Should I remove the EGR valve assembly and clean from there? This is about as deep as I've gotten into the engine compartment.

---DanQ
 
No, it happens warm or cold.

It may be somewhat better in the first minute or two when I assume the EEC is running open-loop.

---DanQ
 
danq989 said:
Now, sorry for the n00b question, but can someone very specifically describe the procedure to get at those passages most easily? Should I remove the EGR valve assembly and clean from there? This is about as deep as I've gotten into the engine compartment.
Click to expand...

Pulling the valve off is always a good place to start. You can spray it out or scrape it clean and also inspect the passages right there.
 
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