FY 92 Festiva Rough Idle Problem

[FestivaLAqua]

I'm just trying to keep my 92original equip. Festy going. So far I’ve kept it going by keeping up withthe regular maintenance, following up on a trouble codes or by guessing whichpart to replace. But, there aren't any trouble codes and I haven't beenable to get guess the problem on this one.

The engine has a very rough idle after it has warmed to operatingtemperature. It also sputters quite loudly and smells of gas fumes atthe end of the exhaust pipe when idling at operating temp. If I keep itrunning for a while, the cat converter and pipe after the converter get hotenough to melt the undercoating above them. It runs well and driveswell at higher RPM's but I don’t want to take it very far with those pipesgetting so hot.

I have done the following since this trouble started:
Tried changing the timing by turning the distributor to many differentpositions. (I can't check the timing very well because of the rough idle. The timing light mark jumps back and forth) I’ve put the distributor back to my bestguess of 10 BTDC.
Replaced the cat converter (Used Davico Mfg #55061 from Rock Auto) and themuffler
Replaced the timing belt and adjusted the timing belt camshaft sprockets tospec
Replaced the O2 sensor
Replaced the ignition coil
Replaced the tune up ignition parts (plugs, wires, rotor & cap) and testedthe spark at the end of the wires
Replaced the fuel filter and the fuel pressure regulator (Posted thread here aboutthe FPR change on Apr 8th)

Any recommendations about other stepsI should take??

Thanks.

[ryanprins13]

What type of undercoating do you have? I presume you are not the original owner, the previous owner may have sprayed undercoating on that cannot handle any kind of heat and your exhaust isnt actually too hot. Do you have any kind of thermometer that can measure how hot your cat is actually getting? Some peoples exhausts glow red to the cat...
Anyway, with the rough idle- have you checked your pcv valve and hose? Are they gunked up? Take your intake tubing off, is there oil in them or in the intake manifold? Also check the accordian piece carefully for cracks. It likes to crack on the underside and even a small crack causes a bad idle and a lean mixture. If you have oil in there that can really mess up your idle, thats whats wrong with mine right now. If that is all fine check the iacv.


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[lessersivad]

My best guess is going to be the Coolant Temperature SENSOR. If I'm not mistaken it is located on the underside of the intake, towards the passenger side. Someone else could probably be more specific.

By the sounds of it the engine is running RICH after it warms up.

If the CTS is still telling the 'puter the engine is cold, you'll have the problems described.

I know this isn't a GM but I ran across 3 different GM products in 2 days with the same symptoms. ALL 3 were the CTS and it was confirmed before the 'parts cannon' was loaded and fired by the use of a live data scanner.

Unfortunately Festys aren't all that friendly to hooking up a scanner so sometimes the parts cannon needs to be used.

Hope this helps.

[bhearts]

Top of the lower intake manifold, between cylinders 1 & 2

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[lessersivad]

Top of the lower intake manifold, between cylinders 1 & 2

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Thanks. I KNEW someone would chime in with the correct info.

[bhearts]

That's the sensor in charge of fuel correction. The other sensor with the single yellow wire on the front of your thermostat is the coolant temp gauge sensor. The gauge in your dash

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[skeeters_keeper]

Sounds like you're running rich, could be the CTS as mentioned but I've seen similar issues from a bad FPR. If you can check the fuel pressure that's easy to trouble shoot.

[FestivaLAqua]

My best guess is going to be the Coolant Temperature SENSOR. If I'm not mistaken it is located on the underside of the intake, towards the passenger side. Someone else could probably be more specific.

By the sounds of it the engine is running RICH after it warms up.

If the CTS is still telling the 'puter the engine is cold, you'll have the problems described.


Unfortunately Festys aren't all that friendly to hooking up a scanner so sometimes the parts cannon needs to be used.

Hope this helps.

I had an 09 CTS trouble code a few years back. At that time the symptom was hard starting after engine was shut off and still hot. When I replaced the CTS back then, the symptom went away. Now there's no check engine light or trouble code. Maybe the CTS is OK but there's coolant sludge or something on it, so the 'puter's not returning a trouble code. I will try pulling it out and cleaning or replacing it. Thanks for the idea. That's a possible easy cheap fix...

[lessersivad]

I had an 09 CTS trouble code a few years back. At that time the symptom was hard starting after engine was shut off and still hot. When I replaced the CTS back then, the symptom went away. Now there's no check engine light or trouble code. Maybe the CTS is OK but there's coolant sludge or something on it, so the 'puter's not returning a trouble code. I will try pulling it out and cleaning or replacing it. Thanks for the idea. That's a possible easy cheap fix...

NONE of the aforementioned GM vehicles had a trouble code. All of them ran 'pig rich' after warm up.

Granted I'm comparing apples to oranges but they're still fruits.