# 91 Stanza, backfires, sputters at operating temperature



## PapaCap (Dec 8, 2007)

Hey guys. I have a 91 Stanza with 130k and a manual transmission. When the car is started cold, it idles and runs perfect. But as it gets to operating temperature, the idle begins to surge and if you give it gas, it hesitates and backfires through the intake. So far I have replaced the:
O2 sensor (new)
Coolant sensor
MAF
Plugs, wires, distributor cap (new)
Idle air control valve
Fuel filter and lines (new)
Half the vacuum hoses on the motor
Cleaned the throttle position sensor (have not replaced)
PCV valve (new)

Note: some of the parts are used. I have a parts car with a blown motor I steal off of.

Next, I plan on fiddling with the timing, although from my experiences, timing issues usually are present regardless of the car's operating temperature. I've been avoiding messing with the EGR valve just because it's just a PITA to deal with, but that may be next. And I plan on checking the plugs/compression per cylinder to see if it's a blown head gasket (I would think this would be a constant problem as well).

Anyone have any suggestions on what it could be? The fact that it happens when the motor warms up would lead me to believe it's electrical/emissions. BTW, the cats and muffler look like they're in good shape (as in they were probably replaced before I bought the car).

I'm new to 4 cylinder motors and I discovered something that I have not seen before in other motors. When you take off the oil filler cap from the valve cover while the motor is running, it blows out air HARD, like a hair dryer. It's been a while since I've worked on 4 cylinders and I just can't remember any of them doing this. Is this normal? Most other motors I've worked on have a vacuum, not a blower (this could be part of the problem).

Also, anyone know what the TAC vacuum motor is? It said to check that in the Chilton's manual, but in usual Chilton's style, there is no information about it.

Any help would be appreciated. Thanks.

PC
:newbie:


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## PapaCap (Dec 8, 2007)

Since I'm not getting many responses, I thought I'd share what I've done today.

I tested the EGR valve by physically depressing the plunger while the vehicle was in operation. The EGR valve seems to be working properly.

So lastly, I adjusted the timing. Voila! She runs beautiful now. It still has a little miss at idle, but the car's been sitting for a few years.

Success is always good. Good luck with your repairs.

PC


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