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espey_16

Rough idle, & check engine light.

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Hey guys, last weekend I bought an 89 gl 5 speed d/r. The check engine light was on when it, and when it was cold it didn't want to idle. Warmed up it ran fine. This weekend I put an air filter, fuel filter, plugs, wires, cap, rotor, pcv valve in it and changed the oil. I filled the tank and put a can of seafoam in it too. I drove it to my dad's house yesterday and on the way home it started to studder while driving. Today it is idling really rough, and when I tap the gas it dies. I checked the dtc's and I'm getting a core 34, 35, and 51. I'm not sure, but would any of those cause the car to idle rough like that?

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A vacuum leak will cause a rough idle.  There are a couple of dohickeys on top of the engine that are connected to the vacuum system.  The nipples on those dohickeys can break off real easy and make for a vacuum leak.  A bad vacuum pump will cause a rough idle.  An oil dip stick that is not all the way down will cause a rough idle.  A disconnected vent hose to the cam tower cover will cause a rough idle.  If you look at the engine sideways, that will cause a rough idle.

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I took the car for a drive the other day, and it started cutting out while driving, and dieing when I stop. I have to pump the gas pedal to keep it running. Im not sure what's going on.

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I think I figured it out. The cat might be clogged. I banged on it a few times and now the car will idle. I'm about to take it for a quick drive and I'll report my findings.

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The car is running well, still a little hesitation around 2500-3500 rpms. But it's an improvement for sure. I just need to go to an exhaust shop now, then I can really get it dialed in.

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You can test for a blocked exhaust by loosening the 4 y pipe to head nuts. Get about 1/2" of clearance, see how it runs. It will be loud. But if it runs good, then you know the exhaust is plugged. Another way to check is to connect a vacuum cleaner to the tail pipe end. Do tye same with the 4 bolts, get space for air to get in. Canister or shop vac style. The vacuum cleaner motor should barely change it's tone when connected vs disconnected from the tail pipe.

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Sweet thanks. The car would only run while I was pumping the gas, then it would bog down if I gave it too much. I pounded on the cat with a piece of pipe from up top and it started smoking, but after a short drive the smoke went away and it still idled good. I just got ack from another drive and now the car is running like poo again, wanting to die and sounds like it's missing.

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Hey guys I'm back. Same car, same issues. I thought the problem was clogged cats, but I opened them both up and they've already been gutted. When I step on the gas, the car studders unless I'm accelerating hard, doesn't matter how fast or what gear I'm in. If I try to keep a constant speed the car studders too. I'm completely stumped on this thing.

Edited by espey_16

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I replaced the fuel filter when I got the car, and haven't put more than 4k miles on it. It's due for its 2nd oil change since I've had it. I'm not sure about stuff in the tank, I'll have to wait on that I just filled her up yesterday. How do I check the injector to make sure it's functioning properly?

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Check fuel pressure and delivery.

 

Injector check:

Once warmed up, shutdown. Disconnect the MAF. Remove the intake boot from the throttle body. Start engine. Look down throat to see fuel spray evenly on throttle plate. Open the throttle, see flow increase. Note, this will cause CEL and a code.

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Hey what's up guys? I'm sorry I havent been able to post on the car, I just haven't had the time to mess with it with the baby on the way. I did some searching and found some posts where people have had similar symptoms and it turned out to be the 2 wire cts. So I went ahead and bought one, and I just installed it. All is well so far, temp is about a third of the way up on the gauge and it doesn't try to die when I give it any gas. I'm gonna let it idle for a little while longer and take it for a drive and let you guys know if that solved my problem.

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Cts can cause drivability issues without triggering a code. It has no effect on the gauge, that's run by a 1 wire sensor.

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Yeah, but before I put the new cts on it would run ok when cold and run like a third when warm.

Edited by espey_16

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Exactly what happens when the sensor partially fails in a way that tells the engine it is cold all the time. Engines don't run well with the mixure balanced for a cold engine when warm. Or the reverse.

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I checked the injector just now, I couldn't really see any spray but I did see fuel hitting the plate obviously. When I opened it up the car hesitated like it's been doing. I can't get it to do that when I'm not driving. Should I get a new injector then?

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When I say spray, I picture a cone shape spray of fuel. I'll try replacing the fuel filter again and see if that has any effect, but there's been only a few thousand miles put on the car since I've had it and I've already replaced the filter once.

Edited by espey_16

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I can't see the spray when looking, the angles don't allow it. I did see fuel hitting the plate, and traveling outward to the edges.

 

Things need to be tested checked measured, not just replaced. That method costs more than a meter and a vacuum gauge.

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