Car is shaky/runs rough after HG repair

Specttor

Registered User
Hi all I got my 91 Tbird SC running last night after a long head gasket repair. When she fires she revs to about 1100-1200 RPM after tapping the gas she drops to about 700-800 RPM and shakes. The shaking seems to worsen as it goes. I am looking for ideas and or maybe something I missed as I am still quite new at this. I included pics of the engine in someone can see something I don't.
 
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I just replied to your last post. Sounds like a vac leak. I can't tell in the pics is the small PVC tube hooked up to the bottom of the intake tube? If that is left open then that would cause a lean condition.
 
Ok would you by chance know of a picture that shows what you are talking about? I added this second post because I had sometime to fiddle with a few things it seems the stalling has stopped and I was able to get some pics. The father in law said to try a method of taking the wires off the module to see if there is a cylinder not contributing. Said to pull them 1 at a time and monitor the RPM differences. Would this be a good idea as well?
 
check the o2's

Did you change the o2 sensors after the HG repair? If they got coolant on them, they are done. When mine popped, it soaked the passenger side one to the point where it was dripping when I pulled it out.

Corey
 
The passenger side o2 is located after the exhasut manifold in the downtube. The driver side one is in the exhaust manifold. I have a feeling if the o2's went, they would throw a code. Do you have a check engine light, have you pulled codes?
 
Looking at your third picture I don't see the tube that connects to the bottom of the intake tube between the air cleaner assembly and the throttle body. If I remember correctly that line runs from there to the front of the drivers side valve cover.

You will need to change your 02 sensors at some point if you blew a head gasket. The passenger side is in the exhaust downtube(right after the exhaust manifold). The drivers side is in the exhaust manifold and is kind of a pain to get to. You are going to want to buy a 02 sensor socket to make sure you don't round off the 02 sensor because they are probably pretty tight and hard to get out. However, your 02 sensors aren't used until the car warms up so if it's not running right when it's cold and first started up, the 02 sensors aren't the problem. I was driving my car for a day with the drivers side 02 sensor unplugged on accident...Car still ran fine, just threw a CEL light once the car warmed up...

I wouldn't bother pulling the plugs wires yet...I'm guessing it's a vaccuum leak...You might want to get a code scanner and see if you have any codes...
 
When the check engine light comes on, a code is stored in the eec. Most places like auto zone can plug into the eec test port under the hood and find out what numbers the computer stored. They they will look up those numbers. I cant remember the number for the o2's off hand. They are in the ford shop manual or a haynes manual.
 
Here's your picture...The vaccuum line should be connected to the black tube on the bottom where the big red arrow points...If that's missing that would cause a problem...
 

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Looking at your third picture I don't see the tube that connects to the bottom of the intake tube between the air cleaner assembly and the throttle body. If I remember correctly that line runs from there to the front of the drivers side valve cover.

You will need to change your 02 sensors at some point if you blew a head gasket. The passenger side is in the exhaust downtube(right after the exhaust manifold). The drivers side is in the exhaust manifold and is kind of a pain to get to. You are going to want to buy a 02 sensor socket to make sure you don't round off the 02 sensor because they are probably pretty tight and hard to get out. However, your 02 sensors aren't used until the car warms up so if it's not running right when it's cold and first started up, the 02 sensors aren't the problem. I was driving my car for a day with the drivers side 02 sensor unplugged on accident...Car still ran fine, just threw a CEL light once the car warmed up...

I wouldn't bother pulling the plugs wires yet...I'm guessing it's a vaccuum leak...You might want to get a code scanner and see if you have any codes...

I think I know which one you are talking about that connects, its a hard plastic tube that runs all along the front of the engine to the big intake tube. If that is the one you are talking about it is connected.
 
Here's your picture...The vaccuum line should be connected to the black tube on the bottom where the big red arrow points...If that's missing that would cause a problem...

Yup that one is connected, see part of my prob is that part of this was already taken apart when I got it and not having a real solid base of knowledge I really am just playing alot of guessing games here.
 
>Said to pull them 1 at a time and monitor the RPM differences. Would this be a good idea as well?

The previous suggestion(s) to get a code reader (pull the codes) is a good idea - in addition, there is a 'cylinder balance test' that is done as part of these diagnostics that will be far easier and safer than pulling plug wires.

Having a code reader and being able to run DIY diagnostics is a basic part of doing repairs on these cars. Best to get started down that road now.
 
It could be a wire/plug issue. I once had to take off the plugs and when I put them back on I accidently pushed the brass connector down inside the coil pack causing one wire to only have spark intermittently. There was certainly some shaking going on with only 5 cly firing. I’m assuming you have new plugs so just check them one at a time that would be an easy test so why not try it.

If it's not a spark issue I would take off all the intercooler and intake stuff and carefully reseal all connections. Just because you have some rtv in there doesn't mean there is a seal, (this is also something I have first hand knowledge with). There are so many different things that can go wrong with these cars and most are minor. Just take it one step at a time and retrace all your steps. Check all seals/connections. If it starts ok but just runs rough then it's probably something small.
 
I think the problem may have worked itself out. The car had been sitting for a few months not being ran since the HG blew. So its old gas and having to work in the new fluids. I added some new gas and some octane booster as well as some fuel injector cleaner and throttle body cleaner and its running alot smoother.
 
Don't you just love those simple fixes? There is a Weigles near me that sells bad premium gas I should have thought of that.

If the car runs fine I wouldn't worry about those O2 sensors. They only go bad if coolent hit them. I personally don't fix what's not broken but then again I have a spare T-bird as insurance for when what I didn't fix finally does break. :)
 
I think the problem may have worked itself out. The car had been sitting for a few months not being ran since the HG blew. So its old gas and having to work in the new fluids. I added some new gas and some octane booster as well as some fuel injector cleaner and throttle body cleaner and its running alot smoother.

Throttle body cleaner wasn't a real good idea on this car. I hope you didn't damage you TPS and IAC doing that.
 
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