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Discussion Starter #1
For those who are curious, I finished replacing my intake manifold gasket over the weekend with the help of a friend. We started Friday night and I finished Monday midday. It was a total of about 23 hours of work, here and there around our work schedules. There were several hangups along the way, nothing too serious that a little thinking couldn't solve. I dont see how anyone could do this by their selves in a few hours....but they do.

I said I would take pictures and hopefully do another writeup on this procedure. Well, after getting started, we didn't stop too often for pictures. Just a few here and there to make sure stuff went back properly. I can post some if anyone in the future would like more info.

The current write-ups were a huge help. Overall it was easier than I thought it would be, even though it took a while. We just took our time and tried to think things out before we took it apart. Really, if you just look at the pieces and understand what you're doing, you can figure most of it out intuitively.

So instead of a writeup, I thought I might just outline my procedure, problems along the way, and conclusions and recommendations. I will try to seperate these by posts.
 

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Discussion Starter #2
First step was to raise the car, remove the passenger wheel, and let it the engine cool a bit since I had just driven to his garage. While this was happening I removed my strut bar, WAI, and battery. Also be sure to relieve the fuel pressure first.

Next we removed the injector/fuel rail assembly and moved the wiring harness out of the way. We also removed the accompanying vacuum and fuel hoses. Also move the throttle and cruise control cables out of the way. This stuff was simple and fun reassembling during the "home stretch." Assorted 12 and 10mm.

Then we moved on to the throttle body. There were several hoses of course, 2 electrical connections (TPS and WOT), a bracket I believe, the cable/spring linkage, and the EGR assembly above it. Be sure to make note or photography what went where. It is easiest to remove all the EGR pieces on top of the manifold and then the iron T that joins the exhaust pipe and BPT line together. After all that is removed, and you remove the 4 6mm allen head bolts, the throttle body should come off.

Next was the starter. Only 2 long bolts under the throttle body, were a bit tough to spot...no biggie though. Then the driver side manifold bracket which bolts into the starter as well. There should be 4 total bolts on this bracket (2 into the starter, and 2 into the manifold). Then unclip the wiring harness and remove the black battery line from the starter and it should drop. Then just remove it through the bottom.

Then we removed the oil filter and adapter plate it sits on. This allows for more room underneath later. You might try and do this before the starter removal....might help if you can. Only 4 bolts and an electrical connection on the plate. Kinda hard to see them all, but you can feel them easily. 12 mm I think.

Then we set our sights on the lower collector. This was held in place to the top manifold with only 3 bolts and 2 nuts, 12mm each. Pretty easy to access. With those out, it should only be hanging by some hoses and electrical connections. The ones left I can think of are brake booster hose, IACV hose, EVAP hose, two electrical wire brackets from below, and any other electrical clips...I know Im missing something here, sorry.

Once it was freed, we were able to maneuver it enough to remove it from the hole between the manifold and firewall...out through where the WAI was. Kinda tricky, but it can be done.

Now go back under and in the center of the block under the manifold is a 3way junction from hell...at least I thought so. Here is the knock sensor, thick stubby coolant hose, and piping bracket, all mixed together and blocking a clear route to either one for removal. Well after some thinking and lots of time, I was able to loosen the knock sensor enough to move its harness out of the way to undo the piping bracket so I could remove that coolant hose. What a mess.
Now the tough part...or so everybody said.

There are 8 bolts and 2 nuts, 12mm, attaching the manifold to the head. The 2 nuts are simple. Now this part I was actually surprised with. Of course, I had the help of a friend. But these bolts only took 10-20 minutes to remove. With a 3/8 swivel and 3" and 6" extension and deep and shallow 12mm socket, just try different combinations for the right length and angles. No problem with a friend. They came out pretty quick.

Now with those bolts removed, the manifold should slide back a bit. Here is where we saw why others recommend removing the PCV valve. It blocks you from fully removing the manifold. So instead we opted to leave the PCV in place and move the manifold back enough to slide the old gasket off and the new one in place. Clean the mating surfaces first and be careful not to scratch or warp the manifold while sliding it back.

With the new gasket ready for installation, and manifold clean, assembly should be on its way. We cleaned the collector at least, inside and out, and put a new gasket on it too. Also cleaned the EGR components real well...you would be amazed at how much carbon gets built up in there. Assembly is the reverse of removal, and this part actually went quicker than I thought it would. Turns out I have a decent memory of where stuff goes. But please, take pictures before..hehe.
 

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Discussion Starter #3
Ok time for some setbacks and problem areas.

Well after the first night I gave myself a 30% chance of actually finishing this. I just for some reason forgot all the research I did before hand. When I looked underneath things weren't what I expected and we only managed to get to the throttle body. That night I read plenty and was ready to go. Removing that starter is necessary for access...and removing the collector before the manifold is a big help too. Duh!

While removing the starter with a long extension, I happened to hit the extension against the transmission breathing tube or whatever that 90 degree tube is. It broke off its base a bit, sorta like a little hinge. But it was attached enough to reseal it with JB weld. Good as new.

Like I said before, that knock sensor area is a mess. Really thought I was finished there for a few minutes. But worked it out eventually, and fixed it during assembly so it will be easier if I ever need access to that mess again.

O, while trying to maneuver the collector out, it seemed to be stuck on something. Just couldn't figure it out. For almost several hours we worked at it, or worked around it during other parts, couldn't seem to see what it was catching on. Turns out it was the little vacuum hose that runs from the EVAP cannister to the throttle body seating area still connected.

Some of those hoses were tricky, but a pair of pliers, needle nose and regular came in handy.

Some of the hardest parts were just being underneath and doing so much with my off hand, or just one hand at a time, and having it cramp up on me so quickly it seemed. I would run out of strength with it so quickly trying to work at this and that. Just take your time, rest for a minute, and get back to it. Also, wear some glasses or safety goggles down there. Stuff in the eyes sucks.
 

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Discussion Starter #4
Conclusions and recommendations.

Uh...pay someone else to do it.

Naw, it wasn't that bad at all. If you have a friend and time, and do plenty of research before hand, it'll will go much smoother. There were hangups, but you learn and work through them. That's the fun of automotive maintenance...right? right??

Have a few flashlights or any type of lighting helps really. Seemed like we were changing out lights and recharging batteries frequently.


Anyways...was this all worth it?

Well, after starting it back up, I was a bit frustrated to see my idle still a bit shaky. It cured it some, but my idle still lopes a bit, the exhaust still has a putt putt putt sound at idle. Its not as bad, so i helped some.

I've only driven it 3 days now since I did this. I've reset the ECU, and I'm still throwing codes. Knock sensor and misfire on #2. At least there's no EGR or lean misfire code. So, now I'm really not sure what to do. I replaced both manifold gaskets, throttle body, EGR, and oil filter adapter (it didn't have one when I took it off, funny). I haven't sprayed for an intake leak since. So that might not be it.

I could change plugs again. I've replaced them twice in the 2 years these codes have shown, and wires twice too. One thing I haven't replaced is the distributor cap and rotor. Might try that. I could try my injectors, test them for resistance...see what I get. Other than that I'm lost as to what it could be.

Also, I am blowing a bit of smoke still on acceleration....valve seals I assume. It looked blue...I hope its blue smoke. Gosh I would hate to do a head gasket repair. I've also checked the compression several times.....like I've said in prior posts, always with 10 psi of 175.


But there you have it. My adventure in replacing my intake manifold gasket. Its done, kinda sad....it was sorta fun. But I suppose my adventure in figuring out these codes has a few more chapters to write.
 

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Snow Kills My Car
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if you not happy about it taking you 23 hours, just think about this: me and two other people had to change the intake manifold gasket for school on a gmc jimmy...at an hour and a half a day, it took about 2 months...we were proud untill my teacher told us mechanics could do that in 6 hours
 

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The Don.
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Glad to hear you got through that ordeal. It is painful but this is good learning experience to have "under the belt".

If the putt-putt sound is steady you should be able to track it down easier than if that sound is irregular. Typically, a steady sound is cylinder related while an irregular sound is vacuum related.

One technique I use to isolate a difficult vacuum leak is to do this,

1. Connect a voltmeter (or scanner) to monitor the O2 sensor swings.
2. At idle the O2 should be steadily reading a lean condition. If the reading is unsteady then pull a vacuum hose and leave it disconnected and unplugged. Let the O2 sensor settle in a lean state.
3. Spray some carb cleaner inside the unplugged vacuum hose to ascertain that the O2 sensor will swing rich. It is very important that the O2 sensor response correctly or you cannot continue with the next step.
4. Next, go around and spray carb cleaner particularly around gasket joint areas. When you hit a vacuum leak it'll send the O2 sensor reading rich like in step 3. Retest to confirm the leak.
5. Just keep doing this until you've uncovered and fixed all the leaks. Finally, put everything together and that putt-putt sound should be gone.

An area which is a somewhat stealthy leak source comes from the two gaskets underneath the EGR valve. These gaskets break down and leaves a thin sheet metal that causes a leak. Also that hose underneath the EGR-BPT tends to leak a lot.

Finally, I didn't pick up any information that indicated you had cleaned the inside of the upper intake manifold. There a four tiny ports in each runner where EGR flows through. If you left any of them clogged up then you will likely create a lean misfire in one or more cylinders. But that should happen during acceleration rather than idle.

Anyway, glad to hear you've made it through this one. -js
 

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Discussion Starter #8 (Edited)
See the thing is I'm not receiving the lean code anymore. Just misfire on #2 and knock sensor. Will it always throw lean misfire if I'm lean? Or is there a way to tell if one cylinder is running lean? I guess just read the spark plugs...even though they all will show signs now since they were all running lean before.
I guess I just dont believe anymore its a vacuum leak. But it does seem more irregular than consistent.

A year or 2 ago when this problem began I just had my mechanic listen to it and he diagnosed it as a burnt valve immediately. Makes me wonder if he really had it right the first time long ago.

I think I will try like you say jserrano about testing for leaks again and reading the 02 sensor. Just backprobe the upper 02 sensor, right? I did not clean those ports in the upper manifold...I didn't remove that part completely for cleaning :banghead:. I have replaced the EGR gasket, but only the one. I think what I really should look for is someone to do a leak down test for me.


O yea, and I'll get a new dist cap and rotor too, zad. heh.
 

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I'm interested in the outcome of your situation. I've got a cylinder 4 misfire but no CEL!

I just changed the cap, rotor, plugs, & wires today and it didn't help. My "putt-putt" sound is very consistent, though. I thought it must be the intake manifold gasket from all I've read but after this I'm weary to go through that hassle if it didn't fix your problem.
 

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Discussion Starter #10
Well it did fix some of the problem....smoothed out the idle some. But the original putt putt sound out the exhaust is still there. If you're not sure if your manifold gasket is leaking or not, just spray some carb cleaner or something around it and listen for any change in idle speed....usually rises and smooths just for a second.

But I have since then replaced my cap and rotor and new plugs. G power platinum NGK...man those things have a tiny tip.

That hasn't really changed anything. My check engine light is still illuminated with misfire on 2 and knock sensor. Which brings me to a few more questions.

1. How exactly does the ECU determine the engine is misfiring...or what exactly is a misfire? How does is differ from knocking/pinging or just general roughness? I would guess it uses crankshaft sensor in determining listening for changes in motor rpm? Is this correct?
And then how does it specifically know which cylinder is misfiring? Again my guess would be over thousands of cycles or a days worth of driving it sees where those changes in rpm speed occur in relation to the overall engine timing. Then calculates this somehow and finds which one is missing. Correct?

Ok, question 2.

2. I performed a leak down test on my car today. Bought one for $35 at harbor freight. Was tricky learning how to use it but I got the general idea. The percentages however were different than what I expected (calibration problems during test setup...again tricky to use the tool). So instead of saying 20% leakage equals too much here, I just got a relative reading and compared each cylinder to each other. Here's what I found:

Cylinders 2,3, and 4 were all within 5% of each other. It said 20%ish leakage. I know thats a lot but again, it was tricky to calibrate it properly.
But on cylinder 1 it read 40% leakage. WTF I thought. My code says #2 is bad or missing. I couldn't hear any air escaping through exhaust or anywhere for that matter. But the compressor was making some nice racket.

So thats where my first question comes in. How does it know 2 is the bad one? I tested and it concluded that 1 was leaking the most. I dont know anymore really. Not like I was gonna pull the head to fix any leaks anyways. I just like to know how it works, what is wrong, etc.

These CEL are a bother I tell ya. Good because they tell you something is wrong. But when you can't fix it for conclude why it's doing what it is doing, it messes with your mind man. Plus, I dont know if they'll let me pass that stupid emissions test.

Good stuff, good stuff.
 

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Yeh, I will try to locate the leak to be sure. I heard a leak a few months ago but couldn't find it. The other main difference is that my idle takes a second to settle if you blip the throttle - it pauses at like 1200 RPM then settles to 750 RPM and stays completely steady no fluctuation. Engine is rough, but no CEL.
 

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The Don.
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iconz21: Your problem sounds more like an ignition or fuel injector problem with #4. An intake gasket leak is more of a random misfire then a solid steady misfire like you've described.

zakgord: A misfire is when one of more cylinder(s) fails to properly ignite the air/fuel mixture. It could occur because the cylinder lacks spark, fuel, or air. Or because the combination of any of those variables are in the incorrect quantity.

The way the ECU determines a misfire is like this. It uses the crank position sensor (CPS) to detect when a misfire occurred. The ECU uses two signals from the optical disc in the distributor; one is for each 1 degree angular movement of the crankshaft - this is called the crank position (POS) signal. The other is for each cylinder piston reaching TDC, it is called the reference (REF) signal. That is why if you look at the distributor optical disc you see a lot of slits around it, and four (4) slits to the inside of the disc. One of those four slits is actually wider and it denotes TDC for cylinder #1. The ECU uses that long signal to sync everything up as it times the ignition.

So between the REF/POS and CPS, the ECU has a very good idea which cylinder caused the misfire.

Stick with what the ECU believes is the problem - cylinder #2. Put a timing light on the #2 ignition wire, and if it is misfiring you see the strobe light miss some beats. The only thing I can think of about the disparity between #1 leakdown and #2 misfire is a head gasket issue. But I hope to God that I am incorrect in that assessment. Consider that only after all options has been ruled out. Good luck.
 

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Discussion Starter #13
See I thought that too. I put a timing light on the plug wires, several times. And they all appear the same consistent flash, even cylinder 2. So I don't really see this "misfire" that the ECU says I have.

I looked for bubbles in the radiator fluid during the leak down test. Saw none during the procedure, and there was no flow from one cylinder to another...pressured air that is. So I really doubt it is the head gasket. Never any white smoke, just blue.

#2 makes plenty of compression during testing, and leakage was fine, at least compared to the others. And the light flashes consistently with a timing light hooked to it. Im thinking there is still a vacuum leak somewhere.
 

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Discussion Starter #15
Not really. It was poor before (21-23) when I was messing around with it a lot and doing a bunch of diagnosis. Troubleshooting, unplugging sensors, resetting ECU, revving and trying different things. But actually the last month or so before I did the gasket replacement I just left it alone and my MPG went up to my normal 26. And that's what I am at now, 26. Haven't really noticed anything different since the replacement other than the really bad dips in rpm are gone now. Now its just 200-300 changes in rpm at idle. Sometimes only 100 or none at all.

Just feels like a small pesky vacuum leak is still occurring somewhere still. Who knows why #2 is "missing."
 

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:banghead:I have a similar problem. I had the head done and replaced last year. I tried carb cleaner recently and found it was leaking near #4 , the end cylinder near the throttle body. I looked at the intake manifold off a previous engine and saw some discoloration on the underside at #4 . I took out my starter, looked, saw discoloration from a leak in that area of #4 but toward #3 rather than the outside. Wonder if a backfire could have done that, blown out the gasket. Anyway I recalled that back in the '50's they'd sometimes varnish a head gasket. I tried sealing the leak with varnish. Hasn't held completely but not as bad as it was.

So, sometime in the next couple of weeks I'll be following suit and replacing the gasket. This gasket was new last year when AAMCO changed the head for me then sent me on my way with a timing chain cover leak. I see a hanger off an outside manifold bolt leaving a little less thread into the head. I got a queasy feeling when I tried tightening the bolt.

I wonder if varnish on a new manifold gasket before torquing might be advisable. Two manifolds and discoloration in almost the same spot it's got to be weak.

Bill

Regarding mileage, after the head and time chain/gears replacement, I was getting roughly 26.5 mpg using regular. I check every fillup. Then instead of 32 psi I went up to 40 psi because three of the four tires say max 45 and the fourth (hit a curb) says max 47. Also I reset my alignment building alignment tools from oak wheel barrow handles. Interesting, the shop set the rear at toe-out. I reset it at the same angle but toe-in reasoning the wheels would spread with increased road drag. I got better than 29 mpg but the fillup was possibly a bit shy. Then it went to 28 mpg. In reality, unless I'm wrong, it's actually 7% better. Apparently a transaxle for a car with 14" wheels was put in and my wheels are 15". Whatever, when I fix the intake manifold leak I expect it will run richer and my efficiency will drop.

Sat. 6/28/8 2:40 PM
Started the process of changing the intake manifold gasket this morning about 9. Starter out, oil filter and stand out, all items above the manifold moved out of the way. Was removing the coolant pipe under the manifold, put a 1.4" drive 10mm socket on the bracket bolt but before I could get it loose the socket came free of the extension and fell somewhere. I got the pipe out after removing the nut using a 3/8" drive but can't find the missing socket and have a sinking feeling it may possibly have fallen into the starter access to the flywheel. If the socket doesn't turn up what are my options?

So, Zakgord, did you ever get the put out of the exhaust sound or make a final determination if it was a leak?

Bill

The top half of the manifold was out by 4PM and the lower half out by 4:15 and there, snugly into the top of the engine mount, was the missing socket. That's a relief. Now on the cleaning the surfaces.

...The gasket surfaces took a little longer to clean than I would have guessed. I coated the surfaces with high temp RTV to hold the gaskets in place and to lower the probability of it going again. I had it all back together and was pouring in the coolant by 3 PM Sunday when it started dripping out from near the PCV valve. By 5 PM I had re-drained the coolant, removed the oil filter and stand, fixed the leak, got it all back together and the engine running. It's 5 days later and it's been running well.


June 4, 2016

I note the 7% was due to incorrect tires not the wrong transaxle. I was a runner then and knew the car was registering the wrong distance.

The car had been running well for years. Tried running distilled water instead of 50/50 antifreeze last year. Boiled the water and ran dry at 70mph on the interstate, warping the head. Replaced the head but recently developed a coolant leak and have the head off again now (wish they sold steel replacement heads for this). Once upon a time a large diameter coolant hose between the manifold and the plenum was replaced perhaps with a heater hose from Lowes. The wall was less thick and over time it deteriorated. Am slowly putting it back together now with a thick walled hose. The head is off and I've been cutting cork gaskets for manifold to head, throttle to plenum, plenum to manifold, and oil filter pedestal to block. Going to be using Permatex Ultra Black on all, including between the injector seals and the head. Don't want to be worried about a vacuum leak needing the manifold off again. Taking the opportunity to replace the steering rack and brushes in the starter.

BillJ
 
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