Got the car going, now a stumble?? - Chevy Impala SS Forum
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post #1 of 25 (permalink) Old 01-16-2017, 07:23 PM Thread Starter
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Got the car going, now a stumble??

So, I got my car aligned, got it all buttoned up and ready to drive and have been for about a week now. I absolutely love it because it handles like a dream now! Car was down for about 2 or 3 months only being once every couple weeks or so when it was actually driveable.

Anyway, I am starting to come to the realization (spoiler alert) that this car still needs a good bit of WORK. Now for the issue I have...

Here is the scenario, I am at a light, or in stop and go, and as I take off in first gear, I get this stumble and it almost feels like a shift. And this stumble usually happens right before or after a shift, maybe a second or so it seems. The engine 'stalls' for just a quick second then it goes right back to running fine. Like I said it feels like a shift, its soft and smooth oddly. The other thing I notice now too is that the thing stumbles very hard when I am stopped. Scenario, sitting at a stop light, foot lightly on brake and the thing will just pull through the brakes for a quick second and you can feel the engine rock the car a little, and then the car stops and goes back to running 'okay'. Its very odd and COMPLETELY random. I also get an extremely noticeable amount of chugging and pulsing using small throttle inputs around 0 MPH, the same also holds true when I try to stop if I am under 10 MPH. Now I know I am of no help considering I have no datalogging capabilities (yet), but to me this has to point to a couple things:
EGR/solenoid sticking from build up causing the stumble. Seems reasonable as the car spends most of its time under 2K rpm, I try to blow it out every so often..) Want to replace when I do intake manifold, f-body of course.
Bad ICM. Replaced coil over the summer.
Opti? Frikin long shot here, but the thought has run through my head. I know it has a wobbly bearing, but a new cap and rotor. like that helped...
Something else I havent thought of..

I checked fuel pressure a few months back, but I really need to check it again, and it was fine. I dont suspect a sticking lifter, I use a friction modifier(whatever that means...)

ALSO, and this might be the kicker, I notice my EVAP doesnt work, crack gas cap and the thing has a TON of pressure Trying to fit in replacing the vacuum line for that here soon. I wonder if my line has collapsed, or worse, separated, and now just sucks straight air and when the solenoid opens it gets a huge gulp of air. Im not sure exactly how the EVAP works, just enough to be dangerous, but as far as I know that could also be entirely wrong.

I have always had a roughish idle once warm. Not as smooth as a grandma car LT1 should be, but it always ran incredibly well once the TB was opened.

Thinking I should just do the EGR because its pretty easy and could probably use it.

Hopefully thats put together in a decent way...

94 RMSB 170K Sat 5 years, ran for 1 of those then remained untouched for 4. Sat because it was slapped by a deer and the owners didnt want to fix it for whatever reason.
Mods, all the free good ones.
Future? Probably pull engine, reseal it, and run it a lot more. Looking to get 250k out of it. PRAYING for 300k.

Last edited by smelonas; 01-17-2017 at 08:13 AM.
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post #2 of 25 (permalink) Old 01-16-2017, 11:20 PM
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Check ALL the vacuum lines. ALL.


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post #3 of 25 (permalink) Old 01-17-2017, 06:31 AM
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Vacuum lines are always a good start. There is also a Sticky that has lots of info on what things to check for with intermittent surging. The chugging you mentioned has been described as "chuggle" and they talk about this and the possible causes in one of the videos in the Buick Know-how videos that are online. The car is a Buick Roadmaster but essentially the same drivetrain as the caprice/Impala and maybe it will give you some ideas.

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post #4 of 25 (permalink) Old 01-17-2017, 06:41 AM
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I edited for clarity. Insights provided. The car may have 'car sitting a long time' ailments, but it sounds like the first tack is to simply attend to all the routine and periodic maint. expected for the age and mileage. You're gathering ideas and that's good, even if a tad scattered about. You will make a lot of headway with search on already well-documented solutions to problems you describe. If you plan to keep the car buy a FSM. It's a really quite good read. Your sig states you want to remove and 'reseal' the engine. Unless there's something exceptional on history, I'm not even close to understanding why you intend to do that.

Quote:
Originally Posted by smelonas View Post
...
.....this car still needs a good bit of WORK. ...

*.... as I take off in first gear, I get this stumble and it almost feels like a shift.
*And this stumble usually happens right before or after a shift, ......
*The engine 'stalls' for just a quick second then it goes right back to running fine. ...
*I also get an extremely noticeable amount of chugging and pulsing using small throttle inputs around 0 MPH, ...

EGR/solenoid ...causing the stumble. ... Want to replace when I do intake manifold.... You don't have to wait 6 months to do an on-vehicle check. Do a search. Why are you "doing" the intake? If it's for leaking and gaskets, then you have one of many sources of stumble.
Bad ICM. Replaced coil over the summer. Why? And why only the coil? Do a search on problems ICM and coil can cause each other.
Opti? ... I know it has a wobbly bearing, How would you know that? but a new cap and rotor. like that helped...I do not understand the statement. Did you install a new cap and rotor?
.....
I checked fuel pressure a few months back, but I really need to check it again, ... Good idea.

....I notice my EVAP doesnt work, Then, you really just need to fix the EVAP.

I have always had a roughish idle once warm. Do a search on "warm off-idle stumble". It might be a stickie.

Thinking I should just do the EGR because its pretty easy and could probably use it. Just see above.
.....

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Last edited by 96 Black; 01-17-2017 at 06:44 AM.
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post #5 of 25 (permalink) Old 01-17-2017, 06:54 AM
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The PCV system can cause all kinds of weird symptoms. Make sure it is working as designed.

1991 OCC 461 (.030 over 454) BBC, 3.23 posi, flash to pass, drop spindles & springs, Impala rims, Recaros, MOMO/wood SW w/QR, custom wood shift knob, Pioneer DEH P77DH
1992 OCC now with 5.7 tbi, DEH P77DH
For a parts list, check http://www.impalassforum.com/vBullet...ion-parts.html
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post #6 of 25 (permalink) Old 01-17-2017, 08:01 AM Thread Starter
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It was my intention replace ALL rubber lines, EGR, PCV VALVE, OPTI, ICM and a couple other little things. Reason being for all the reasons you think. A lot of those parts are probably bad, almost bad OR causing problems.

I know about the coil/ICM thing.(think money at the time)

I do suspect a China wall leak, still waiting to see if my oil cooler adapter repair stops the flow of oil on the outside of the engine...

I did rebuild the OPTI with a new cap and rotor. Acdelco of course. New plugs and wires. Bearing is shot. I have done a pretty extensive amount of maintenance to this vehicle.

Minus what I said I haven't done obviously..

I run extremely short on time trying to constantly maintain 3 vehicles and 4 motorcycles. That's not anyone's problem but my own. But if I had the time and money and tools to do all the work that I WANTED to do, all that would already be done. It's easy to say all that stuff, but I'm not retired, nor have I won the lottery, nor do I repair vehicles for a living. So everything takes a lot of money, time and resources to do. For me at least.

Removing/cleaning/reinstalling the intake is going to be a 2 day job between trying to replace vacuum lines and everything else I want to do while it's off.

I appreciate all the responses though!

I will address this when I get the time to, probably start off with little things I was going to do anyway and see where it all goes. And search my way to some other threads pertaining to this of course.
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94 RMSB 170K Sat 5 years, ran for 1 of those then remained untouched for 4. Sat because it was slapped by a deer and the owners didnt want to fix it for whatever reason.
Mods, all the free good ones.
Future? Probably pull engine, reseal it, and run it a lot more. Looking to get 250k out of it. PRAYING for 300k.

Last edited by smelonas; 01-17-2017 at 08:12 AM.
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post #7 of 25 (permalink) Old 01-17-2017, 08:09 AM Thread Starter
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Quote:
Originally Posted by 96 Black View Post
I edited for clarity. Insights provided. The car may have 'car sitting a long time' ailments, but it sounds like the first tack is to simply attend to all the routine and periodic maint. expected for the age and mileage. You're gathering ideas and that's good, even if a tad scattered about. You will make a lot of headway with search on already well-documented solutions to problems you describe. If you plan to keep the car buy a FSM. It's a really quite good read. Your sig states you want to remove and 'reseal' the engine. Unless there's something exceptional on history, I'm not even close to understanding why you intend to do that.
I did check the EGR.. it kills the engine.

I do have all 3 FSMs for the 94 model year.

I want to 'reseal' to do new timing chain, all new front cover seals and gaskets, rear main seal (if it can even be done with the engine still in one piece) and clean the thing up and give it a paint job.

It's coated in about 1/4 to 1/2 inch of sludge, grease and bucknasty on all sides.

No real reason to do it other than I just want to. I plan on keeping the car going for a good long while, so to me it's an investment in my bank account to make sure it is fresh, reliable and easy to work on (NOT COATED IN GREASE)

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94 RMSB 170K Sat 5 years, ran for 1 of those then remained untouched for 4. Sat because it was slapped by a deer and the owners didnt want to fix it for whatever reason.
Mods, all the free good ones.
Future? Probably pull engine, reseal it, and run it a lot more. Looking to get 250k out of it. PRAYING for 300k.
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post #8 of 25 (permalink) Old 01-17-2017, 08:14 AM
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If you do all the subassemblies before starting, the work on the manifold should be about 1 day. Get a friend to help you, because the manifold is heavy enough that you can not hold it up, and place it by yourself (unless you are an Olympic weight lifter).
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1991 OCC 461 (.030 over 454) BBC, 3.23 posi, flash to pass, drop spindles & springs, Impala rims, Recaros, MOMO/wood SW w/QR, custom wood shift knob, Pioneer DEH P77DH
1992 OCC now with 5.7 tbi, DEH P77DH
For a parts list, check http://www.impalassforum.com/vBullet...ion-parts.html
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post #9 of 25 (permalink) Old 01-17-2017, 08:19 AM Thread Starter
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Quote:
Originally Posted by Fred Kiehl View Post
If you do all the subassemblies before starting, the work on the manifold should be about 1 day. Get a friend to help you, because the manifold is heavy enough that you can not hold it up, and place it by yourself (unless you are an Olympic weight lifter).
Thanks for the insight! I didn't know it was so heavy! I thought since it was aluminum... ya know, it would be lighter.

The EGR is obviously stupid easy to clean/replace when the manifold is off. But this is also a B body so I shouldn't really be complaining in the first place..

The PCV is right there too. I'll probably start off by replacing that because it's the easiest/cheapest to do, besides inspecting the vacuum lines. I haven't forgotten that!

Better to do one at a time anyway, that way you know what fixed it, or made it better or worse..

Let the games begin.

Sent from my SM-N910V using Tapatalk

94 RMSB 170K Sat 5 years, ran for 1 of those then remained untouched for 4. Sat because it was slapped by a deer and the owners didnt want to fix it for whatever reason.
Mods, all the free good ones.
Future? Probably pull engine, reseal it, and run it a lot more. Looking to get 250k out of it. PRAYING for 300k.
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post #10 of 25 (permalink) Old 01-17-2017, 08:31 AM
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The manifold is not extremely heavy, but you must hold it out at arms length when installing it. It gets heavy quickly, because of the leverage disadvantage. Try holding 20 lbs. out at arms length, and see how quickly you put it down.

1991 OCC 461 (.030 over 454) BBC, 3.23 posi, flash to pass, drop spindles & springs, Impala rims, Recaros, MOMO/wood SW w/QR, custom wood shift knob, Pioneer DEH P77DH
1992 OCC now with 5.7 tbi, DEH P77DH
For a parts list, check http://www.impalassforum.com/vBullet...ion-parts.html
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