High RPM control from computer

[Nicoleb3x3]

I have an abornally high RPM (2000) while coasting and comming to a stop. After I stop RPM slowly return to normal 1k and idle is fine. It's only while driving I have this problem.

If I put car in neutral RPMs easily go up to 2200 and slowly (sometimes 20 seconds later) return to 1k idle.

It's like the computer is over-compensating --normally the ecm holds a slighly higher RPM when slowing to a stop to prevent stalling..this is normal ecm stradgey; but; it's over doing it...2000 rpm instad of like 1200 and it takes longer to respond to the fact that I let off the gas and comming to a stop.

Car basiclaly drives itself down the road without throttle...doesn't appear to be mechanical such as the throttle cable sticking because of the way it acts is definately ecm control.

I notice a "whine" from either the distributor or the front of the intake...hard to tell if it's a vacuum leak or if it's maybe the bearing from the dizzy?? could the dizzy itself leak air from maybe the oring? When I shut off the car the noise lingures and slowly goes away...sounds like air to me, but when the car is running it sounds like a supercharger whine almost...could be I have both issues? bearing from dizzy whining and an air leak?

I have low manifold vacuum at 12....I would think it should be at 14 or 15 with my cam: XE266HR

I'll try to take a video and post it....

Nicole

 

[Nicoleb3x3]

video posted below....I'm 50/50 about if there's a whine AND a hiss or if it's the same noise and if it has anything to do with my high rpm issues

Video Here




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[Nicoleb3x3]

here's another video at a quieter idle...mechanical only 700 rpm
you can hear the noise better

700rpm idle video 2



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[liljoe07]

Sounds like a vacuum leak. Which would explain the lower vacuum at idle, and the High Idle.

Go over the vacuum lines first.

 

[liljoe07]

Another thing, because of the noise being loudest at the Distributor, its possible its an intake end seal gasket problem. Or even a Lower intake to head gasket.

 

[Nicoleb3x3]

I definately checked my vacuum hoses the best I could already, they're all new and fitted securely
also the noise is not from any of the back where most of the lines are.

...I'll try to investigate the lower intake a bit more....

 

[jerryD]

just the VSS doing its job. check the IAC , otherwise its prob a vacuum leak. if you are stopped and blip the throttle, does it hang or come back down to normal idle? unhook the vacuum line going to the vacuum tree and check for vacuum there. are your valves adjusted properly, correct pushrods?

 

[jerryD]

i kinda read your website, did you only go a 1/4 turn past zero lash on your rockers? that is a VERY loose setting, plus you will get a little valve train noise. is there a reason you went that loose? it may be part of your vacuum problem cause your valves aren't opening as much. depending on the intended use for this engine, go at least half past zero lash. i went 3/4 on mine.

 

[liljoe07]

You loose vacuum from TOO MUCH preload or incorrect Push rod length. Every top end Ive done, has been 1/4 turn on the rockers. And depending on the Cam, Ill pull anywhere from 14-17hg of vacuum. Mostly in the 16-17 range at Idle.

Was the lower intake removed lately?

 

[Nicoleb3x3]

I ended up re-adjusting them to 1/2 turn...they're about the same noise. I consider them a bit loud..but they are 1.7s and the cam is likely another reason why their noisy. I made very good HP for my auto on the dyno, so I don't think I have a problem with them.

As for blipping the throttle, I tried this and it actually aggravates the problem, same if rolling/coasting and same if stopped...If I tap on the gas the idle tends to "hang" high. The only time it starts to act normally is if I stop at a red light it'll idle down again after 20 seconds or so; sometimes longer....

also...I noticed that I seem to be losing oil....I have a leak at the rear main seal; but the amount of oil lost seems to be increasing. I haven't been able to study the exact amount of oil loss because I stopped driving the car on a daily basis until I fix this other issue...but I think I went through minimum of 2 quarts in 500 miles.

 

[Nicoleb3x3]

lower intake hasn't been removed since initial install...I probably could have re-torqued it though...

I have take teh upper off a few times, but it ran fine for 3 weeks

the only thing that was happending before this mess was my batter lost a good ground during start up, power died when cranking....I wiggled the ground it got it to start...I fixed the batter was hitting the ground, so that issue went away, but now i have these other issues.

 

[Nicoleb3x3]

btw; I pulled #1 spark plug and it showed no signs of burning oil....it looked perfect actually.

 

[Nicoleb3x3]

if my pushrods aren't the right lenght...then it's by a hair. I had an experience friend help me measure and we could get away with stock length or...slightly bit longer (I forget the measurement but probably have it written down somewhere)

if my pushrods are ever so slightly too short, will that cause oil consumption?

 

[jerryD]

yes too much preload will cause vacuum issues as well, but what we are talking about full turn or less here, we are gonna be ok.

You loose vacuum from TOO MUCH preload or incorrect Push rod length. Every top end Ive done, has been 1/4 turn on the rockers. And depending on the Cam, Ill pull anywhere from 14-17hg of vacuum. Mostly in the 16-17 range at Idle.

 

[liljoe07]

Oil consumption has no bearing on Push Rod length.

Now, bad ring seal and Valve seals, along with leaky seals will.

Try and re-torque the lower intake. Thats a must do anyways. Most times they will loosen up after a warm up.

Any Diagnostic codes present?

 

[liljoe07]

yes too much preload will cause vacuum issues as well, but what we are talking about full turn or less here, we are gonna be ok.

But too little preload wont cause low vacuum.

 

[jerryD]

just checking to make sure you used a solid lifter and an adjustable pushrod during the process. was the marker pattern good and in the center of the valve tip. the length shouldn't affect the oil consumption issue. other than the rear main leak, are there any spots left on the ground? other wise maybe your rings haven't seated.

if my pushrods aren't the right lenght...then it's by a hair. I had an experience friend help me measure and we could get away with stock length or...slightly bit longer (I forget the measurement but probably have it written down somewhere)

if my pushrods are ever so slightly too short, will that cause oil consumption?

 

[Nicoleb3x3]

we use an adjustable pushrod checker and fully pumped up lifter (it's all we had available), we watched to make sure it wasn't bleeding down during measurement, ...anyways I looked for myself, it was pretty damn square on the nipple thing, maybe slightly slightly hanging to the inside but still considered center. (thus the reason why he said I could go a bit longer but he felt the stock length would be fine)

What would cause the valve not to seal?

 

[liljoe07]

The valve seals I was talking about, seal the valve steam itself. If they start going bad, you get oil into the intake port of the heads. Usually youll see some smoke out the exhaust though. High oil consumption is mostly related to burning oil. So valve seals, piston rings or even a faulty PCV system is possible.

 

[Nicoleb3x3]

the only code I got that was not present before is 26 (maf) but it was only on one of the no-run test. (not on the run test) I don't have any check engine light on at the momment. I ran with the hanging idle issue for a full week and no engine light came on....then I the engine light came on once after I reset the battery for 30 mins and went for a test drive...funny the car was driving normally for 15 mins..engine light came on a few times then didn't come on anymore; then the problem returned...

anyways...the deeper I get into this the more scatter brained I'm getting- with a new engine and all new stuff I have no idea what to expect. I could have many issues accumulating here.

I plan to re-run my scanner in a non-run test to see what I can turn up (see if the maf code repeats)

I wish i could fix the hanging idle so I can drive the car and see what's happending with oil consumption or if it's simply all from leaking...I thought I was adding 1 quart every 3 weeks before, but recently I added 2 quarts in 4 days so I'm a bit worried about that more than the hanging idle.