Idle Problem in Drive Only - Stumbles, Shakes

madrivage wrote:

Quick update.I dropped off the car (at dealer...I know...) to replace the rear transmission mount...it was shot.I asked him if they had a Motorvac unit,and they do not.However,they do have a Wynn (sp.) machine which works on the same principle.He said they pull the f. pump relay and tap into the fuel rails and run the chemical through until it's gone,then clean the throttle body,and finish off with a tank treatment dose.I am keeping my fingers crossed that this will clear up any slightly rough idle,slight ping at W.O.T.,AND the supposed carbon build up in #3,which may be the cause of all of the aforementioned probs.

Which is EXACTLY what I described! The Wynns setup is what I have also. I prefer the BG system, but we got a better deal on the Wynns.

I have changed the wires/plugs,cleaned the MAF 3x,changed the fuel filter,seafoamed it,cleaned the IAC,even paid to have Wynns fuel system flush done (think Motorvac).After ALL of this that little bastard stumble is still there!!! I was told by a mech. that my O2 sensor was a tiny bit slow,but it was not a big deal(he smogged my car and it passed with flying colors).He also said my MAF was a little sluggish as well,but again not enough to bother buying a new one (according to him).So...do you think the O2,and the MAF being a little sluggish could cause a slightly rough idle(only in drive while stopped at a light)??I believe he said instead of 10 mili seconds the O2 was taking 16 miliseconds...don't know about the MAF. Thanks in adv. Don

AA wrote:

Hope the treatment doesn't cost too much, and hope it works.

But, I still have to ask... have you seen any more misfire codes since you replaced the #6 plug wire? Imo, that wire was causing the miss on #3.

Well I picked up the car today after the "treatment" ...the little stumble is still there.
The check engine light came on today after driving for a little while,but I am suspecting that it is just some residual crap from the "treatment" possibly fouling up the O2 sensor a bit.I will keep my eye on it and see if it goes off again.It still runs great otherwise.

Have you gone thru the vacuum hoses yet?

Might as well replace that O2 sensor. At 100k miles, you're due. They're reasonably priced if you order online. If you go to the dealer, you'll pay.

Read the code if you can. I wouldn't assume it's the O2 until you can read it.

Don-On typical L67s I've dealt with, when the owners suspect a MAF is causing a stumble or stalling condition; they will unplug the MAF and allow the system to just run off the MAP sensor to rule out MAF issues. I'm guessing that should work the same on your 97 Riv as long as it is the SC setup. I know faulty O2 sensors will make a car run a little rough and make fuel mileage suffer terribly. A faulty O2 sensor can/will cause the system to run very rich. What does you gas mileage look like? Also be sure to check the air filter. If it is clogged, you'll get all kinds of issues at anything more than light throttle.

HTH

Eldo wrote:

Have you gone thru the vacuum hoses yet?

I checked every one I could see tonight...I need to check behind the backside if there is any there that is.I suppose it could be a little leak at the LIM huh??I'll spray some carb cleaner around when I can.

I still don't see any Fuel Injector leak down test readings.................................................

Abaddon wrote:

I still don't see any Fuel Injector leak down test readings.................................................

I don't have any way to do that kind of test...

Here are a few more clues to what it's doing.It only does it when it's at operating temp,not when cold.It also does NOT do it when I have the a/c on.Weird thing is the idle rpm's in drive with a/c is the same as without (650),yet it does not do it with a/c on.

As far as only doing it when at operating temp could that point to the O2 sensor?I know that #1 is a little lazy...I think I'm just going to replace it along with the MAF,but the MAF is gonna have to wait till I get more cash to throw at it.

I don't think O2 or MAF will cause that problem. Can you take a video of the engine idling and stumbling? Maybe set the e-brake and leave it in drive?

madrivage wrote:

Here are a few more clues to what it's doing. It only does it when it's at operating temp,not when cold. It also does NOT do it when I have the a/c on. Weird thing is the idle rpm in drive with a/c is the same as without (650), yet it does not do it with a/c on.

I hate to say it, 'cuz I know you've checked most of the lines, but this info makes me think of vacuum leaks again...

The operating temperature only applies to the engine itself, because the heated oxygen sensors come online after only about 90 seconds. If the heater was dead, it would (theoretically...) throw a code and light the SES light. However, the fuel map still starts with a richer mixture for colder temps.

When the A/C is on, the PCM knows to adjust for more idle load, and adds more fuel & air, which would mask a vacuum leak... Also, if everything is working correctly, I think the RPM should be the same with the air on - the computer is just trying to make up the difference.

Now comes the worst-case scenario: Where else can a vacuum leak come from... the intake manifold gasket?

Eldo wrote:

Now comes the worst-case scenario: Where else can a vacuum leak come from... the intake manifold gasket?

all too possible.

madrivage wrote:

I have changed the wires/plugs,cleaned the MAF 3x,changed the fuel filter,seafoamed it,cleaned the IAC,even paid to have Wynns fuel system flush done (think Motorvac).After ALL of this that little bastard stumble is still there!!! I was told by a mech. that my O2 sensor was a tiny bit slow,but it was not a big deal(he smogged my car and it passed with flying colors).He also said my MAF was a little sluggish as well,but again not enough to bother buying a new one (according to him).So...do you think the O2,and the MAF being a little sluggish could cause a slightly rough idle(only in drive while stopped at a light)??I believe he said instead of 10 mili seconds the O2 was taking 16 miliseconds...don't know about the MAF. Thanks in adv. Don

You sound (more than) a little frustrated at this point.

Consider this:

1) if the O2 sensor is switching at 16 milliseconds instead of 10, taking 60% longer than it should. That is more than "a little sluggish." A new one, although not absolutely necessary, would not be a waste of $$. Cheapest way to go would be to get the crowfoot wrench needed to replace the upstream O2 (usually the downstream ones don't go bad unless the car is misfuelled or they get fouled with silicone somehow) and a OEM or 'exact fit' sensor - try rockauto.com - and put it in yourself. AutoZone will loan the tools to you under their tool loan program (and surprise surprise you don't *have to* buy the O2 sensor there). In the store on the parts counter there usually is a placemat or counter mat that shows what tools are (supposed to be) available under the loan program.

2) If you did not remove the MAF to clean it, consider doing so and also when you remount it do so carefully to prevent air leaks at the mounting area. if there are air leaks at the mounting area the MAF won't send true readings to the PCM and in turn the PCM won't hold idle nor will it run the engine optimally under load. Thinking about it, I suspect the MAF's not dirty per se but rather there is an air leak near it. It's important not to have ari leaks near the MAF and some mechanics think a little leak is the same as no leak and that is just not true.

3) "Rough idle" usually means the RPMs are varying a lot per unit time, evidenced by the tachometer needle wavering (some mechanics call it "hunting"). If your idle looks steady on the tach, you don't have rough idle, you probably have the engine whacking around the cradle because of a worn/torn motor mount. So you might want to roll the car up on a pair of ramps and look at the rear transmission mount. What you are looking for is cracks or tears in teh rubber, or evidence of weakness (the rubber in the mount looks bent). I suspect it's time to replace the mount. For instance you say the idle smooths out when the AC is on. Well, when the AC is on the car's engine is under load and it is using the (kinetic) energy that was used in bopping around in the cradle instead to run the A/C compressor, and also the alternator is working a little harder to power the engine and HVAC fans. Plus the thing Eldo said (below)

4) Eldo wrote, "When the A/C is on, the PCM knows to adjust for more idle load, and adds more fuel & air, which would mask a vacuum leak... Also, if everything is working correctly, I think the RPM should be the same with the air on - the computer is just trying to make up the difference." Point being you need to check all the vacuum lines not just the convenient ones. There are not that many on the Riv, some of them are clumsy to get to but except on the early ones they are all pretty much topside. One convenient way to renew all the vacuum lines is take the car to an auto parts store (preferably one that has an experienced counter person who works on cars) when they are not busy. Tell him you want to replace all the vacuum lines to solve an idel problem and could he please take a look under the hood to help determine what sizes to buy. IIRC a couple feet of each of 2 or 3 sizes is all you will need for the Riv, plus a "HELP" pack of caps and connectors. The whole shooting match won't run more than $25, and depending on that store's pricing may be a lot less. Take the whole mess home and replace those lines one by one. If you are unsure of a size between a couple sizes, use a line that's tighter fitting on the vacuum fittings. Since you have already replaced some, getting the rest won't be too bad. I recall there is one that seems to be a special molded hose, fitting is bigger at one end than the other - IIRC I replaced mine by making up a hose with an adapter from the HELP kit and a length of vac hose that fit tightly, with a little "Goop" (a silicone cement) smeared on where I coupled the hose to the adapter (rubber tire patch cement whould have been better but I did not have any).

5) Eldo also pointed out that there's other places vac leaks can be. Did you take a spray can of starting fluid and spray around the intake manifold? Ask your mechanic, he/she might have done this already. Point being that manifold leaks that are too small or too large to whistle can be found by spraying starting fluid at the intake manifold while the engine is running. It does not take much at all. If there is a leak the engine speed will change when you hit the leak with the spray. This has to be done carefully to avoid risks (fire and what have you) but is done routinely by experienced mechanics to find leaks that are not obvious.

6) An hour of diagnostic time from a mechanic costs the same as an hour of mechanic's time to replace spark plugs. Point being that it might be a good value to you to offer to pay the mechanic to do the diagnostics that you can not do. Such as the fuel injector leakdown test. An experienced mechanic can run a lot of diagnostics in an hour.

How all this sums up:

- if the tach is showing steady idle, check your motor and transmision mounts.

- if the tach is showing wavering idle, time to remove the MAF and TB, make sure they are clean, and reinstall. You can get MAF and TB cleaners at auto parts stores intended specifically for those jobs. You will need a disposable plastic or metal pan to use in cleaning the MAF. Also replace the remaining vac lines and check the intake manifold for vac leaks.

- then it's time to try the other things that have been recommended, including testing the injectors and such.

Finally a word to the wise: So many people have 'weighed in' on this that I doubt seriously whether posting more symptoms will get you any closer to fixing this problem. Time to try some stuff that eliminates possible causes.

Albertj

albertj wrote:

Did you take a spray can of starting fluid and spray around the intake manifold?

go for something a lot less flammable, like carb cleaner. Otherwise, great instructions to follow at this point.


It also depends what missing at idle is like. My symptoms were an occasional 'spit', every few seconds. Replacing my injectors with a set that has truly been cleaned (OFF THE CAR) fixed it. See this thread for more details:

https://rivperformance.editboard.com/for-sale-f22/cleaned-flow-tested-stock-injectors-t6106.htm?highlight=injectors+cleaned

last time I had a set cleaned by him (a few months ago) it cost $80 plus $6 shipping each way. I still have some injectors to be cleaned if you are interested.

deekster_caddy wrote:

albertj wrote:

Did you take a spray can of starting fluid and spray around the intake manifold?

go for something a lot less flammable, like carb cleaner.

Agreed. But watch out for whatever spray you use, as it may interact with the paints and plastics under the hood. For instance on the normally aspirated engien, the intake manifold is plastic IIRC.

Albertj

O.K. update time... my engine leaks like a sieve!!! I sprayed around and I have a leak at the PCV valve cover plate,and under the front side base of the supercharger (looking at it from passenger side head on) where it meets the LIM,and on the side closest to firewall (also at base of supercharger).I didn't find any leaks at the LIM (imagine that),however if I'm gonna do the supercharger gasket I might as well do the damn LIM gaskets at the same time.I just don't know how far I should go with all of these repairs though.Keeping in mind I have some mysterious low "running" compression test result in cyl #3 should I take off the damn heads too and check the valves??I would hate to do all of the gasket work only to find it still doesn't run perfectly when I'm done!! The static compression was fine btw... So how difficult is it to get the supercharger and LIM off to do this job??Do I need to pull the whole front of the engine to do it??You know all of the damn pulleys,and alternator etc.?? Damn,I really like this car I guess I have to bite the bullet and do all of this stuff if I want it to run as it should.That's the real bitch btw...other than the vacuum leak stumble at idle it seems to run like a bat outta hell!! One last question,how much would it cost to have thi done at a shop approx. (if I decide I don't want to hassle with it)? Shank you very much...

Have you read this Write Up.?

https://rivperformance.editboard.com/series-ii-engine-transmission-f4/write-up-lower-intake-manifold-gaskets-t2283.htm#24393

madrivage wrote:

O.K. update time... my engine leaks like a sieve!!! I sprayed around and I have a leak at the PCV valve cover plate,and under the front side base of the supercharger (looking at it from passenger side head on) where it meets the LIM,and on the side closest to firewall (also at base of supercharger).

Sounds to me like you have excess combustion chamber pressure that should be relieved by the PCV system.
If the internal crankcase pressure has no where to go, it will do as you are explaining.
Have you pulled the PCV valve to see if it is free and clean and working. (step #1)

Pull the oil fill cover on the valve cover while it's running and see if there is any blow-by or pressure being relieved when you do that.

Should not have all this internal pressure. (Try some Gas X) just kidding.

Need to find out what's up.

Actually Rick, I believe he is talking about finding vacuum leaks by spraying around with carb cleaner, as we told him to above, not stuff leaking out of the engine.

OH, I guess i didn't understand and didn't read back far enough. I thought you had all these external oil or oil vapor type leaks. Have seen that before and it's not a pretty site and can take a bit of work to solve it.

Still, if all those spots are showing signs of leaks by spraying carb cleaner or whatever, what you gonna do to solve the problem.????
But, you still have problems to solve., sorry.

madrivage wrote:

O.K. update time... my engine leaks like a sieve!!! I sprayed around and I have a leak at the PCV valve cover plate,and under the front side base of the supercharger (looking at it from passenger side head on) where it meets the LIM,and on the side closest to firewall (also at base of supercharger).I didn't find any leaks at the LIM (imagine that),however if I'm gonna do the supercharger gasket I might as well do the damn LIM gaskets at the same time.I just don't know how far I should go with all of these repairs though.Keeping in mind I have some mysterious low "running" compression test result in cyl #3 should I take off the damn heads too and check the valves??I would hate to do all of the gasket work only to find it still doesn't run perfectly when I'm done!! The static compression was fine btw... So how difficult is it to get the supercharger and LIM off to do this job??Do I need to pull the whole front of the engine to do it??You know all of the damn pulleys,and alternator etc.?? Damn,I really like this car I guess I have to bite the bullet and do all of this stuff if I want it to run as it should.That's the real bitch btw...other than the vacuum leak stumble at idle it seems to run like a bat outta hell!! One last question,how much would it cost to have thi done at a shop approx. (if I decide I don't want to hassle with it)? Shank you very much...

One way to look at it is that the engine had the good manners to let you know of all this maintenance at one time. Done right, these are more or less "once and done' issues until the engine requires a bottom-end overhaul. None of it ais all that difficult, but it is time consuming.

As for the pulleys and alternator, they are not that big a deal except the one idler pulley that's behind the front motor mount, and even that is not too bad except you have to undo (well you should undo) the front mount. (if I could figure out how to get a serpentine belt tool in there with a torx bit on it I bet that pulley could be changed without pulling the mount because once the bolt's cracked loose you could wind it out/snug it up with fingers).

For the miscellaneous gaskets, consider just buying a sheet of neoprene-impregnated gasket material from a parts store (Autozone has them but you have to ask they are not on the shelf) for about $5.- then cutting the gaskets yourself using a box or x-acto type stencil knife. That will save money and hassle. PCV, throttle body, and many other gaskets can be made that way. LIM gaskets you have to buy *but* the LIM gasket is a weak point anyway...

As for cylingder # 3 you are not done yet. You have the 'running compression' test but IIRC you have not done a leakdown test. You need leakdown in combination with other tests to figure out if it's a valve or head gasket issue. Also IIRC the leakdown test is covered elsewhere so I won't go into detail.

And oh by the way when it's all said and done, be sure to loom the spark plug wires correctly. Many misfires and subsequent engine problems are due to sporadic extra spark plug firing caused by misrouted/crossed spark plug wires. The right 'wrong' timing of a misfire can cause serious engine damage over time.

But back to your problem: I think if there's an issue here, it's most likely that you were not expecting to have to get into this amount of diagnosis and repair with this car. Well... ahem... if the car did not have these issues it would not have been so, well, affordable to purchase. You'll have a good bit of sleuthing and some work to do but when you are done you'll have quite a car.

Albertj

Hey Albert,I went back down and they replaced it with another no questions asked.It now works as it should.as far as the K&N I did not oil it,it is as stock fresh from the box.I also haven't messed with the TPS at all.Only bummer now is with ll the spraying of carb cleaner to check for vac. leaks I have cleaned out some of the gunk that might have been partially sealing the edges around my leaks...now it's slightly rougher at idle.

madrivage wrote:

.Only bummer now is with the spraying of carb cleaner to check for vac. leaks I have cleaned out some of the gunk that might have been partially sealing the edges around my leaks...now it's slightly rougher at idle.

Hell, look on the bright side: it confirms your diagnosis...

(That's not a bug, that's a feature!)

madrivage wrote:

Hey Albert,I went back down and they replaced it with another no questions asked.It now works as it should.as far as the K&N I did not oil it,it is as stock fresh from the box.I also haven't messed with the TPS at all.Only bummer now is with ll the spraying of carb cleaner to check for vac. leaks I have cleaned out some of the gunk that might have been partially sealing the edges around my leaks...now it's slightly rougher at idle.

Yes but you *know* where those problems are instead of guessing. And you might want to check if that K&N requires oiling. Finally, what do you plan to do next?

Albertj

I can't figure out how to do the multi quote deal,so...
Eldo: Yeah,it feels good to at least nail it down.

Albert: The K&N is only 2wks old at best.As far as the next move...well I'm running out of cash to throw at this thing for the moment,so I think I'll live with it for a while.I am fully capable of doing it myself,but one tool I come up short on in my rollaway at the moment is PATIENCE!! I just don't know if I can dive into that job any time soon without blowing a fuckin' spoke.I might just wait 'till I can scrape up the bread and pay the shop to do it (I know it's lame),but seriously I don't need another task or headache right now.I still want to check out that #3 situation too before I dig into the vac. leak issue.Not to mention I need to see if I'm still having the random misfire after changing the plugs/wires a few days ago.I don't have a scanner and it's really limiting as you can imagine.I have the battery disconnected right now so I can clear the codes/ses light.It would be nice to see that bastard not come on again now that I have changed the offending sensors.I'm keeping my fingers crossed that the misfire doesn't rear it's ugly head again.Do you know if a bat. disconnect will clear the saved codes as well,or just clear the ses light?