hesitation
 

This might be the wrong place to ask, but, since it is the same car as a Bonneville really, thought I'd give it a shot.. '99 Olds eighty-eight, not supercharged, 37K miles, flawlessly maintained, flawless runner, great mileage, no codes. When warm, she sometimes hesitates or lacks power under very light acceleration, like in stop and go city traffic. Nail it, and it runs great. Idles perfect. Cruises perfect. I pulled the plugs, they are all the same and look perfect. Now I know that this can be caused by a million things, just hoping someone can say "Had the same thing.. check the bla bla bla!" Any input would be appreciated. Thanks, Mike.

Typically plugs and/or wires. 90% of the time. How old are yours? Moving to "other H bodies" for you.

Plugs and wires are definitely a good start.

I'd also change the fuel filter too. For $8 it's good insurance anyway.

On a similar note... I had the same issue with my 99 Bonneville. I'm at 124K now, but it was going on for the past 25K or so. It ended up being weak fuel pressure at the rail. I was only getting ~ 38 lbs. Two weeks ago I ended up changing the pump and it's running better than ever now. I'm now getting a consistent 48 lbs. of pressure. Check your fuel pressure too. ;)

hesitation
 

Plugs are brand new, when I pulled them to see how they looked, I replaced them, just in case. The wires were new just before I bought the car 5K ago, but I swear the hesitation got a little worse with the new plugs, so I was thinking maybe I had a funny wire, and messing with the plugs made it worse. Also, it has the feel of being lean, so to the point of low fuel pressure, my thoughts were not necessarily to the pump, but maybe the regulator was sticking, and not increasing pressure when engine vacuum drops, unless it dropped a lot, like when you nail the gas.
Still love my Bonneville, the restoration is going great, but I also love my Olds... I'm probably a little older than most of you, and I like the cushiness.... Plus, I don't think they are as popular, my last two daily drivers have been the Olds, and it seems that both times I have gotten comparably equiped cars for about 10% less than the Bonnevilles.
Over the weekend, I'll pull my plug wires and put and check their resistance, then I'll measure fuel pressure at various vacuums...
This leads to a question.. the '93 had an electrical pigtail near the battery that when hooked to the battery, would make the fuel pump run with the car off. This was excellent for testing fuel pressure, since then you could put your trusty vacuum pump on the regulator and see how the regulator was performing. Is there a similar pigtail on this 99?? Thanks. Mike

I'm not familiar with the pigtail you described. How I tested my pressure was just to turn the key "on", but not start the car. That gave me the at rest pressure. Then, I started the car to get the running pressure. I'd watch the fuel pressure fluctuate (it shouldn't much) when I'd slightly rev it at the throttle body.

Did you get a recall for your fuel pressure regulator? All the 99 L36s got a recall. You might want get that replaced as they were faulty. It could be something as simple as the free fix the dealer is offering! ;) You said you just bought it...I'd call the dealer and see if the fix has ever been performed.

Yes, I have to agree with you on the comfortability factor on the Oldsmobiles. The 94 Royale I have rides like air! It's no performer in the turns or anything, but it's an awesome highway cruiser. It just floats. The taller gear ratio is nice because I save a little in the gas department too.

Where are you from? We might have someone local that could help you out.

hesitation
 

You should have that pigtail right by your battery on your '94, on mine, it is a red wire with a green connector, female spade connector. This is VERY helpfull when pulling your tank, you can run the fuel as low as you dare, then remove the RETURN line from your fuel rail, thus giving you a 5/16" steel pipe to connect a rubber hose to, put that hose in container, connect the pigtail to the battery, apply vacuum to the regulator so it allows maximum flow, then sit back have a beer and wait for the pump to change pitch, signifying that you are sucking air... TANK EMPTY!! I don't know about you, but I HATE pulling a tank down with even 1 gallon of gas in it. Of course you can't do that if the pump failed. :)
Again, I don't know of a pigtail on the newer ones, sure would be nice if there was one!!

I live in Northeast Ohio, about 30 miles due east of Cleveland.

I'll look for that on the 94 today. That would be handy.

I just replaced the tank on my 99 and it had about 2 gallons left in the tank. It wasn't bad, though because I used a transmission jack. That was a life saver and key to making it easy!

Too bad I didn't know about your issue sooner. I just returned from the Cleveland area on Tuesday. I was free all night Monday. We have a plant in Oberlin, OH that I was visiting. I could have easily come by and helped out....

hesitation
 

Ha! Figures! My family was out of town this week, spending time with grandma, so I have been pretty free this week too!! You could have checked out my Bonneville project too.. Well, what are ya gonna do, win some, lose some.
I check these few things on the Olds, see what happens...
thanks for everything
Mike

That pigtail should be on all 92-99 Bvilles and similar cars. If you jump it to 12V (the conveniently close battery), your fuel pump should come on. If you read resistance through it, you read the winding resistance of the fuel pump.

If you read resistance through it and turn the key on, it should open the circuit (infinite resistance) as an indication that the fuel pump relay is working and has changed state.

Didn't the 99 have a recall on the bleed down of the FPR causing intake explosions? Pull the vacuum line off your FPR. If there's gasoline in it, change the FPR or call the dealer to check on the recall. Have your VIN handy.

hesitation
 

Did a little messing around tonight, the fuel pressure, per the GM manual, is right on the money. I looked up "hesitation, sag, stumble" in the manual and checked some of the basic things, all seems okay. By the way, I can't find that fuel pump pigtail near the battery, not that I need it now, but I can't find it.
Now here's a potentially dumb question... The car was idling, and I removed the oil fill cap to reinstall the plastic cover, and I noticed that the crankcase seems to be at a tremendous negative pressure. When I removed the cap, it made the swoosh sucking noise, then the idle went to hell. With all these cars I've owned, I guess I've never removed the oil cap with the engine running - but is this normal? Also, when I shut the car off, you can hear the suction going away in the engine for a second or two after the engine stops. I know I have never heard this with my other cars.. Is this normal??I understand that this may be part of the crancase vent system, but it seems excessive. It idles great when the cap is on, but maybe it has "learned" and adjusted for a problem? Please reply. Mike

Re: hesitation
 

hooooooo!!!!! thats not goooooddddddddd at all, but with my limited experience, ill let the old farts :lol: diagnose this one cuz ill probably end up saying the wrong things ;)

Replace your PCV valve and make sure the O-ring is in there. That should solve some or all of your problem.

I couldn't find the pigtail on EchoSSEi's 97, either. I gaurantee it exists on all 92-95's.

crancase suction
 

When I first bought the car, I had a coolant leak, a little research and I quickly learned about the upper intake issues, so I bought the Dorman kit. Once I got it apart, I found that it was only very slight, and was only leaking between the throttle body and intake, and only externally, so there wasn't any coolant in oil issues. Anyway, it was after this fix that I noticed the "after swoosh" when I turned the car off, and it made me stop and ponder, but it idled fine, seemed to run fine, etc... That PVC valve was new then (6K ago) Could I have something wrong with my reassembly? I am very diligent, careful, clean worker... I design, build and maintain sophisticated mechanical equipment for a living, I only say this to assure you all that I am not a hack.. But, if something was wrong, why would it idle like garbage with the cap off? I would think it would be the oposite. Also, with this kind of negative pressure in the system, wouldn't it goof something else up and set a code or something? Now I'm nervous. Thanks. Mike

You haven't done any serious damage.

Carefully inspect the o-rings in the UIM where the PCV seats. It's likely that you forgot to reinstall one of the two. If both o-rings are properly seated, change the PCV and let us know how it running!

BTW, did you change the lower intake gaskets when you did the UIM? On my 99, at 77K miles, my lower intake gaskets were toasted. Just food for thought...

Re: crancase suction
 

I guess that the theory here is that your PCV valve isn't restricting flow as it should, and so the full manifold vacuum is being transferred to the crankcase. Removing the oil filler cap produces a leak in your newly expanded vacuum system, which causes a bad idle.

Just a thought: When you do fix/replace the PCV, you might pull a plug or two and make sure that they're not fouled. I just wonder if the free flowing PCV might have inhaled any oil?

EDIT: I think that the "after swoosh" sound could also be caused by your engine being turned into a vacuum canister. The sound you hear may be the air still rushing in from somewhere to fill the crankcase.

PCV Theory
 

Ha, I had a 10 hour drive (in the family minivan) today to retrieve my family from Grandma's house, so I had a lot of time to contemplate my sins here, and crankcase venting theory... and yes, it would appear that full engine vacuum has now been extended to the entire crankcase! And yes, the afterswoosh is the system equalizing once the engine is shut off. However, on simpler cars, like my trusty '73 Chevy, (may she rest in peace), the PCV would suck in all the vapors from the crankcase, but wasn't there some sort of place where fresh air was introduced to the crankcase, so things could "flow"? I can't remember, it was years ago.. Or, did it just remove what positive pressure got in there via blowby, etc..
I will have to study the airflow in the engine, I am not completely sure how the vapors go from the PCV to the combustion chamber.. I will study my old intake, which I saved. By the way, I did not change the lower gaskets.. I will take a look tomorrow and post back. Thanks!

Sounds like you're on the right track. That PCV is the prime suspect.

solved!
 

Let's recap... I bought the car in March, and promptly changed the upper intake. Since then, it has this hesitation, which I couldn't be 100% sure was caused by me, because I only drove it about 20 miles before I changed the intake. I have since changed the plugs, tested the fuel pressure and spent a few hours under the hood checking for mis-routed wires, loose connects, etc., trying to find the source of the hesitation. But I never gave a second thought to the "afterswoosh", which was a drastic oversight / mistake in engine running theory. What is even more disappointing, is I had a '95, which had the same engine, although it was OBD1, which never had the "afterswoosh"
So, last night, I go out into my garage in my socks, and in about 3 minutes I have the PVC valve in my hand, minus the smaller black O ring. I put my shoes on and go down to the workshop and grab the old upper intake, and remove that PCV valve, and take the O ring from it, and properly reinstall the PCV valve in my car. No "afterswoosh", no vacuum in the crankcase, and this morning, seemingly no hesitation. I won't know for sure until I drive it for a few days.
In my defense, that upper intake came with the PCV valve installed, I only had to attach the sensor, so I never checked the new PVC valve. I'm glad I saved the old upper intake, so I could reference it for proper assembly, and ultimately steal the O ring from it. THANK YOU ALL!!!! Mike

No problem. Glad it worked out for you. ;)

:)

this happens about 3 times a month (maybe more, I don't read all of the posts like willwren :) ).

oh, and to answer your question from above (before you fixed it), the crankcase gets its fresh air from the throttle body. if you look at your old intake, you'll see a couple of holes on the face where the TB meets up. the round hole that is just to the right, and slightly below the center of the main opening is your air supply for the crank. if you follow that further, you'll find that the hole it matches to in the TB mates up with a passage that grabs air from before the throttle plate, to ensure that there's a constant supply of air, regardless of throttle position.

I haven't proof read what I just wrote, so sorry if it makes no sense...