99 olds eighty eight hesitation, sag, stumble

[Troyport]

120k on the odometer. babied and maintained. I've had this slight hesitation off idle (like at a redlight) and a sag at low speeds for thousands of miles, like 70,000 miles. Can feel it sag and surge ever so slightly on a slow speed cruise, like 35mph on a flat smooth country road. I have never been able to find the problem. No codes ever. Great gas mileage. Plugs, wires, filters have been changed with no help. Fuel pressure is normal. Runs much worse with the MAF disconnected. No vac leaks. Injectors have been removed and professionally cleaned, reinstalled with all new orings. It feels like it is running lean, but the data on the 02 sensors do not support that. There are 2 things that help: 1) if I disconnect the battery to reset to factory settings, then it runs great for a while until it seemingly "relearns" to run with the hesitation and sag. 2) If I whip it for a day, it runs better for a short amount of time, then returns to running crappy. I have learned to live with it, I suppose... BUT, it is just one of those things that bugs the crap out of me, have I missed something? No amount of tuning up or maintenance has ever made a difference. The only thing I can add is when I bought the car with 34,000 miles on it, it ran great, except I only ran it about 50 miles before I changed the upper intake (it wasn't leaking, but I wanted to get that OEM intake changed, I put on a dorman) and I forgot the o-ring on the PVC valve so I drove it about 200 miles before I discovered what I did wrong. After that, I had the problem I have described. But, for all I know the battery had been disconnected just prior to when I bought it, so that is why it ran great for the first 50 miles. Thanks, Mike

[Jrs3800]

Mike are you also comparing this with your 1993 SLE? Torque hound with 3.06 gears...

Does the Olds have the 2.86 or 3.05 Gears?

Also I wounder is some of the issues you feel could be a tune related issue... There is a lot of junk in the 98-99 PCM's... Also what timing does the PCM command while you are driving and at idle...?

Your car might feel a lot like my 03 Bonneville... Lots O Torque Management

[Troyport]

Interesting you should mention this... because I've often wondered if GM just tweaked the programming to get a little better fuel economy to keep the govt happy, also knowing that it was the last year for the eighty-eight... and therefore have the sucker about as lean as possible.
That said, yes, it has the high gears.. Not only is it an eighty eight (old man car) but it is the anniversary addition, which really screams old man car.. so I wouldn't call it fast off the line. I don't remember what the timing was at idle, I will check in the next few days.
When it sags, if I play with the throttle I can make it stop sagging. If I hold it steady, it will stay in "sag mode" until it upshifts... One time, and one time only when it was very hot out, I actually got it to backfire through the intake.
I really don't think this is just a tuning issue.. I really believe most people would complain about this.. Heck, my wife can feel it sometimes!

[Jrs3800]

Have you ever swapped the ICM from the 93 to the Olds 88 as a test? I also wonder if you are having any issues with a knock sensor... If the PCM sees knock it will kill timing trying to correct it..

I am taking guesses here... This one has me a bit stumped...

We had issues like that with a members car... 98 SSE... Never really completely figured it out... But my Gut was eyeballing those knock sensors as he had KR at the strangest times... and at random for no reason..

[LeSabre in Buffalo]

Mine occasionally has massive hesitation on slow-speed acceleration. It doesn't happen all the time, but is far more pronounced whel turning. I'm leaning towards a knock sensor, after exhausting about everything else such as TPS, MAF, even replacing the PS pump and transmission PCS. Just haven't gotten around to plunking down $100 for 2 new knock sensors since it doesn't bother me. Although I'd love to know just for knowing.

[Troyport]

I love the feedback, because I too have wondered if all this was spark being retarded.. It really is the only thing I haven't looked into. Is there more than one on this car? And if it is only a one-wire sensor, what would happen if I just disconnected it? A few years ago, I was parting out a honda CRX and it had 8 gallons of old gas in it. Just for kicks, I put it in the Olds and the Olds ran better than ever. I couldn't believe it... I don't know if that means anything but all hesitation was gone. And by the way, I have swapped entire ignition systems with the bonny.. including wires.. and bonny still ran great and the olds was still lousy. Mike

[Jrs3800]

The 99 Olds uses dual knock sensors front and rear bank, each knock sensor is on its own channel... And out of curiosity, has the car ever been crank variation learned?

[LeSabre in Buffalo]

Don, my car was, at least according to the dealer I took it to when nobody else was available when installing my Intense PCM.

Check the connectors to the knock sensors. I'm thinking a flaky connection near the PS pump is responsible for mine.

[Troyport]

I'll check the connections tonight, and there has never been a crank variation learn done since I have owned it.. Thanks, Mike