Slow Acceleration Sometimes

I've been having issues where sometimes I take maybe 7 seconds to 60 and other times, those 7 seconds get me to only 40. I have no idea why the hell my car is doing this. It shifts gears fine. Just feels like sometimes I have no power and other times I can haul ass. No engine light either.

Also, I have brand new AC Delco platinum plugs, and brand new AC delco plug wires. It did this both with and without the new intake. Would a broken IAT sensor cause this? Possibly my MAF sensor is bad?

Bad throttle body? I'm pretty sure if any of those were bad then I'd have check engine light, but why else would my car take twice as long to get to 60?

...not sure why in your case but in general you're describing a lack of spark advance. Question is why.

Albertj

How do I diagnose spark advance?

could be a lot of reasons. When is the last time your fuel filter was changed?

The best way to find out what's going on is to get an ODBII scanner that is capable of datalogging multiple sensors. It will take some detailed information to figure out exactly what the problem is. Otherwise you can just throw a bunch of parts at it, watch your $$ fly away and maybe you'll get lucky.

deekster_caddy wrote:

could be a lot of reasons. When is the last time your fuel filter was changed?

The best way to find out what's going on is to get an ODBII scanner that is capable of datalogging multiple sensors. It will take some detailed information to figure out exactly what the problem is. Otherwise you can just throw a bunch of parts at it, watch your $$ fly away and maybe you'll get lucky.

agreed... I forgot to ask the host of questions needed to reckon the state of your Riv's maintenance. Rivs are not maintenance -free and if you are behind it will not run well.

Oil was just changed 2 days ago, brand new intake as well. Tyranny fluid is fine and it shifts fine. No engine light. Brand AC delco platinum plugs, brand new plugs wires, engine sounds healthy but sometimes it flies and other times it won't acellerate for shit. No idea why.

EDIT: no.idea.when the fuel filter was last changed. I have to ask my step dad. How often should it be changed?

Try to better describe to us what is happening. You say sometimes the car is fast to 60 mph, and other times it's slower. First thing: a stock SC Riv typically runs 0-60 in 8.5 secs, so there's no way you're getting a 7 sec 0-60 time. You might want to use a scan tool or a stopwatch to verify how quickly you are really accelerating, to get a benchmark.

When the car feels slow, what are the conditions? Does it happen when you launch the car from a stop, or does it happen while you are rolling? The point is, most any car will accelerate more slowly while rolling from various speeds, due to the PCM's decision to downshift or hold the gear. So what you're describing could be normal - unless you can show the car is measurably slower than a previous run under the exact same conditions.

Hmm, a surcharges buick gets 8.5 sec 0-60 how does a grand prim get like under 7 second 0-60 with the same portrait and retrain? And my speedmeter us broken lol.

So it feels really slow from a standstill compared to how it was when i first got jt, and lets say rolling at 30, sometimes it will pull fine if i step on it, others it will barely accelerate. Past 60 the car acts more like.normal but i can't really fell because gauge is broken.

For one, the GTP weighed 300 lb less than a Riviera. That weight makes a big difference. Also, more of the w-body's weight is over the front wheels - good for straight line traction. Firmer suspension in the GTP also helps.

8.5 sec 0-60 is what I measured with my car stock, on the street. Reviews from magazines usually have slightly better numbers, since they test at a track (stickier surface). I think the '95 SC Riv got a 7.9s 0-60 time in one magazine, and I'd bet the test car Buick supplied for the review wasn't their slowest one.

Quote :

lets say rolling at 30, sometimes it will pull fine if i step on it, others it will barely accelerate.

This might depend on what gear you're in. At 30 mph, the transmission could be in 1st, 2nd, or 3rd depending on what you're doing. From memory, my car did the same thing before it was re-tuned. Still does it on occasion.

Hmm. Wish this car came in manual lol. Would be a lot easier to eliminate the gears. What did you do to re tune your car?

Auto is the way to go for best acceleration, imo. According to the scan gauge, my car regularly sees shift times of between 125-250 ms, and has even seen 75 ms. That's on par with some of the best autos in the world, and leagues beyond what manual shifters can do. Everybody thinks they can shift faster than a machine, but really most "quick" manual shifts are about 500 ms, and the fastest I've found is 260 ms. In a drag race, you want auto. Even on road course tracks, auto is becoming more and more common.

Link: http://mbworld.org/forums/c63-amg-w204/252476-manual-shift-speed.html

What the manual can do is ensure you're in the right gear (relies on user) to accelerate from a roll. But from a stoplight, the auto will win, assuming it's an efficient design. Ours are pretty good.

Here's a thread on tuning a NA Series II:

https://rivperformance.editboard.com/t8462-tuning-series-ii-na-engine-pcm-park-avenue

AA wrote:

Try to better describe to us what is happening. You say sometimes the car is fast to 60 mph, and other times it's slower. First thing: a stock SC Riv typically runs 0-60 in 8.5 secs, so there's no way you're getting a 7 sec 0-60 time. You might want to use a scan tool or a stopwatch to verify how quickly you are really accelerating, to get a benchmark.

When the car feels slow, what are the conditions? Does it happen when you launch the car from a stop, or does it happen while you are rolling? The point is, most any car will accelerate more slowly while rolling from various speeds, due to the PCM's decision to downshift or hold the gear. So what you're describing could be normal - unless you can show the car is measurably slower than a previous run under the exact same conditions.

Hey AA - A stock SC riv will do 0-60 in about 7 sec under **perfect** conditions. There is an "error bar" around the 7-and-change 0-60 time and I suspect most come in closer to 8 on the street.

Be that as it may, a while back, friend of mine in a Mercedes club told me "seven is respectable but the number is five."

Finally - c0reyl it's time to "get real" - if your speedometer is broken, you are **not** current on your maintenance. Leading me to suspect the real issue may be loose nuts in the left front seat... Just kidding. But you really need to get caught up on those minor repairs.

The 8.5 secs was probably from a hot summer day. Here are my mods in order, with 0-60 times recorded. It shows 8 secs flat, stock: http://www.cardomain.com/ride/657082/1998-buick-riviera/page-5

Review for SC '95 - 8.2 secs: http://www.cars.com/buick/riviera/1995/expert-reviews/?revid=31837

Review for SC '95 - 7.9 secs: http://consumerguideauto.howstuffworks.com/1995-to-1999-buick-riviera-6.htm

I think 8 secs is a fair spec for stock Riv 0-60. Series II has more power, but Series I has more torque down low, getting the car moving in a hurry. I think these characteristics cancel each other out in the 0-60 mph sprint.

AA wrote:

The 8.5 secs was probably from a hot summer day. Here are my mods in order, with 0-60 times recorded. It shows 8 secs flat, stock: http://www.cardomain.com/ride/657082/1998-buick-riviera/page-5

Review for SC '95 - 8.2 secs: http://www.cars.com/buick/riviera/1995/expert-reviews/?revid=31837

Review for SC '95 - 7.9 secs: http://consumerguideauto.howstuffworks.com/1995-to-1999-buick-riviera-6.htm

I think 8 secs is a fair spec for stock Riv 0-60. Series II has more power, but Series I has more torque down low, getting the car moving in a hurry. I think these characteristics cancel each other out in the 0-60 mph sprint.

Fair enough - an SC Riv rolling in good repair on the street with all-season or better tires *will* reliably do 0-60 in 8 (or a bit less).

c0reyl still has work to do.

Haha, i was mostly speculating on my 0-60 time, didn't say what it was for sure because i really can't tell with my speedometor broken :p