FAQ: Hesitation, Stutter(Studder), Shudder, Stumbling, on Acceleration/Load

Have you pulled and inspected the plugs? Double-checked the wires? They can easily rub on a metal bracket if a wire is a little tight, and wear right through the insulation. On my engine every place an ignition wire crosses another, I have it covered with split-loom.

Again, the mechanic has looked it over, and said that a coil is not outputting the proper voltage.
I found a place online that has reman'd superchargers for my car for under $500, plus a $200 core charge. I can handle $500, but would like to find a used one for less than that. Under $300 would be outstanding. Got one quote for a used one for $700.

I doubt it's the blower. Have never heard of an Eaton blower going bad on these engines. How is it determined that it's not working? Making noise?

FIx the coil first. Might be the only thing wrong.

Quote :

At idle, advance is around 23 degrees. While driving down the interstate, around 3k RPM, advance was at upper 30s. When I got on it, accelerating, advance dropped to between 9-15 degrees. That causes alarm.

Seems perfectly normal to me.

yep those are about the same advanced timing numbers i see, except i dont recall it ever pulling down to 9*. 11 maybe, but 9 seems low IMO.

I will agree about the blowers - they do sometimes get noisy but very unlikely it is 'bad'. If you are hearing loud metal grinding noises from the blower it might be 'bad' but otherwise a little rattling is okay.

I need help. About 2 weeks ago the Rivi gave me the finger. I was on my way home from school on i95 an she started sputerin. It didn't cunk out. It just started sputerin everytime I pushed the gas pass a certain point. So I got off an pulled into the sunoco an took a quick look. Everything looked fine so I babied it home an it hasnt moved since. I drove it yesterday an it was still doin the same thing. It doesn't stutter at idle or when not under load. It only does it when the car is in a drive gear. Any sugestions as far as what I should do or check?

When was the last time you replaced plugs, wires and checked the vacuum lines for cracks under the engine site cover?

I would immediately suspect spark plugs and/or wires.

So, superchargedmoney, do you know how to check the plugs and wires?

Albertj

Well, sounds like to me as if it may be either bad plugs and wires, bad fuel pump, or, a bad or clogged fuel filter.

Car runs fine, even accelerates moderately just fine - but if I nail it the car sputters and strains. I'm not sure what the problem is given I just replaced all six spark plugs. We thought again, possibility of water in the gas but that would make the car run badly under moderate acceleration as well and it doesn't. What's the problem?

No idea if it's related but the car really struggled to start a couple days ago (But it was something like 5 degrees out). I cranked it over for 5 seconds and it didn't catch. When I tried again it did though. When it didn't crank it almost reminded me of a dead battery kind of thing but the battery is good and the car starts normally (requring it to be in the on position and let the fuel pump get going before cranking over).

you must be making too much boost... and your fuel cutting...


But really!!!! ITS YOUR SPARK PLUGS.... gap them CORRECTLY also check to make sure your spark plug wires are seated correctly... do this now ..

98riviera98 wrote:

you must be making too much boost... and your fuel cutting...

X2....try shutting that gash under your nose

What's the history on your ignition wires? Are they new?

See if the ignition wires are rubbing on anything. There are a lot of brackets on top of the engine and tight rubbing wires can arc through causing a bunch of issues.

Double-check your spark plug gap

What kind of plugs did you install?

Shintsu: you may have a weak fuel pump, and/or a slow/small fuel line leak that lets the pressure bleed out when you are parked.

Do you ever small gas by the car when you park it after driving?

Albertj

I don't smell gas but I smell a hot smell after I shut the car off, not quite sure where the smell is coming from.

As my siggy says, I have NGK Platinums. They were all properly gapped when put in. I put those in less than 3,000 miles ago, I don't see how any of them could have been messed up already. Checking the gap is not an easy task given the ice cold wheather and my total lack of time to do it - I'm busy with school every day and when not I'm busy watching the dog and doing schoolwork. We replaced I think 2 or 3 out of 6 spark plug wires (simply robbed from the GTP - it had new wires when the motor blew with less than 50 miles on them). I will most certainly wiggle the wires and make sure nothing is too tight or loose.

A new set of wires is ~$60 and takes 15 min to install. Easy fix.

If that's not it, test coils, replace as needed.

That's what I'd do if it were me, especially if the wires were aftermarket, and especially if they've been swapped from another car.

There's another way to test without spending the money, but it takes some time and patience. What you do is detension the SC belt, slip off the belt, and carefully tie it off to the side, making sure it doesn't contact the crank pulley. Drive the car. If it doesn't shudder at WOT, it's almost certainly wires. If it continues to shudder, it could still be the wires, or could be something else.

I've had this same problem. It drove me nuts until Tim King and Scott Cook of INTENSE got involved. It even took them 1/2 hour or so to figure it out. And that's the way they did it.

You know - if the car is "dumping" fuel the catalytic converter will heat up more than usual.

You think maybe worn injectors? along with the other things people have mentioned?

Comments?

Albertj

Okay, let me clarify since I said sputter. When I floor it it's fine for the first little bit but as it nears the shift point it kind of hesitates even though the pedal is to the floor, then it finally shifts and instead of just smoothly accelerating it's kind of hitting spots where it hesitates somewhat. I wiggled all the sparkplug wires and none of them looked worn from my examination nor were any of them stretched too tight or anything.

Does this extra info help anymore in the determination of the problem?

My wires were in visually perfect shape at the time they failed. They looked barely older than the new ones I replaced them with. I'm not saying it's the wires 100%, but if it were, you cannot detect from cosmetic inspection.

Hesitation can be caused by many things. First two things that come to mind is KR or a clogged fuel filter. Hesitation like it is surging a little bit? We think of 'sputtering' as more like a misfire.

Ok, my friends GTP had this exact same problem. We replaced the plugs, wires, coil module, fuel filter, and had no sucess. Well, we finally gave up and took it to a family mechanic. Well, he checked everything that we looked into and also checked the fuel pressure. Everything checked out fine. Well, we forgot to check one thing. The catylitic converter! It was the catylitic converter making all the trouble! Have that checked out.. I believe this is possibly your problem.

dscott2000 wrote:

Ok, my friends GTP had this exact same problem. We replaced the plugs, wires, coil module, fuel filter, and had no sucess. Well, we finally gave up and took it to a family mechanic. Well, he checked everything that we looked into and also checked the fuel pressure. Everything checked out fine. Well, we forgot to check one thing. The catylitic converter! It was the catylitic converter making all the trouble! Have that checked out.. I believe this is possibly your problem.

That's so random, not to mention we just put this new high flow cat on it in say '01 or '02 (possibly even '03). Erm, how exactly am I supposed to have it checked out? I thought it was more a matter of get a new one put on or don't - not really any middle option.

Are you sure its not the transmission slipping?
Does the problem occur as the vehicle approaches the shift from 1-2 and the shift from 2-3 ?
Watch the Tach when the "sputter" or "hesitation" is happening and report back with your findings.

Bert