Surging/Hesitating After Getting on the Throttle a Couple Times

ledzilla

ledzilla

Road Pirate
So, I've been trying to pinout the issue, but I think I finally found the pattern. A few weeks back I started noticing some odd surging/hesitating when traveling down the highway. At the time seemed mostly when slowing down. But I decided to try to see if I can figure out when it shows up.

So far only seems to happen after having reached operating temp. If I drive nice and smooth, everything feels normal. But if I get on the pedal a couple times, it shows up.

What I experience is the car kind of bucking. It's most noticeable when trying to get going from a full stop. It will suddenly kick and chirp the tires. When cruising down the road, it feels like it loolses throttle then suddenly re-engages. However, if it's being experienced when overdrive would be engaged, turning off overdrives causes it to stop, and it will stop misbehaving for a short while once overdrive is turned on again.

Any thoughts on what this is?

Sent from my SM-G986U using Tapatalk
 
Usually it's the coils packs that cut the power out like that. I'm not sure if the trans is acting up but it could be.


Sent from my iPhone using Tapatalk Pro
 
03Merc said:
Usually it's the coils packs that cut the power out like that. I'm not sure if the trans is acting up but it could be.


Sent from my iPhone using Tapatalk Pro
Click to expand...
I was wondering about that. I changed out the coils many years ago, somewhere between 60K and 80K, and I suppose I've reached the typical expiration point on the coils by now. But there are no DTCs yet, at least not to the point of illuminating the CEL. When I last replaced the coils, I got a code and at first just replaced the affected cylinder.

Sent from my SM-G986U using Tapatalk
 
badass mm said:
Maybe a throttle position sensor

Sent from my SM-J337AZ using Tapatalk
Click to expand...
I'm leaning away from that. It all runs ok all through the throttle range, and the hestitation/surging occurs regardless of throttle position and goes away at higher speeds with OD off.

Sent from my SM-G986U using Tapatalk
 
ledzilla said:
However, if it's being experienced when overdrive would be engaged, turning off overdrives causes it to stop, and it will stop misbehaving for a short while once overdrive is turned on again.
Click to expand...

In what gears does the problem show up? Seems strange that turning off OD would eliminate the problem in gears 1-3.

Did the problem immediately show up or start slowly over time and get to the point where you decided to post about it?

Things I'd start checking/datalogging/live monitoring:
1) Fuel pump intermittently going bad? Monitor fuel pressure and O2 sensor voltages. Fuel pump cutting out will make them instantly go lean.
2) Bad harness to coil packs? All coil pack or some? Monitor spark and O2 sensor voltages. Spark cutting out will make sensors instantly go rich.
3) Monitor throttle position %. Sudden changes without moving your foot could indicate a problem.
4) This ones a stretch but the infamous IAC motor?
5) ECU? Im not even sure how to start diagnosing that bad boy.
6) Vacuum leak? Monitor engine vacuum, look for sharp changes with no throttle input.
7) Bad crank sensor?
 
dmjarosz said:
In what gears does the problem show up? Seems strange that turning off OD would eliminate the problem in gears 1-3.

Did the problem immediately show up or start slowly over time and get to the point where you decided to post about it?

Things I'd start checking/datalogging/live monitoring:
1) Fuel pump intermittently going bad? Monitor fuel pressure and O2 sensor voltages. Fuel pump cutting out will make them instantly go lean.
2) Bad harness to coil packs? All coil pack or some? Monitor spark and O2 sensor voltages. Spark cutting out will make sensors instantly go rich.
3) Monitor throttle position %. Sudden changes without moving your foot could indicate a problem.
4) This ones a stretch but the infamous IAC motor?
5) ECU? Im not even sure how to start diagnosing that bad boy.
6) Vacuum leak? Monitor engine vacuum, look for sharp changes with no throttle input.
7) Bad crank sensor?
Click to expand...

It happens in all gears, but when in OD and I turn it off, it helps. And the issue doesn't occur the entire time while driving, only after giving the throttle a good romp or two. It first started a couple weeks ago while driving down the interstate and hitting the gas to pass slower moving vehicles. I'm honestly already considering the IAC. Someone some odd years ago heard something while the car was idling, and mentioned something along the lines of "sounds like your IAC is going bad". I've been meaning to replace it, and the TPS too, but have been blocked along that path due to the heads of the mounting screws getting soft and corroded.

I should also mention that nothing happens at idle. Ever. It just idles smoothly, so if any of those tests have to be done at idle, they won't show anything. But it seems like some of those I should be able to do with my Bluetooth OBDII reader and the Torque app, right?

Also, I forgot a detail. Except for when initally starting from a stop, it will be fine while accelerating, so long as it isn't that minimal acxeleration done when already moving and trying to speed up a little. It's mostly when holding speed or coasting. Give it maybe 1/4 throttle or more, just fine. Also seems ok when maintaining highway speeds above 60-65 mph. Didn't give me any trouble on that first day of the issue while running about 80-90.

Sent from my SM-G986U using Tapatalk
 
Data log the FPDC at WOT. When my original fuel pump went bad it did pretty much everything you’re describing for almost a year off and on.

If you use an Xcal then keep in mind the percentage you see needs to be doubled. 50% (or is it 49%? can’t recall) equals maxed out.

Keep in mind that when you turn overdrive off you are changing RPMS thus changing air/fuel. When pumps go bad they can go bad in a hundred different ways.

Nice easy place to start at least.


Sent from my iPhone using Tapatalk Pro
 
It could be air idle control valve.
When was the last time you changed your fuel filter? Replaced mine today.
Big improvement in power.


Sent from my iPhone using Tapatalk
 
Mine started bucking when the plugs were bad. I had copper plugs in at the time, don't remember how many miles but I thought that I should be able to get more out of them even for copper. When I finally pulled them the gap was really high. I replaced them and even gaped them down some from what they were supposed to be and the problem went away. My bucking happened under relatively heavy load but also at relatively low RPM. If I went WOT and it kicked down it would go away. In hind site I may also have had a vacuum leak at the PCV valve that was contributing. The plugs cured the bucking, the vacuum leak cured my downshift problems (wanted to lug and not downshift).
 
Last edited:
One quick thought. Clean MAF wire? Unlikely to be the cause by itself but its a cheap and easy way to check off an item and remove a variable
 
BLACKMARAUDER04 said:
It could be air idle control valve.
When was the last time you changed your fuel filter? Replaced mine today.
Big improvement in power.


Sent from my iPhone using Tapatalk
Click to expand...
I suspect the IAC, but the mounting screws are so bad I can't remove them. I think I've had a replacement sitting and waiting for a while now. I'll try to get a photo of those screws soon. Last time I tried to remove them the screws just starting coming apart, like they were way too soft.

Probably can't hurt to replace the fuel filter. No idea when I last replaced it. But I might have done that somewhat recently. The car doesn't get many miles per year these days, and I seem to recall getting proper clips to swap the filter out and secure it with clips instead of yet another zip tie. I'll probably have to get under the car to be sure.
justbob said:
Data log the FPDC at WOT. When my original fuel pump went bad it did pretty much everything you’re describing for almost a year off and on.

If you use an Xcal then keep in mind the percentage you see needs to be doubled. 50% (or is it 49%? can’t recall) equals maxed out.

Keep in mind that when you turn overdrive off you are changing RPMS thus changing air/fuel. When pumps go bad they can go bad in a hundred different ways.

Nice easy place to start at least.


Sent from my iPhone using Tapatalk Pro
Click to expand...
I have no idea how data log it. Inhave an XCal II, which doesn't seem to have any data logging features that I've noticed. Best I have is a Bluetooth ODBII reader and the Torque app.

However, I wouldn't doubt a fuel pump issue, now that you mention it. I wanted to pull it last year but I couldn't get at that connector for the sensor that sits on top of the tank. Spent a couple hours on it, but couldn't get it loose at all.
Green96 said:
Mine started bucking when the plugs were bad. I had copper plugs in at the time, don't remember how many miles but I thought that I should be able to get more out of them even for copper. When I finally pulled them the gap was really high. I replaced them and even gaped them down some from what they were supposed to be and the problem went away. My bucking happened under relatively heavy load but also at relatively low RPM. If I went WOT and it kicked down it would go away. In hind site I may also have had a vacuum leak at the PCV valve that was contributing. The plugs cured the bucking, the vacuum leak cured my downshift problems (wanted to lug and not downshift).
Click to expand...
I'm sure it's due for plugs and coils. I don't remember the bad coil back in the day causing the car to be quite this rough, though. I also have to be careful due to a helicoiled cylinder. That's made me very apprehensive about changing plugs.
BLACKMARAUDER04 said:
I also had to replace the hose at the PVC valve to cure a vacuum leak.


Sent from my iPhone using Tapatalk
Click to expand...
I replaced that a few years ago, and it's still in good shape. No cracking, no collapsing.
dmjarosz said:
One quick thought. Clean MAF wire? Unlikely to be the cause by itself but its a cheap and easy way to check off an item and remove a variable
Click to expand...
This thing is weird about the MAF. I've driven around with it disconnected (because I forgot to plug it back in) and the car behaved normally. Didn't know there was a problem except for the CEL. That came on quickly, but the car ran fine.

Sent from my SM-G986U using Tapatalk
 
Ok, so I took it out on several ~10-12 mile drives (round trip to get coffe about 10 miles, so fun). Was nice and easy on it all three times, and not a hint of trouble. Behaved well all day. What would be the most likely thing to examine that causes this issue after romping the throttle?

Sent from my SM-G986U using Tapatalk
 
ledzilla said:
This thing is weird about the MAF. I've driven around with it disconnected (because I forgot to plug it back in) and the car behaved normally. Didn't know there was a problem except for the CEL. That came on quickly, but the car ran fine.

Sent from my SM-G986U using Tapatalk
Click to expand...

Not always the case, but typically if you unplug the MAF and the car runs better, then the MAF is bad.
 
The easiest way to diagnose it is by seeing what the ecu sees and is doing. Only way to do that correctly is by using a moates quarterhorse.

$250 for the moates QH. TunerPro RT is free download it and you can drive around logging and see exactly whats not reading correctly when it acts up.
 
decipha said:
The easiest way to diagnose it is by seeing what the ecu sees and is doing. Only way to do that correctly is by using a moates quarterhorse.

$250 for the moates QH. TunerPro RT is free download it and you can drive around logging and see exactly whats not reading correctly when it acts up.
Click to expand...
Hmm... That may be awhile. Money is tied up in severe weather recovery right now, with a generator rental and having bought 50' of 240V cord to power my well pump. So, is this combo a more sophisticated version of the Bluetooth OBDII adapter and Torque app I currently have?

Sent from my SM-G986U using Tapatalk
 
blazen71 said:
Not always the case, but typically if you unplug the MAF and the car runs better, then the MAF is bad.
Click to expand...
What I have experienced during the 15 years of owning this car is no noticeable difference with the MAF unplugged. Happened multiple times over the years.

Sent from my SM-G986U using Tapatalk
 
Where are you living nowadays Mike? If I could ever get a free moment maybe I could stop over and have a looksie?


Sent from my iPhone using Tapatalk Pro
 
You must log in or register to reply here.
Back
Top