97 safari is jerking/bucking while shifting gears

97 safari is jerking/bucking while shifting gears

Postby lowbudgettuna [OP] » August 8th 2016, 2:06am

hey everyone,

i found this issue in a couple forums, but none of them show a solution.

I have a 4L60E a/t, the transmission was 100% replaced less than a year ago and this issue was present both before and after the tranny was replaced.

When shifting from 1-2 and 2-3 at normal acceleration it bucks several times before locking into the next gear.
It's tremendously worse when it's humid or raining outside. And there's no Service Light on

Four months ago, I originally thought it was moisture getting into dist cap, etc.,,, so i replaced cap, rotor, plugs, and wires.
SInce then it hasn't bucked once and i considered it a good and lucky guess and problem solved.

Now 2 days ago i felt it buck. Yesterday it bucked at lot worse and at the intensity it was before the tune up.
Today it rained and the van was literally bucking longer than normal driving. (just went around the corner, so i was shifting in the lower gears a lot).

So basically it's exactly as it was before the tune up.

Please help. Does anyone have any ideas what this could be? TPS? EGR valve? Fuel filter? Exposed sensor? Bad tune up mechanic?
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Re: 97 safari is jerking/bucking while shifting gears

Postby chevymaher » August 8th 2016, 2:06pm

A few questions. Are you sure it is the engine doing this? Does it run well otherwise. Does it act like it is in 2 gears when it does this. I don't have any idea what is going on but kinda looking for what it is actually doing wrong.
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Re: 97 safari is jerking/bucking while shifting gears

Postby HoosierDaddy » August 8th 2016, 2:51pm

Maybe the converter is trying to lockup at low speeds. Perhaps you could disconnect the wiring at the pan rail on the passenger side and see if it still shudders.
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Re: 97 safari is jerking/bucking while shifting gears

Postby Mmusicman » August 8th 2016, 4:18pm

Engine problems can often "feel" like transmission problems.

My 2000 developed jerking/bucking... which usually became more obvious just before a shift, and eventually got worse. It got so bad it would start bucking while cruising down the highway too... but initially it was only just before a shift.

Turns out the bucking problem in my case was a worn distributor! I never received any fault codes either... but the bucking got quite bad.

While watching my OBD readings... I discovered it would start "bucking" ONLY when the timing got between or above 35-40 degrees advance.. a condition that typically happens at higher rpms with strong vacuum.

A new $40 distributor COMPLETELY solved my problem.

My bad distributor showed no obvious signs of damage... just some back and forth play. My original distro had about 150,000 miles on it.

I can't say if your issue is the same... I'm just sharing my experience. :)
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Re: 97 safari is jerking/bucking while shifting gears

Postby lowbudgettuna [OP] » August 8th 2016, 4:20pm

i'm confident it's the engine doing this because the issue was present before and after replacing the transmission. They changed the torque converter as well. It was a full $2200 job.
Also, when i did the tune up, the issue went away completely for the passed 4 months.
Now this weekend the issue has presented itself again full force. It's considerably worse when raining or humid, leading me to believe it's the TPS or another sensor which is currently exposed to the weather. There's no service light, but in your opinion, do you think this thing would give a code if no service light is on?
I researched more after starting this thread and the most common fix for this type of "transmission" problem seems to be the throttle position sensor. Of course i don't know, but all of your opinions are greatly appreciated and I'll do them one-by-one.
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Re: 97 safari is jerking/bucking while shifting gears

Postby lowbudgettuna [OP] » August 8th 2016, 4:46pm

Mmusicman wrote:Engine problems can often "feel" like transmission problems.

My 2000 developed jerking/bucking... which usually became more obvious just before a shift, and eventually got worse. It got so bad it would start bucking while cruising down the highway too... but initially it was only just before a shift.

Turns out the bucking problem in my case was a worn distributor! I never received any fault codes either... but the bucking got quite bad.

While watching my OBD readings... I discovered it would start "bucking" ONLY when the timing got between or above 35-40 degrees advance.. a condition that typically happens at higher rpms with strong vacuum.

A new $40 distributor COMPLETELY solved my problem.

My bad distributor showed no obvious signs of damage... just some back and forth play. My original distro had about 150,000 miles on it.

I can't say if your issue is the same... I'm just sharing my experience. :)



Thank you for your input. I originally thought distributor cap when the code came back saying it was the spark plug wires. And then especially once the tune up was done, the problem went away. But now that it's back, i assume it's something along the same lines. I'm leaning towards the TPS, but can't work on it until the weekend. Keep your fingers crossed and input coming. I've been having a string of bad luck with this thing. :(
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Re: 97 safari is jerking/bucking while shifting gears

Postby ThisGuy » August 8th 2016, 5:35pm

subbed. interested in solution... good luck
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Re: 97 safari is jerking/bucking while shifting gears

Postby Astro Pop » August 8th 2016, 6:39pm

Everything on our vans is computer controlled. Whats the first thing to do on a computer problem....Reboot. Pull the battery terminal, wait...oh say 20 seconds, put it back on and see what happens next. Fixed a hard shift for me once. BTW the engine sensors are sealed internally so not exposed to elements. When they fail it's just plain worn out.
Got a code reader that gives data stream? That'll give you a wealth of info on the running of the engine.
Good luck and let us know how it goes. Especially if you find an answer, so many new posters get their answer and then just vanish which doesn't help the next guy with the same problem.
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Re: 97 safari is jerking/bucking while shifting gears

Postby lowbudgettuna [OP] » August 24th 2016, 3:41pm

sigh. the bucking's been getting worse, and a the engine light finally came on while it was in the middle of bucking 6 times. I thought that was awesome because now i can find out what the problem is, but guess what, the guy with the code reader said the obd2 plug isn't getting any power. arrrgh! does that plug have a fuse that'll blow or is the guy with the reader an idiot and i should take it somewhere else?

If anyone has any good ideas on what this may be, please let me know. because of my low wages, i can only replace one thing a week if i'm lucky. I'm jotting down every idea you all give me and am trying them one by one. Unfortunately because of my low wages, i can only fix one thing a week if i'm lucky.
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Re: 97 safari is jerking/bucking while shifting gears

Postby chevymaher » August 24th 2016, 5:16pm

Mine used to act silly like that before I blocked the EGR, I would look into that. Block it see if it goes away. Then if you just got to have one look into making it work better.
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Re: 97 safari is jerking/bucking while shifting gears

Postby Sailing_Faith » August 24th 2016, 5:26pm

As other have said, you likely have either an ignition issue or an EGR problem.

You can make a temporary block off plate for the EGR valve to trouble shoot the issue from a beer can.

Cut the top and bottom off of the can, use the gasket to trace the pattern on the can (I like to fold the can in half to get a double thickness). Of course, cut the bolt holes, but not the holes for the EGR gasses.

Bolt the EGR valve back in place with the block off plate in place.... Drive and see what you get (sure it will store another code, but will otherwise run just fine).

If that does not fix it, replace the only high voltage ignition part you have not yet changed... The coil.

One of those two is bound to fix it.

Just sorry you had to replace a transmission to get to this point in your troubleshooting. :(
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Re: 97 safari is jerking/bucking while shifting gears

Postby Mmusicman » August 24th 2016, 7:17pm

lowbudgettuna wrote:If anyone has any good ideas on what this may be, please let me know. because of my low wages, i can only replace one thing a week if i'm lucky..

I actually did offer a suggestion and told you what my bucking problem turned out to be, a few posts earlier. At least check the distributor for play and wear. Not saying for sure it is YOUR problem (other possibilities as well)... but it was mine. With my OBD reader, I discovered the bucking started when the timing was between 35-40 degrees (in practically any gear) ... which pointed me to the direction I took.
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Re: 97 safari is jerking/bucking while shifting gears

Postby Leeann_93 » August 24th 2016, 10:10pm

Yes; the OBD port is on the cigar lighter fuse circuit (don't ask me).
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'02 Astro LS AWD vin X
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'99 Safari XLE AWD - broke
'93 AWD EXT vin W - real broke
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