car randomly "bucks or jerks" while cruising

[84sithlord]

the title says it all. i'm ASSuming it has something to do with a wiring gremlin. it doesn't buck while under acceleration or boost. only does it while cruising. no hard codes.....not even a flash of the ses. recently had driverside header welded....thats when it started. doesn't do it when i hit bumps in the road. completely confused and not sure where to start chasing this. any thoughts?

 

[84sithlord]

i ready a thread in the engine forum...it mentioned a bad maf....i know my transmission has issues with flare...can this be some result of bad transmission or torque converter....what about the rear end posi going out?

 

[standupjskiguy]

Mild bucking?
Maybe running lean for some reason. Try disconnecting the ox sensor see if it runs better in that mode. Maybe you just need a new ox sensor.

 

[84sithlord]

thanks for the input. do i unplug it before or after i start it?

 

[standupjskiguy]

Unplug it before you start. The oxygen sensor doesn't put out any signal until it warms. The ECM runs in the open loop mode until then.
It will just run in the open loop mode and if it runs better, that tells you the oxygen sensor is giving a false signal and the ECM is adjusting the fuel too lean.
On newer carsm, the ECM will detect no oxygen sensor and light the SES light. I'm not sure if your ECM will or not.

 

[84sithlord]

i drove it home from work (20miles) yesterday afternoon and the O2 didn't make a difference. This morning, it didn't do it....once again leading me to believe its a wire somewhere. what about the maf? i have an lt-1 w/translator.......

 

[standupjskiguy]

I don't know anything about translators to be able to advise you on that.

I suspected lean because my 87 GN with the factory chip would buck and chug a little form time to time while cruising.
After I bought a Turbo Tweak stock chip, the car ran smooth. I especially noticed the chug just after the one-two shift.
So, I thought since factory chips run lean, your problem could be from running lean.

Just how bad is the buck, mild or like somebody turns the ignition off for a half second?
Does it do it when the car is cold or only when warmed up?
Does it do it at all speeds, I.E. 30 mph and 60 mph?

 

[TurboBuRick]

Get scanmaster numbers engine warm, idle in park.

Get the bl number when your cruising and during the condition.

RL

 

[84sithlord]

the buck can be mild to wtf. lol! almost as if it hits a wall for a split second. it seems to happen when warm and until yesterday, i thought it only happen around 55 and under. it happen yesterday around 75mph. I will get the numbers this evening and post tomorrow. thanks guys!

 

[CGASTON]

the buck can be mild to wtf. lol! almost as if it hits a wall for a split second. it seems to happen when warm and until yesterday, i thought it only happen around 55 and under. it happen yesterday around 75mph. I will get the numbers this evening and post tomorrow. thanks guys!

What model of translator do you have? Do you have a powerlogger? I would get rid of the E3 plugs and go back to a set of R43ts. What ignition system? Everything sounds like an ignition system issue or a powerdrop from a broken wire. Not saying that it couldnt be your MAF but they usually cause a surging. Let us know.

 

[84sithlord]

i don't have the E-3 s in now. i put in the AC Delco R42 or 43s...cant remember which....gapped at .031. i have an 87 ignition system (with Casper's adapter n hot wire kit). no powerlogger...yet. lol! and the adjustable MAF translator that is mounted on driverside wheel well and i have to remove the 4 screws to access the switches n knobs.

 

[CGASTON]

When this is happening...... Are you watching your tach? Does it drop or change RPMs? Do you lights flash, flicker, or go out briefly? Do you have a spare ignition module? Does it do it under boost? Do you still have your stock MAF? You could try switching back to that and see if it changes.... What about your fuel pressure? Is it dropping off as your car surges?

 

[CGASTON]

Also does it do it after it is warm? Been running for a while?

 

[84sithlord]

it's happening while cruising. not under boost or acceleration. don't have stock maf. extra coil packs but not ignition module. not sure about fuel pressure. last time i checked, 45 line off. it occurs while its warm and usually after i have been driving it for about 10-15 minutes. no lights flickering when it occurs.

 

[Jerryl]

Check for loose/bad ground wires.

 

[CGASTON]

I was thinking..... You said that it kicks/surges at around 55 and 75MPH. That is when the torque convertor locks up. Your torque convertor can be kicking in and out..... Causing that jerking........

 

[Jerryl]

I was thinking..... You said that it kicks/surges at around 55 and 75MPH. That is when the torque convertor locks up. Your torque convertor can be kicking in and out..... Causing that jerking........

Very true.
When I had this problem . . . . It was a conbination of things . . . I think.

Grounds made the biggest improvement.
I played around with fueling on the TT SD chip many years back. . . . . and got that jerky feeling at cruise around 17-18:1 ratio. At 16.5:1 it ran clean.

 

[84sithlord]

well i'm still feeling around for the wires but they are still my main suspect. drove it around at lunch (enough to warm up) and this is my first reading at idle approx 500 o2 mil
af 08
l8 43
batt 14
int 128
blm 121
00
clt 168
ats 71
rpm 1025
tps .42
iac 00

i felt it "hiccup" on the ride back to work. steady cruising approx 45 mph blm's jumped to 142, let off gas, 117-122. didn't pay attention to the rpms. second ready when i got back to work in park, idling

approx 480
af 07
l8 41
14.1
128
122
00
167
71
975-925
.42
00

no fault codes or lights flashing.....thanks guys!

 

[84sithlord]

still chasin a vacuum leak that i can't hear during idle.....i think i hear somethin when barely accelerating but the breather is loud so it drowns out any other "hiss" sound.

 

[CGASTON]

Get some carb cleaner and spray around your plenum and vacuum lines.... if the RPMs jump then you found your vacuum leak..... which is also a reason why your IAC is off. Fix the vacuum leak and then adjust IAC...... Then chase your stumbling..........