Just recently, while driving to work, I noticed that under light acceleration, the car has a slight buck, a surge if you will. It is not as prominent at lower RPMs, but defiinately noticable in OD at around 1500-2500 RPM. When at WOT, it will do it once at the down shift and sparatically while accelerating. Checked the TPS and it is at .45mV, so it doesn't seem to be that. TCC in the tranny maybe? Tranny is out of 88 SC and engine is 87 LB9 with new plugs, wires, cap, and rotor. Anyone else ever come across this problem or know how to correct it?

 

Yes, my TPS caused that issue. It had flat spots at normal driving ranges which caused the output voltage back to the ecm to be flakey. The fix was take the TPS off, soak with carb cleaner, work wiper arm (LOTS), reinstall. BTW, the TPS setting is.54vdc at idle and 4plus vdc at WOT. When setting the vdc to .54 at idle, watch the vdc as you open throttle, do it slowly and watch vdc, it should rise steady and not bounce around alot or zero out. Hope this helps.

 

To check the TPS for "flat spots" unplug it and hook an old analog ohm meter to it and slowly open the throttle while watching the needle on the meter, it should move smoothly with the opening of the throttle, if it doesn't...clean or replace.

 

I'm having the same problem over there in my thread that now has nothing to do with hesitaion as it is titled. I am experiencing the EXACT same symptoms, to a 'T'. My TPS appears normal. It is .57v closed and 4.22v at WOT. It transitions smoothly from one to the other also with no anomalies. Mine is from a '92, but I thought about the TCC also. However my transmission deal is MUCH more complicated. 4L60E + TPI isn't quite easy to do. My TBI computer runs that and then the TPI computer runs the TPI as though it was in a manual car, all via my TBI harness modified by JimsPerformance.

Now that I reread your post your TPS was a bit low, and my truck only "bucks" after I am finished easily accelerating from a redlight to about 45-55 mph. But it is basically the same thing. I just figured I would bring my problem in here instead of having 2 simultaneos "unexplained surge thingy" threads.

 

Ok, he is the situation.....I unhooked my MSD 6AL from the coil and hooked everything else back up stock. While driving today, I was getting it to surge in both 3rd and 4th. The guy who rebuilt the tranny 1-1/2 years ago said to try to get it to do it by power braking it in a parking lot and see if it would do it. Well, I did it and sure enough, so did it, right around 2000 rpms. Jerked the whole car, and afterwordsa, it does it in 2nd too. This seems to me more of a tranny thing. Could it be the ignition coil? That is the only thing left to replace. The wires I will check resistance later tonight maybe.

 

2 of the spark plug wires were not all the way on, but that didn't seem to make a difference. I also reconnected the MSD. I re-adjusted my TPS to .552 mVolts...not a dramatic change, still does the bucking/surging. I have no idea what else i

 

Try locking your converter up (pin G I believe on the ALDL) and see if it still does it. Sounds like it may be going in and out of lock up for some reason.

 

that isnt the case with mine because going down the interstate i thought of that and after it did it once, i tapped the brake just enough to send a signal to the computer and the TCC unlocked (rpms jumped a bit). I am beginning to think we have different problems though, just with similar symtoms, because mine wont do it if I load it up sitting still. Only at about 1500-2000 after cruising for a while... and it only happens maybe once a trip (5 minutes from my Apt to Campus).

 

OK.....Transmission guy brought out his fancy computer diagnosis thing while we went on a test drive. He said it is throwing no codes and the TC was hard wired and it is not that....sounds like it might be ignition related. So I went home and tested the coil, checked out ok,and the wire resistance, nice and low, around 140 or less in each, depending on the length. Now what? Could it be the plugs? Those are only 6 months old, Bosch Platinum. I am stumped!!!

 

Read your MSD 6AL info, it tells you not to use Platimun plugs, use standard AC Delco or simular. You can also have a fuel issue like injector/s?? Possible vacuum leak?? Knock sensor?? And last, the ECM, either having a problem adjusting timing or fuel, either or.

 

I ran those in my car once....ONCE! Thet fouled in less than 200 miles and made the car surge under load, In my book they are utter CRAP.

 

Well, i did just put in a new Walbro 340 about 3 months ago, but fuel pressure is a steady 38 PSI at idle (no AFPR). And it happened all of a sudden, so I will try switching out the platinums for some good ol' fashioned AC Delcos and see how it goes. Any good way to test injectors?

 

I am in no means a know it all, but I have read about this on these boards alot, and MSD has do's and don't when using their ignitions. It is also advisable when using MSD ignition parts on your car, use them all, not just the cap, ignition box, wires, they are designed to be used as a complete system. So many times you read a post and someone has piece mealed his ignition and peppered it with all kinds of odds and ends and can't figure out why his car will not run right. Sorry for the vent, but come on guys, help me out. If you don't do your home work, it is best to leave the car alone. If you have not read this, do it. It might clue you in as to your problem, hopefully.

http://www.msdignition.com/pdf/6series.pdf

 

I have MSD 8.5mm Super Conductor wires and an MSD Cap/Rotor set...hmmmm

 

Coolguywalt
That post was a general rant, I wasn't pointing it at you, just throwing it out their because some people do need to see it.
BTW, you are using Platinum plugs right? I would swap them to see if it helps.

 

ok I have a little insight on this subject My 91 bird was doing the same thing first thing to try is the EGR valve plug the vaccume line going to it and see if that changes things. did not fix mine but seemed to help a little. second I unplugged the O2 sensor so the car would not go into closed loop and the problem seems to have dissapeared. Not sure exactly what the culprit is but i'll replace the 02 as soon as I get a chance. My car also had a haunting idle problem that this seemes to have fixed. Hope this helps some.