Car is Bucking During Cruise and Decel
 

ok here's the prob. my car 86/na has been running f**king great. bone stock, yesterday i take off from house and car acts/bucks like i'm in wrong gear for about 2blocks,then returns to normal till i stop and park for 1-2hrs. the trip was approximately 2-3 miles. so i go to leave and car starts bucking really bad and i end up driving back 20mph in 3rd gear with car acting like maybe starving for fuel. where do i start? i was considering before this to check my tps and adjust or replace but car had been running well as said before so i was waiting to get time to do that. car has new fuel filter, spark plugs/wires, alternator, starter, oil/filter? pleeez give feedback asap, thanx rob

vac leaks, cloged intake, maybe TPS, getting full spark
could be a shit load of things, start with one and knock 'em out

mine does that when its down to about 3 gallons left in the tank, most likely rusted out baffles. I would change the fuel filter because its cheap and simple then follow up with other stuff

i got the bucking on decel... stupid TPS

I edited the thread with an actually useful title...

As for your problem, first check the TPS. It may have simply died, or become unplugged.

Check ignition to make sure that you're not getting intermittant spark (loose wire or coil).

Replace the fuel filter since it's probably never been done and a clogged filter will cause this...

Then get back to us after doing the above. :)

I would also recommend doing the grounding mod. Stopped bucking at cruise/accel on my 87, tho I didn't have any probs with decel.

The grounding "mod" is pointless. :) Just clean and service your existing grounds. Adding more is not required.

Well of course it's pointless. That's why it ended up in the archive and manages to take care of alot of problems for people.

i just did the ground "mod" and it helped a lot. i tried cleaning my originals and it did nothing.

If you go by the logic, "Well, it was working yesterday, so it must be fine today", nothing on a car would ever break. It's working fine from the factory, so it will work fine the next day, and the next day, etc.

Check the above listed things. I'd start with the TPS first - if it's bad, you'll get fuel cut over 1500 RPM at inopportune times.

-=Russ-=-

I had the same problem as this discussion.I added new ground wires
and it took care of the problems,so its not pointless!!!

It's pointless in the sense that all you need to do is fix the stock grounds. If they are working properly (and there are MANY stock ground points) then it is absolutely unnecessary to add a million more grounds.

It's in the archives because it's an option to bandaid the problem. To FIX the problem means actually making sure the stock grounding points are in good shape (which they almost certainly are NOT).

Or instead of tearing in the engine harness,the ecu and everything else,I added 2
thats 2 not a million and it corrected my problem
Thanks again---and thanks for the pm

You don't need to tear apart the harness to fix the stock grounds. But you will have to remove the intake manifold to get at the ECU ground properly.

If fixing the stock grounds did not work, then it means there is a problem with the harness. In that case it is prudent to fix the harness properly instead of bandaid the problem by adding more grounds.

I have NEVER had to add grounds to fix a grounding problem, and I've worked on some cars with horrendously poor wiring.

Maybe try running higher octane gas. When i first bought mine it was bucking at cruise and decel, and i just thought it was something those crazy rotary engines did. When i found out you should be running higher octane for turbos i switched to 93 and the bucking stopped immediately! Of course i know yours is na and mine is turbo, but maybe its worth a try? Someone correct me if this is bad advice. ;)

NAs work best on low octane fuel. In fact I'm fairly sure that the TII's manual also says to use 87 octane in most cases.

If you are bucking and premium fuel fixes it, then it's probably a vacuum leak (or several).

To add to the grounding discussion...

If more grounds were needed, Mazda would of put in more to begin with...