Real Fiero Tech

The car
-86 Fiero SE
-2.8L
-Manual

The Problem
-when cruising not giving or taking away any gas, the car will start to jerk.
-it doesn't matter what gear your in
-when given gas it does fine
-seems like its an engine problem and not a drive train problem

Recent maintenance
-new intake gaskets
-new vacuum lines
-egr removed

I think it might have something to do with the fuel.
Are the injectors different between the two v6's?

that do you guys think?

1st pick is the EGR. during light throttle is when it is most active. unless you have a chip that disables EGR
2nd pick - TPS. the very beginning of the throttle position sensors wears off the quickest, and the ECM get 0 throttle, even if it slightly open
3rd pick - MAP sensor - not being sensitive enough
4th pick - Ignition Coil. not quite sure why. do a OHM check - easy enough

cruising at what speed?

every manual 2.8 and 4cyl fiero i've ever had would jerk when not on or off the gas but right in the middle in that zone when going slow like 1st and rarely 2nd gear. infact i think my subaru did the same thing.

seemed like it was an issue with the what the computer was set up to handle power combined with some slop int he tranny and rubber mounts.

Yeah its a common thing with manual transverse cars without the best mounted drivetrain and soft dampers... emphasis on the soft dampers. My blown KYBs in the back make it nearly whiplash-inducing.

alright so I'm planning on putting my egr back on.
now onto the egr vacuum solenoid.
I know one nipple goes to the egr and one nipple goes to the TB. my question is does the top or bottom go to the EGR?

the vacuum diagram does not show this clearly. :scratch:

Speaking of EGR problems, I still get a code 32 from the damn thing, even though I made sure the EGR tube is connected properly. The EGR valve works, I think......it's not stuck and it stalls the engine if I force it open.

Maybe the vacuum solenoid? I have no way to check that, that I know of.

only way to check it really is to swap on a known good one or dismantle it..

they have a tendancy to corrode to peices inside and freze in place.

an easy test is to swap the two vac lines at the end of the solenoid. this will fool the sensor into thinking it is seeing vacuum when it wants to open the valve making it not throw a code.. if that fixes the code then you need a new solenoid

I have a v6 that is throwing a 32. Could it also be the map sensor going to crap?

32 is egr not map.

Is it an engine problem or a loose drivetrain?

If your engine and trani mounts are originals and you have a loose dogbone you can have the type of jerking you are describing. Its the slack in the drivetrain causing the car to jerk. When on the gas you are loading the drivetrain and the jerking stops.

if its in 1'st at low speed then i'd say loose tranny, our big trucks do it too haha. its more of a rocking sensation than whiplash in those. i've got it in my 5spd f-450 too. but i think thats a worn slip yoke.

REDse86 wrote:alright so I'm planning on putting my egr back on.
now onto the egr vacuum solenoid.
I know one nipple goes to the egr and one nipple goes to the TB. my question is does the top or bottom go to the EGR?

the vacuum diagram does not show this clearly. :scratch:

Anyone able to answer this? I'm trying to figure out if I have mine reversed or not so I can figure out if the solenoid is crap or not.

the schematic of the selenoid in the service manual indicates it is symetrical and either port works. grounding the diagnostic termianl will open the valve, so get a vacume pump and hook it up to your selenoid on either port, and see if it holds. Now ground pin b on aldl connector and see if you cnt hold a vaccume. Simple test.