on heavy acceleration at 4000 rpm it feels as if it hits a wall. If i slowly accelerate it will go past 4000 with no problem. someone please help.

 

that would be the 3800 rpm hesitation, 3800 rpm is when your secondary injectors come on.

 

1) clogged cat(s)
2) secondary injectors not working, or are flooding engine (aftermarket injectors)
3) bad/ dirty grounds, especially the rear rotor housing ground/ tranny-to-firewall ground
4) clogged fuel filter(s)
5) Hmmm, gotta be more...

 

i haven't checked the cat, but new injectors checked with noid light and ohm meter and i am getting power and a pulse.Ground looks good and it has a new filter with a new pump and strainer.

 

It's the lack of an orifice in the boost/pressure sensor line or the grounds on the small plug on the ECU need ....reinforcement i.e. splice in a good ground wire to them. I vote additional ground on the small plug of the ECU.

 

I've already grounded and spliced the boost sensor, the hose doesn't have an orfice tube,I recently removed it but it was already doing it when it was in. and what small plug on the ecu

 

The small one on the far left- the 2nd from left and last pin (looking at the back of the plug) on the upper row are the grounds (they go to that rear rotor housing ground)...Find the orifice & put it back in- I've removed it for troubleshooting also, & it made matters worse...There's a reason it's there...

BTW- that's an 86-88 ECU pin layout

 

today i took the hose to the boost sensor and hooked a hand vac pump to it. I applied 20inHg. and left it hooked up while i drove it . the car drove fine and it took away the problem. does anyone know the specs to the boost sensor or the specs on vacuum at the manifold.

 

connect the boost sensor normally (with the orifice), and read out the pin on the ECU from the sensor (to ground) while taking a drive. You'll be amazed how much that reading jumps all over the place, it's hard to make sense of it...You're in the same boat I was in 'bout a year ago- kept thinking "bad boost sensor", but it was actually other components/ engine getting tired causing the problems...Are you pulling real-time codes? The ECU uses the sensor outputs to help schedule fuel- you can't possibly be doing the engine any good by rigging it up to a static vac source...

 

I'm obviously a bit slow on the uptake. Did you leave a vacuum on the sensor or pressure??? Or put another way......20inhg vacuum or 20inhg pressure??

And of course you know that if the vac hose on the boost sensor is disconnected ......the secondarys will come on line any time/any where once you hit 3500 rpm (see manual [FSM}).

 

when i was working on my fc...i did a jet ecu upgrade just to fix that problem...and it did just that...

 

what is this orifice and what does it look like? I have a 87 NA

 

The restrictor (or delay valve if ya want to call it that) is a little 3/8" black plug with a metered orifice drilled through the middle.

Most of the time it is located at the end of the boost/pressure sensor hose that attaches at the nipple on the intake manifold.

It is used to dampen the vac/ boost "pressure spikes" so that a smoother voltage signal is sent to the ECU from the boost sensor.

 

My is gone I guess. Do not have one of those.

 

JET ECU Upgrade?

 

sorry to hijack the thread.What about if you relocate the battery + earthing into the hatch area ?