EmbassyBlack

ok so here we go again, i have an 87 NA.
iv searched everything, nothing helped. iv tried mostly everything in the fsm, nothing helped.
it bogs down really bad right before 4k, but if i give it a tiny bit of gas it will go all the way, so when theres no load. i tried using 2 different boost sensors, 4 diff computers, i unplugged the tps and boost sensor..nothin, cleaned the grounds.. the screw in the pulsation damper was unscrewed and i thought that might be the problem but it isnt. i also put a 12v onto the injectors to free them up, that didnt work..
im all out of ideas other than replacing the wiring harness which i hope i dont have to do.
if you guys could help me out maybe give me something else to try that i might have missed that would be really kool. its been like this since i got the car and i really wanna drive it how its suppose to be driven its killin me
thankss

Nem

Icemark

You will need to replace the pulsation dampener no matter what if the screw has come out. Unless you have a pressure bench there is no way to put the screw back in the correct depth.

But that won't cause the 3800 hesitation.

90 percent of the the time, the problem will be related to bad grounds either on the ECU or the engine. There is a ground found under the intake manifold on the back of the motor, that often looses conductivity (don't confuse this with the tranny ground found on the back of the motor and running to the firewall).

So run an extra ground wire there, to the fire wall, run another to the ground wires at the ECU, and then run an additional ground from the ground lead on the pressure sensor to the back of the block, and run an additional ground from the block to the battery or firewall.

THis should solve the issues.

If it does not, next step will be looking at the injectors. If the 2ndaries are dirty they will stick, so pull the intake and have all the injectors professionally ultrasonically cleaned and flowed.

If there is still a problem, the timing and ECU will be the next things to check. A burnt TPS or BAC transistor will also cause the issue, but that you have changed the ECU, unless the TPS and BAC were smoked already, chances are the 2nd ECU is fine.

EmbassyBlack

thanks icemark ill reground everything and update the situation when im done..
i hope it works

EmbassyBlack

oh ya.. will the screw coming out cause it to flood?

Icemark

no, but it will cause the PD to leak, which then drops fuel onto the exhaust manifold, which then ignites and solves the hesitation problem by burning the car up.

EmbassyBlack

hahahhaa
i think im ok with the burning because its been like that for a while now, and i just noticed it a few days ago.. so far no fires lol

Icemark

Maybe this will help:



if it has not yet failed, it will soon.

HAILERS

On my 87 car, I had hesitation at 3800 rpm. The place the secondarys come online if the car is under Load.

I solved this problem by adding an additional ground to pins 2C, 2R, 3G and 3A. This was originally done by following the black wires from 3G and 3A up the harness about a half foot, and finding where those wires come together inside the harness wrapping. There I soldered a single new wire to them and terminated the other end of that new wire on one of the studs that hold the ECU in place.

I've a hunch that all that was really needed, was another ground wire added to pin 2C. This could be done by depinning that wire and soldering a 16-18 gauge, single strand wire to the shank of the termination of 2C and then reinserting that termination back into the plug. Then put a ring terminal on the other end of that wire and secure it to one of the studs that hold the ECU in place.

Anyway, I can make that hesitation come and go, just by unbolting the ring terminal of that new wire on the ECU bracket.

I've no real idea why this works other than the 2C wire goes to all the sensors in the engine bay and acts as their ground wire. There are several sensors and they all get spliced together inside the harness wrapping with mechanical splices and terminate at 2C. Bad splices inside the harness??? Got me.

And yes, my ECU grounds on the engines rear rotor housing is just fine and dandy and was in that condition long before adding the *extra * ground.

Please don't ask me how to solder. I just give humble advice on what worked for ME. Plus NZCONVERTIBLE and some others with series four cars. This has worked for others long before I ever owned a series four.

I attached a jpg and have a red or green dot where each of the splices I mentioned above are in the 2C *wire*, plus how it interconnects with the 2G, 3A and 3G. So you can see how it all comes together and related to each other. The jpg is for a Turbo car, but the non turbo is almost exactly the same.

Then again, this has NOT worked for some other people. Not my problem.

EmbassyBlack

thanks hailers.
i made a new ground for everything u mentioned above but still no go. now will these new grounds make it so i wouldn't have to reground everything under the hood? if they do then the problem is a ground its gotta be something else i guess.
got any other ideas?

HAILERS

The things I listed are the grounds for the internal circuits of the ECU on the whole. The secondary transition is controlled by the internals of the ECU. I really don't know other than that. I know it works on a 86-87 series four in my case and others. I think there is a item in the archives on it.

The ground from the batt neg post to the chassis and the engine/transmisison should normally be good enough in their stock locations without adding additonal gnds to the alt etc.

An unproven thought is that a alt with a bad diode in it might cause problems thru leaking a/c into the circuitry of the ECU. Never seen that myself. Just a possibility.

EDIT: Well the archive on the ECU gnds is missiing in action. IT was by RXster and he mentions it in one of the three threads he made on the last page of the Archives. He used to have a site that seems to be not there anymore and I also remember a site called BURNTOAST that mentioned it. I'm pretty sure it's RXstr who got me on to fixing my car by gnding the wires I mentioned. Solved my problems in spades, and like I say, I can make thirty eight hundred rpm hesitation come and go by just removing the ring terminal of my new gnd from the ECU chassis stud. And I used common eighteen/twenty two gauge wire, not the the gauge wire RXter used.

Talking series four cars.

EmbassyBlack

ya i guess the next thing ill do is take icemarks advice and add new grounds in the engine bay, while im at it might as well go get my alternator test to see if the diode is good.

EmbassyBlack

i added new a ground to the boost sensor and routed it to the one on the engine ground then to the firewall and then to the battery ground.
im pretty sure it works now but i cant dive down the street because we just got **** on by snow and my tires are balddd.
i was in first gear and it revved past 4 while i was trying to get out of the snow so i think it work finally.
thanks icemark!

EmbassyBlack

well the streets cleared up and i went to take the car for a spin and still no go.
i dont think its the injectors but im not 100% sure.
i was thinking of making a switch that would manually turn the secondaries on at 3800.
has anyone every done that?
if anyone knows some other way to fix this problem that i havnt tried yet let me know because im about to drive my car into the detroit river.. which seems like the only way to fix it.

HanniganFC

i think i got the fix for you , located under your airbox there is a resistor for your secondary injectors its a small box bolted to your fender just pick one up used or from a buddy, unplug yours plug in a new one and that should fix your problem. seems like you tried everything else..

EmbassyBlack

ya thats the only thing i havnt tried, iv been trying to find one but no one around here has one that i know of.
anyway i think i figured something out but it doesnt make sence.
ok so when i redid the ground under the engine bay i did something wrong.

i spliced a ground on the wrong wire to the boost sensor, and the car drove normally except for still hesitating, now when i realized that i did the wrong wire and i put it on the actual ground lead when i go to turn on the car the main fuse blows.
so im thinking maybe i blew the boost sensor when i did it the wrong way the first time and now that i fixed it its causing a short in the sensor and blowing the fuse.
other than that i dont know where the short could be coming from.

what i did was added another ground to the boost sensor ground, then to the ECU ground, then to the firewall and from the firewall to the battery ground.

EmbassyBlack

ok i fixed everything and now it will keep goin past 4k when the engine is cold, but when it heats up it starts hesitating again.
would that be my coolant temp sensor?
if not any other remedies?

Icemark

have you checked TPS?

EmbassyBlack

yup, idles fine