ok so my friend just bought a 86 n/a gxl with 68,000 original miles on it. it ran fine for about a day. but t hen he started getting hessitation, his alternator died aswell so he got a new one. the hesitation stayed.

i went over to drive it and this is what i found. first time i drove it. it was already warmed up. i took it for a drive, it did NOT go over 3800 rpm. we checked tps. i ajusted it very slightly. and we added grounds. then took it for a drive. it drove ok for about 5 min then the symptoms came back, just like my co-worker said . it goes away but then comes back with in a short period of time.

my idea, from reading other threads on this problem. is that maybe there is corrosion in the clips for injectors OR tps.
its not the mas because it idles PERFECT.
also he already ran sea foam in the gas.


any one have an idea?

 

Ports might not be opening or could be the secondaries are intermittent.

 

Bad connection to secondary injectors (corrosion in pigtails, chafed leads) would be my guess based on what you have said so far

 

sea foam in the gas????

never herd this before. what does this do???

 

yeah but. when my rx7 was n/a i didnt let my ports open when i had to wire them open cuz of new exhaust. i never wired them open. they were ALWAY closed.

ya thats what i am thinking too but dont know to much about it. he'll be checking the clips.

its a brand of injector and oil system cleaner. its not "sea foam" its just the brand/product name.

 

ok so he changed out injectors to different ones on the 2ndary. and the problem is still happening! though he did say that not much fuel came out of the rail when hechanged them. so he's going to be checking the fuel lines.

 

what do you mean by adding grounds? did you check voltage to fuel pump?

 

Secondary injectors come online when there is a Load on the engine (seen by the pressure sensor) AND you've reached 3800 rpm. On a series four car, the primary injectors duty cycle is cut in half at the same time as the secondarys come online. Like the primary duty cycle was maybe 60* and now it's 30* along with the secondarys being 30*.

On early 86 and 87 cars Mazda noitced the hesitation and came out with a fix where they added a second ground wire to the pressure sensors already existing gnd wire. They terminated this new wire on the water pumps thermostat housing. They added this wire to the boost sensor gnd wire, not because the problem was boost sensor related, but because it was a afm related problem according to the bulletin. The reasoning behind this is, all the gnd wires on the sensors in the engine bay, are all spliced together inside the EM harness. Add a gnd at one point effects all those sensors gnds. All those gnds that are spliced together, end up at the ECU's middle plug. Pin 2A if memory serves, maybe 2C, I forget and I'm not going to look it up.

So the gnd enters the ECU at the middle plug. Well it's still looking for a gnd point. The ECU's internal gnds exit the ECU and end up on top of the rear rotor housing (series four).

Some people, and more than a few, have found that finding the ground wires for the ECU, where they Exit the ECU plugs, and then soldering another gnd wire to those existing wire, will fix the hesitation problem. I've done this on a 86 and grounded the new gnd wire to the bracket that holds the ECU in place.

This requires unwrapping a couple of inches of wrapping on the harness, and then finding where those gnd wires attach to the 02 sensors shielded cable. That's where you could add the *extra* gnd mentioned.

Common sense says to first, make sure the existing gnd wires for the car are clean and connected. Like the gnd wire from the batt neg terminal goes to the chassis below the left front strut tower, then goes on to attach to the long starter bolt or at least to one of the transmisson/engine bolts nearby.

Then again, you don't say much about the 3800rpm no go. I mean, if you left your foot in it, would it get over the hesitation and then keep going to 6-7000 rpm. Or did you mean it got to 3800 and just would not go any further no matter how long you held the pedal down? If that were the case, then the secondarys are just flat not coming online at all. Plugs off the secondarys.

 

Are you sure theyre the right injectors? Friend had a car with low impedance injectors in the 2ndary spot, car was an 88, switched to high impedance injectors and problem went away.

 

I read on one of the forms that around 3800 rpm when the secondaries come on that the primaries get cut to half flow. Have you heard this one? Is that why if you have poor secondaries it jerks and sputters?

 

the same thing happend to a friend of mine N/A. but the way his happed was because we were ripping the crap out of it. the alternator went bad andwhenever we changed it, it started hesitating.

i would say do the same thing i did. check your coils and change out the one that is bad.

 

Assuming the secondaries are coming online as intended, don't rule out the possibility of fuel delivery, such as clogged/restricted fuel filter, dirty fuel pump sock filter (usually causes hesitation during left turns) also check volts at fuel pump connector (should be around 12 volts during hard accel and around 8-9 volts at idle/cruise).

 

yeah so apparently his fuel tank is SOOOOOOOOOO bad that even after changing out his fuel filter 3 times its still getting clogged and lowering the psi in his fuel rails.....


sooooooooooooooooooooooooooo
thats the issue.
bad fuel clogging fuel filter

 

Sounds like it's time for a trip to a salvage yard or a post in the forum classifieds for a good used tank. There are plenty out there still in good shape.