The Real Truth 3,800 RPM Hesitation
01-21-02, 02:41 PM
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The Real Truth 3,800 RPM Hesitation
OK. So everyone has their own opinions on this one, but let's find the real truth here. It appears that the reason for the hesitation is the secondary injectors kicking in and they are either plugged or not functioning properly. So, most say just yank them out, get them cleaned and calibrated...however some say that doesn't make the hesitation go away or that it makes it worse. My car hesitates minimally, only 50 percent of the time when I pass 3,800 RPM. So, if you truly know what you are talking about, have done the fix, and it works perfect please post.
01-21-02, 02:43 PM
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there is a bulliten on this it is caused by a loose/dirty ecu ground. of course they decided to put the ecu ground under the intake on the rear rotor housing
mike
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01-21-02, 02:48 PM
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Well...
the problem is that there are a number of things that cause it.
- bad ECU ground
- bad battery ground
- sticky primary injectors
- sticky secondary injectors
- flaky ECU
- rotary gods not smiling
There are a multitude of things that work, some of them for some cars and not others. Basically, you've got to "go down the list" until you fix it.
Brandon
- bad ECU ground
- bad battery ground
- sticky primary injectors
- sticky secondary injectors
- flaky ECU
- rotary gods not smiling
There are a multitude of things that work, some of them for some cars and not others. Basically, you've got to "go down the list" until you fix it.
Brandon
01-21-02, 02:55 PM
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Mine stumbled at 3800rpm and all my research said bad earths. So I added extra earths to the boost sensor (as per Mazda TSB), the ECU (x2), the bellhousing, the intake manifold and the battery. It still stumbles at 3800rpm. I don't think it's earths anymore.
01-21-02, 08:02 PM
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I guess it just isn't as simple as everyone has made it out to be. Too bad Mazda didn't realize this problem and fix it before the later models. I have had many japanese cars and have never come across this problem until now. Oh well. Can't win em' all right guys?
01-21-02, 08:35 PM
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Well, the ultimate cause of the stumble is simple - fuel starvation during the secondary injector switchover. When the secondaries are supposed to come online, the primaries cut the amount of fuel that they're injecting. If the secondaries aren't firing as soon as they're supposed to be - boom! Hesitation.
Now, fixing the problem is a whole 'nother ball of wax...
If Mazda had wanted to fix it once-and-for-all, they would have had to revert to a dual-injector setup like was used on the GSL-SE 1st-gens. BUT they would have had to use much bigger injectors, which would have driven the cost of the car up. Bigger injectors both cost more and are harder to tune for idle and low-RPM operation. So in a sense, the dual-stage injector setup was a cost-saving measure...
That's my diatribe for the day...
Brandon
Now, fixing the problem is a whole 'nother ball of wax...
If Mazda had wanted to fix it once-and-for-all, they would have had to revert to a dual-injector setup like was used on the GSL-SE 1st-gens. BUT they would have had to use much bigger injectors, which would have driven the cost of the car up. Bigger injectors both cost more and are harder to tune for idle and low-RPM operation. So in a sense, the dual-stage injector setup was a cost-saving measure...That's my diatribe for the day...
Brandon
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01-21-02, 09:18 PM
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j9fd3s
hit the nail right on the head,
Step 1:
Go crimp some ring connectors on a chunk of 4 or 8 awg wire (like amp wire).
bolt on end to the engine somewhere... (I used the rear-most drivers-side bolt that mounts the IC to the bracket)
Remove a bolt on the chassis near by, and re-install it with the ring connector attached. (I actually used a Brake Master cylinder stud, since it was close)
Step 2:
get to your ECU (under your passenger side floor board). find the Ground wire that leads into the engine compartment... Cut it, then spline in a chuck of 14 or 16 awg wire, and ground it via the remove a mounting nut to the ECU bracket. (do not just cut the wire, you'll need to leave it attatched... you are just reinforcing the ground...
I used to have this problem, only when the car was cold, during warm up, then it subsided as the car came to operation temps... I had the IC off while changing clutches, so i did this while i was there....
this should hold me over until I relocate the battery on thursday..
hit the nail right on the head,
Step 1:
Go crimp some ring connectors on a chunk of 4 or 8 awg wire (like amp wire).
bolt on end to the engine somewhere... (I used the rear-most drivers-side bolt that mounts the IC to the bracket)
Remove a bolt on the chassis near by, and re-install it with the ring connector attached. (I actually used a Brake Master cylinder stud, since it was close)
Step 2:
get to your ECU (under your passenger side floor board). find the Ground wire that leads into the engine compartment... Cut it, then spline in a chuck of 14 or 16 awg wire, and ground it via the remove a mounting nut to the ECU bracket. (do not just cut the wire, you'll need to leave it attatched... you are just reinforcing the ground...
I used to have this problem, only when the car was cold, during warm up, then it subsided as the car came to operation temps... I had the IC off while changing clutches, so i did this while i was there....
this should hold me over until I relocate the battery on thursday..
01-21-02, 10:31 PM
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I had this problem and it was as simple as the injector plug not being connected. But to my dismay, it wasn't that simple either. The rubber backing on the plug was cracked and the wire was coming out of the plug.
After 3 months of wondering why the hell it kept happening and why it kept coming back, a roll of electrical tape came to my rescue.
After 3 months of wondering why the hell it kept happening and why it kept coming back, a roll of electrical tape came to my rescue.
01-22-02, 12:34 AM
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if its any consolation the fd's do it just as bad...
mike
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12-02-03, 10:11 AM
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Originally posted by Flobb
I had this problem and it was as simple as the injector plug not being connected. But to my dismay, it wasn't that simple either. The rubber backing on the plug was cracked and the wire was coming out of the plug.
After 3 months of wondering why the hell it kept happening and why it kept coming back, a roll of electrical tape came to my rescue.
I had this problem and it was as simple as the injector plug not being connected. But to my dismay, it wasn't that simple either. The rubber backing on the plug was cracked and the wire was coming out of the plug.
After 3 months of wondering why the hell it kept happening and why it kept coming back, a roll of electrical tape came to my rescue.
12-02-03, 11:23 AM
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Originally posted by Peruvianrx7
so u saying you used electrical tape to conenct teh injector plug to the actual injectors... has anyone else used anything more drastic liek superglue or something
so u saying you used electrical tape to conenct teh injector plug to the actual injectors... has anyone else used anything more drastic liek superglue or something
I seriously doubt he was taping the plugs to the injectors.....
12-02-03, 11:28 AM
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yeah, I was talking about the boot. but actually that was only a temporary solution.
It turns out that when I went to have my pulsation damper replaced (unrelated to hesitation) the mechanic did end up using some kind of glue to stick it on there.
It turns out that when I went to have my pulsation damper replaced (unrelated to hesitation) the mechanic did end up using some kind of glue to stick it on there.
12-02-03, 12:38 PM
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I added an additional ground to 3A and 3G (I'm pretty sure 2C is tied in the also) and I can make the hesitation come and go at will just by removing the additional ground. Can make it go away again just by reattaching the additional ground.
That said, when the car was a n/a, I found a hesitation at the 3500 crossover and it was caused by the crimp splices that someone other than me, had put on the secondary injectors. Soldered the same wires and that was put to bed.
The additional grounds at the ECU were added at the splice in the harness about a foot from the plugs. The harness braid had to be cut back to find the splices. Follow the black wires from 3A and 3G up the harness til you run across it.
That said, when the car was a n/a, I found a hesitation at the 3500 crossover and it was caused by the crimp splices that someone other than me, had put on the secondary injectors. Soldered the same wires and that was put to bed.
The additional grounds at the ECU were added at the splice in the harness about a foot from the plugs. The harness braid had to be cut back to find the splices. Follow the black wires from 3A and 3G up the harness til you run across it.
12-02-03, 07:36 PM
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Originally posted by skotter
I have had many japanese cars and have never come across this problem until now.
I have had many japanese cars and have never come across this problem until now.
Do people with standalone systems experience this?? Would having a better ECU fix some of these hesitation problems?
this doesn't happen on standalones because the injectors don't turn on and off at 3800rpm.
12-02-03, 07:41 PM
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Originally posted by Scott 89t2
this doesn't happen on standalones because the injectors don't turn on and off at 3800rpm.
this doesn't happen on standalones because the injectors don't turn on and off at 3800rpm.
12-02-03, 07:51 PM
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Not to take this off topic, but I believe I saw PaulAber's car at Revolution in Indiana. Very nice, especially for someone with a soft spot for 1st gens, yet a dislike of carbs. 
12-02-03, 09:39 PM
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Originally posted by PaulAber
Most people keep the injectors in bach mode with standalones. I do
Most people keep the injectors in bach mode with standalones. I do
they normaly come on with boost.
12-02-03, 09:49 PM
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Re: Well...
Originally posted by No7Yet
the problem is that there are a number of things that cause it.
- bad ECU ground
- bad battery ground
- sticky primary injectors
- sticky secondary injectors
- flaky ECU
- rotary gods not smiling
There are a multitude of things that work, some of them for some cars and not others. Basically, you've got to "go down the list" until you fix it.
Brandon
the problem is that there are a number of things that cause it.
- bad ECU ground
- bad battery ground
- sticky primary injectors
- sticky secondary injectors
- flaky ECU
- rotary gods not smiling
There are a multitude of things that work, some of them for some cars and not others. Basically, you've got to "go down the list" until you fix it.
Brandon
12-03-03, 06:09 PM
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Originally posted by Scott 89t2
but then don't turn on at 3800 hence no 3800 hes
they normaly come on with boost.
but then don't turn on at 3800 hence no 3800 hes
they normaly come on with boost.
12-03-03, 06:23 PM
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How bad is the hesitation you guys experience mine is horrible; so bad in fact that my car wont tach above 4 grand it just feels like its hitting a brick wall. It pisses me off because I hesitate to rebuild the engine if i am going to continue to have this problem after the rebuild. As a follow up to this can anyone recommend a good stand alone ECU system.