Bucking/ hesitation
 

I have a 88 rx7 gtu with a rebuilt engine that was street ported as well as a 3" down pipe and 3" inch exhaust with the cats stripped and a resonator for back pressure.
About a year and 1/2 ago i blew my oil cooler lines and replaced them with a set of mazda trix stainless steal performance lines. After replacing them i drove my car around and it started bucking around 3500 rpms and would rev limit me going up hills or on a flat surface but worked fine going down hills. I parked the car for about a year and 1/2 and started it and drive it around the block about every two weeks to keep verything lubed before I could get around to woking on it.

I read multiple posts on here about the dreaded 3800 rpm hesitation and one sounded exactly like mine and his problem was the afm (air flow meter) so i bought a reman one however that is not the problem either. The car runs better with it and does not rev limit me anymore and also runs very smooth in neutral with no hesitation. I drained the old gas in it and put a higher grade and fuel injector cleaner in thinking if it was not the air maybe it was a fuel deilvery problem. That however also did not work. Any suggestions as to what the problem could be??

Most hesitation problems are due to bad grounds. The main ground for FCs are on top of the engine under the intake manifold. here is a good link about it. http://fc3spro.com/TECH/FAQ/3800.html

I had this problem for a good long time. I checked the AFM, The Ground connection, and the actuators. Finally i just went and bought some brand new secondary fuel injectors and poof! gone. If you want to test them first, when your low on gas, throw a bottle of injector cleaner and run it passed 3800 to circulate it into the secondaries. If it occasionally works and then does, then replace them. My 7 would go good on downhills and occasional half throttle.

Thanks guys for the help I bought a mechanics stetoscope today and ohmmeter to test the secondary injectors as well as the crank angle sensor and a few other things tom morning hopefully by tom. ill know for sure.

Any luck with that my 89 is having the same issue as well as error codes 26 27 33 do you have any of these codes ? Also my tach doesn't work and the clock sometimes flicker I thought is was fuel so I replaced pump and filter didn't help the issue seems to kick in along with the check engine about 15 miles a hour shoot me a e mail if its permitted hsilive@gmail.com thanks rx7 club your great !

Any luck with that my 89 is having the same issue as well as error codes 26 27 33 do you have any of these codes ? Also my tach doesn't work and the clock sometimes flicker I thought is was fuel so I replaced pump and filter didn't help the issue seems to kick in along with the check engine about 15 miles a hour shoot me a e mail if its permitted hsilive@gmail.com thanks rx7 club your great !

Sry guys I havent been on in a few days I work 2 jobs so free time sometimes gets limited but electrical is kinda a weak point for me on cars so hsilive what did u use 2 pull those codes off and also can anyone tell me what are good points to mount my grounding wire from my engine at i know where on the body to ground them I just dont know where to run them from?

what i have done
 

Well I thought it was a fuel problem so I have replaced the fuel pump and filter no avail I checked the codes by bridging the single green connector next to the battery to a ground on the neg battery cable I then read the flashes on the check engine light and got 26 27 33 witch are oil meeting pump and mass air check valve oil seems to be metering and I have no idea where that air valve is those are the next things I will fix after I get the 3800 problem fixed I've put one ground from the firewall to a bolt on the intake didn't help I'm putting another from the altinator to the neg and new battery clamp soon we will see soon if it fixed it any input from you all would be great

Error code 26 and 27 which relates to the oil metering pump which is telling you that the car is likely in limp mode which prevents the car from being driven in such a way as to damage it. If the problem persists the ECU will be damaged in addition to the omp.

rock on i think you got it
 

I think that's it I've asked a million shops and what not if they had a limp or retard mode like that everyone says it doesn't ok so it looks like I am metering oil so I need to test that I'm sure I can find a article about that lol I put some two stroke oil in my fuel to make sure I was getting lubed I have driven it about 1000 miles since the issue if I am metering what could be wrong ? and also I can't find nothin on that code 33 the dealer can't even tell me where the mass port check valve or whatever that code was is and dude your a smart cookie I didn't think it was my injectors just didn't feel right so where do I go from here Mr rx almighty lol ?

Error code #33 refers to the Port Air bypass solenoid located at the ACV and its wire goes to pin 2N at the ECU. This is for emissions purposes and only works for the first 20k miles out of every 100k on the odometer (works from 0 to 20,000 miles then turns off for 80,000 miles then turns back on for the next 20,000 miles).

Ok so the code 33 doesn't really matter since I don't have e/m where I am right ? And I'm going to check electrical connectors on the pump I did replace that lower radiator hose maybe I knocked it loose what other things could I do to check my omp ?

well heres my update
 

I had a couple hours today so I tried a few things here it goes first I jacked up the car checked the wires going to the omp they looked good no visible damage no damage to the oil lines either so I lowered the car checked the codes had 26 27 33 same as normal something else I might have left out the check engine light only comes on after about fifteen miles a hour before that no check engine and normal throttle response so next thing I tried was to disconnect the electrical connectors going to the omp at the pigtails on top of the motor with them disconnected I read my codes and got these 12 17 18 20 26 27 33 cleaned everything and plugged it back in went back to the three first original codes and none of the others also had the same problem at close to fifteen miles a hour I'm still trying to figure if its the 3800 problem or the omp by the way I'm using a cell phone for the web I wasn't able to review the awesome shop manuals you sent me the link to

Injectors...
 

Im tellin ya man...just buy some new injectors, either way if they haven't been replaced it would be good for better flow. I went through all this shit for months and months when i new i should have just replaced the secondaries. I was on here talkin bout codes and goin through all this run around...just find a place with them for cheap. And go from there!

ok ill give it a go
 

So you had the same prob huh did you get the same omp codes as well and did they disappear after changing the injectors ? And the ecu is that control box at the driverside side kick panel right ? I want to see if I fried that as well

what do you think?
 

Hey satch I want to know what you think bout this I do need to change those anyhow and I'm going to have to drive it about 400 miles until Ivan get home to the shop and work on the omp any impute ?

Ok guys I got a new symptom now the car chugges the whole way through the rpm band until it gets 2 3800 then it bucks and hesitates.... so im thinking maybe the fuel injectors are bad on mine .... has anyone else had this problem on top of my other problems lol also its rev limiting me again in neutral at about 3800

checking up on this post
 

Some say it does work some say it doesn't I just ordered my injectors from rockauto.com they are cheap around 30 bucks a piece if you havent changed them before its prob a good start mine doesn't limit while in neutral are you getting codes I would be interested in knowing if you are.

Injectors...
 

I never rechecked the codes after installing the injectors, i just new that the engine worked...honestly everytime i approach 3800 i cringe still expecting the hesitation lol, trips me out how long i dealt with that and now paying for it....And no, the ecu is underneath the passenger floor panel i believe.

Injectors...
 

Yea its like 30 a piece for primaries and over 80 for secondaries, may as well purchase them all. Be sure to apply some sort of lube before installing them.

injector sizes
 

So primary and secondary are different sizes ? Shiz what are they mines a 89 no turbo ?

You need to triple check your power harness grounds and power connections, I have had this problem also, than once that checks out, try injectors/ fpr..good luck!!!

I had, the same problem and it's a pain in the ass, the car wouldn't go over 3500 rpm
What I found out was that my Air flow sensor harness was loose, and when i was bleeding the radiator, fluid soaked the throttle sensor connection, after adjusting and cleaning everything, ir ran really fast.

Im checking my fuel filter first and then the air flow sensor harness to make sure nothing got knocked looose when I installed the new afm and then im ordering new injectors mine is a non turbo but is ported would it hurt anything if i got turbo fuel injectors or would I need to change other things as well to do that?