motor bogging under throttle? help!!
 

This is starting to stump me. I can't figure it out. There were no prior signs the last time that I drove it. I started it up and it started acting funny. It starts ok, and the idle is a little choppy, but under throttle it falls flat on its face and about dies. I'm running a t04 single setup, with stock fuel and a PFS piggyback at ten psi. I have all the solenoids removed , the rats nest is gone and all emissions are blocked. I have replaced all the plugs(9's), made sure that I had fuel getting to my injectors, and I am getting spark on all four plugs. I have unplugged the spark plugs and turned the engine over and it sounds fine, as everything internally is fine. I am about to rip out the injectors and clean and check them. Before I do, can anyone give any suggestions as to what to else to check? has anyone else had this problem?

my stock '93 had symptoms exactly like the ones you described. after starting it up a few times, it began to blow some crazy white smoke. not only that, but i could actually hear coolant pouring into a rotor housing. i'm not saying that's your culprit, but that's what happened to me. from what i can tell, it was falling on its face and sometimes dying due to a blown coolant seal and coolant flooding the housing... have you noticed any white smoke? have your coolant levels been steady or are you losing coolant?

does sound like a chipped apex seal to me. I had the same problem (twice). The car starts up and idles (but not 100% normal) but under load it falls on its face. Soon you'll probably find that it won't start at all (if this is the case). Check your boost gauge to see if there is any fluctuation of the needle at idle. If it moves up and down slightly at idle, that's probably the problem (unfortunately).

The only thing I can think of is that it would be running SUPER rich, but you'd know that by seeing a bunch of black smoke out the tailpipe, and probably a few flames.

I have that problem (running super rich)

It falls flat on its face for a second or two when trying to accelerate after coasting for a few seconds. If i stab the throttle quick and then go back to coasting i get a 3-4 second flame from the exhaust :D

I like it :) :)

PFC will be fitted soon though which will fix it hopefully.

Is this problem happening after doing any changes to the car?

I also had the joy of leaking and stuck injectors. Same basic symptoms. It would buck like mad whenever I tried to get into it at all. (Of course, it was running way lean, so it's really good I couldn't make boost or I'd have popped my engine).

Dave

THIS IS KILLING ME!!!!!!!!!!! WTF IS WRONG??? I started it up today and it was like nothing was wrong, took it out and it was fine. Left it alone for awhile and tried it again and the same thing happened, falling on its face. I have went over my engine time and again looking for leaks, loose wires, exhaust leaks, anything I can spot. I'm a process of elimination type guy and I can't get anywhere if it works and then it doesn't.


I don't have any white smoke, actually hardly any smoke whatsoever. My coolant levels are fine and the temps look good too.


As for a chipped apex, I don't think so. My symptoms would be a little more drastic I think, however if I can't figure it out I will rip off my exhaust manifold and check the insides of the housings for scratches. My compression is ok, and like I said it started today and ran just fine.


Could I just have a loose wire messin with me or something.What about a coil going bad, or a bad ground or something? anything else at all? I will try anything.

i dont know if it helps but my fd had a clogged cat converter. i couldnt get it to boost more than 2 or 3 psi and was choppy at idle sometimes. i found out by putting my hand on the intercooler pipe off of my turbo and it was red hot just after startup. engine is cold but pipe was hot. i took off the cat, busted it out, now car runs like a new car and boosts better than ever.
hope it helps

No man, I run 3" open back to a muffler. i am beginning to wonder if it has anything to do with my tps..... I am pretty sure that it is fuel related though cuz there used to be a considerable amount of smoke out of the tail pipe from all the excess at startup and now there is hardly any. I am about to cange the fuel filter check all the lines, and maybe rip out my injectors, test and clean them.

To be honest, sounds like maybe your TPS took a shit.. so the "accelerator pump" action from the ecu doesn't occur and bogs as soon as throttle is applied ( to lean).

I'd pull the tps and check to resistants range to make sure its it well with in spec.

I think this is the answer.

I feel strong about this because i had this problem a couple of months ago. The car would start up perfectly, hot or cold and idle fine (after about 30 seconds). Then when i get on the throttle it will buck, rpms would stick during shifts etc. Sometimes if i blip the throttle repeatedly when moving in tight spaces, the car would die out.

Had TPS in spec and car is back to normal. Idle is a bit high but in my case, its not the TPS, its something else, something ill address sooner or later lol

this sounds like it might be the problem. It would make sense cuz i recently polished my intake manifold and that is the only thing that I have changed or messed with, come to think of it i did move my throttle body ALOT. I will check and see if it is loose or that I can move it. I'll search for how to adjust it properly but if anyone wants to give me a quick reference i would appreciate it. cross your fingers!!!!!

wait, quick question. Would your engine run lean if your tps is off a considerable amount? cuz I use to have a rich idle and alot of exhaust, and there is hardly any smoke at all now. This is why I thought that it was fuel related....

well, the tps checks out in spec. i looked it up on the lightning in a world of thunder, and according to his specs they are where they should be on both wires. It is rough to start now and if I get on the throttle the same thing is happening, falling on its face,if it is a slow increase in throttle it sounds ok. So now it moves to something else. I am going to check the fuel pump relay and the fuel pump resistor. any other suggestions?

Check obvious things, spark plugs, make sure the wires are on the boots correctly (i had this problem last winter)

Check your coils too.

plugs are good. i just replaced them. and I know that I am getting fire on all of them. My engine was flooded though was the reason that it wasn't starting. so I took the plugs out and cranked the engine over to get all the excess fuel out and cleaned my plugs, starts ok now. but I think that I am going to rip the coils out anyway and test them. Might do the injetors at the same time. As long as I am easy on the throttle it is ok. But if I really give it open it falls and stutters bad, lots of backfiring.

another question. Even if the tps is registering the proper volts, could it still be bad?

Hi,
Just bought a 2000 Series 8 import after owning a Series 2 for the last 14 years.

Within 4 days of owning it it started to do the same thing. Drove down the street under normal revs came to an intersection and then if started bucking, starting and stopping it did no good. Managed to limp home and the next day it ran as sweet as !!

Mechanic cleaned fuel system and injectors, replaced spark plugs with 7's and 9's and everything was sweet for a few days then it all happened again. Limped home , let it rest and then the car ran sweet again ... WTF ....

After that I left it with my mechanic and he had the bucking happen to him and then the car died completely and currently after owning it for 4 weeks it is sitting in his workshop with no compression in the back rotor.... ahhhhhhh

I am looking at a total rebuild but even my mechanic is at a loss as to what the heck went wrong. It was uncanny as the bucking only ever occured when the tank was 1/4 full . There was no smoke, the idle was a bit rough and a 'scan tool' indicated code 45- a solenoid problem ! Suffice to say the back rotor currently has no compression and looks like a rebuild... Bugger... So I am eager to hear if you fix your problem as if sounds awfully similar.... Good luck and I will be keeping an eye out ....:)

Oh one last thing , i always ran 91 octane in my 81 series II and was told not to run anything less than 98 octane in the series 8. Unfortunately I put in 95 octane once. I am hoping this was not the cause of the cars death !!! Any thoughts?

Yes this sounds similar to mine as I can't really figure out a pattern to what is wrong. However, I don't think that their is anything internally wrong with mine at the moment. I think that I was experiecing something going out and the WTF !!!!effects. People have suggested that it may be a bad coolant seal, highly doubt it. A bad coolant seal gets reports of large amounts of white smoke out the exhaust and symptoms unlike mine. My car falls on its face completely while under any load at all, not just sputtering and lots of white smoke(however there is backfiring when I try and give it heavy throttle) Others have suggested chipped seal, don't think that this is the culprit either b/c my engine doesn't shake, my pressure out of the pipe is as good as it has always been, and as long as I keep a gentle increase in throttle in park and at idle it will act and sound pretty normal. Then it was the TPS and I really thought that this was it, however everything checked out for voltage. So now I am onto ignition, possibly a bad coil or bad wires maybe. After that I am going to check for fuel issues, bad or unclean injectors, maybe one of them stuck open, those kinds of things. If none of these turn out to be the problem, then I may have to bring it to someone else and pay the money..... :wallbash:

i'm not sure if this is going to help but allow me to share tps specific experience i had two days ago.

The car runs perfectly with 7's on all faces (mazda Comp. tester) My issue with the car right now is the rpm's seem very hesitant. Traditionally a blip of the throttle gets the rpm building up quickly but with my car it builds slowly. I've tried everything including replacing coils, igniter,plugs,plug cables, fuel filter but the problem still persists.

I decided to try adjusting the tps via datalogit (i have a pfc) I set tps within spec and drive around, not improvements. I park the car and turn it off whilst and notice error on the datalogit for TPS. I tried again this morning and the same thing. I'm going to try to narrowdown the tps. Let me know when you solve your prob.

^ hence my asking, can the tps be bad even though that the volts are registering properly. Today I am going to try and reset my computer and replace my plug wires. If nothing changes I am going to check the coils and then the injectors.If none of these are going to work out then I am going to replace the tps alltogether.

If you decide to, let me know, i have one with low miles and ill sell cheap :)

will do

-Assuming that you ditched the MAF....

-Not the 02 sensor, because is only a fine tuning device on these cars

-Did you check TPS in all positions and verify voltage sweep?
-Check for a bad/loose ground as this seems like the most probable cause: https://www.rx7club.com/showthread.p...ensor+symptoms

-Also look over your engine bay wiring with a fine tooth comb to make sure you didn't break or pinch any wires. You'll want to look where the wires meet the connectors and check for breaks.


GL

check injectors. you could be running rich or it could be cutting out.

what kind of "T04" turbo are you running?

I just checked the MAF and it is reading 2.6 according to the manual while the key is turned on, and it increases as boost tries to build. I am going to replace the O2 sensor anyway, and yes the tps volts did vary considerably when I was adjusting it. I have went over the bay a few times but I probably need to do it again and I will check all my grounds again. but I am running out of things to look for and just start replacing things. :crying: