Runs great cold, then hesitates and bucks when warm.

[MX5RACER]

I have searched and it seems this car might need the re-flash, but my issue seems to be slightly different.

Background. I bought my third MSP with a blown motor. I put a new motor in and had some collateral damage as the stock turbo ate itself shortly after. Turbo number 2 was DOA. Turbo number 3 is a Nissan T25. Fastward to my issue. When the car is cold (First start in the morning), the car will run like a ***** ape, boosting 8-9 psi, reading 20 in vacuum with the A/C off and 18 or so with the A/C on. The car will warm up and get slower and slower until it feels like it accelerates better just before boost. Once boost comes on, it will feel like the car is slower than a N/A Protege. The plugs are under 1000 miles old, the coils are fresh and I have replaced the PBV with another stock unit and cleaned the MAF. On the highway in 5th gear if I plant my foot the car slowly accelerates and will sometimes buck while boosting and holding 8-9psi. Half throttle runs will cause the turbo to spool and make 8-9 psi, but the car will not really accelerate. There is no leakage heard and I have tested the system with a boost leak tester at 10 psi. Originally there were leaks at each injector, which I fixed with O-rings.

Digging a little further, I hooked up my scan-tool and viewed some data. The spark advance will be around 26-30 degrees at part-throttle cruising, but as soon as you accelerate into boost, the timing will drop to NEGATIVE 4.5 degrees advance. Does this sound like an issue with a CAM or CRANK sensor, timing belt issue (Not having enough tension), the knock sensor detecting knock and causing serious retard on the timing or the flash on the ECU?

Thanks for your help.

 

[BRIAN_MP5T]

4.5 Degrees of retard is not even required to run 20+ PSI on this engine. (Advance Happy Motor)

That is most definitely the manifestation of the issue.

As to what would cause that is a mystery.

If the Cam/Crank sensors were in error there would be a CEL, Period. The belt tension will have no bearing on the running of the car unless it has jumped a tooth, then it would run like ass Warm or Cold.

The bucking sounds like a weak spark, either the coils are weak, the plugs are weak, the wires are failing, OR the coils are being triggered improperly because of some issue with the ECU or other sensors feeding bad input.

As the intake charge pressure climbs, it becomes harder to burn the mixture reliably, which is why the car might run fine off boost then struggle.

Also, sometime the coils are strong cold, but then due to some problem as they become warmer, the case separates and they start to act up.

 

[MX5RACER]

Thanks for the suggestions. It seems that the buck is a single event, not like a missfire event. It is a single, large buck. I am going to check the knock sensor tonight when I get home and make sure that the resistance is within range. With heat the resistance might be changing and fooling the ECU into thinking that it is seeing knock. (Just throwing crap against the wall and trying to see what sticks at this point)

 

[thecrash91]

could it be fuel cut? do you have any sort of engine management? fuel cut is when you hit a certain amount of boost the ecu cuts fuel to the engine and the car basically feels like it shut off for a split second. does this sorta describe your symptoms?

 

[MX5RACER]

Don't think it is fuel cut, but could be. I noticed this thread where someone describes the exact symptoms I have and a reflash solved it. I will cross my fingers when I get it flashed.

 

[f1yen]

I was having similar problems, It has to do with the car going into open loop when boost sets in, whether it is noticing the MAF and just goes to 100% load, or the EGR sensor notices the boost, it will pull a crap ton of timing and add all the fuel. And at low rpms will bogg the crap out of the car.

(it was very obvious with a WB, and boost gauge next to eachother, once I hit 0.1 psi, the WB would sweep to 10.1 - 9.8 ) I just checked the other day with a OBD reader, it is pulling into open loop as well.

I got a reflash and it cured this problem, (as in, waits for 4200 rpm to go to open loop)

The problem for me now, is that some times (even with the flash) it will behave as described above. Somehow it gets caught in while loop (that somehow notices the boost and kicks to open loop(which in turn is pig rich and slow if the RPMs are low)) ... When she is fully warm, I politely pull over, turn 'er off, and try again. Then it works like expected. It only happens every other month or so.

 

[BRIAN_MP5T]

Stock ECU is an enigma.

the easy fix is also a really hard one. Get a stand alone ECU it is the only way to fully remove all control from Mazda.

 

[thecrash91]

Stock ECU is an enigma.

the easy fix is also a really hard one. Get a stand alone ECU it is the only way to fully remove all control from Mazda.

ive been contemplating a megasquirt, as they are standalone and are very cheap. 278 if you build it yourself, around 450 preassembled.

 

[pbarton14]

I've also had this issue for over a year now but I never had the issue till I had my motor rebuilt. At any rate, I would love to see a solution. I think it's something more than just a sensor, the only ones I haven't replaced are the map and the knock

 

[BOOSTR]

Don't think it is fuel cut, but could be. I noticed this thread where someone describes the exact symptoms I have and a reflash solved it. I will cross my fingers when I get it flashed.

Its been sometime and many miles since I drove unflashed but the symptoms you describe are not what I recall entirely. I had no bucking and it ran like s*** randomly under all conditions and time periods. Definitely would feel like it was going nowhere while underway and trying to get on to the interstate.

Amazingly not one time since being flashed and driving aggressively from a take off have I experienced any preflash symptoms. But when driving normally they do pop up from time to time. Changing gears and throttle application seems to help then.

 

[Installshield 2]

Stock ECU is an enigma.

the easy fix is also a really hard one. Get a stand alone ECU it is the only way to fully remove all control from Mazda.

totally agree...although, technically, you mean remove all control from...Ford...as unless you're in Japan, these damn ecu's were built by Ford...

 

[f1yen]

totally agree...although, technically, you mean remove all control from...Ford...as unless you're in Japan, these damn ecu's were built by Ford...

Well, If I recall correctly, Mazda did the tuning, the EEC V hardware is of course a stock thing, but the way it was tuned, by Mazda was crap. Talking with TwEECer, the deciphering of the Mazda code is near impossible, (compared to the ford ones)

If we could find a ford EEC V ecu from a similar ford... that is supported by TwEECer etc. That would be the best solution, for emissions and performance.
Just my $0.02

 

[Installshield 2]

Well, If I recall correctly, Mazda did the tuning, the EEC V hardware is of course a stock thing, but the way it was tuned, by Mazda was crap. Talking with TwEECer, the deciphering of the Mazda code is near impossible, (compared to the ford ones)

If we could find a ford EEC V ecu from a similar ford... that is supported by TwEECer etc. That would be the best solution, for emissions and performance.
Just my $0.02

very true...the way i understood it was Motorcraft built it to begin with (as they had a huge hand in OBD-II standards to begin with), and Mazda tuned it to spec...but certain fundamental design gives poor control over certain conditions...no matter what mazda would've done...but in either case, its not really important who to blame i guess...

I thought i read years ago that late 90's mustang's used a version of the EEC-V...but that the US BJ proteges were the last cars in production to have it...so they're the 'newest' cars with this shitter...The mustang crowd is not a community i had any real want to go asking questions to...so i just gave up...11 years later...i'm a few weeks away from a stand alone haha...

 

[MX5RACER]

Well, happy to report that the Reflash has transformed the car. It actually accerlates now, regardless of temp. Thanks for all the input on this.

 

[pbarton14]

I wonder if that is all of our fix.? cuz I tried using a whole different ecu from a msp and it ran exactly the same way. Cold when fast, slow when warm . One thing I've noticed with it is, while in neutral you can hit the rev limiter a few times , let it go back down and then drive and the power will be back until u shut the car off and try to drive it again , it'll be right back to normal

 

[Stiki]

a piggyback would be just as effective as a standalone?...stumbling wen i hit positive boost makes me want to cry.

 

[Dr0]

ssafc does NOT cure it. it does help but the problem is still there, its just a little more sporadic. im going to try the flash tommorow and im pretty confident it will help.

the only reason i think this is because anytime i read these stumble/hesitation posts the one thing they all have in common is that they had un-flashed ecu's

 

[Spiced MSP]

There are some that have still had the issue with flashed ECUs

 

[Dr0]

yes ive heard, but its a hell of a lot cheaper of a fix then going with a standalone

 

[Stiki]

i was confident the flash was gonna help, but wen i went to the dealership it turns out i already had the flash all along :/