Crazy hesitation problems
 

Recently rebuilt the engine on my 04 rx8 manual. after reinstalling with new plugs coils and wires i am getting a crazy skipping on my car. only code im getting is a misfire. I know everything was done right and the engine has good compression cuase i can run it for 45 mins and it starts right up when i cut it back on. but at idle the car will rev down to 500 rpm and back up to 1700 rpm by itself or sometimes when i crank it it will idle down for about 3 seconds then cut off. when i give it gas to rev up it stutters and heitates and the car shakes like crazy and sounds terrible and then like it should when i first pressed the gas it revs up. the main issue is below 5k rpm but it skips in the higher rpms with a sudden press of the gas. if i rev it up and hold the gas steady it runs perfect and smooth even all the way up to 9k. it can't be a internal engine problem. I'm thinking that it has something to do with the air or fuel. it sat for a couple of months, but i don't know if that affected the fuel pump or filter. the maf is clean and the throttle body looks clean. it also has an aem intake. I can't find anything with an issue like this.

This wall of text thing is getting to be a real problem on this site.
Let me guess, this was posted from your phone?

First, I just love how you've mentioned that everything is done right and you know you have no internal problems. That's BS, because you don't, or your wouldn't be here.

Second thing, seriously you couldn't find anything, nothing anywhere on this site this is a similar situation as this? I don't believe this either.

https://www.rx8club.com/series-i-tec...t-here-222280/

https://www.rx8club.com/new-member-f...causes-249529/

Not that I think you'll read the threads.

Basically dude, the engine has been out of the car and rebuilt.
That effects every system on the car.
Yes it could be fuel, or air or electrical. It could be anything.

Go out and make sure you've put the spark plug wires on correctly.
Clean the ESS and reset using 20 brake stomp method.
Check spark plugs are in tight
Check Maf screens

Also, I would suspect the injectors have not been connected correctly.
It is very easy to get the injector wiring order messed up.
Actually it's hard to get those things to seat correctly as well.

Reving up slowly without a problem is suggesting that at extremely low airflow levels everything is fine, and it stumbles when it gets more, either because the ECU is not expecting it or because it is having trouble with the volume.

Start with WCS's list, because they need to be re-checked anyway.

Plus:
- Get a timing light or a spark tester and test your coils (yes, I know you said they are new, test them anyway)
- Check for missing engine block grounding points.
- Make sure your MAF is seated correctly AND PLUGGED IN
- Check for vacuum leaks (OBD2 data, STFT + MAF is optimal way, assuming everything else is fine) there are a lot of vacuum hoses that were removed, and many of them are not obvious. Including the LIM nipples

by everything done right internally i mean, that all the seals, rotors, ect are correct. 5th one i have rebuilt so i know its right. i have found nothing that matchs my issue to the extent that i have explained, but thanks for pointing out the obvious maf, spark plugs, typical routine stuff that is obvious that i would have checked, i am here asking for help not condescending remarks.

Most install problems ARE something obvious. You shouldn't take much offense to people suggesting you run back through them.

not you, and yeah i know, i have rechecked everything 10 times, the dealer told me that they had no idea whats going on, and quoted 1500 to "check and diagnose everything" not taking offense, just frustrated.

Yeah, a dealer will be worthless.

I would agree with WCS though, something wasn't done right since you have a problem, and not 'everything' has been re-checked, since you haven't found it.

I'd guess that the frustration is making you skim over something too quickly. Be methodical.

If you don't have a way of watching OBD2 data to see what the engine is doing when it's on, get one. If you already can, take a look at AFRs, STFTs, MAF and tell us what it's doing when you, and when you aren't experiencing the problem.

yeah i need to get a code scanner. but i have another rx8 automatic (girlfriends) we got for 2500 with a blown engine that i rebuilt, long story short by toying with it "unpluging hoses, plugs, maf, ect" i cant duplicate anything close to the situation im getting with my car. i know the manuals are different but i cant get a misfire even close to the one im getting with my car. i marked all the hoses, wires, ect so theyre all back to the way they were before i rebuilt it. the only reason i think its air/fuel is cause im getting a lot of backfiring when i let off the gas. the car is completely driveable and runs perfect if i get it on the highway and set it on cruise. im gonna recheck everything slowly tomorrow though.

If you have a smartphone or tablet, order a bluetooth OBD2 adapter, pair them up, download an OBD2 app (Torque is best for Android, no idea on other platforms), and have everything at your fingertips.


It's sounding roughly like what I dealt with when I left the MAF unplugged one day. Tons of extra fuel as the RPM climbs, the faster you try to get it to climb, the more it stumbles and chokes itself with fuel.

Do all this like RIWWP said! Plus make sure your AEM intake screens are properly placed. Does your ECU need a reflash perhaps?

lude1888 What exactly do you mean by reflash? Would a dealer have to do the reflash? None of the other ones i have done needed to be reflashed after rebuild but its worth a try at this point.

RIWWP Awesome thanks for the help!

No, reflashing does nothing different, a stock flash is a stock flash. The only thing that dealers do (or should do) during engine replacements is to reset all the ECU parameters to let the ECU re-learn the new engine. 20-brake-pedal-stomp accomplishes what the battery disconnect doesn't.

I had the same exact symptoms once in my old Jeep. I found a leak on the underside of the intake. I know the 8's fuel system is much more sophisticated. I'd bet the problem is air/fuel related but likely much harder to isolate than a simple intake leak.

Let me get this straight.
The OP can rebuild an engine.
The OP has also the skill set remove the engine and reinstall it.

However the OP cannot figure out how to isolate a misfire or search the forums.
The OP does not have a ODBII scanner.
Doesn't have a data logger.
Doesn't understand what is meant by a reflash.
The OP does not have a fuel pressure tester.
The OP does not have a Vacuum Gauge.

I'm sorry guys but this whole thing does not add up.
I simply cannot believe that someone that has the skill set to rebuild an engine, and be convinced that nothing is wrong with the rebuild because he did it, and he's that good ... but needs this kind of help.

Furthermore he reinstalled the engine himself and is here looking for help, convinced it's an air/fuel issue?

Honestly every system all the entire car has been impacted.
Where do you start?

Given that we need to believe the OP has actually installed the Coils and Plugs correctly.
The OP needs to provide detail feedback to the items given here in this thread.

It looks like English is not the OPs first language but so you need to spend more time on your posts for clarity and quality.

- Have you checked the ESS
- Have you actually gotten a CEL and what/if so is it?
- Can you get/buy a HEI Coil tester?
- Can you get/buy a Vacuum Gauge
- Can you get/buy a Fuel Pressure gauge
- A means to perform a data log would be very helpful
- Seriously ... those injectors can be a right pain in the ASS ... Check them

I know the OP is not going to receive this post well, given his previous responses but frankly I don't care.

This guy needs to provide some quality responses to assistance already given or this is an effort in futility on such an epic proportion that it makes most troubleshooting threads look like person success columns.

Haha dude the engine is fine. it's not hard to remove and install an engine

But yes I am incapable of understanding the rest of your text and I am unable to figure out how to use a translator to convert the text to my language because aparently english isn't my first language. Who would have knew?

But anyways I have never came across this problem. The first one i rebuilt with a guy that's a rotary expert and from there I kind of learned on my own.

Maybe it's just dumb luck that all the other ones I reinstalled ran perfect after resetting them.

I will however purchase a scanner, a vacuum and fuel pressure gauge and get back. The original post was composed for help, seeing that maybe someone knew something that I was overlooking.

Hopefully that double spacing between sentences helped you read :)

@ OP.

Sounds like a vacuum leak to me. A bad one. Check the 3 lines coming off the intake tube. Make sure none of them are seeing outside air. Make sure the Jet Air like is hooked up, that is a good leak source. That will confuse the ECU. Check crap on the ESS sensor as well, and look for crap on the ESS position plate..

Other things? Fuel Injectors plugged in right? Plugs hooked up right? Wires to coils hooked up right?

Yeah i've checked all the vacuum lines multiple of times and can't find a leak anywhere.

The injectors are right according to factory spec and i cleaned them before installation but it's possible that when i did first crank the car something got in them because it sat for so long and i never drained the gas:(

Plugs and coils are correct. 100% positive

The ess has a small dent on it but it was like that before the rebuilt and i never had a misfire before or a problem with it. and i don't think it would be starting as quick as it does if it was bad. It will start in the first second even when the engine is fully warmed up.

I'm leaning towards PCM failure at this point. I have an extra one i bought (all the numbers on the front match) I plan on programming at the dealership.

I just want to be positive i'm not overlooking anything before i take it to a dealer. but thanks for all the suggestions guys.

Good news guys, took the upper intake manifold off and fuel injectors and BAM! one of the primary injectors was dry on the bottom.

Got a new injector, and car runs perfect, i suppose that makes sense since the 2 lone injectors work by themselves until around 4k rpm or something like that.

Car does run great and pulls strong but after completing a couple of drive cycles I got a p0171 code, i'm guessing it's my CAI since its missing a screen, do you guys think that's what it is?

Were getting pounding with snow here in NC so i can't go out and drive it. and with it being overdue emissions I need to fix it so i can pass cause the cops around will bust you in 2 sec.

From what i've read i'm assuming thats it, I do have a p0420 code also but i'm pretty positive that's from a gutted cat, which i have a midpipe with a new cat to install, I was just waiting for the misfiring to stop.

you would need a downstream O2 defeat code in the ECU to pass emissions, or put a cat back on it..

without an OBDII live information feed the p0171 could be anything.

Yeah i'm just gonna put the cat back on for emissions at least.

Unfortunately i don't have the live feed, so i'm going to try with the CAI and if that doesn't work follow the service manual on the proper troubleshooting procedure.

It still could have something to do with the fuel injectors maybe the other one is slightly clogged, probably would've been smart to replace them both but i went the cheap route.

or just drive the car for a week or so and see if the problem corrects itself.

Well I went out and checked around today, turns out my dumbass broke off the nipple that was capped on the intake from the removal of the stock air box system.

the VRAD nipple i believe it's called (the one behind the throttle body).

It was sucking air so i covered it with some gasket maker and bam my idle dropped about 50rpm, now that I think about it, it may have been idleing high.

I'm hoping that solved the problem!