Is this fuel cut?

[jayson427]

i have a 96 420a 10.5:1 compression, stage 2 camshafts, ported head, aftermarket intake, 55mm throttle body, 24lb injectors. i have no wideband or piggy back. i bought most of my stuff from cimotorsports and they said i would be fine with 24lb injectors and everything else. well im not sure if im getting fuel cut or not. my spark plugs seem fine but sometimes when im driving i hit 4000 rpm and its like im hitting the rev limiter. other times it runs just fine and has pleanty of power. when its acting up like this it doesnt seem to matter if i punch it or barely give it gas it stutters at 4000 rpm each time. i tried looking up older post on here but everything i found was on turbo problems which doesnt help me. so any advice would help thanks!

 

[96 420a-t]

The only way to hit fuel cut is positive boost. What are you monitoring with? What kind of tuning?

Nvm. I saw it.

 

[knochgoon24]

You can tell if your steering wheel has bite marks from the sudden decel when it cuts fuel.

EDIT: Scratch that. I'm not sure if fuel cut with the 420a is the same way or not.

 

[eclipse420ags]

Mine did that at one time I replaced the coolant temp sensor and the TPS and it works fine now. They were both sending erroneous signals to my ecu.

 

[Fotowntalon]

i have a 96 420a 10.5:1 compression, stage 2 camshafts, ported head, aftermarket intake, 55mm throttle body, 24lb injectors. i have no wideband or piggy back. i bought most of my stuff from cimotorsports and they said i would be fine with 24lb injectors and everything else. well im not sure if im getting fuel cut or not. my spark plugs seem fine but sometimes when im driving i hit 4000 rpm and its like im hitting the rev limiter. other times it runs just fine and has pleanty of power. when its acting up like this it doesnt seem to matter if i punch it or barely give it gas it stutters at 4000 rpm each time. i tried looking up older post on here but everything i found was on turbo problems which doesnt help me. so any advice would help thanks!

Your problem is, you are running bigger injectors ( bigger than stock, and bigger than you need), have a lot more air and fuel put into the engine that its use to, and no way to tune it, so if I had to guess your ECU is struggling big time and your AFR is way the hell off. Not to mention camshafts don't really do anything with a stock ECU, because by the time they would make any power your ECU beings to pull timing.

 

[xcasbonx]

Check your MAP sensor. 9 times out of 10 if the RPM is bouncing at 4K, it's a MAP problem.

Also what Steve said above. If you're not running anything to control fuel, with the current setup you have (ported head, cams, etc) you are just dumping way more fuel than required. The stock ECU has no way to compensate for those modifications.

 

[jayson427]

what would be the best way to fix that? i have seen aem's computer and other piggy back systems for my car but i was told not to waste my money on it.

my check engine light is on but when i went to checkers it only picked up the egr sensor which i have blocked off. so that was a dead end. i also changed out my iac because it wouldn't idle right. if i take off the vacuum line on the throttle body that comes from the evap (i think its the evap) it idles better.

i havn't thought about the map sensor, how do i tell if its right or not?

if i got a afpr and wideband how would i know where to tune it at? and would that be the way to go? sorry guys im not good with all the computer stuff on the car i know what everything is but not how and what is needed to make it run 100 percent.

 

[xcasbonx]

what would be the best way to fix that?

You need to look into EFI management, (Megasquirt, Accel DFI, etc..)

i havn't thought about the map sensor, how do i tell if its right or not?

You need to test the voltage output of the sensor. KEY ON, motor not running, test the signal wire to the map and you should get a 4.5v +/- 0.1v reference. Anything below that and your MAP sensor is faulty.

Alternatively, you could go to the parts store buy a new MAP put it on and see if it fixes the problem. If not, return it and get your money back.

 

[Fotowntalon]

What Cas said, but the simplest way for you to tune (is idiot proof and I love it) AFX Computer 1996, 420A Manual Transmission

 

[jayson427]

alright thanks guys! i just got back from autozone and it picked up a map sensor. it said map does not change from start to run. so i got a new one, im just about to put it on and see what happens. so that afx is legit? that was one i was looking at but didnt know much about it.

 

[Fotowntalon]

Its legit as in "what it does" but not legit as far as emissions.

 

[jayson427]

Ok i just put the new map sensor on and took it for a drive. It ran really sweet for about 5 mintues then went back to the same problem. Its starting to get a little frustrating. What would be the next step?

Is it ok to be driving my car if i drive it easy? I just got the motor broken in so I dont want to mess it up.

 

[Fotowntalon]

Tun would be the next step/ via piggyback/ AFX or MS. honestly though if you do a piggyback or MS, you can only get it decently close with a wideband, best most accurate way is to take it to a performance shop and get it dynotuned.

 

[jayson427]

Alright so I checked the voltage on my map sensor and the readings were 5.12, 0.01, 4.12. So is that my ecu not working right?

 

[Shake_Zulla]

so that afx is legit? that was one i was looking at but didnt know much about it.

Its legit as in "what it does" but not legit as far as emissions.

Alright first of all this made me laugh for some reason... Then you asked this...

Alright so I checked the voltage on my map sensor and the readings were 5.12, 0.01, 4.12. So is that my ecu not working right?

That question has already been answered here...

Your problem is, you are running bigger injectors ( bigger than stock, and bigger than you need), have a lot more air and fuel put into the engine that its use to, and no way to tune it, so if I had to guess your ECU is struggling big time and your AFR is way the hell off. Not to mention camshafts don't really do anything with a stock ECU, because by the time they would make any power your ECU beings to pull timing.

So like what was already said you need a means to tune. The 3 basic ways its done on our car is as follows...

AFX Computer 1996, 420A Manual Transmission
easiest way, replaces your ecu
MegaSquirt MS2 EMS ECU - SymTech Laboratories
Called ms for short (different versions available) can run with the stock ecu or replace it altogether (hardest option to install)
Hahn Racecraft - Automotive Turbosystems
Probably 2nd easiest option but most expensive, probably would want to go back to stock injectors.

Of course I don't see anything about a walley 255 fuel pump or a fmu or a fuel cut defender in your post so that could be your problem too. How much boost are you using?

EDIT: I get in a bad habit of calling the Walbro a Walley sorry... For google purposes the fuel pump you NEED TO TURBO a 420a is called a "Walbro 255".

 

[jayson427]

Im not boosted at all, its all motor. I just wantd to make sure I was going in the right direction with that AFX tho. With the voltage I wasnt sure because someone said if its below 4.5v then my map is faulty, well it was above and below when i check all three prongs on the sensor. So i just wanted to post it and see what answers were out there.

 

[Shake_Zulla]

My bad then. I would go back to stock injectors and see if that fixes your problem, if it doesnt then your still searching. The ecu is one of the biggest power robber though so the afx would be a great investment. Thats what I get for late night posting...

 

[jayson427]

Its all good man I appreciate any information. I had my stock injectors in already the first time and it was way too lean. I could hear it and my spark plugs were white so I put 24lb injectors in which was recommended for my build. Guess ill have to get that afx and see what happens

Is howell automotive the only company to sell this AFX? I have called them the past two days but no one has been there to help.

 

[xcasbonx]

Its all good man I appreciate any information. I had my stock injectors in already the first time and it was way too lean. I could hear it and my spark plugs were white so I put 24lb injectors in which was recommended for my build.

How do you know you are running lean, and how do you "hear" you are running lean? You described above that you have nothing to tune with or verify AFR's. Just because someone tells you it's OK to run 24lb injectors doesn't always mean they are right. Put the stock injectors back in, reset the ECU (unplug the neg battery terminal for 15mins) and see where you are after that. Sell the 24lbs and use that money towards an ECU.

For the record I am running similar mods you have and then some, minus the 10.5 compression with STOCK injectors and my vehicle has never ran lean.

Yes, Howell is the only place that sells the AFX ECU. It could take quite awhile to get one, they are not a big company that just has parts laying on the shelf all the time to just grab and ship. Your other option is to find someone selling one for your year/trans.

 

[Diamond Star Werks]

Im not boosted at all, its all motor. I just wantd to make sure I was going in the right direction with that AFX tho. With the voltage I wasnt sure because someone said if its below 4.5v then my map is faulty, well it was above and below when i check all three prongs on the sensor. So i just wanted to post it and see what answers were out there.

It was above and below on the three wires because one is a 5v reference coming from the ecu the other was the ground and the other was the return signal going to the ecu. Your MAP sensor sounds fine to me I wouldn't worry about it. Sounds like your running rich to me. You need a way to tune. Then get it dyno tuned. That would be the best way.

 

[jayson427]

It just seemed like I was running lean but your right I don't know my afr. I wanted to run more rich then lean till I got it tuned so I didn't burn anything up. I only have 400 miles on the motor. I still have the problem I originally posted about so I still can't figure it out. I'm hoping this afx will fix my problem.

 

[Shake_Zulla]

I would get a wideband if you are worried, how are you going to be 100% sure it's not running lean even after you get the AFX. You might not have a problem.

 

[kipcrown]

I have 1 97 eclipse GS 420a wth AFX computer. Ive had my motor done by a drag team, The did the hole motor just like thier motors nothing lft to chance, Im running stock injectors with a RISING FUEL REGULATOR. AND A WIDE BAND 02 SENSOR. Get your AFX and go back to regular stock injectors. Then get your car dyno tested. If you have as much money as i do in a 420a motor your wanting to finish it right. Or you will blow your money up in smoke....I hope this will help any one or every one out on 420a motors..

 

[jayson427]

Well my car still isn't tuned but im currently not driving it so I don't mess it up. I was recommend by bulletdsm to run 24lb injectors. Im still working on a wideband and getting on a dyno. But thanks for the feedback.

 

[H@xtGSX]

You can tell if your steering wheel has bite marks from the sudden decel when it cuts fuel.

I snorted beer out of my nose laughing when I read this... Perfect description.