so i just got my 86 4+3 running, entire new fuel system.. car was running well for 1 day then this started happening... while driving if i get over 2400 rmp the engine begins to die off (regardless of throttle postion).. if i put the clutch in, normal engine returns.. This happens in every gear. i have noticed if i get the RPMs up and then release the clutch with the engine over 3K itsstill slugish but doesnt die. Also the OD doesnt seem to be engaging, i put the cluth in and push the top of the shifter and nothing happens.


additional info:


Car idles fine..


car is currently popping code 36 (maf burn off), and intermittantly popping code 24 (speed sensor, although ive tested the sensor and my speedo works fine)..

I have replaced the MAF and the two relays.. so im thinking this is a wiring/ecu issue... Yees i know i need to fix this but i dont think this is related to my drivability problem...


car has all new fuel/ new plugs, new wires. fuel pressure is right around 43 when at idle. and when in neutral or sitting still will climb the RPM range like it has normal power.


i kept thinking my maf sensor was my problem, but it still had the problem with a brand new maf, and when it was unplugged...


now im starting to look at maybe a trans issue of some sort? but im not that familiar with the whole 4+3 thing..


any thoughts or pointing me in the right direction would be awesome.

 

How old is the o2?

 

unknown, although i have new one coming. just incase... i not optomistic that this would be the problem as it only happens while in gear.

 

install and let us know.

 

Does it still have functioning cat converters? if so possibly restricted. The 24 can cause a computer default run not so great or "reconnect VSS mode". So you may want to check it out. Do you have access to a scanner and FSM? If you unplug O2 sensor how does it run? Your condition would be called "under load"as opposed to in gear. Restricted fuel filter? Have you driven car with fuel pressure gauge taped to windshield to see if pressure falls?

 

update, so new o2 sensor installed. cleaned the cap and rotor and while doing so noticed one screw holding the rotor on was somewhat loos so thightened it up. could still move the hole rotor assembly about 1/8 inch or less, I assume that's normal. and set timing to 6degrees before dtc.


checked some wiring on maf and it has power, ground and signal... still working toward the burnoff issue..


problem still exists.. has gotten a little better but still exists.
heres where I now sit...


I can accelerate with full throttle up to 2K, if I hard accelerate above 2k it completely falls on its face.. complete stall...


if I accelerate with minimal throttle I can wind the car almost all the way red line.

 

Tape the fuel pressure gauge to the windshield and see what it does while running. Careful not to crack the windshield when closing the hood. How old is the fuel filter?

 

well its got all new fuel pump, fulter, injectors off my lt1, so slightly higher lb/hr. fuel pressure is set at 42 at idle. if a completely mash the gas the pressure drops, but will go back up to 42 within a second or so ish... at idle/neutral.. engine runs through the rmp range exactly as it should... only does this under load...

 

Oh **** new info what year injectors on what year car?

 

injectors in my 86 are off my low milage 97z28.. they are 24lb hr , stock tpi are 22 , and from my readings this was a fairly common mod..


as I said, in neutral the car goes through rmp range completely normal... it only does this under load,


I cant imagine its the injectors.. or it wouldn't go throught the rpm range at neutral, atleast that was my thinking

 

Did you reprogram for them? I believe a call to Jon at FIC is in order and check your oil for fuel. Do not want a grenade. looks like they would work for a 85 but not a 86.

 

I'd definitely check them. Not sure what stock fuel pressure or injector size was in your year. Could be different.

 

no I didn't reprogram, but that doesn't explain the problem im having... from all my readings it isn't needed for such a small change..


I haven't checked the oil in a bit, so I guess I will just incase... but fuel in my oil from running rich? ide have to have shot rings and leak down, I highly doubt that's my problem, running rich would be more likely to nuke my cat.. but that doesn't seem to be happeneing either.
car doesn't even smell that rich at the exhaust...




guess ill call FIC to get their opinion and ill buy some remanned injectors from FIC if needed, but that doesn't seems to be the issue....


I reitterate that rmps and throttle are normal when not in gear,




**** my z28 runs much richer than this car and its runs exactly as it should.

 

His takes 22lb I think we found his problem. self inflicted.

 

ASSUMING that your stock fuel pressure is 43psi AND your stock fuel injector size is 22, you are correct. OTOH, if either of those are wrong, well......

 

Do you happen to know what the stock fuel pressure and injector size in that car is? I don't

 

Yes I saw that it ran good in neutral but not much fun to drive like that. let's get a experts opinion call Jon.

 

ill call him in the morning.. It just doesn't make sense to me that slightly richer would cause this issue.


my thinking is ... when you get on your throttle.. you drop your fuel pressure because your using more fuel.. so it drops for just a bit, until the pump catches up.. and me running slightly bigger injectors would allow more fuel to reach the cyl during this period.. so if anything it would run rich... not stall and die.. unless there is something im not considering..


ive read multiple threads about people doing this swap with no problems..


on a side note this car was sitting for 5years im guessing before I got it running again.... fuel system/coolant, tstat, wheel bearings, maf, maf relays, o2 sensor, brake system, etc etc all gone through.

 

You are right. The ECM will compensate TO A POINT. If you exceed the point, it messes up and this could be one of those things. If your stock pressure is 30 psi, you are running way richer. If your stock injectors are 19pph, same thing.

If the pressure drops, the regulator closes and the pressure builds up.

What year was involved? What other mods did they do that might compensate for it? Without all the variables, it is hard to say.

 

my car is 86 vette, donor injectors were 97camaro lt1. stock vette pressure from what I read is 40-45.. stock 86 injectors 22#, stock lt1 Camaro is 24#.. my car has headers and that's about it..


I wouldn't understand why a load issue is being diagnosed by people as an injector issue, but maybe that's my lack of knowledge...


ill call FIC tomorrow.. but if I were them im sure they'll say yeah you need um, spend a bunch of money with us...


just would seem odd if its an injector issue that itll rev perfectly not in gear.