4k rpm fall flat (searched)
 

hi folks,

i have done searches on this...and was just looking for more feedback on this... basically had rebuild done & car is starting fine. But when taken for test drive...around 4000 rpm the engine falls flat and is like hitting rev limit. I do have a ACCEL 300+ ignition system but that isn't configured for such low rev limit.

I have so far tried bypassing ACCEL 300+ unit, checked TPS, currently checking secondary injectors... i will check grounding (increase ground points to block)... what about KNOCK SENSOR...??? can this cause it falling flat...., MAP sensor faulty...??

any other things I may have overlooked...???

thanks for your input...

Possibly fuel pump relay. The ECU will put it into limp mode if it isn't telling the engine to dump enough fuel. Other fuel issues could cause this, too.

yeah i had a fuel pressure meter connected and pressure seemed fine... will check relay and all....cheers for that.

You shouldn't be exceeding 4k rpm on a fresh rebuild.

Is this occuring under vacuum as well as boost?

yeah the engine builder took it for a run to make sure all was ok...so i could pick it up... but now got this shit going wrong... pin pointing the culprit be hard...

he said he had one showing similar symptoms and it turned out to be a fault air temp sensor... thing is he ran the diagnostics and no faults are coming up...

What else is done to the car beside the ignition?

With the stock system, values from the Knock Sensor can retard the car.

I must question why you (and us) are trying to do your mechanic's job for him. It is something errant with the install, which is his responsibility to fix.

You also might be running in closed loop instead of open loop also. I know my friend had the same problem so now it just runs open loop all the time and he does suck down more gas than normal but it fixed it.

At anything other than pure cruise, the car will be running off maps at 4k rpm, not the open loop o2 sensor feedback.

nothing else except the ports being cleaned up (stage 2 port).

you are right... but i started this tread in case someone else has the same issue; its just one more avenue for information gathering.....but yeah he will need to sort this out... i just wanted to cover all usual suspects...

will keep u folks posted..

Please do, posting the answer your mechanic discovers will likely prove useful. :)

You didn't really answer my question regarding boost/vacuum, but this problem could be a boost leak/control problem or it could be the secondaries not coming online, or the fuel pump not switching to high output mode, etc.

Stop exceeding 4k rpm on a fresh rebuild though. :)

ohh i will definitely not not exceed 4k rpm for the 1st 1000 k's but its just good to let the mechanic know that buck stops with him (in this case)...i will eventually go power FC;

in regards to boost/vacumm what do you mean... run the car with one IC pipe
off... to see how it goes under NA conditions

thanks for all the feedback...really appreciate it...

so the car idles fine?

No, creep up to 4k rpm in vacuum, it's not that hard to do, especially in the lower gears. Then go up to 4k rpm in light boost (usually easy to manage in higher gears). See if the car reacts the same in vacuum as boost.

you dont want any boost until 1000 miles not (km).or is km more??
then creep up in the rpms, 1200 miles go to 5000k, 1500 miles go to 6000k and so on.
mine kinda does the same thing but its only tuned to 4000k because of the new motor. 300 more miles till meth!!!!!!!!!!!!

i wanted to be safe so i went to 2000 with no boost.

well just to update... i have got the car and the freaken hesitation is still there... but i will put some km's on the engine first... in the interim i will add more ground points to the block, chasis and ECU...even if it doesn't help it can't be bad can it?? then next bet will be to move fuel filter to the front (engine bay) by then hopefully have 1K kms plus and finally will try fuel pump resistor bypass (temporary) i will just jumper the connector going to resistor... (it will run rich @ below 3K rpm) but wanna see what happens above it...

** just realised the circuit open relay bypasses it... hmmm will have give juice straight & will also do fuel pump rewire mod....

I was wondering if you have found out what the problem was cause i am having a similar problem?
-thanks

I don't know if this is the same problem you are having, but I had a bad secondary fuel injector once. The car could be driven very lightly up to 4000 RPM, but it would fall on it's face at that RPM. Any amount of boost below 4000 RPM would also make the car stumble hard in the same manner. I think other folks have had the same problem due to having a bad connector on a secondary injector, or just forgetting to plug it in.

My injector was seized, and would not open when fired. As a diagnostic step, it would not "click" when I applied 12v across it's connector terminals. Good injectors do "click".

-Max

hey mate sorry i could reply to your pm cause i dont have 15 posts yet"

hey mate,

i dont have a picture but its the little black box in front of the top manifold prob under your strut brace, there should be two hoses connected to it, have a look where they are going my one was cracked. if its all sweet then its a solenoid problem. actually some guy from out west using this forum helped me out at his home, he knows a tonne of stuff. he posts under kerry chandler. very nice guy see if you can get a hold of him.