Headache and a Half -starting/rev cut

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Jinsoku
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Headache and a Half -starting/rev cut

Postby Jinsoku » Wed Feb 03, 2021 11:49 am

Hello Everyone, I hope all is well and you're staying safe!

I purchased my Friends 86 a couple of years ago and it was in storage for a few years before that but I knew it worked fine and had zero issues the last time it was out and he took it to Laguna Seca and a Local AutoX.

Engine Rebuilt in 2010 with all OEM Parts.
4AGE 16/20 with about 6K miles on rebuild.

During this stay at home mandate, I have been working on it and noticed a few issues that I would like to remedy.

upon cold start, it has to turn over for about 5 seconds before it starts but once it starts it ides fine, and when at operating temp you can start it back up with one turn but if left for over 4 hours it'll take a couple of quick turns to start up again.
The other issue I'm having is that it loses power or feels like a fuel cut after 6k-6.5k and will not rev higher.
On that note, if I do some light-spirited driving and take a turn(even a 10 mph turn) it will stay on but lose power for 2 seconds then act normal again.
I can drive the vehicle all day for whatever distance and it'll be fine as long as I'm not Max Maxin it everywhere!

No Codes
No CEL
New Battery
New Fuel Pump
New Fuel Filter
New Spark Plugs
New Gas 91 Chevron (old gas was good but why not)
Plug Wires are good
Injectors are good(tried 2 sets with same symptoms)
Adjusted Throttle Body according to FSM
Good TPS
Spot on Timing
Solid Compression
Grounds Connected, I have a grounding kit and added more just cause. Lower intake ground is connected.
OEM intake/filter
OEM Header
New Cali approved Cat
2inch piping Catback(hmmm?)


Can't Hear the fuel pump prime when in the ON position but once started car idles and runs good until you try to go above 6K.
Diagnostic FP jumped to B+ kicks activates the pump when in the ON position.

I'm leaning toward a Fuel Pump prime issue for my cold starts but what about my 6k Rev Limit?
They have to somehow be related and that's where I am asking for some help..

I'm going to check the Fuel Dampner and if that's good I guess I will focus on inadequate fuel pressure from the pump to the injectors.

Any Tips or Tricks?
Thanks for reading my story!

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not mine
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jondee86
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Re: Headache and a Half -starting/rev cut

Postby jondee86 » Wed Feb 03, 2021 5:55 pm

Hey brother... good to see you are still beating on an AE86 :D

Sounds like you have an electrical problem going on. Assuming you are still running
the OEM distributor, I'd say the first thing to look at would be the wires where they
come out of the distributor. You are looking for a soft part in a wire where the constant
flexing of the wire with the movement of the free swinging plug has caused a fatigue
break inside the insulation.

In the normal straight ahead progress of the car the ends can still touch, but when
you swing round a corner the "pendulum" effect of the plug bends the wire and opens
up the break. Get back to straight ahead and the ends touch again. If this actually
turns out to be the cause of power cut around corners, there is a good chance that
fixing the wire will also solve the high rpm rev "fuel cut" issue. Good luck :)

Cheers... jondee86
The reasonable man adapts himself to the world; the unreasonable one
persists in trying to adapt the world to himself. Therefore, all progress
depends on the unreasonable man.

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Jinsoku
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Re: Headache and a Half -starting/rev cut

Postby Jinsoku » Thu Feb 04, 2021 12:19 am

jondee86 good to see you too man!!

just ordered an NGK wireset, should be here later today(12am now).
i actually questioned the wires and should have replaced them anyway, they're the magnacore custom wires and im not sure how good they are. new cap and rotor have about 1hr runtime(idle) but 0 miles.
i'll keep you updated and thanks for the help, you and oldskewltoy are like the club4ag technical guru's!!
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jondee86
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Re: Headache and a Half -starting/rev cut

Postby jondee86 » Thu Feb 04, 2021 1:57 am

Yeah... but I was actually referring to the skinny wires that take the pickup signals
out of the distributor to the igniter or ECU. Should have described that better :)
One of those wires sends the Ne signal and if the ECU does not get that signal for
a few turns of the engine it will default to base timing or some such nonsense,
which will feel just like a fuel cut. Depends a bit on exactly which version of the
AE86 ignition system you are running.

If you have yellow disconnect plugs in the signal wires you can probably hook up
your multimeter. See if you can get any of the wires to go open circuit by twisting,
stretching and bending the wires one at a time. Sorry about the confusion.

Cheers... jondee86
The reasonable man adapts himself to the world; the unreasonable one
persists in trying to adapt the world to himself. Therefore, all progress
depends on the unreasonable man.

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Re: Headache and a Half -starting/rev cut

Postby Jinsoku » Thu Feb 04, 2021 3:27 am

LOL no worries, I wanted to get some wires anyway!

I’m running a kouki GTS distributor and I will check the wires with a multimeter tomorrow, thanks again!
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Re: Headache and a Half -starting/rev cut

Postby davew7 » Thu Feb 04, 2021 3:41 am

I think you are on the right path with the fuel pump. Let the car set over nite and than crack the fuel rail banjo fitting and see if you still have high pressure in the system. Sounds like the pump check valve is leaking down and the pump can not keep up with pressure and volume at higher RPM.
Davew7

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Re: Headache and a Half -starting/rev cut

Postby Jinsoku » Thu Feb 04, 2021 1:37 pm

jondee86 was right on the money, I was able to find the wires on the distributor that were broken but still in contact enough to give signal then when I take a turn they would separate and interrupt until the loose wires came back into contact!

I removed, cleaned, soldered and reinstalled!
An immediate difference as far as throttle response and although I did not try to rev it past 6k I’m sure she’ll go!!

Time to figure out my fuel Issue.
I have 7mge injectors with some old pigtails with cracked clips so I removed all of that and soldered on some fully functional pigtails and switched out my injectors with some known working 2jzge ones, same cc.used O rings but in great condition(soaked in oil for a few min before install)
Regulator vacuum line had no gas in it and if i disconnect the vac line with the engine running it revs higher.

Image
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https://youtu.be/6QOtiSrmVUA

Fully charged battery, I still can’t hear the pump prime!!
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Re: Headache and a Half -starting/rev cut

Postby Jinsoku » Thu Feb 04, 2021 2:04 pm

davew7 wrote:I think you are on the right path with the fuel pump. Let the car set over nite and than crack the fuel rail banjo fitting and see if you still have high pressure in the system. Sounds like the pump check valve is leaking down and the pump can not keep up with pressure and volume at higher RPM.
Davew7


dang.. i need to do this!!

Thanks for the advice davew7!!!
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Re: Headache and a Half -starting/rev cut

Postby jondee86 » Thu Feb 04, 2021 4:36 pm

Good progress... one problem at a time is the way to go :)

AE86 does not prime the pump when you turn the key ON. The pump does
not turn ON until you turn the key to the crank position. If the engine is slow
to start when cold you should check that your cold start injector is working.

If you have been mixing and matching injectors you need to check the injector
resistance to make sure you are not running low-res injectors on a high-res ECU
without the resistor pack. If you are running high-res injectors on a high-res ECU
then you don't need the resistor pack.

Basically, if you don't match the injectors to the ECU you will run into problems
at higher rpm. Low-res injectors are 3-4 Ohms and high-res are 12-14 Ohms.

If the injectors are correctly matched then you will need to be checking that
the fuel pressure is not dropping at high rpm.

Cheers... jondee86
The reasonable man adapts himself to the world; the unreasonable one
persists in trying to adapt the world to himself. Therefore, all progress
depends on the unreasonable man.

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Re: Headache and a Half -starting/rev cut

Postby Jinsoku » Thu Feb 04, 2021 6:13 pm

Here’s what I came up with:
4age: 210cc 2.4ohm 20.6lb/hr
7mge:314cc 13.8ohm 30.9lb/hr (23350-70080)
2jzge: 312cc 13.4ohm 29.7lb/hr (23250-46030)

I’m using the 312cc high impedance w/no resistor

It came with this setup so I do not have low impedance injectors but I do have the resistor.
(It’s removed and in the toolbox)
So I have to source some 220-250cc that are low impedance that will fit my pigtails?
Or will high impedance injectors without the resistor be okay if I can get close to the factory setting but with high impedance?(high comp injectors?)
From what I’m trying to understand, the issue is what the ecu is thinking/sending(low ohm) to what I’m actually running (high ohm no resistor).

Then my other issue, checking the cold start valve!

It’s close, thank you so much guys!
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Re: Headache and a Half -starting/rev cut

Postby Jinsoku » Thu Feb 04, 2021 7:01 pm

Image
Image

Inj 1: 13.6
Inj 2: 13.7
Inj 3: 13.6
Inj 4: 13.6

Cold Start injector: 3.3

FYI I have no clue how to mess with the cold start injector and I’m “meh” with injectors in general. My last 86 was 7 years ago and it had Mikuni 44’s.the ones before that never had issues.
I’m seasoned and can follow directions LOL
Thank you for you’re time everyone!

I did a few tests to see if I get any power to cold start injector with fuel pump and coil wires detached. no matter what I did there was no voltage while cranking.
I remember jondee86 did a tech write up some years back and I’m sure he hates repeating himself multiple times a year so I’m going to up my game and understand the system before I go any further.
https://www.club4ag.com//forums/viewtopic.php?t=14683#p98025
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Re: Headache and a Half -starting/rev cut

Postby jondee86 » Fri Feb 05, 2021 1:00 am

I guess that a 16/20 4AGE is a 16V head on a 20V bottom end. In which case you will
have obtained some increase in compression but otherwise the fuel and air requirements
will not have changed much from the factory 16V setup. Thus if the OEM injectors were
210cc/min low-res then they would be your best option. They may run a little lean up in
the 6000rpm plus range, but for normal driving they would be fine.

By way of comparison, IIRC the 16V smallport had 235cc/min high-res injectors and that
ran 10.3:1 compression. It is generally OK to run high-res injectors on a low-res ECU as
stated here... http://performancefuelsystems.com/Injec ... Corner.htm
So if you happened on a set of smallport (green) injectors for cheap, you could give
them a try. If you have high-res clips wired up they will plug straight in.

High-res and low-res injectors have slightly different response times which can screw
with your mixture, but oversizing the injectors by 50% more than stock will definitely
have you running super rich and ugly wit it :)The factory ECU doesn't know what size
injectors you have plugged in and just delivers the pulse width it was taught at the
factory to run the stock 16V with 210 injectors. To get bigger injectors to run right you
need to have an aftermarket ECU where you can adjust the pulse width to control the
mixture.

Cheers... jondee86
The reasonable man adapts himself to the world; the unreasonable one
persists in trying to adapt the world to himself. Therefore, all progress
depends on the unreasonable man.

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Re: Headache and a Half -starting/rev cut

Postby Jinsoku » Sun Feb 07, 2021 4:41 pm

Looking for 235-240 hi-res injectors cause it is really rich and I see there is no need for the current injectors.
I didn’t take a vid but a driveway rev and burnout(I always tell my neighbors!) have confirmed she’ll go past 8k!!!

After letting it sit I loosened the banjo bolt on the fuel rail and no fuel came out.
Also the IACV is capped.

Image
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I have an in line check valve with gauge on the way so I can confirm if and where there is fuel pressure loss from the pump to the rail.

Then I have to figure out what the cold start injector needs to activate and make sure it has it but I gotta remove the CSI and confirm it is not functioning!!

As is she can drive and drive good but I have all the exterior lights removed to prep for paint.
I’m trying to get to Laguna Seca(Mazda Speedway) sometime this year so that’s my motivation!

Thank you all again and I appreciate all the help!
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Re: Headache and a Half -starting/rev cut

Postby oldeskewltoy » Wed Feb 10, 2021 9:03 am

Hmmm, from memory... mid/late 80s Honda 2.0 liter efi uses 240cc low ohm injectors.... Pretty sure they'll do the trick - check Rockauto
OST Cyl head porting, - viewtopic.php?f=22&t=300

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Re: Headache and a Half -starting/rev cut

Postby Jinsoku » Wed Mar 02, 2022 11:02 am

hi comp injectors, new OEM TPS, reset timing and cleaned up all ground wires.

SHES GOOD TO GO!!!

Thank You so much 4AFamilia!!!
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