I'm running a DOHC ZC with stock intake manifold, stock TB, I/H/E, stock cams/cam gears, chipped PM6 with a stock PM7 program. At about 4000 RPM, the engine bogs hardcore, at any amount of throttle. Lightly accelerating (1/4 throttle) it bucks pretty bad at times, like the ignitor is going bad. Anywhere above 4500 RPM, at WOT, the engine pulls hard like any other ZC. Whenever its bogging, the intake gets really loud, and it kinda acts like its bouncing off of a 2 step launch control.

About a month ago, I had a completely stock D16A6 motor in the CRX. It did the EXACT same thing! I used the same wiring harness, same computer, same fuel rail/injectors, same TB, same exhaust setup, same drivetrain.

Things I have tried: Known good ignitor/coil, known good TPS, different TB, PM6 program, old PM7 program (tuned on JG cams and high compression).... The exhaust isn't clogging, its wide open. The mechanical timing is right on, spark timing is right on...

Any ideas?

EDIT: I have a temporary fix for the problem. See the first post on page 2


Modified by I8ayellowcrayon at 1:13 PM 4/26/2008

 

Now I have also...

Put in new spark plugs, double checked timing, replaced the CYP sensor with another, replaced injectors/fuel rail/fuel pressure regulator, adjusted the valves (they were clacking).

I'm thinking MAP sensor... I can't imagine it would be anything else considering there wasn't much else that was on BOTH motors...

 

what kind of crx? dx or si/hf, sounds like wiring

 

How are your grounds?

Funny how the lack of some .50 wires can cause such a headache.

 

Its a '91 Si, with the original Si harness. If it were a wiring problem, the ECU would notice it as soon as its turned on correct? The ECU is showing no codes.

When I put the motor in, I cleaned all of the grounds. I have the factory ground on the thermostat housing, factory ground on the valvecover, and a bigger ground on the transmission; all of which have good continuity.

The battery is relocated to the trunk. I didn't have any problems with it for the 4 months I was driving the car with it back there, but the car was also sitting for 6 months, and there is a water leak in the hatch area... I'll check those on my lunch break.

 

id look into the MAP sensor and extended grounds from the battery relocation.

 

my Si is doing the same thing

 

is the cam angle sesnor wired?

 

i had the same problem...pretty sure its your tps

 

Its not TPS, I've installed another one that I know works. I'm not ruling out TPS wiring though.

The cam angle sensor is wired, and is wired correctly.

I installed a known good MAP sensor on the car, and it didn't help at all. I put another ground on the valve cover, cleaned all of the other grounds, and lowered the fuel pressure about 5 psi (to 40psi at idle), and it runs a lot better, but it still hesitates at 4-4.5k RPM. I'm going to put the wideband on it today to see if its rich or lean when it happens. I know adjusting the fuel map for that would just be a bandaid, but just for ease of mind, I want to know what its doing.

 

Bump. I've also tried a good PR4 ECU.

 

I have a similar problem in my B16 DX hatch.

At WOT it will bog down. Don't matter if its @ idel or @ 5k rpms.
I've tried the same things you have so far, and I'm about to try the fuel pump.

Freind @ work told me when his fuel pump was going it , it would also bog down. I just got a spray bottle, and sprayed down the IM, and have found a small air leak on the IM gasket. Not shure if this is affecting it much, but I'm going to try a new one of those too.

 

The fuel pressure on mine is holding steady at WOT, and it runs great at WOT at higher RPM. I'm ruling out fuel pump on mine, but that does sound like it may be the problem for yours.

I'm thinking its something on the car that is causing the problem now, because everything that was on both motors has been replaced with another part...

 

not getting enough fuel - have you checked the injector resistor box?

 

I have not. I don't believe I have a spare either. How can I check it?

 

 

From the power they're all at about 6.8 Ohms, and from one to the other, they're all at about 11.6 ohms.

Fuel filter maybe? I haven't replaced the fuel filter in 20k miles (with Walbro 255), and the car has been sitting for 6 months with 101 octane in it (running 91 now)...

 

i don't think it would be fuel filter - usually a clogged filter would make it get worse as rpm went up - do you have a stock PM6 or PG7 ECU that you could try?

 

I do not. I've tried multiple programs in the PM6 and the PR4 and it seems that the leaner I make the program, the better it runs.

I got a new filter anyways

 

I checked the mechanical timing again, because it feels like a timing problem to me.... The engine pulls HARD from 6-7k RPM.

So I advanced both cams one tooth, and it barely ran. Just to humor myself I retarded both cams one tooth and ended up with the same outcome.

I have thought about putting my JG cam gears on this motor and degreeing just to make sure its right...

Now that I say that, I realized that the machine shop milled the head .014", would that be enough to mess up the cam timing enough to cause these problems???

 

It seems like you are having the same problem I had a year ago in my crx. After trying many things, a new cap an rotor fixed it for me. here is the thread, read through it
https://honda-tech.com/zero...age=3

 

The weird situation with mine, is that it ONLY messes up around 4-4.5k RPM. In your situation, you couldn't get over 2k RPM. Besides, I've already tried a different distributor, and the cap/rotor look good on both distributors... Thanks for the tip though.

I think I need to clarify, it runs great anywhere before 4k RPM, and pulls good after 5.5k RPM. That area though is horrible.

 

I had a similar problem on my B16 a while back and tried everything you did.

Make sure you're not throwing any codes...Although your CEL light may not be coming on see if the ECU has or is storing a code.

Reseat the connectors shock tower harness on the passengers side...I had a friend who's wiring had several breaks and after doing this it correct the problem for a short while then came back. After replacing his Crank angle sensor wiring the problem went away so you may want to try that as well as a test.

 

I've checked the ECU to see if its flashing, but its not storing a code.

I'll take a look at the shock tower connectors and see whats up.

BTW, I tried to hook up my wideband last night, but the power supply apparently wasn't worrking. Time to send off the LM1... AGAIN!!!

 

my car was doing the same thing and i turned out all i needed was a new cap and rotor. just my .02 cents
good luck with the car.