Ok so I'm trying to figure out what this could be.


I have a p75 converted to a p72 following the instructions on xenocron and pgmfi.org website. The chip job and vtec conversion is good, I've already tested all the traces and whatnot to verify nothing was burnt or damaged/broken. I've also tried the ECU in a stock 95 ex coupe and it runs that engine perfectly fine

So here is what the car is doing when I run a stock p72 basemap.

I get no CEL. The car will crank and occasionally sputter.
I tried using a stock p28 virgin ecu with the exact same results, as well as a stock p75 ecu. All three are acting the same.

Here is the kicker, if I pull the chip out of the ecu (or burn a bad rom, aka put it into limp mode) the car will start and drive around just fine.

So car starts and drives in limp mode, but won't start with a good ecu, even oem stock ecus and my chipped one.

SO anybody have any ideas what it could be?



Modified by bambbrose at 9:13 PM 6/29/2007

 

Ok I've been trying to think of ideas.


What exactly is the ECU doing when it goes into limp mode?
I'm thinking that perhaps it just doesn't refer to any sensors and runs on its own internal map.

If thats the case could it perhaps be a sensor that is causing a no start but when in limp mode it ignores the sensor?

What sensors could cause a no start?

I have all my sensors wired up to the correct pin locations however I'm wondering if perhaps the plug pins could be reversed on the engine side of the harness

 

ok checked my ecu in another vehicle. it works fine without any CEL.

Pulled my dizzy and checked the coil on it. Thats fine.

Also checked over the dizzy wiring again to make sure, it looks good as well

 

where is the tech in honda-tech these days?

 

Ok, maybe a dumb question but... have you checked your timing? There's quiet a few things that could cause the car to start and then die.

 

Timing is good to go.

It is electronic wouldn't you think considering that switching to a bad ecu lets it run, but a good ecu won't start up?

 

Perhaps the ECU isn't the problem after all. Obviously if its going into "limp" mode, it sees something is not correct. You 100% sure all your plugs are on the right sensors? Nothing like switch map with TPS perhaps?

Stock P28 isn't going to work as its setup for 240cc injectors, which H22's do not have. You will not have enough fuel to run the engine off the stock ECU. You don't have a stock prelude ECU to test with I take it?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Hybrid96EK &raquo;</TD></TR><TR><TD CLASS="quote">Perhaps the ECU isn't the problem after all. Obviously if its going into "limp" mode, it sees something is not correct. You 100% sure all your plugs are on the right sensors? Nothing like switch map with TPS perhaps?

Stock P28 isn't going to work as its setup for 240cc injectors, which H22's do not have. You will not have enough fuel to run the engine off the stock ECU. You don't have a stock prelude ECU to test with I take it?</TD></TR></TABLE>

from what the OP said, i dont see that it puts the ecu into limp, he said when he manually puts it into limp via playing with the chip, it runs.

evidently the engine itself doesn't put the ecu into limp mode.

 

I'm manually putting the ecu into limp mode as stated above.

The ecu does not see any codes or show any issues when I have my chip installed.

I've tried a p72 map and it would not start on my car, but would start on my friends civic. From reading online the p72 should run the prelude motor completely fine.

I did some fundamental checks today.

I most definitely have spark, I have 12v at all injector clips, and they are grounding when the engine cranks like they should.

CYL 1 is at TDC when both cam pullies are pointing up.

I'm going to ohm test each wire on each plug now to the corresponding ECU pin and see if I find any shorts.

 

quick question.

Say I unplug my ecu so that all memory is erased.

Then I plug it back in, and turn the key to the on position, but never try to start it.

Is there any sensors that when unplugged would automatically throw a CEL?

 

hmm, i think most would...

i'd try it for you on mine but i run a PowerFC

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by bambbrose &raquo;</TD></TR><TR><TD CLASS="quote">I'm manually putting the ecu into limp mode as stated above.

The ecu does not see any codes or show any issues when I have my chip installed.

I've tried a p72 map and it would not start on my car, but would start on my friends civic. From reading online the p72 should run the prelude motor completely fine.

I did some fundamental checks today.

I most definitely have spark, I have 12v at all injector clips, and they are grounding when the engine cranks like they should.

CYL 1 is at TDC when both cam pullies are pointing up.

I'm going to ohm test each wire on each plug now to the corresponding ECU pin and see if I find any shorts.</TD></TR></TABLE>

The P72 map is again scaled for 240cc injectors. I would think that it would have issues running with the larger prelude injectors.. although I have never personally tried it myself. What program are you using to make these chips? Crome? When you said you are putting the ECU into "limp mode", what exactly are you doing to the chip?

 

when I put it into limp mode I'm just removing the chip, not doing anything else.

P72's are known to run the h22 just fine.

The p72 is scaled for 240cc, but the prelude has similar values in its map, just uses the larger injectors to account for engine size.

I am using crome. I am burning my chips correctly with the proper addresses.

I'm still trying to source a factory p13 but they seem to be difficult to find.

When I use my chip, The main relay does the 2sec fuel pump prime and then the cel turns off like normal, but regardless of what sensors I unplug it'll never show a cel. I'm wondering if it still could be some sort of ecu issue.

I'll be gone all weekend but please give any input or ideas guys.

Thanks and I hope to figure this out asap

 

I'm going to vote ECU issue. Toss a stock ECU in it and I'd bet money it fires right up.

When I first did my swap I didn't have any real modifications done to the motor except for what's nesscary to get it in the car and running. After I took it out and made sure it ran fine, then I started messing around with larger injectors, AFC, all that good crap.

 

why is it so damn hard to find a stock p13 lol.

I've been looking for a while and I'm about to resort to Ebay