HELP trunk battery culprit??

[dohcfiend]

got this car from some1 and finally got to drive it yesterday. had a buddy of mine with me and all so i wasn't really focused nor was i expecting any problems other than a slightly jumpy idle at cold startup.

i cracked down on it and about 5k it sounded like it was starving for fuel. runs like shit at WOT. so basically i am trying to figure out some1 elses gremlins.

so 1st step was a tune-up today which consisted of changing wires to another set i had on hand and knew for a fact they were 100%, new plugs, inserted a bottle of injector cleaner with about 25% tank volume, new air filter and new fuel filter. nothing really lost here b/c these steps are standard when getting a used car.

no codes btw.

let it idle for a little while and circulated the cleaner. took it out again under more controlled conditions, the problem resurfaced but this time i noticed the lights dimmed slightly and the charge indicator was flashing.
which leaves me to believe the coilpacks are starving instead of the fuel system.

also the new filter fixed the cold idle lope

now that you guys know what it is doing, here are my areas of concern for troubleshooting.

clogged exhaust: highly unlikely considering a new cat, steps i will take for troubleshooting will consist of unbolting the downpipe and mixmatch the flanges so there is free exhaust flow. note:this guy has it setup so so you can seperate it in front of the cat.

fpr: will have to buy a new one and also switch out the injectors with a known good set while i am at it.

chip: he created his own custom chip and i fear he may have goofed somewhere so i will have to acquire another chip.

trunk mounted battery: step 1 will consist of me borrowing a heavy duty truck battery from my buddy and see if it helps. step 2 relocating battery to the front(shudders).

i plan on doing this least expensive to most expensive/labor intensive. so probably heavy duty battery swap 1st, exhaust trick 2nd, rewire 3rd, fpr/injectors 4th and chip 5th.


QUESTIONS: have any trunk mounted battery peeps had this problem be4? also can you hook up 2 batteries in series or will that blow up something?

note: i think the alt may be partially to blame if there is a charging problem and if the battery is the culprit. but 1 thing at a time.

sorry for the long read.

[SappySE107]

RE: HELP trunk battery culprit??

I had my battery in the trunk and the only thing it did to me was not want to start on warm/hot startup. Was an issue with wiring though and didnt affect the engine running at all. FPR should be fine, as should the injectors. I bet those heads are causing problems and perhaps the tuning. I know he never got it tuned 100%. Stock chip might help. If you want to send the chip to me and some money for return shipping, I can check it out and also put the stock fuel and spark and any other values that look way off back to normal.

[Scott205]

Have the battery checked, but most of the power once the car is running comes from the alt. Check those wires, make sure it is charging in the 13v range. Usually wiring around the alt or the alt is the issue.

[dohcfiend]

re-relocated the battery back to the front of the car today using factory wiring...nothing. oh well. next is the exhaust since i have to repair a leak anyway. but after i do the exhaust, i will go through the testing procedures that some peeps told me about on the alt to see what it is doing.

[dohcfiend]

ok broke out the scanner for a capture today but i guess the primitive obd1 does not support this feature.

but i had a theory that maybe the noise from the tranny was setting off the knock sensor? monitored it from the scanner...not a lick of KR.

next i monitored the voltage from the scanner. pretty much a constant 13.8v, so that takes the alt out of the picture.

later i plan on opening up the exhaust and eliminating the cat as a factor as well as replacing the the icm and coils with a known good set i have laying around.

then getting a fuel pressure guage(which i have been meaning to get anyway) and monitoring f/p.

after all that i will look into the chip next week. only other culprits i can fathom are mechanical timing, crank sensor or the ecm itself.

note: i may break down and run some jumper wires and get a voltage reading from an actual meter as well as unplug the knock sensor while i am under the car.

[dohcfiend]

well, not icm or coils.

[Juglenaut]

also can you hook up 2 batteries in series or will that blow up something?

Ahh okay... 24 volts?? Hmm let me think. I would think parallel is what you are wanting to do.

The only way to hook up 2 batteries in series to the charging system is to purchase large diodes and a load manager system.

Starve the engine of fuel at mid throttle and see if it throws a code, pull the map plug at idle, pull map vacuum, tap the IAC, unplug the TPS and try to start it does it start fine or hard to start and maintain idle? Unplug the O2 anything change?? Plug it back in and tap the O2, anything change, pull the chank position sensor plug, does it stall and restart sort of normal and still runs decent or does it do nothing.

Basically what I am trying to say is force the ECM into fault to see if others pop up unrelated.

[dohcfiend]

well i popped off the map be4 b/c he has 3 of the map plugs wired in there. for what purpose i am not sure. i think he said one of them was for a 2bar map which leads me to believe that possibly he has a tgp chip instead of a lq1/5 spd chip. other than that the scanner capture function will not work on this setup and the ecm does not show engine speed but the speedo does.

does the tgp have a 5500 rev limiter by any chance?

[dohcfiend]

almost got it nailed now. uncorked the exhaust and unplugged the knock sensor. does really well. so now i just have to narrow it down between the 2.

[dohcfiend]

think i got it nailed now. hooked the sensor back up with the open exhaust and everything is ok.

only other thing i noticed with the open exhaust is a jumpy idle. i am guessing due to 02 readings and/or lack of backpressure.

now all i have to do is bolt it back up tomorrow after i gutted the cat.

p.s. this exhaust is different than stock, the cat is connected to the rest of the exhaust instead of the downpipe. meaning the downpipe is still installed when i ran it.

[dohcfiend]

captain's log stardate 12.17.05 final entry: got it nailed. it was a combination of a little leak in the plenum gasket(which was about 10% of the problem) and the chip(the other 90%). i got DARTHFIERO to hook me up on that. thanx man.