no power up top

[RoadWarrior222]

I also have a MSD SCI box with a blaster 2 coil, what are the chances that that would be causing the problem?

80% better than the stock ignition doing it...

[Ondonti]

Still try the downpipe but the MSD = not reliable for many people.

[Big_P]

if it's easier, pull out the O2 sensor and drive it, instead of lopping off rusted exhaust bolts.

[Murphy]

The car has been good lately, but it was REALLY bad last night. At one point I could redline 3rd gear, and 2 minutes later I would hit the wall at 5K in first. I really hate inconsistent problems like this... I haven't tried tried disconnecting the cat yet or MSD yet.

[Sundance 6g72]

when i ran my stock computer with 33# injectors i would get a 10:1 afr (min my gauge will read.. probably even richer than 10) and i could not hit the limiter at all. way to rich

you dont have a wideband? Maybe sometimes your 02 reads correctly and maybe sometimes it does not.. and when the car trys to guess your afr is assumes 48psi and not something in the 50s.. this is just a guess.

[Murphy]

it is possible. The O2 is also decently new. Maybe i'll try the one out of my daytona. I don't have a wideband in this car.

[Sundance 6g72]

i would just fix the fuel pressure for sure then. It should always be too rich when WOT though because the ecu dosnt tune that part.

[Murphy]

so how can I get the FP down? Should I get a new regulator?

[Sundance 6g72]

that would be my guess.

also, your vacuum line going from the fpr to the plenum is in tact right?

[Ondonti]

I don't think any talk about being rich has anything to do with your problem. Don't be too lazy to try the easy stuff but somehow have enough energy to chase your own tail.

[Murphy]

So an update on this problem...

Swapped the rail and regulator with one from the junkyard and the fuel pressure is STILL ~54psi. I also put on a 58mm TB, a plenum without the center divider, 3/4" spacers and spun the intake around.

When the ECU is first powered on (first connect the battery) the car runs GREAT! Once it starts 'learning' it wants to dump tons of fuel. About 2 days in its dumping so much fuel that I've killed the engine hitting the gas trying to take off from a light. I can watch the it idle with my dawes device sitting at blue and occasionally come down to green, which is like .96+ volts at the o2. It seems to be learning better and taking out fuel now, but this whole learning thing is really annoying. I've tried 2 different ECUs, a 93 and 94 5 speed ECU, I might try my stock auto ECU. The only codes have been 12,35,55. 35 is a fan thing...

I noticed my fan isn't coming on. This did happen a few months ago and I figured it was due to my SDS being unhooked. I hooked the SDS up again and it seemed to be working the past couple months. Now the fan isn't coming on again. I have a manual fan switch hooked up and it tosses the code for a bad relay as soon as I hit the switch.

So, I'm thinking since it isn't a consistent problem, its not a restriction anywhere like the cat being clogged. Since unhooking the battery seems to help, I think its the ECU's learning curve. What would cause the ECU to think I need more fuel or pull timing? When I get a chance I will try bypassing the MSD and see if it makes a difference.

[Sundance 6g72]

i think coolant temp sensor will pull timing if its unhooked? isnt that how base timing is set? i never did it.


try running with tps and map sensor unplugged from the harness. same with o2. the car should default to limp mode and run off the table (do this after diconecting the battery)

that might get it drivable and have a spot to start.

[c2xejk]

Have you put a scan tool on the car to see what the ECU is seeing for the O2 sensor?

The fact that it seems to learn the injector pulse width larger, implies that the ECU is seeing a lower voltage signal than the A/F gauge...

[Murphy]

I've been thinking the CTS might be screwy, which would explain the fan no coming on. I think the temp has a large effect on timing and fuel.

I don't have a scan tool, but my cousin should have I can borrow. I really would like to see what my ECU is seeing and try to determine what its thinking.

[Sundance 6g72]

if you didnt flip the plenum, cts change would be easy :P


i ran a chevy temp sensor with my stock ecu when my megasquirt got screwy. it idled really lean until it warmed up, then all was fine. Thats completely irreverent though...

if the fan isnt coming on, id suspect cts as you just stated. but i still think its worth it to force it to rely on open loop. not like it can hurt anything. It makes sense too because the car runs "fine" when you turn it on for the first time after resetting the ecu. so reset it and FORCE it to not learn and trim the map.

[Ondonti]

My scanner sure helped me out.

Try unplugging your 02 also. Then there is no learning. It wouldn't be learning if the o2 wasn't telling it something that probably ain't right.

[Murphy]

I THINK i got this somewhat figured out.

So it seems what was happening, was the coolant was boiling over from the fan not coming on, then the CTS wouldn't read the temp correctly. I would refill it when changing the battery or ECU or whatever, which is why that seemed to help... So now it is running fine, but the fan still isn't coming on. I've been living with the manual switch for now.

The odd thing is, when this problem started last year, I wasn't having a problem with the fan or loosing coolant.

[RoadWarrior222]

Kinda sounds like it's had/got air trapped in there... either that or you've got a funky waterpump fail where it's sometimes moving coolant, sometimes not..... probably due to the impeller being loose on the shaft, or the belt slipping when it catches on the block or something.

[Sundance 6g72]

yeah i think the ecu should pull timing if it thinks the cts isnt reading right

[Ondonti]

Hope your headgaskets are okay.

Time to check the relay system (try manually jumping the relay) etc. See what part of the system is not doing its job.