Cascade Crew

flea · Posted: Sat Dec 24, 2011 9:12 pm Post subject: post swap blues

A little while back we did the great 305 to 305 swap. went from a L03 to LB9. Along with this we changed the computer to -730 and have an aftermarket ebay special memcal installed. Speed density wiring harness, VSS, knock sensor, plugs, cap, rotor, coil, and wires are all new. All the injectors read 16-16.1 resistance.
Engine idles fine, but when given even a little gas it misses coughs chokes and backfires through the throttle body. This was changed to a TPI too by the way. It seems that the ecm is going into limp home mode because it doesn't like something it's being told. . .or not being told.
I need suggestions here, bad sensor? bad ecm? bad memcal?

Speedo has never worked for me, it still doesn't despite new VSS. incidental or symptom?
Oil pressure gauge is pegged off the chart on the high end, incidental or symptom?
Positive firing order is correct, and timing is set at 6*
I'll stop writing now cause you've probably already stopped reading.

Twilightoptics · Posted: Sat Dec 24, 2011 10:52 pm Post subject:

Speedo worked before the swap? Clearly a wiring issue.

What does the fuel pressure do when you give it throttle?

A TBI fuel pump WILL NOT keep up with TBI. It's not designed to run the 40psi TPI injectors need to run properly. If you didn't swap pumps, that's you're runability problem.

Oil Pressure gauge pegged is a sender or wiring issue. That wire is unrelated to the engine, so if you put the new motor in with the sender from the car it should work. If you didn't swap your sender in, likely the sender is bad. You'd need to verify the wiring for it because with it's integration into the fuel circuit I'm not sure how you guys worked it back in.

Limp home mode will show itself by a check engine light. You did wire that back in right?

My money is on the fuel pump until I hear otherwise.

Very Happy

chevymad · Posted: Sat Dec 24, 2011 11:06 pm Post subject:

Speedo's never worked.
Fuel pump was changed with brand new.
Wiring harness is complete 91 camaro piece to go along with the 730 ecm.

chevymad · Posted: Sat Dec 24, 2011 11:40 pm Post subject:

He really needs someone who can scan this thing for him, and give it a good lookover with a new set of eyes. I still don't have a working scanner yet.

aaron_sK · Posted: Sat Dec 24, 2011 11:51 pm Post subject:

I stopped by Jim's place when I was out in Willipa a few weeks ago. It was below freezing, I had no tools with me, and we had to run the car jumped off my truck's batteries so we didn't get far. Rolling Eyes

The car throws code 43 (ESC/knock sensor) and one more that I don't remember (I think it was O2 lean). The codes don't throw immediately, it takes maybe 20~ seconds before they come up. I pulled a couple plugs and they looked very white but they were consistent.

He's running some sort of backdoor PROM he bought from some guy on eBay. This guy claims he makes them out of V6 730 chips and he removes the knock sensor stuff from the chip. The guy also claims that the limp home mode is still the V6 setup...? I smelled fish (might have just been the harbor Razz

) but without any datalogging or ability to read the chip I can't say.

I think the car needs to come back to civilization for a fuel pressure check, and a known-good ECM and chip installed to make sure Jim didn't buy some fleaBay snake oil.

91RSVert · Posted: Sun Dec 25, 2011 6:01 am Post subject:

I agree with Aaron.

Twilight had good suggestion, but thats been taken care of.

My oil pressure is pegged tell the car warms up, then it goes down to about 50-60 when warm.

Speedo, depeneding on year/motor of car, there is a vss buffer box that goes under the dash. That could be bad, or missing.

flea · Posted: Sun Dec 25, 2011 8:32 am Post subject:

The car is a 91, it does have the buffer box. According to all I've read the -730 ecu needs 4,000 ppm to work properly while the buffer box effectively splits this signal between the ecu and the speedo. However with the SD harness does have a tail that goes to the VSS and nothing that goes to the buffer box (I think) so unless I got lost somewhere tracing wires, the buffer box should be out of the loop.

The speedo never worked, always assumed it was the sensor, but now with a new parts store unit in there it still doesn't. Unless that is a possible cause of it running bad. I'm too too concerned about the status quo right now, so if that is an unrelated problem I won't worry about it right now. I'll probably kick myself for letting Gabe's dash get away if it's the speedo it's self, but thats another topic.

Is there someone going down to the holiday get together that wouldn't mind swinging out of the way that can datalog? The way it sits right now, the only way the car will get to civilization is on a trailer. If thats what I need to do, thats ok but it's so much easier if civilization can come here for a few minutes.

BTW. Merry Christmas everyone.

91RSVert · Posted: Sun Dec 25, 2011 9:38 am Post subject:

My understanding of the way the buffer box is wired..

The vss goes TO the buffer box. It splits it between cluster, ecm, cruise.

This will cause a few driveablity issues, but not the ones you mentioned. So we can put that to the side for now.

flea · Posted: Sun Dec 25, 2011 9:50 am Post subject:

It goes to the buffer with the stock harness, but does it still go to the BB with the SD harness?

aaron_sK · Posted: Sun Dec 25, 2011 9:52 am Post subject:

The buffer box is not important!!!

As Brandon just said Jim's speedo has never worked.

The buffer box is still under the dash but is not hooked up and is not needed because he is running the later speed-density setup in which the buffer box is built into the ECM. What he needs to do once the lean issue is fixed is tap the speedo-out wire from the ECM to his gauge cluster.

Currently the VSS harness is properly connected and the ECM should be getting VSS signal.

Further, it would throw code 24 if it was not correctly hooked up and it does not. It is possible that the ECM is not seeing the correct speed but that would not explain all the issues he is having.

This is a red herring. The issue is that the car is either not getting enough fuel (due to lines hooked up wrong, DOA pump, bad injectors, faulty ECM, ect.) or the spark is totally wrong (bad ignition module in ECM, crappy chip burn, ect.).

flea · Posted: Sun Dec 25, 2011 10:03 am Post subject:

And back to wanting to check known good ecu and known good chip.
It could be DOA pump, god I hope not. I will check fuel pressure as soon as I can.

aaron_sK · Posted: Sun Dec 25, 2011 10:06 am Post subject:

Does Red have a gauge you can borrow?

flea · Posted: Sun Dec 25, 2011 10:13 am Post subject:

dunno. bet he has one i can buy, they only 40 at summit, so they can't be too much even at Red's Emporium of Auto Parts

Twilightoptics · Posted: Sun Dec 25, 2011 1:36 pm Post subject:

You still need to put a fuel pressure gauge on it.

And if that checks out, then scan tool.

Have you verified that the speedometer itself works? Sounds like chasing a tail without proper confirmation of parts.

chevymad · Posted: Sun Dec 25, 2011 1:55 pm Post subject:

I'd like to see if the scanner shows mph myself. If so you'll know the sensor and wiring to the ecm are working. I'm betting the speedometer is busted. Still not the real issue. Need to get her running correct first.

flea · Posted: Sun Dec 25, 2011 2:15 pm Post subject:

Alphius · Posted: Mon Dec 26, 2011 11:56 pm Post subject:

My gut feeling is that a new chip would straighten it out.

eBay dude sounds sketchy as hell.

BluFbdy · Posted: Tue Dec 27, 2011 2:10 am Post subject:

Yeah vtekstore or whatever his name is? Fishy. All my research showed hit or miss with those, this may sound retarded but do you have the right knock sensor? The 730 needs a specific one according to what I've been told and idk any way of identifying one from theother beyond p/n's

flea · Posted: Tue Dec 27, 2011 6:31 am Post subject:

I don't know if it's the right one or not. I wasn't aware that the 730 needed it's own short bus version. The engine is an 88, so it makes sense that one was wrong, but I don't remember if the one I bought was for the 88 motor or for the 91 car. either way it sounds like it's wrong.
More research is on tap to find the correct 730 knock sensor I guess.

aaron_sK · Posted: Tue Dec 27, 2011 7:59 am Post subject:

That's some interesting info on the knock sensor. I was under the assumption that only displacement changed the knock sensor, not ECM.

Read this:

http://www.eecis.udel.edu/~davis/z28/ecm_swap_730/165KS.txt

Not so much his info about putting a resistor in it, but his info on the resistance difference. If he is correct you should be able to easily check what KS is in the car.