Nidan/Kelly idle problem

[Bill usn-1]

Originally Posted by Nidan

Bill-
I have been through just about every post i could find on pirate and you seem to have the best and most common sense knowledge about the GM TBI system. I thought i would try to skip all the BS and try to get to the source of the problem.
I hope that you don't mind, and I apologize in advance for just contacting you out of the blue...I will
attempt to give you as much info as possible and maybe you could steer me in the right direction.
OkayHere we go:
First off...I been around GM TBI for quite a while and I have done two conversions in the past with zero problems...I am far from an expert but i do understand the TBI system fairly well. I have been struggling for nearly a month on this and am just spinning my wheels and about ready to give up.
Okay...Here's the background info: I just finished rebuilding a SBC 305 from a 91 camaro...The motor is actually in a 71 fj40 now. I did the assembly on the motor myself and from Top to bottom this this thing is new. Headers and a cam is the only thing that is not stock, the cam is a comp cam with these specs: Xtreme Energy; Camshaft; Hyd. Roller; 1000-5000rpm; Adv. Dur. 258 Int./264 Exh.; Valve Lift .480 Int./.488 Exh.; Lobe Angle 112 deg. Not a very hot cam in my opinion. Anyways, Got the harness from Fuel injection connection, All the stock components are there except for all the smog stuff (no VSS, EGR, oil press sensor, etc) and I run a manual tranny, it utilizes the ESC & Knock. I have a 7747 ECM and chip from Harris performance.
From day one this thing won't idle, it has a terrible miss not matter if the motor is cold or at operating temp, and is running super rich. The only way i can keep it running is to hold the throttle, as soon as i let off it will die. it will also not start unless you open the throttle plates. It will foul plugs inside of 5 minutes. I have performed all the voltage tests on the ecm pinouts and sensors and everything checks out okay. Fuel pressure is at 13-14psi. I have quite a few spare sensors and nothing changes if i swap them out. I have had it hooked to WinALDL from day one as well. The only code it will throw at me is code 33 Recently i got a lean code for the 02 which is weird because it's running so rich...I have checked the vacuum and it's right around 15-18 Hg" but it's very unstable because i can't make the engine idle... at least that's what i think. Regardless of any timing adjustments on the dist it won't idle and it continues to miss. I can't even set the timing because it won't idle on its own...it's all over the place. I pulled the distributor twice to make sure it wasn't 180 out and checked the firing order, I even changed the distributor with a back up i had in the shop. Nothing changes regardless of what i do. I tried bypassing the ESC by connecting B7 to C14 to see if that helped but it didn't change a thing. I did realize that right now i have 4.3 injectors but i have some 5.0 injectors on the way. It would be hard to believe that 4.3 injectors would be causing all of this. I've never been a big fan of throwing parts at something when you don't know what the problem is...Right now I wouldn't know what to buy anyways! I have never had this kind of issue with TBI...I'm totally stumped!!! Any help or info you would be willing to offer would be greatly appreciated! Thanks again.

Kelly

Kelly,
I don't mind helping but I'm out of PM space here.
Log in to binderplanet and I will copy some of the specs over there.

Take a look at the FAQ's there and get me a log and blm.
Lower the fuel pressure down to about 11psi and check your temp and map specs against the data I have in the faq's.
Well go from there.
IIRC the 4.3 inj are larger then the 5.0.
I'll have to look at the FAQ's again....it's been a while.

[Nidan]

Will do Bill...It's raining pretty steady here and not top on the rig...As soon as it quits i will log some data and send it to you. Thanks again.

[Nidan]

Bill, I'm gonna try to log some data tonight if i can keep this thing running...I'll report back as soon as i have some data.

[Nidan]

Bill-

Okay...I can't keep this thing running steady or long enough to log any data right now but i think i may be on to something...

I started up tonight and put a timing light on it, the light starting flickering as usual but then stopped, then started, stopped, etc. until it flat just quit. hooked it to another wire to see what the heck was going on...on some wires it will pick up a spark but it's definitely not firing the way it should be. I also hooked onto the coil wire to see if could get a constant pulse out of the light but i wasn't getting anything out of the coil? How in the heck could this thing be running like this? the only way i can keep it half way running is to keep the rpms up but runs the same and really just wants to quit. Just to be sure the timing light wasn't malfunctioning i hooked onto another known good running vehicle and sure enough it works perfectly.

Obviously it's getting some spark because it will run but as i said it misses horribly so the spark is marginal at best. The motor has a brand new coil & distributor as well as new plugs and wires, although i bet the plugs are nice and black now.

I just checked the coil and it has power...started checking for spark and the plugs are completley fouled...a little carb cleaner and wire brush, they have a good spark...so i gues that solves that. This is killin' me.

[Bill usn-1]

Does it run any better with the cleaned plugs?

What if you unplug 1 injector?

[Nidan]

iit doesn't run better after i clean the plugs it will just run a little longer until it fouls them again...I tried unplugging one injector and seems like it kills one side of the motor, that doesn't seem to help.

[Bill usn-1]

Are you sure your fuel pressure is good?
Need to turn it down to about 11psi and make sure the return line is no more than 1psi.
Are you running any ignition add ons?

[Nidan]

I'll double check the fuel pressure...I think the gauge i have on there right now might be faulty by my doing. I was pinching the feed line at one point to try to slow the fuel, while doing so it spiked the gauge for an extended period. Before i did this it would always read 11-12 psi, but in it's current condition it's reading 14-15 psi, (just not sure if that's accurate) I will get a new gauge an put it on there. I will also test the pressure on the return. I know right now that the return line is 1/4", I have read most people run a 5/16" return. The reason i have a 1/4" line is because the outlet on the return is set up for a 1/4". But even so, if the return had to much pressure wouldn't that raise the inlet pressure?

Also, ignition is all stock...no add ons.

Will report back soon.

[Nidan]

Got a new fuel pressure gauge, turned out the old gauge was off (like i suspected) new gauge read steady at 12psi. I turned down the regulator on the injector pod as far as it would go and the pressure won't go down below about 11.5-11.75psi. I also ran a 5/16" return line into a gas can to make sure nothing was blocked up. it filled up a 5 gallon jug to 3/4 full pretty dang fast...I would say in a couple of minutes, is that normal? Fuel pressure stayed right at 11.75psi at any RPM. It seems to almost instantly foul the plugs. The idle screw is at it's max and still won't idle or really run for that matter. The only way i can make it idle or run on it' own is if i create a huge vacuum leak. I did this by unscrewing the IAC vavle completely. It will idle up pretty high and surge around but it's still misses horribly. I'm guessing that this is because the plugs are fouled. It also gave me a code 33 when i did this. But stands to reason because of the vacuum leak.

On a side note this is with a new...well slightly used injector pod with the correct 5.0 injectors. I'm at a total loss.

[Bill usn-1]

Have you actually done the voltage checks from sheet 1 of the wiring diagrams in the FAQs?
It sure sounds like the map or temp sender circuits are bad.
And with a code 33 you need to measure the map readings against the values in the parts required faq.