Driveability problem

[NullHead]

So, my stock L03 5.0L TBI engine was rebuilt by someone other than myself, then passed onto me when I got the car. Well I've had it running for a while now, and when I'm driving, after heavy load (like accelerating in a spirited manner ) a code 43 is set. The engine looses all power and runs a little more rough.

So, I suspect my harmonic balancer could be spun so timing could be off. I have it timed to 2/3 degrees right now and the vacuum went from 18 to 20, 0 degrees and 2/3 degrees respectively, and it idles smoother and has more power ... This engine has headers, and a stock(ish) camshaft in it. Most likely it's an aftermarket stock replacement, or close to it. I honestly don't know what's going on inside the engine.

So my question is this: Will need to have a chip burned just because I have headers and a possibly modified engine? I'm thinking I might need a new prom burned .... and with that, who can recommend someone to help me get it tuned? I got me one of those USB ALDL cables, but I can't get it working. The engine runs great before the code is set, so my guess is that the engine is running good but needs a tune ... any help is appreciated.

[hoogiesngrinderz]

2/3 degrees?

Stock initial timing is 6 degrees BTDC. Make sure this is set with engine up to temp and the tan/black wire disconnected. TBI do not do well with modifications so you could be getting a lean knock.

I think Collins Automotive in Waterford can burn chips

[NullHead]

Hmm stock timing is 6 degrees for a TBI car? My hood sticker says 0 degrees, same as my truck's L03 engine ... The car does WAY better with the timing mark off the timing tab. I'll see if any of the guys at my work can burn a chip for me. It's possible that one of them can ... The can really does run very well until the code gets set. I got a code 42 and code 43 yesterday. Also, no smog or EGR. I have the stock catalytic converter on it, although I know it doesn't effect anything but backpressure ... the catalyst elements are busted inside of it so it makes a nasty rattle sometimes ...

[hoogiesngrinderz]

Forgot that TBI was typically 0* but they usually can run up to 4* initial without knock. TPI usually is 6*

Set the #1 cylinder to TDC of the compression stroke (via plug hole) and see where the mark is. I can burn chips but you need a Moates adapter.

Just to make sure, you are disconnecting the tan/black wire by the blower motor, right?

[1BADAIR]

have you changed the sensor? also check the wire

[NullHead]

No it's the sensor that came on the engine. It has been replace before, as the sensor is nice and shiny, but there's no guarantee that it's the correct sensor.

Yeah I did disconnect the wire by the blower motor, warmed up the engine, and I'm 80% sure that the knock sensor wire is plugged in good n' tight. Knock sensors aren't that expensive, so I might just pickup a known good 305 sensor and put it on just for a known good part. I might have the ability to put it on a scanner today, so we'll see what the data shows.

[hoogiesngrinderz]

I'm wondering why you got a code 43 though...


As for the knock sensor make sure you don't over torque it, 14 ft lb is what I've been told. Make sure that the knock sensor plug is on the knock sensor and not the cooling fan switch on the head (passenger side towards the rear). I think in '91 the KS wire is dark blue and the fan wire was dark green/white?

Code 43 Diagnostics per the manual: System performs a test once per startup to check the ESC system. To perform this test, ECM will advance the spark when coolant is above 90C and throttle is at WOT. The ECM then checks for the signal at B7 to see if a knock is detected. If no knock is detected the SES light will remain on until the ignition is turned off or until a knock signal is detected.

[NullHead]

dude that might just be it! Holy crap I never even thought about that. Funny ... my cooling fan doesn't work by its self either .... I'll run out there and check that right now! Gotta grab a flashlight ...

Also, I think I seen some of the guys at the cruse in front of the Lowes/movie theater parking lot on Gratiot today. You guys have some pretty nice lookin' cars there! Dont know if anybody else seen me, but I was at baker from 3:30 to 5:30 in the back ... but I crused from 2:30 to 3:30ish. I was in this car:


Took that right after waxing/cleaning tires/cleaning glass etc. Had the T-Tops off and everything! What a great day for a cruse

Anyways, I'll let you know if I have those plugs switched or not.

[NullHead]

By George I think I've got it! You were right, the fan switch and knock sensor, or "detonation sensor" as Chilton's wiring diagram calls it, were switched! Dk Blu goes on the KS, and Green/white goes on the fan switch.

This explains why my fan doesn't turn on .... I have to have the A/C turned on to enable the fan .... alright. Initiate test drive. Will report if there is any change.

[NullHead]

Well the code 43 is gone now ... turns out my fan switch would turn on my knock sensor code when the switch decided it needed the fans on. Imagine that! So now my cooling fans work, my knock sensor code is gone, and the car runs MUCH better. I'm glad I stopped putting 91 octane in it ... stuff's expensive. Just filled 'er up on 87 today. Haven't noticed the difference, honestly. The only engine light that came on now was for the IAT ... only because I put a spectre flying saucer intake on it and forgot to move the sensor to the new intake.

Also, for the record, a 5.7L LT1 with a ported LT4 intake and a 5 speed with posi is WAY faster than my poor ol' bird. Just sayin'. My 305 will be a boat anchor some day. I'll drain the fluids, put the block and everything in the parts washer to clean it up, then tie it to a chain and dunk it off of my boat that is waiting for me at the boat store ...

Thanks hoogiesngrinderz for the ideas, turns out I had the wires swapped. Seems like an easy and common mistake to make. I have become better from this situation ...

[hoogiesngrinderz]

Glad to hear it was something simple! Advance the initial timing to 4* BTDC and call it good, you should still be safe from knock with 87 octane.

GM ran the motors very warm in third gens to get emissions down. They ran up to 230 degrees! There are ways to get the little 305 to put out some decent numbers for not a lot of money, enough to keep up with a stock LT1 anyway.

[TylerT/AZ28]

theres a car exactly like yours usually parked on the south side of harrington right by where my girlfriend lives

[NullHead]

Yeah I guess that Lt1 I raced- er, drove quickly right next to ... and then behind ... had a mild cam too. So cam + intake + posi and a 5 speed manual. I actually held my ground for a little while. I'll definitely bump up the timing .. now that I have my air density sensor relocated to my new intake, the car actually runs pretty darn good.

Suggestions as far as cheap L03 upgrades? I'll be getting some new plug wires ... think that'll help any? My premium Carquest brand wires are a little too long, and two of the boots are the wrong style so they're resting on the headers. I'll be getting a "test pipe" installed in place of my catalytic converter too. I think that'll help.

[hoogiesngrinderz]

Yeah I guess that Lt1 I raced- er, drove quickly right next to ... and then behind ... had a mild cam too. So cam + intake + posi and a 5 speed manual. I actually held my ground for a little while. I'll definitely bump up the timing .. now that I have my air density sensor relocated to my new intake, the car actually runs pretty darn good.

Suggestions as far as cheap L03 upgrades? I'll be getting some new plug wires ... think that'll help any? My premium Carquest brand wires are a little too long, and two of the boots are the wrong style so they're resting on the headers. I'll be getting a "test pipe" installed in place of my catalytic converter too. I think that'll help.

New plug wires....50/50. Getting an aftermarket set with all 90* boots may help. Will they help for sure? Not necessarily, but if the current wires are getting burnt and the spark is arching to the header then you will see a miss in the motor.

Test pipe - I don't like cutting out the cat(s). Call me a tree hugger if you will, but a good cat will not restrict a 305. I run a high flow on my heavily modded 355...it might burn out soon with the radical cam I have, but I might move to the east or west cost after graduation so it is necessary for visual and sniffer tests. I have it setup where I can swap it out in 20 minutes.

Cheap upgrades would be a set of LB9 heads with a quick port job on the exhaust chambers, LT1 cam, and 1.6 roller rockers. I'm not sure what cam they ran on later TBI motors but the original cam for my IROC was low .400's lift (aka peanut cam to the third gen community) and now I'm running a radical .575/.585 111 LSA cam I got for free.

What mine sounds like - it is a dog under 2500 rpm, but being a manual I keep it in the band

[TylerT/AZ28]

all tbi cams were low low .400s and crappy if i do say so myself, good for low torque other than that useless up top. LT1 cam should waken it up nicely with 1.6's you could do the easy tbi mods such as porting/polishing your throttle body, intake and heads would be another good start if you have the ability as both dont flow very well. a set of vortecs or tpi heads would work much better than the tbi ones and can be come by for rather cheap. if you use vortecs you need a different manifold and that may result in some hood clearance issues but im not entirely sure.