Ok the car is a 91 formula tpi. Car runs, but stumbles and misses a lot, sometimes runs ok, sometimes it hardly runs. I know i need new injectors. Im also getting code 43 and 44. 44 is lean exhaust. I know that could be from the injectors. But what about the code 43? Could it be the knock sensor or the distributor? is there anyway to test these? thanks!

 

I think Code 43 is Knock sensor related. Mine throws this code when I put the pedal to the floor and get up over 3-3.5k rpm.

My problem is the wire/connector, I'm just lazy and don't want to **** with it haha. I'll probably mess with it tonight though...

 

If you haven't done it already, put a new o2 sensor in it. It's probably old and worn out causing your engine to run lean which is probably causing the knock (code 43)

 

Hello codes suck - but I can help code 43 is - Electronic spark control - Probanle cause's are , Poor electrical connection, open or short in circuit; defective ESC module; defective Knock sensor ; defective ECM and for code 44 Lean exhaust ,probable cause's are , lean condition caused by malfunctioning carburetor/fuel injector , vacuum leak . low fuel pressure ,etc ; poor electricalconnection ,open or short in circuit ; defective Map sensor; defective oxygen sensor ; defective ECM . I would also replace all plugs and wires ,coil/ maybe see what the cap ,rotor and distrib look like and maybe replace them if need too be also have the cars timing checked and possible pressure / compression check etc if problem cant be fixed , also hows the trans cuss a trans will make a car run out of wack hope ive helped u yoURS streetdemon -z28

 

lean code is def the injectors. The ohms are out of the ballpark. all between 5 - 19 ohms. im ordering new ones. Once i get that taken care of it should run better and should get rid of lean code. Then just the knock/esc to work on which shouldnt be TOO hard...if im lucky. So besides wiring, connector, and o2 sensor, any other circuits or wiring i should look at? how many volts should the knock sensor recieve(91 style sensor) and how many ohms should the sensor itself have? how can i test or tell if its the ESC inside the computer? thanks, Joe

 

Tech on the knock sensor

https://www.thirdgen.org/forums/tpi/...tml?highlight=

 

that would make sense if they are switched around because my fans are hardwired on ALL the time and my gauge doesnt work(is it the same sensor?)! Im betting someone messed with it, or since it has a new engine the installer/s got it wrong, then hardwired the fan when it didnt turn on anymore, and then pulled the engine light bulb because it was always on. Also I unplugged the battery for a while to charge it and i started the car today and immediate light with the same 2 codes again. Im gona have a look tomorow. So that means the ecu is registering a knock sensor error right away and before any knock is actually detected.

 

Both sensors are single wire right? I found one unplugged brown connector that is smashed and melted. Thats probably my problem! what color is the other? And is there a good way to see down there without taking the exhaust off? I cant get to the ones in the block/head

 

Your knock sensor is on the pass side of the block, you really have to be underneath the car to get to it, sorta sit above/around/over something (been awhile) buty is a round-metal looking thing...can't miss it if you spot it

I agree with the above post about changing the 02 sensor...thing with an O2 sensor is they monitor Oxygen...so as they get older and "foul"-like a spark plug, they get a bit sooty...so, now they don't see enough Oxygen to give proper feedback top the ECM...so the ECM interpets this as "Lean" and pumps more fuel...so, you can have a code 44 lean, and actually be running real rich...pull a spark plug or two and see what it looks like. If sooty, then you're running rich, but O2 sensor is probaly shot and giving bad (for ECM calculations) info.

 

PS...

On a cold start, say tomorrow morning (since it'll be saturday, and maybe your day off from work), clear the ECM by disconnecting the battery again, reverify you only have the "12" poppping up...

Now start the car and let it run for just a minute or so...shut it down and recheck codes...

Thing is, the "44" should NOT be present (unless you've wired in a heated O2 sensor), since the ECM waits for the O2 voltage (and time) to start looking at it and count the O2 crosscounts to determine lean/rich as wella closed loop operation...so...if after only running the car (from a dead cold start) that you immeaditaely get the code 44, I'd be thinking ECM...since it'd be "hard wired" to fail for the 44...also, I think your code 43 is either the off-wire for the KS, bad KS or bad ESC module.

 

Ok thanks ill try that tomorrow. I already ordered the injectors. And i dont think the ecm is hurt because it pops up codes consistent with other stuff. Like when i was messing around with the tps voltage i started it and reved it a little and the code 22 came up. Is there any real way to test it? I think either the ecm or fuel pump is gone in my 2.8 v6 too so i need one of them to run!

 

A little update for my old post, I got around to changing the injectors, and now im getting a code 42 and 43. I have to change the knock and oxygen sensors but i dont have a lot of extra time for this car. Its not my DD. It has a full tune up, new injectors, and all on a brand new long block from jasper. Its still missing/low on power and back firing like its running really rich, but it cant be the o2 because its doing it as soon as i start it up. What else can make the MAP cars run real rich? or just bad in general, in open loop mode? It has all new intake gaskets, no vac leaks, also. I also just thought that maybe the egr is stuck open, but wouldnt it register a code for that? I also need to check my fuel pressure

 

Is your jasper engine totally stock? Map systems rely heavily on manifold vacuum to determine fuel and spark delivery. A larger cam may throw off the readings enough to affect the way the motor runs if your still using the stock chip

 

it was the only part number they had for the 91 tpi when i looked it up on the website. I have the receipt ill look for it tommorow. I believe they use all stock/stock spec stuff. Is there any real way to test if the ecu is fried or not? the car wouldnt run at all right?

 

well i basically went through the flow charts for both codes and they end in faulty ecm. so i guess ill be replacing that now! I pulled the ecm out to check it out and it is a service number 16198262. is this correct for a 91 firebird formula? it also says remanufactered for ac-delco so i think this was messed with before. is there any way to determine if this is the correct box or memcal? or what tests can i do to it to see if it is still good and not a wiring problem? thanks!

 

bump?

 

Factory ecm for 90-92 SD TPI cars was the 730 ecm
Yours is aftermarket so there is no telling by the number
Remove the cover and read the MEMCAL number

ECM test
Since you pulled codes, Part I is out, here is part II


If you suspect the ECM is at fault, go to a junkyard and get another one
Thankfully the 730 was used in nearly all GM V6 cars around that year
https://www.thirdgen.org/forums/diy-...30+application

Just swap in your memcal and go

 

Ok so i did this test...
http://chevythunder.com/EST_code_42.gif

the terminals they state are for an older car. I had to use c8 and c7, instead of d4 and d5.

I got some weird resultes. I think its pointing to faulty ECM. I got .3m(?) Ohms from white(c8) to ground. And .284 volts. With the 12v on c7, the resistance went up to 3.08k ohm. When i unplug the EST plug, the white wire(c8) is open. So thats not shorting out. I dont know what .3m Ohms are. miliohms? so very low? and 3080 ohms isnt quite >5000, so does that mean yes or no? This just brings me one step closer to swapping it to carb!

 

well i decided to cast away codes and the internet for now and i went out and did some pulling apart/checking/reinstalling of everything. Plugs looked good. All wires ohmed/looked ok. IAC and idle checked and adjusted. knock sensor ohmed good, but the line had 12v. Doh! it was the fan switch plug on there. the knock plug was melted. So i cut the fan temp plug off, soldered it to the knock sensor wire, and that was good to go. I have my E fans on a relay with a toggle switch, they didnt work when i first got the car, soon to be replaced with an adjustable thermo switch setup. Im looking for around 180 for fan 1, and 185 for fan 2 maybe, with a 170 deg thermostat. Next, The code 42...the distributor cap screws are stripped somewhat. enough to hold it on there, but it was making shitty contact. So i clamped it down with 2 vice grips and it ran great, no codes. Thanks to everyone who helped! im sure ill have another problem with the car soon enough. Off to replacing the distributor!

 

Couple of tyhings here...

#1...don't replace your distributor just yet, you'll get a code 42 everythime you disconnect the EST bypass connector to set the timing...it'll (code 42) stay stored for 50 or so starts of the car, unless you disconnect the battery.

So, if the Code 42 is still there, then make sure the EST bypass is connected, it's a tan wire with ablack stripe (IIRC...been a looong time since i popped the hood on my IROC).

#2 the fans...

I assume your description about the fan plug thing was also on the passenger side of the engine, up between #6 and # 8 plugs on the head? if so, that's the 2ndry fan switch...the ECM controls the primary fan relay, but if you cange tht 2bndry swutch to a on 200/off 185, you'll be good for go with a 170 T'stat...on the MAF cars (least my '89) when the fanswitch activates, both fans will turn on...this is great for cruise/stop and go tarffic as the engine never gets over 200.

#3, the switch ni the driverside head between #1 and #3 plugs, is not a switch (like on the other head), but a sensor...it just changes resistance and tell the ECM what the coolant temp is, so when the coolant temp reaches the setpoinbt in the PROM, it activates the primary fan only...iirc, it's in the 225 range...so, in effect, if you just change the 2dry fanswitch, you're killing two birds with one stone, and still have the ECM backup on the priomary, in case the 2ndry switch fails.

Now, depends on who rewired the switches and what they actually did, and if they did it correctly.
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Forget the typo's, I'm too lazy to edit

 

Which of these sensors runs the gauge inside the car? Basically the temp sesnor and knock sensor plugs were switched, on the passenger head/block. How many temp sesnors are on this car and which does what? I thought the one on the passenger head turned on the fans...and on the TB was for the ECM...What your saying is totally different than what i thought. There is one on the driver side head that tells the ecm? so what does the TB coolant sensor run? Shed some light please....and thanks for the help again!

P.S. Edit - The fan harness was cut when i got the car, so i hooked up each one with its own relay. they are on toggle switches now, but im going to buy or wire up my own thermostat and replace it with that. My temp gauge isnt working(hence the coolant sensor questions) so i have just been turning them on after the heat in the car starts to get warm. it never gets hot, so i guess its never really warming up. I am planning to fix all of this before i put the car back on the road! cant wait for that

 

You're correct...I goofed, the sensor in the driver side head between #1 and #3 plugs, is for the gauge...the sensor in the front of the intake is the CTS, and is what the ECM uses to determine temps, sorry for the mis-info...one too many Coors

The sensor on the pass side head between #6 and #8 is the 2ndry fan switch...this is the one you replace to lower your fan turn on temps.

As I mentioned before, this switch (on my '89) will control both the primary and secondary fan relays...i/e both fans turn on and off at the same time (my switch is now an On-200 Off-185) and both fans go on and off at the same time.