I have worked on TPI in the past on a c4 vete' but never really had any issues with it, needless to say its a new world for me to troubleshoot.

lowdown: 87' IROC with 101,xxx miles, bone stock, automatic. Engine allegedly has 50,000 on it (stock gm replacement)
recently replaced the MAF as it was bad, no more then 300 miles on the distributor/module in it, plugs, wires

I have the timing set at *6 BTDC as it should be. Its been pinging near WOT but ran fine otherwise.

however yesterday all of a sudden it started chugging at idle and overall it just has NO power at all, it runs like total garbage at the moment. I'm getting a code 43 when I drive it around for a bit. Fuel consumption seems to be WAY up from what It usually is as well.

I put a tech1 on it and it would get 0* of KR even when I could hear it pinging, then all of a sudden it went to 12* and set the SES and stayed at 12* for awhile afterward before going back to 0*

I believe it said TPS was at .70v when I was parked
Spark advance at warm idle in park was about 19-20*

oh yeah the EGR solenoid was unplugged as well for some reason, I plugged it back in and it seemed to have no effect on anything.

to me it seems like I might have multiple issues at once.
I am curious to know how healthy the injectors are, they look to be OEM, I'l have to ohm them out
Knock sensor might not be good??
and possible EGR issues??

can anyone give me some good starting points? I have read that these old injectors are not the best, if they are bad what is a good replacement?

thanks in advance

Does the car runs better when cold? does it gets worst as it heats up? check the plugs see if some of them look ok while others look fouled. I had the same problem and it turned out to be the injectors. I warmed the car and checked the resistance on all injectors and 2 of them were completely gone.

hope it helps

If you have stock injectors they are more than likely multecs. You are correct, those injectors are "junk" LOL, they are very problematic and prone to coil failure. When you check out the resistance if you get a reading that is less than 12 on any of them, do yourself a favor and replace them and get yourself a set of bosch lll's

It runs about the same cold or hot, I'll have to test the knock sensor further. I have my doubts about it working right.

Looks like I'll be pulling the plenum and checking the injectors out, also gona pull the EGR and test that.

From what I gather the Ford yellow top injectors are a good replacement for the multitecs?

thanks for the help, I'll report back what I find.

Got a chance to ohm out all 8 injectors all ohmed between 17.5 and 17.8, seems about right to me, now does that actually mean they should be functioning right?

Did you check them with the engine at running temp? or with the engine cold?

i checked them after it cooled for an hour or 2

Not necessarily. By testing ohms/resistance of the injectors an abnormal reading would be indicative of coil failure. Checking ohms tests the injector's coil windings for shorts or opens in the windings.
However you cannot tell if an injector is clogged/dirty or leaking just by
checking the ohms.

www.southbayfuelinjectors.com
516-492-6504

You should try checking them while hot. Also code 43 is the Electronic spark control (ESC). Disconnect the battery to clear codes, then start the car and leave it at idle to see if code comes up while at idle if it comes up do the following. With you voltmeter check ECM Terminal B7 while the car is on idle, it should read below 6 volts then turn off the car. Now with the ignition in on position recheck terminal B7 it should still read under 6 volts, if reads more you might have a bad ESC Module. If you don't get a code raise the RPMs to about 1600. them tap the engine block near the knock retard sensor to see if the RPMs drop if it does you might not have ESC problem or at least not permanent.


hope this helps

the code never comes up at idle. just while driving.

I'm unsure where to go at this point. I might swap the injectors out, but paying $150+ for injectors is not my bag, anyone know if the older ford yellow tops are good for a 305, I have heard they are rated at about 19lb / hr.

When I get a moment i'll pull the plenum and check the egr and do some more testing on the knock sensor

Finally got a new set of injectors in today, went with a set of Ford/Bosch Yellow 19lb from a 95-ish Crown Victoria or something, same ones that I run in my Turbo GP. made an immediate difference, Car has not run this smooth since I've owned it.

Also checked out the EGR I could push the diaphragm up and put my finger over the vacuum port and hold it in place that way so I'd say its alright, the EGR ports seemed clear of carbon build up. I did find a damaged vacuum line leading up to the TB, replaced that.

That said I still sometimes notice pinging, not near as often now though.

When I get a moment I'll have to check out the knock sensor and see what its up to.

Replaced the knock sensor today. Nearly convinced that my ESC module is bad now, I can smack the knock sensor and not see any knock, And the car has gone back to pinging bad under load or much more then 3/4 throttle. Still seem to be running 20*+ of advance all the time according to the scantool.

Thinking I might be talking to myself at this point, but got the new ESC module, replaced my spark plugs again to date I have replaced:

Distributor/cap/rotor
Plugs/wires
MAF
ESC
injectors
knock sensor
fuel filter

at this point it runs nice, I get a EGR code once and awhile, not really consistent though.
Under most driving conditions it is fine. under WOT near 4000 it will start to ping, not always though. however once it shifts it will ping downright awful and if I don't get off the gas fast enough it will trip the SES - code 43.

it seems like I have plenty of fuel pressure, however I have not put a gauge on it to observe under driving conditions.

Next place I was thinking about going was dropping the fuel tank, don't want to do that if I don't have to though.

Any thoughts before I go crazy?

What octane gas do you run in it? If 87 throw a tank of high test in it and see if the pinging stops or at least maybe gets better.

i've been running 93' in it.

I found that I forgot to plug in the EGR solenoid, removed it tested it for operation, reinstalled it. checked the timing to be sure that it was *6 BTDC, it was.

rented a fuel pressure gauge; at idle around 35psi, under WOT its seeing 40-45, KOEO is around 42/43 psi so I'd be inclined to think its getting all the fuel it needs.

at this point I am completely beside myself. by all rights it should be running just fine. but it still pings under WOT. any ideas?

So since I can't think of anything else to do I started playing with the timing, retarding it made it ping worse, I set it to 0* after that and aside of the car feeling slower it pings less now. No one has any idea? thinking of seeing if I have a spare ecm and swapping that in?

Replaced the ECM, reset the timing back to *6 BTDC. pings still. I give up. I have no idea what this is, apparently no one here does either. I now get why people rip this trash off and dump a carb on it.

Pings worse when retarding the timing...huh??

Check the casting number on the heads. You may have TBI heads since it is a replacement motor. TBI heads won't take the total advance like TPI heads. I posted a advance vs. coolant temp table below for TPI. Just a thought.

It does not make an ounce of sense to me either. The fuel trims are more or less right on, tps seems to be working fine.

lately i've noticed on a totally cold startup it will stumble some and throw a code. I don't know what it is as i've had a few. i'll try once its fully cooled down and see what it is.

Have you tried a different distributor or at least a new distributor module? I don't know why I didn't think of the module before but a bunch of people have had problems with them, even the new aftermarket ones (assuming you have the small cap HEI)

I still do have a few spare modules, the distributor is new reman and came with a new module. I can try that. Also I have not changed the coil at this point either. At this point I'm willing to try about anything.

yeah those modules can be problematic, even when brand new....i remember someone around me had a camaro that wouldn't start and it had a new distributor and a whole slew of other parts, the guy that bought it hit the module with a screw driver a few times and she fired right up....in my experience that part needs to be new not remanned and if you can find an ac delco thats a step in the right direction

I saved the GM one that was in the car when I got it, and I have another new one. So I'd like to think that one of those should work. I have my doubts but at this point....

I put my old GM ignition module on it tonight, the car ran great for about an hour. I let it sit for about 30 minutes and when I got back in it was pinging under moderate acceleration. I can't catch a break. I still have one more new (not gm) ignition module that I could try but I don't even know right now.

My car did this very thing when the injectors where leaking, I pulled the timing down to 10 degrees trying to get it to stop. Replaced injectors and all my problems went away. Things I replaced before I bite the bullet: distributor, spark plugs, knock sensor, gas type, driving style. nothing helped till I replaced the injectors.

I'd go swap in a coil next. Something is causing erratic timing, figuring what that something is can be a b*tch some times (some meaning most). Just don't take it out on the pets

I've already swapped the injectors at this point. I don't want to think that the new ones are also bad, yet. Even if they are used. Right now the coil is the ONLY thing I have not replaced. I even have a spare sitting around too. I'll swap that in after work tomorrow.

I seem to have a way of getting up close and personal with the engine of any car I buy...

I've been thinking... when I first got the car I was having issues with it throwing a code 43 fairly often. I am wondering if by putting in this old Ignition module I just got my old issues back. After the 4th I'll get back to it and swap in yet another module and see what happens. This one seems to have made the issue not as bad as the other one was doing, at this point the car performs ok about half the time.

welp changed to another ignition module, changed to another coil the problem is still there.

I seafoamed the car the other night, made a huge smoke screen, but did not change anything. I cannot fathom what is causing it.

Hmmm. Are you 100% sure the knock sensor and ESC are for a 305? Did you try a different memcal?

I can send you the memcal and ESC out of my 89 (was 305/700r4) if you want to try it. I'd have to look up the pinouts to see if they same.

some folks on the DFI/ECM board told me that my memcal (ACXT) was the proper one for my car. The Knock sensor was purchased brand new from Advance Auto so I'd like to think it is the right one. the ESC module another member sent me, it is a different part number then the original one but swapping it didn't seem to make any difference.

I could try a different memcal/ESC I mean I have nothing to loose at this point. I've changed everything.

I should have looked up code 43 earlier that is a fault in the knock sensor circuit, voltage too high or too low for over 20 seconds.

Some areas to go wrong:
Bad wiring/ground, cracked wire
Burnt out ignition module (use dielectric grease or they will burn out, and fast)
Bad knock circuit on the memcal
Bad ESC/wrong ESC
Bad knock sensor/wrong sensor
Bad injectors


I'd grab an ohmmeter and check the wiring. Here is what I'd do:

Check the knock sensor wire from plug to pin E on the ESC. Grab the harness and move it around a bit to see if resistance fluctuates. Check the voltage, should be 5v to the knock sensor wire when unhooked, around 2.5v when plugged in. Check the grounds on the back of the heads. The brown wire is ground (pin D), black wire (pin C) should have 7-9V and will drop to 0v on knock (tap the block with a hammer with motor running), the pink wire with a black strip is 12v (pin B).

I'll check this tonight, however lately the code 43 only seems to trip if I don't get out of the gas when it starts pinging fast enough.

I think I got it fixed.

Lesson learned, never assume that because something was installed one way is the way its supposed to be.

I was going through the code 43 diagnosis on the manual tonight, the knock sensor wiring seemed questionable, I could not probe it from end to end and get continuity.

Ended up unhooking the fan switch and discovered that someone crossed the fan switch plug with the knock sensor plug at some point. switched them back and suddenly the pinging is gone, everything seems to be behaving normally. Who knows for how many years they have been like that too. Time will tell.

That's great news! I'm glad you didn't give up on it and found the problem. Grats!

I'm really relieved to have it running right for the first time. I guess I at least know my way around a TPI setup after this. I may just take it to work tomorrow if rain stays away.

Great to hear!

Been driving it for a week or so now, only one issue that comes off as odd to me, sometimes when I start it, it will pull a SES lamp for Code 43-ESC. But only the first start of the day. After I get to work and turn the car off it will not come back the rest of the day. I want to say 3 days out of last week it did, then 2 days without then today it did it again. Not sure what gives with that.

Also usually on the first start it will idle up to 1400ish then start to die before it goes back and does the cold idle that eventually comes back down after a few minutes. I need to get a scantool on it and see what gives, could a out of adjustment TPS cause this? I think mine is about .71v at idle.

Bring your TPS down to .54 volts at closed throttle, yours is far too high.

yeah the want the TPS at .54 volts at idle +/- .05 volts

Could this be happening to my friends car too. He replaced all sensors and Fuel injectors. He replaced knock, ign. module, cap rotor, coolant temp sensor, tps sensor, IAC Valve, MAF sensor, and egr valve. Fuel pump was replaced also. Fuel pressure has been checked as well. Can it be the connections that are crossed between the fan switch and knock sensor as well. The car has never ran good since it was bought. The car has no power at all. The car shakes alot and gets worse when you put it in gear. The car is a 90 gta with a 350. Please help.. Thanks

make sure the fan switch has a black wire run to it, the knock senso uses a white wire. It sounds like he might have some bad injectors.

well anyhow I reset the TPS down to .54 that seemed to make the idle nicer.

turns out the code I am getting at startup (sometimes) is a 32 - EGR which seems to point at that temp switch on the EGR. any idea where a new one can be obtained?

I know every other part of my EGR system works, the valve is good, solenoid checked out. that temp sender is really all that is left.

Pretty sure it is a discontinued part although I have found a couple websites that are still selling them (most likely out of stock). I think I have one or two extra, I'll look around in the garage.

PM me with a price if you find one. I did see a new one on ebay listed for a Corvette but at $400 I'd sooner work out something on my own.

If I find it, I'll trade for an EGR solenoid if you have one.