quickcat

So to solve a high-speed miss/backfire I have, I replaced:
1. Northstar ignition module (part of Delteq kit)
2. Coils
3. Wires
4. Spark plugs
5. O2 sensors
6. Fuel pressure regulator (found it leaking and believe it is not related)

I feel that the injectors (that have about 200k miles on them) are probably not working as they should. I am reading rich though at WOT throttle and the computer is trimming for rich conditions at normal driving.

I just can't think of anything else though. I am going to try to do a balance test tomorrow night to prove it out.

Any other suggestions?

Matt

Pwnage1337

You could clean the plugs, or install new ones, do a WOT run, pull them and read them to see which injectors are leaking.

Just a thought

jfb

Miss and backfiring is caused predominently by spark timing. My money is on it going away when you put the stock ignition back on the engine. There are aftermarket ignition components because those people want a much higher income. There isn't anything wrong with the stock HEI system.

0Paul Ruggeri

200K is lot on a set of injectors. Have you checked them with an ohm meter?

383tpi

pfft 200k is a lot on injectors, i have 168 on mine and they work as well as they did when they were new

jfb

An ohmeter will only find gross coil failures. An ohmeter cannot show a turn to turn short and injectors work with pulses and cannot work properly with a turn to turn short. A qualitative test on coils can be done with an impedance bridge. Impedance bridges measure the inductance and Q of coils. I found a bad injector that had half the inductance and half the coil Q, but an ohmeter showed the same resistance as all the other injectors.

CFI-EFI

Did any of those many parts test to be defective, or are just into throwing money at the problem. Keep trouble shooting and only replace parts that prove to be defective.

Race on!!!

corvette95

until you replace them and say wow what a difference

jfb

I own an 87 Corvette with 238,000 miles on it, I drive it everyday and the injectors were replaced about 40,000 miles and my engine runs like it did when new.

JrRifleCoach

200k is a lot of time on a set of injectors.
I installed a new set of Five-0's on my 86 and a set of FIC's in my 92.

Performance (overall) was greatly improved!

You will say WOW, why didn't I do this in the beginning?

RetiredSFC 97

Until you ohm your injectors and doa fuel pressure test I will not second that emotion

quickcat

So you are saying that there is NOTHING wrong with the optispark design? I disagree. My car ran better after I put the Delteq kit on and I understand that replacing the opti would have had the same result but I chose not to take my engine apart to replace a part that was located on the engine with poor judgement.

Matt

quickcat

I agree completely, and have tested the following:
ignition module (failed but did not fix the problem)
spark plugs were definately past due for replacement
O2s (were reading a bit on the lean side when my nose said rich, follow-on data supports this..... 80,000 miles, they were due)
fuel pressure regulator (fuel in vacuum line and hard to start.... definately bad, I think this developed while I have been troubleshooting the miss)


Now, I have no way to test coils for high speed operation at hot temperatures. I replaced them blindly against my better judgement. The wires could have gone either way.

I am going to try to get a balance test done on the injectors before I replace them but I don`t have much time. I have a road trip coming up and don`t have access to a test kit like I used to. If the auto hobby shop here has a kit I can use I will be ok but if not I will have to change them and go..... there isn`t much left.

Matt

quickcat

That`s what I figure. I am looking at getting a set of FIC design IIIs. With the mileage I have on the stockers it is probably worth it anyway.

Oh and to answer the others who are talking about resistance/impedance..... I measured the static coil resistance and they are all just above 12 ohms (12.1, 12.4...... 12 is the bottom limit) but one is 13. I do not have the equipment to test them dynamically to get an impedence reading. If anyone in western Ohio wants to lend me an injector test bench I would make good use of it.

Thanks for the inputs.

Matt

jfb

You still have an optispark on your engine! The OP installed a Delteq ignition module and he still has a miss. That doesn't speak well of Delteq now does it?

corvette95

"LEND" you a bench test injector kit? Not exactly that easy! I although WILL bench test your injectors free if you mail them to me.

Mo_Bandy

Perhaps a long shot , but... Could your fuel filter be plugged? Leaning out under high fuel demand?

Just a thought .

MO

quickcat

Now let's take it easy here...

First I am the OP.

Second, I am well aware that the Optispark distributor remains in place on my engine AND serves a critical function. I am familiar with its operation. I also know that I do not have to remove my water pump and crank damper to change the cap and rotor, which should be done every.... let's say 50,000 miles or so....and the worst part is that the whole thing gets replaced and it is very costly. The cap and rotor for the ones that can be changed out are very expensive. Yes I know many run longer, but that ends up being the problem. Carbon buildup from ionized air finds its way to the optical triggers and interferes with its operation, reducing performance or disabling the car all together. Not to mention the loss in delivered spark energy that results from the buildup.

I noticed a performance improvement after I installed the Delteq. Not because it is a super high performance gadget off of a Formula 1 car.... it was delivering spark that didn't have to travel through a layer or two of carbon. That tells me that there is significant buildup in there.

I am happy with the kit and have ruled it out as the problem at this time. I changed out the ignition module (Cadillac Northstar type) because it failed a test. I did the coils because it seemed the next logical step. I had sourced all those parts from the junk yard when I bought the Delteq "bare bones" kit to save a buck and was good for me at the time. It seemed logical to replace them despite the fact that they have given me loyal service for years. The Delteq parts are functioning rock solid.

There is however a small chance that the Opti is acting up. I don't think so because I am not getting codes.

I do get injector bank and driver errors when scanning with TunerPro RT. No codes though.

So, please don't claim that the ignition on the LT1 and LT4 is without fault and nothing can improve on it. That is clearly not true.

After saying all of that I do have to say that I think the Opti is an excellent trigger for the ECU/PMU as long as it can remain clear of debris. Combining the high voltage with it in such a hard to get to place is just poor judgment.

Matt

quickcat

I know it is not that easy..... I was speaking with some sarcasim... I know it is hard to tell from text. Maybe I should use these silly faces...

I would send you my injectors, but I think bench testing them is just gee whiz at this point. I am going to try to get balance test on them if the auto hobby shop on base has the tools for it. Beyond that I do not have the time.

Seriously..... what do you think the chances are that a set of factory injectors with nearly 200,000 miles on them are operating perfectly? If you have a test bench I bet you have some good insight on this.

Would I really want to pay to send you a set of old injectors and pay for your time to set them and find out "yup they are f'ed"?

I am not trying to be snotty just realistic.

Matt

quickcat

Good idea but the data I am seeing is showing rich running at wide open throttle.

I changed it about three years ago but I will probably do it when I do the injectors just for good measure.

Matt