Thread: I have a miss. :(

It appears that number 3 isn't gettin enough fuel. Ill list mods quick.

Accell injectors 15lbs part number 0101128 they have about 6 races on them.
1.6 ratio crane roller tip rockers.
Custom cold air intake.
Custom duel exhaust, exits just under the car.
Gasket matched intake and heads.
180 degree T-stat.
Removed EGR valve.
It has stock internals except whats listed, have to run the automatic trans.

Now to the problem. The car has been perfect up until 2 weeks ago. I was running the feature, and with about 3 laps to go we had a caution. As we ran around under yellow, the car started to miss. It never got any better, went from leading to finish second, to a ffffford.

Well I pulled the plugs the next day and the number 4 cylinder plug was snow white. (I run bosch platinum) So I chenged the plugs, changed fule filter, and ran injector cleaner through it. Took it out this past Friday and it idled fine, ran fine, till I got about 4 laps into the heat race, then it started the miss again. Same thing in the feature. Pulled the #4 and 6 plug, 4 looks a bit light, but they really didn't have enough time on em to get a good color. So i changed the injector and put a different throttle position sensor on it since my old one had the tab missing. Started the car afterward, and let it run, was smooth during idle and reving, but when I tested it in front of the house after it warmed up, it started the miss again, I really noticed it if I power break it at about 1500 rpm.

I am wondering if maybe the coil packs are going out once they heat up a bit? Thing I don't quite get is the plug color. Maybe I should run a conventional type plug?

From the plug diagram I have, it says plugs are getting too hot. (Recomendations) Check for the correct plug heat range, over advanced ignition timing, lean fuel mixture, intake manifold vacuum leaks, sticking valves and insufficient engine cooling. This is what my book is saying. Hopefully it helps you.

Stock is 32lbs (thanks brian for refreshing my memory) Do you know wich injector could be messing up causing the lean condition? Thats what i was asking. But again the pcm has to be reprogramed when changing the injector size.


If you dont know wich injector it is then you could be changing out a good one for another good one...


Try the coil packs and let us know

It is 4, all the other plugs looked normal.

I looked all over for stock injector lbs and couldn't find it. I have no idea where I got 16 from I can't find it again. I'll let you all know how the coil swap goes.

Not sure where in my area I could get the PCM programed I'm about the only one that knows much of anything about these engines around here. If it's not a SBC with a carb on it, it's foreign to them lol, The info I had was very little except what I have tried on my own.

TDC might can give a little better insight on this, but you could talk to Will at overkill and see if he could help you out with your PCM. Not sure what he'd charge, but he's a member on here. WillOverKill I beleive is his screen name.

At the risk of sounding like a idiot, what are L67 and L32?

While I have ran the car for a year, I really didn't delve into the performance part of the engine till I had to replace stuff like bad injector, so I bought a whole new set. Unfortunately it appears I wasn't armed with near enough information. Maybe I should just pull the Accell's and get some stock ones from Autozone for now?

Something that I didn't mention in any of my posts was what the engine was. The car is an 89 GP with the 3.1. I don't know if that makes a difference in injector sizes or not.

Another quick question, if I ohm out the injectors will that determine which one is bad? I read that above 12 ohms is acceptable. Is that right?

Originally Posted by Doug_Guilds

Something that I didn't mention in any of my posts was what the engine was. The car is an 89 GP with the 3.1. I don't know if that makes a difference in injector sizes or not.

Wow. Well that would be an obd1 system wich i dont know anything about. And the 3.1 I also no nothing about.

At this point after reading all this, it could be a PCM problem. If you think about it, you've changed the most likely culprit parts....it might be time to put in a new computer to see if it fixes the issue. I had an 88 olds that had the exact opposite problem, it was over fueling the #3 cylinder...changed plugs, wires, coil pack, and injector because I thought the injector was sticking open. Turned out the PCM was bad. Those things can be goofy sometimes.

Ok guys Thanks for all the info and help, I am going to change the module, just for kicks since a friend of mine has one he's gonna give me, then probably head into the PCM since like Reptile mentioned it's about the only thing I haven't tried yet.

I'll post back when I get this stupid thing straight, and let you all know what fixes it.

Oh hey quick question for anyone that may know, would a PCM out of a mid 90's model G/P with same engine/trany work or should I just order one?

The PCM from 88-91 shows to be the same, however, I would take the Eprom out and keep the original one with the car. Those are different, and can be a ton of varieties.