I have a 1989 IROC 350 TPI with a miss. I have changed the plugs, cap, rotor, wires. Ignition module was bad, replaced that. Fuel pressure is 45 psi, vacum is at 18 and steady. I unhooked the idle air control valve then I pulled each injector lead. Cylinders 5 and 7 have no change in RPM, so I believe they are dead. Is there anything else I can check. Mind you I am not a technician only a shade tree that used common sense.

This all happened at once and initially the car wouldn't start which is how I figured out the module then it missed, did everything else that I mentioned and yeah now I discover this injector issue. Help is greatly appreciated.

Thanks,
Chris

 

24 hours and nothing. Interesting, guess this has got to be a unique problem.

 

Pulling 5 and 7 with no idle change doesn't mean they are dead. These engines can start and idle just fine on 6 cylinders. Are you getting spark on all cylinders? Have you checked voltage on your injectors? Have you checked your timing? Looks like you've got a good start with the things you've changed out. Just a few suggestions. Some of the smarter guys should be checking in soon and give you better direction than I have.

Steve

 

To check to see what cylinder or cylinders are missing, you should keep everything hooked up. That means keeping the IAC plugged in. Dont worry about unplugging the injectors to look for a miss. You should unplug the spark plug wires 1 at a time at the distributor cap. Careful doing this so you dont get zapped. Insulated pliers will aid in this. There will be a very noticable change when you unplug a good firing cylinder. A bad cylinder will have no change or very little change compared to a good cylinder. Doing this will find a cylinder not firing and you can also check the quality of the spark if you hover the plug wire boot over the cap. Good spark will jump pretty far and compare it with a good firing cylinder. Once you know exactly what cylinder isnt firing, we can go from there. Did it miss before you put on the parts or after? Did it happen all of a sudden?

 

History??

I'm assuming, you weren't just driving down the street, and all the sudden out of the clear blue like a thunderbolt with no warning, this just magically appeared out of nowhere?

That would seem to be the clue, right there.

Swap what YOU THINK are the #5 and #7 wires, at the dist cap. Come back and tell us what happened.

 

Thanks guys and keep the suggestions coming. I will pull each plug wire and go from there. I am honestly frustrated and I really want this car back on the road.
I also have a buddy coming over with tool to test the injectors. This is a challenge from going from working on a carb to TPI but it is also 27 year old technology...
Thanks again
Chris

 

NO.

Just swap the ones that YOU CURRENTLY HAVE HOOKED UP AS #5 and #7. Leave all the others alone.

Keep it simple.

 

Be sure to follow up and let us know what you find out.

 

Guys sorry for the lack of updates, its called a 3 month and 3 year old. Yes 5 and 7 were switched around, but the miss is still there. This happened after the car sat awhile and my bad on the reconnect on wires, but the problem was there. Now what?

 

Just for my knowledge, what is the reason to only swap 5 & 7 ??

 

Since you had those wires backwards and since you still have a miss, I would go back thru and pull the wires off one at a time off the distributer and see which cylinders makes changes and which one that doesnt. If all cylinders make a change, I would say that it would be a fuel related miss. Did you check the injectors with your friends tool? Did you test injector pulse with a noid light or did you use a meter to ohm the injectors?

 

Because they're the easiest to get swapped.

The reason NOT to mess with the others, is because the car RAN... at least SOME of them must have been right. Best to start with the most likely, the "low hanging fruit" so to speak, and not take the risk that you might accidentally bollix the whole works.

Now that you found those 2 swapped, fixed it, but there's still a problem, I'd say that the next problem probably lies elsewhere.

Try a new set of plugs. Yeah I know, I read it; do it anyway.

LEAVE THE TIMING ALONE. Timing affects all cyls equally; a miss is various cyl not firing the same, or at all; therefore this proposed "explanation" doesn't fit the facts. (see my signature for troubleshooting logic) All that you will accomplish by messing with it, is to create extra work that once you find the REAL problem, you'll just have to go back and UNdo whatever you did to it.

 

Guys, well the car runs like a champ. After I swapped the wires for 5 and 7 it was still missing. A buddy of mine has an 87 and a noid light. All injectors were getting juice, but still not running right. The car has been hard starting and he noticed my distributor sat different from his. We looked at them and advanced mine. The car idled fine but still not 100% at WOT. decided to put in new gas and throw some Lucas injector cleaner in. After about 4 miles she ran fine. Not sure if my injectors were stuck, but I have put about 40 miles on since with zero issues. Thanks for the info guys it was all useful!
Chris