Guntar13

1989 Sport, Auto Trans
Okay so over the weekend i did the 703 injector swap. I got everything in no problems and reset the ECM (three times exactly), and am having some issues with the ride. At first it fired up and really ran like crap; it just kinda chugged a long, so i reset the computer again and fired it up and it sounded a lot better. I unplugged each injector one by one and noticed a change in the engine every time so i know they are firing. When its warmed up it runs decent but seems to be using a lot more fuel (did not notice any fuel coming from the tailpipe). I got in it this morning and let it run for probably 15 seconds and then took off, got down the street and made a turn and it started to bog down and sputter then died. I finally got it rolling again but had to hold the pedal to the floor to do it. After it started it was running fine. I don't know what the heck the issue could be i don't see any leaks in the fuel anywhere. While i was working i took out the intake air temp sensor and cleaned it with carb cleaner and a light brush (never noticed a blue diode in there, more like a silver disc). Also just some background i did a full tune up while i was working on the injectors (plugs, wires, cap, rotor, fuel filter, refreshed some ground connections also) I guess i just need input from people that have done this as to how it ran after they did the swap. Thanks everyone!

ZINGGG

Did you gap the plugs correctly? Did you make sure you had the firing order correct? Did you make sure all boots are fully seated on the plugs? If you did, recheck!

This is like deja vu, because when I put in my 703s, I actually made those same exact repairs at the same time (plugs, wires, cap, rotor and fuel filter). After I reset the ECM, I fired her up and she idled like crap for a couple minutes but was better than ever afterwards. So I'm not too sure exactly what could be going on other than my suggestions above

Guntar13

I will check again, to make sure everything is tight as a whistle, as far as the gap goes .035, just like it said under the hood and in the books, plugs are autolite platinum, wires are belden from napa, accel cap, and bwd rotor, I know it did idle really bad right afterwards, but then after resetting the ecm again it was better so drove it around for about a half hour. There was some hesitation at first from a dead stop but then it warmed up and seemed to go away. I'm almost to the point of just putting the old injectors back in and calling it! Thanks

ZINGGG

If I were you, I'd take back those spark plugs and get some Champion Coppers. That's what the early 4.0s like the best. That might even solve your whole problem right there. It's hard to pinpoint exactly where the problem area is since you changed quite a few things at the same time

Guntar13

yeah, i started thinking about that also, thats what was in it and i wouldn't be surprised if they were the original plugs. (only 127700 miles on the jeep). I might try that tonight. I totally agree about the changing things thats my frustration!

ZINGGG

Yeah definitely try that and then report back! I'm going to assume you will see positive results after that.

gpeade

If you seacrh the threads about injector swaps you will find some posts regarding resetting the ECM. I seem to remeber reading somewhere that a full reset requires 50 colds starts to fully relearn the system. Until the "learning" is complete it's not unusual for it to run like crap.
Not from experience just relaying something I have read.

ZINGGG

I remember reading that too. From experience, however, I only had a REALLY rough start the very first time firing it up after the injector swap. The few times after that it got a little easier, but still started a little funky. But after that, I'd say about on the 5th time starting after the swap, it started and ran like a dream

Guntar13

don't get me wrong it runs good after its warmed up, i wouldn't say its a vast improvement over the way it was, but some for sure. its just the warming up thing that sucks, i didn't have to do that before the swap...

fishtaconc

You may want to check the vacuum line going to the map sensor, for cracks, etc.

Guntar13

Okay so switched to champion copper plugs, it did smooth out the idle some but the warming up problem is still there. Let it go this morning and could hear it idle down where it wanted to die them surge back up to normal idle speed. It didn't do this reptatively just every minute or so till it smoothed out and got warmer. Map sensor line is good tested with a vac guage and no leaks. Bout at my end and just put the old injectors back in!

Guntar13

And the gas mileage is horrible!

cruiser54

Unfortunately, Renix ECUs do not reset like the 91 and later 4.0s. They are not adaptive. Any effect perceived by taking the power away from the ECU and giving it back is imagined.

OP:

Wiggle the injector harness while it's acting up and see what happens. That all got moved during the swap. Did you get teh right plugs on the right injectors?

Guntar13

Im pretty sure i did get the correct plugs on the connectors, any way to tell for sure just in case? Also i pulled the plugs one by one while it was idling and did notice a change in the sound of the engine so that tells me that they are all firing. So your saying that it will take something like 50 warm up cycles to get it to learn the new trim? BTW thanks cruiser on the advice on the grounding refreshing, all mine were "cruddy" and now the intermittent wipers work better than ever!

krazynezz

Your ecu wont relearn.