KA starts then dies soon right after. halp!

[enerj]

Vehicle background; the car/engine/harness /ECU are all from different places unfortunately. Regardless, I need to get them working together like champs.

Mods; everything is nearly stock. I have an EGR blockoff plate and I am running just headers now until i get this thing running.

I had the injectors cleaned/serviced although they recommended I put them right back in and run them because they can lock up, but I took a few months before I was able to run them. I have new sparkplugs as well but not cap/rotor.

Problem;The vehicle has a bit of trouble starting and sounds a bit off but then it will usually start and revs will jump to 1500 rpm. If I don't play with the throttle to keep the revs up, the revs will quickly drop to 0 and the car dies.

There is no idle period. This has made it difficult to even check any sort of timing. The compression has been checked on the engine and it is all good.

Diagnosis;The ECU is throwing IAT sensor code and IACV code. The IACV code is the only thing I could imagine related to my problem, but I don't think it could cause something this severe.

What I want to do (and hear opinions about this) is check that all the spark plugs are getting spark and all the injectors are firing. Spark test is easy enough, however the fuel is a little complicated. I know I could use a stethoscope, however seeing the injectors squirt would be more reassuring. Anyone ever pulled the rail while it's still hooked up and just shot it into a bucket?

Aside from starting with these 2 things, I'm a little stumped. Do you think open headers could be messing things up?

Any input welcome!Thanks

[Razi]

Perhaps the engine and ECU aren't compatible with each other?

But, I'm not sure since you didn't mention the year of the engine and ECU, but if I were you, I would check the IACV (Idle Air Control Valve), that is what lets your engine idle.

[enerj]

Thanks for the response Razi. I have two ECUs from my days of throwing money at this beast. I mostly use the first one, although I have plugged in the second to check if the ECU was a problem.

First ECU3C - A18-B92 G21 95 240SX N M U OBD2 S14-KA24DE 23710-70F01

Second ECUCA - A18-E27 G49 96 240SX N M U OBD2 S14-KA24DE 23710-?????

These results were returned from the JWT list. The only thing I can think off is that my car is a 95' OBD1 S14. Both ECUs state OBD2. Could this be an issue?

Going back to the IACV, the pages covering it are from EC 110 - 114 in the FSM. One of the diagnostic procedures calls for me to idle the car for 30 secs and do some things, obviously this isn't possible.

However I will go through the other portions of the instructions to see if I can find anything. Although the IACV may be causing some problems, I can't imagine that they can be this severe, can they? Wouldn't it have to be a terribly big leak through the IACV to have the car not even able to idle?

I still think I have an issue with my fuel/ignition but I will get a friend to help me with that and make sure all injectors and plugs are firing.

Lastly, I bought a cap and rotor from pepboys. The strange thing is, when i just play around with the cap and rotor without the actual dizzy, I can see that the middle point in the cap can't touch the flat metal part on the rotor that feeds the voltage to the plugs. The plastic part on the rotor is too tall and hits the plastic of the cap before the springy middle contact in the cap can touch the rotor. This isn't correct, right?

Thanks again!

[Razi]

If your engine and harness is for ODB1, and you run an OBD2 ECU, you would run into problems.

As for the IACV, it could be jammed shut and malfunctioning and not letting any air into the engine, thus only being able to idle by revving the engine via the throttle body.

As for the rotor and cap, I'm not exactly sure what you're having problems with.I replaced a rotor and cap for my S13 and they were parts from Pepboys, and I haven't had any problems.But, the S14 dizzy and S13 dizzy could be different.

So is your engine a S14 OBD1, and ECU for OBD2? How about the harness?

I'm not all that knowledgeable about compatibility between OBD1 and OBD2 parts so hopefully someone wiser than come in and lend some advice.But so far, it seems like the IACV is the most likely culprit.Try removing it and cleaning it with carb cleaner.

[sfoster]

Try removin the iacv and get a plate to weld over that spot. You be able to set your idle at the throttle body

[enerj]

Won't this hurt the cold idle? Good suggestion though, I may try it to eliminate possibilities, despite the welding part

[rioredstang]

I don't know if obd1 and obd2 will work. You will need a pin voltage chart from each of the 2 ecu's and compare pin locations. They may have moved a few wires around and this is probably why you have iacv codes. You need to find out the ecu issue before you do any other daignostics. If the computer is not working correctly it will lead you in the wrong directions.

[enerj]

Very true, I don't want to waste time with this. You're saying only locations may differ, not voltage values, correct?

So I should compare pin locations between an OBD1 and OBD2 ecu?

When I work on her saturday, I will start with the IACV harness/unit trouble shooting guide in the FSM. I guess I need to use OBD2 fsm.

[rioredstang]

That is correct. Valves should stay the same, but the wires colors and locations may be different. A pin voltage chart in Mitchell has the wire color and value for each pin on the ecm connector. You should print them for each ecu and compare.

[enerj]

is that accessible for free? Isn't that a broad car repair application?