dfully

I have a 91 NA6 that I just completed an engine swap with another 1.6. The new engine is stock and has 160k miles; the only thing brand new is the clutch and flywheel. It ran before it was pulled. I ended up tucking the engine bay, which led to extending lots of wires that I’ve triple checked that they go to the intended harnesses. I was having a grounding issue, the (+) on the starter was touching the block which was grounding out the car and fried a pair of jumper cables. Needless to say, I’ve fixed that issue.

My main issue right now is it cranks strong but will run for no longer than 2 seconds and will not rev up higher than 1000 rpm (usually around 200-500 if I don’t give it throttle). It was throwing 4 codes: 1- No igf signal; 2- No Ne signal; 26- Evap canister purge; 34- ISC valve. I’ve replaced the CAS, coil pack, and fuel pump relay with known working parts from the old engine. No change. I have no vacuum leaks, I have fuel pressure at the rail (the fuel pump kicks on while jumping F/P and GND), the injectors have been cleaned while the engine was out, and spark plugs were replaced. While checking for spark by pulling a spark plug wire (which are new within the past year) and connecting a spark plug on the end to visually record arc, the driver side coil is firing, but the passenger side is not, hence the reason I replaced the coil pack. Even after I replaced it, no spark was observed on the passenger side coil, which led me to a bad CAS (not sending a signal to ECU when to send spark to cylinder), but still the same issue occurred. The voltages on the harness of the CAS were in spec (12 5 5 0 volts) as was on the harness for the coil pack. After replacing the Ignition control module the engine still would not start but codes 1 and 2 went away.

Finally, I was getting somewhere and I moved my attention to the other two codes, the evap canister and the ISC valve. I’m not surprised the 26 code was thrown because of air in the fuel lines during the swap. But after further investigation, the previous owner removed the evap canister in the engine bay and the open hard line goes back to a smaller canister in front of the rear passenger wheel. And I’ve cranked the engine many times over the course of 2 weeks that the air should’ve worked its way out of the lines or at least be negligible. So I don’t know why that code is being thrown still because it was not throwing it before I removed the engine.

So onto the next code (34- Idle Speed Control Valve). The voltage on the harness is in spec (12 0 volts) and the resistance of the valve itself is also in spec (13 ohms) I cleaned it the best I could with it still attached with TB cleaner. While cranking the car to try and diagnose this issue, I noticed code 1 popped back up, great! Now I’m completely lost.

Where I’m at now: I know the ECU is working because it is throwing codes, the CAS and coil pack are not broken because they have been replaced with working parts, the timing belt is not broken as I have checked with valve cover off, no fuses are blown, I’ve triple checked my engine grounds, both the main relay and circuit opening relay are working and click when they should. The only thing I have not checked is spark in the passenger side coil as I installed the ICM yesterday and didn’t have time to check. I’ve got to the extent of my knowledge and have done everything I know to try and diagnose the reason it will not stay running.

Any ideas??? Any help will be greatly appreciated.

gooflophaze

Fuel. Air. Spark. Compression.

Check your wires end to end for continuity, especially your CAS and AMF wires. There's a idle air screw adjustment on the throttle plate, crack it wide open (lefty loosy) so it'll idle (high, but idle) without needing the valve.

Braineack

iTrader: (62)

live by the wire tuck, die by the wire tuck.

shuiend

iTrader: (24)

Is your AFM hooked up?

sharkythesharkdogg

Are you still running the old flapper style air meter? You description sounds like it could possibly be something to do with that.

EDIT: Beat me to it

dfully

So I cracked open the idle screw, followed and double checked the CAS wiring and its good, and after starting it, there was no difference. The MAF was plugged up originally, but tonight I unplugged it to see if it would make a difference, to try and diagnose it, and what do you know, no change. So the connection to the MAF or the MAF itself is bad. I did not extend or touch the wires on the driver side (which includes the MAF wiring) while doing the swap, so they haven't been tampered with. I researched the voltage, resistance and wiring diagram of the MAF and to be honest I don't really know what I'm looking for when I test it, I did test the two pins that turn on the fuel pump for continuity and there is none when the flap is closed and there is continuity when it is open, so that part is not broken. On the harness the two grounds had continuity and the (+) had 5 volts (which is spec), and the other two pins I'm not sure what they should read.

So how do I diagnose between a bad MAF and bad wiring?

gooflophaze

Which is more likely - that your MAF broke while you were tucking your wires, or that you put a wire back in the wrong place?

Flapper wiring:
A - B - Ground
B - LG - FP relay
C - B/LG - Ground, tee's to TPS and 2D 2C
D - LG/R - ECM 2K
E - B/LG - Ground, tee's to Coolant Sensor and 2D, 2C
F - R - ECM 2O
G - R/G - ECM 2P

Yes, both pins C and E are also in the passenger side harness. You need to continuity test each pin end to end.

dfully

what do you mean by 2D 2C?
there is continuity in the b/lg wires between the MAF and CAS, MAF and TPS, and MAF and coolant sensor.

gooflophaze

Pins on the ECM.

dfully

Ohhhh ok! I gotcha I'll be checking that today