2.2 OBD2 swap into ‘85 Brat

[Greentractorfarmer]

Hi All, I’ve been learning from this wonderful site for half-dozen years, so let me start my first post with a hand-clapping thanks to the many people who’ve helped me along.

I bought an ‘83 GL new, kept it all these years, and in 2021, swapped in a 2000 Impreza 2.2, California spec. My fun with that wagon ended with a roll-over, last year. I’m lucky to have found a running Brat (1985) and began pulling over the parts from the wagon, which included the 15” wheels and 2.2 fuel injected engine, wiring harness, and pretty much all the interior fittings.

Now to the point of this post. I am unable to make the engine run in the Brat as it did in the wagon. The engine starts, idles smoothly, and can have full power. But intermittently. The stutter/cut-out is throughout the whole range of throttle, and depending on the rpm, can best be called ‘bucking’.

The fuel system in the donor car had an in-tank pump with sensors for fuel level, pressure, temperature, and control valves for drain and purge (not the purge valve at the fuel rail). None of the sensors and valves came over to the Old Gen cars, although I did preserve the sensor wires to the area of the ECU. I ran a 5/16” line from an external Ford fuel pump to supply the engine, and used the original 1/4” supply as a return, and the 3/16” as a vapor line from engine to tank. That worked fine on the wagon, but I suspect the current problem is related to this set-up.

I’ve replaced a lot of the sensors: front O2 at the exhaust, knock, throttle position, engine block temp, crank sensor, and tested the purge control valve to be operational with voltage, also the ECU with another. Also new plugs when moving the engine to the Brat, and then a new coil. The plug wires were new 5,000 miles ago, so don’t think the problem is in the ignition. 

I realize this is a vague description of what is in place right now, and hope someone will be interested and start a conversation to help with the next step. I’m wondering if anyone has opinion/experience with the Cali-spec engine and whether my wiring loom can support an older (Gen1) intake and its ECU. I’m feeling pretty desperate and leaning toward finding a mechanic willing to work on this swapped set-up, with the thought that a more sophisticated diagnosing kit could narrow down the issue, whether the ignition or fuel is quitting.

I’m working with a simple OBD reader, multimeter, pin-out chart for the ECU, and a 72- year old brain. It’s tough. Thanks for your time.

[bushytails]

I'm having a hard time understanding your post.  You're using the same engine and harness and ecu that you used in the rolled car, in the new car, but now it bucks?  Or this is an entirely new swap?  If it's all the same parts that worked before, it's obviously not incompatibilities between them or what the wiring harness supports.  Or did you mismatch intakes when you originally built?  Again, if it worked before, not the problem now.

Since you're suspicious of the fuel supply, start with a mechanical fuel pressure gauge.  Extend the hose long enough to route out through the edge of the hood and tuck under your windshield wiper.  Take it for a test drive.  Fuel pressure should be solid, and should go up 12 psi when you go from idle to full throttle.

Does it buck at idle, or only above a certain amount of engine load? 

On your obdii scanner, use the live data mode (if it doesn't have live data, bin it and spend $50 on a new one), looking for any sensors that move in a sudden fashion, especially if it correlates with the bucking.

If it's a fuel injection issue, an oscilloscope is really handy...  Here's a couple pics from last time I was troubleshooting a bucking issue:  https://imgur.com/a/RwWTdwG  In these images, the jumpy green trace confirmed the bad component - MAF sensor.

 

[Greentractorfarmer]

Correct, the engine and wiring from the first GL swap are installed in the current Brat GL. I have a fuel pressure gauge, downstream of the filter, rigged just as you describe so it can be read when driving. 38-40 psi at idle, high 40’s when throttle opens, and holds when shut down. Actually the pressure slowly rises from 38 to 45 at engine off, holds at there for a hour, then slowly falls to zero over several hours. I think the pressure increase at engine off is heat expansion and assume the injector system is okay since it holds awhile before decreasing. The tank always pressurizes quite a bit, to the point that gas vapor smell is obvious, probably through the gas cap vent. This seems to be the only difference in the first GL with this engine and the current Brat GL-buckeroo. 

Your statement about the oscilloscope is helpful. It’s what I’ve been thinking is next step. (This particular model 2.2 didn’t use MAF, instead has manifold pressure sensor plus intake air temperature sensor.) I will need to get a shop to do this, but am concerned the Frankenstein aspect might add difficulty to getting that help. I’ve tried to use live data on my reader, but don’t get far. I also have back-probed at the ECU to read voltages of various sensor signal while driving, all looks solid. But the scope can show oscillations, while the meter only shows steady 12v at the injectors, for example.

Thank you for the input. It’s encouraging.

[bushytails]

It's really hard to diagnose something like that without the "feel" of what it's doing that a test drive gives...

Does it idle well, or does the problem happen at idle too?

[Greentractorfarmer]

Starts and idles just right. (Am I right that the idle circuit uses less info from sensors/ECU?) The first gear shows gentle surge pulses, and in second gear, between 1700 and 2500 rpm, the rougher ‘cut out’ happens pretty consistently. If I’m driving at low speeds 1rst and 2nd gears, I can get it to even out, but when running on the open road at 40 mph and faster, the throttle pedal has to be feathered to avoid pretty violent on - off power cycles that are split second in length: bucking.

Temperature doesn’t seem to affect this problem. Engine load (uphill grade) might make it worse, but that’s not definitive.

The TPS was always suspect, but tested fine for voltage and resistance, so I didn’t change that immediately, and several days ago when I replaced it, no difference. 

[el_freddo]

Did you use the Brat’s fuel tank or bring the one over from the wagon? 

If using the Brat’s fuel tank I reckon it’s getting clogged up as you drive, fuel starvation then occurs as the pump struggles to get fuel to supply the engine under load. This doesn’t match what you said about your fuel pressure readings though. 

Is the ignitions switch on the Brat good? These can sometimes cause intermittent issues but seem more likely to die outright rather than a slow, twitchy death. 

Maybe list the things that are similar/same between the two vehicles that were swapped and not swapped. Something might show up there. 

Eg:
- fuel lines 
- fuel tank 
- body harness 
- EJ power “pick up” points - where? Changed/same? 

Cheers 

Bennie