Signs of wrong ECU / engine combination

[Gmac34]

Hello

In the last few days I started gathering informations regarding the various ECU modifications and therefor learned a bit about the different versions/colours.

My car is a 89 Turbo
but the previous owner swapped the engine from a 91 Turbo cat

In retrospective it was a poor decision to buy this car knowing about the swap, but all seemed fine.

I later discovered a few problems, and it is evident that the swap hasn’t been done by the brightest mechanic.

I.e. the breather hose of the coolant expansion tank changes between the two cars,
on the donor it connected the top of the radiator to the expansion tank as opposite on the 89 car it was connected to the back of the engine, where the heater is also connected.

well in my car, wen I bought it, the breather hose was completely missing and the water would not circulate correctly, luckily I had the radiator from the donor car and was able to restore the correct water loop for that engine.

So I would like to know what I can check to see if the correct ECU was fitted when the engine has been exchanged.

I checked the colours and both ECU I have installed are orange, is it a correct pair with a 91 engine?

The engine runs smoothly and has no problem starting
the only bad behaviour I can report is that, when going downhill with the gas pedal depressed, there is some unburnt fuel that arrives in the exhaust and so I get a few small “bangs”

Thanks for the help

[cranna21]

i get the exact same in my 91 N/A ES, and my engine is mostly un tampered with, i have a stainless exhaust on my car, so it makes the pops a bit louder, however my pops as far as i can tell are from running lean! going by the colour of my spark plugs anyway.

the pops are apparently caused by excess air and the heat, my plan to rectify this was to add an aftermarket fuel pressure regulator, just to put a bit more fuel into her, might make it faster, probably not, but will solve any damage caused by running lean! likewise a brand new standard fuel pressure regulator may also solve the issue

[Ade]

I can pretty safely say that mine ('90 turbo, no cat) is as is came from the factory as regards original engine and ECU's and mine are orange too. Does this suggest that your car has its original ECU's running the replacement engine as your car would have been *identical* (ecu and engine wise) to mine when new and presumably this suggests that orange ECU's are set up for the pre-cat turbo models?

I guess the ECU's may have had to change to accommodate lambda (and maybe other stuff) which mine doesn't have and I think maybe the car from which your engine came did. I would think that when the swap was done, your cars original exhaust was kept with no hole for the lambda sensor and some bits would have been swapped onto the new engine from your original if there were any obviously different components relating to the car/ignition system/fuel system/engine 'interface'. It would have been made to work, which it obviously does, but the question is how much thought went into the process of 'making it work'. The water circulation is a worrying thought

I would imagine that all the major components of the engine are very little changed between older and newer models and so if you strip it back far enough and install the new engine with all the original components that are different to the donor ones it should be ok.

You'll be pleased to know that mine pops too

[Robou]

If there are no noticeable changes in the loom and the auxiliary waterpump is correctly activated by the Jetronic you better stick to orange. Otherwise a red combination is asked for.

[Gmac34]

The loom seems stock around both the jetronic and the fuel ECU, the auxiliary water pump seems to activate correctly, I ear it buzzing every time I switch off the car.
I guess that since the car run fine it is not a case of ECU / Flywheel mismatch.

I don't thinks they made much effort in to making all work, I noticed how many mechanics tend to work without doing any research, replacing parts before asking questions.
About the "water circulation" my own mechanic replaced the water pump, the thermostat and two hoses before realising that one was missing, even thought I gave I'm the schematics of the entire system to check on.

I'll probably look for a modded orange ECU then, or to get mine done, but not before I get the car running smoothly, I started to get white smoke at idle shortly after I brought the car home, so a new head gasket is needed, if it isn't something worst.
I guess the previous owner had to choose between scraping the car or dumping it on some other fool and choose the latter.

Thanks for the help