Sr5 to gts conversion running rough or not starting

[Oddbot]

I feel like a a**hole just coming straight out of the gates asking for help but I'm at a loss. I've owned many a car in my time but never a toyota/ae86, I've owned mostly Mazdas. I bought(saved) this car from its previous owner who had no clue what he was doing or what he had. The only information I could really get out of him was that it was a sr5 that had been converted to a gts that's all that he knew. So after a lot of looking up part numbers and basic trouble shooting im stuck. The car never ran right and I only drove it once which was to my house where it's sat in my shop since. When I bought it it was missing a tps, all the vacuum ports blocked off as well as a hacked up wiring harness. Bought a tps, hooked up as many vacuum lines as I could and capped the rest, replaced the spark plugs and wires, checked fuel pressure(cranking and priming). It has fuel, it has spark, but it doesn't go boom, so it has to be signal related. After checking the part numbers I found I have a mr2 ecu, a 87 engine and afm. The afm is bad and a new one is currently on order. The car would never start after I got it home, but after pushing the afm flap all the way open it idles rough and dies if throttle is applied. Finding a wiring harness would be next to impossible but I can make one if I find a company that sells the connectors I need.

If you need pictures or more explanations please let me know. I'll do almost anything at this point to get it running. Thanks for listening to my long rant and horrid grammar and punctuation.


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[jondee86]

Sounds like s fueling issue. The AFM is the primary load sensor, and by
measuring the airflow into the engine, the ECU can compute how much
fuel to provide. Make sure there are no air leaks into the ducting between
the AFM and throttle, and no vacuum leaks into the manifold. The engine
will not start if the AFM flap does not open while cranking. There is a
switch operated by the flap that turns the fuel pump on.

The TPS tells the ECU how fast you want to go, and whether you are
accelerating, cruising or on the overrun. It needs to be adjusted correctly
so that the IDL switch inside the TPS changes state when the throttle is
fully closed. This tells the ECU that the engine should be idling, and the
ECU will adjust the fuel and timing between IDLING and RUNNING.

The ECU needs to get 12V on the STA pin when the engine is cranking.
This signals the ECU to supply extra fuel and air to help start a cold
engine. The 12V signal comes from the starter solenoid circuit.

If the engine dies when you open the throttle, it usually is because the
engine gets extra air without getting extra fuel. The mixture goes too
lean to combust, and the engine dies.

Cheers... jondee86

[Oddbot]

Dialed in the tps, installed new afm and starter. It would start and idle rough for 2 seconds max then die. I messed with the distributor and now it won't even start so I'll fiddle with it more tomorrow and see if I can at least get it back to where it was. My friend who's a professional mechanic is coming over tomorrow to take a look at it so I'll keep you guys updated with the progress.


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[saiGone]

2 seconds and dies. I vote that you are running off your cold start.

[saiGone]

w. key on, hold your afm door open, if they FP comes on, your COR and AFM should be good to go

[Oddbot]

Is their a page I can look up these abbreviations to get acquainted and up to speed?


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[Oddbot]

The mechanic friend I have came by and got the car to run somewhat. The issues I have now is that I need to buy new injector clips and wire those in, and check the fuel pressure while the cars running to see if either the fuel pump is bad or if the pressure regulator is bad. The timing on the distributor turned out to be way off, and the clips are all really broken so like I said they need to be replaced so the injectors are getting good signal. Also my car doesn't seem to have a diagnostic box that I can find, do I just jump the two terminals on that one yellow round plug then to get it to go to base timing?


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[yukesrevolver]

Yup, just jump that plug coming off the main loom behind the intake manifold. There should actually be two, but one should be capped from the factory.

It should also be noted that along with everything else, I've seen this exact symptom (starts and dies quickly afterwards) from a loose ground wire. In that case, it was the one that went from the engine to the firewall, right in the middle of the car. Although I'm sure any loose ground could also cause it to do so.

Also if I'm not mistaken the ECU won't go into base timing if there's an error code. Again, could be mistaken. Its been awhile.

[jondee86]

Have a read here....

AE86 16V - Diagnostic Plug and FP Test Plug - DIY by jondee86

Cheers... jondee86

[Oddbot]

Right now I can start the car with the throttle half way down but the rpms are slow to rise and aren't responsive to the throttle input. I have a leak someone under the car where gas is pouring out that I need to address first, I'll probably get the car on the lift tonight to check.

Unrelated to the current problems, when ordering replacement parts for the chassis like tie rods is their any difference between sr5 and gts parts? I usually order from rock auto, but 80% of the time I order for the wrong model. That's why I have about 300$ worth of parts for a fx16 or some crap.


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[Oddbot]

Well it was bitter sweet tonight. First the car moved under its own power for the first time since I bought it last October, couldn't find the leak which makes worry a little. Then as I was lowering the car on the lift I snagged the door and tweaked it pretty bad which means more body work, I'm really disappointed in myself because it was a amateur mistake. But the car will start and idle if I clamp the return line closed, although it idled really rough I can rev the engine freely. Also got new injector clips so I need to pull the harness and wore those in.

That's all the updates for now.


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