AE86 starts then dies after starting

[DJManila]

So got in it one day and it just would not start. I had it sitting on idle as I was having a battery issue then I came out the car was off. I thought I was just out of fuel but the gauge showed it has fuel (I dont trust the gauge) so I added a gallon and it started but then dies after starting.

I am going to add more fuel to see if that helps. Any advice as to what else it could be? Starter, Alternator, and everything else is somewhat new as it is a rebuilt engine.

[Red]

" I had it sitting on idle as I was having a battery issue"
Then rebuilt or not, you have to check the battery and alternator to resolve that "battery issue". If you speak about vague "issues" instead of specific problems, no one can give you good answers.

". I thought I was just out of fuel but the gauge showed it has fuel (I dont trust the gauge) so I added a gallon and it started but then dies after starting." The gauges on these cars could say "Yes/No" and that would still be good enough. If you ran out of fuel, you could clog the in-tank filter sock with dirt and debris and putting in one gallon wouldn't unclog that. the tank holds 50 liters (13.2 gallons) and when the fuel light is on solid, you still have 4 gallons left. But the owner's manual tells you, NEVER run it down that low. So putting in one gallon? If you were really empty? That's about four gallons less than the minimum you needed to run the car.

"Any advice as to what else it could be? Starter, Alternator, and everything else is somewhat new as it is a rebuilt engine."
Forget about the starter. The starter only starts the engine, if your engine quite while it was idling that cannot have anything to do with the starter.

Do a little homework, read some older threads and don't be so vague. Does the starter spin up? Does the starter engage the engine and make the engine spin up? If it does, then it works and the problem is the engine not starting. If the starter does not spin up and it does not spin up the engine, then you've got a starter problem.

If you just had the engine rebuilt and replaced, then a lot of work was done and a lot of things can get knocked loose under the hood. If the work was just done by a shop, then you've got a warranty (I hope!) and you should be taking the car in to them to look at.

[DJManila]

Thank you Red. I apologize for being vague.

The car does start and I know that it is not the starter. It starts, revs then rpms fall and die. If that makes sense. I am thinking it could be the fuel pump. However, I thought a faulty pump wont let the engine start at all.

[Hyrev86]

sounds like a fuel delivery problem, maybe your fuel filter is restricted or a big vacuum leak? hook up a fuel pressure gauge and see what kind of pressures you get koeo. I once had the same problem, car starts and rpm dropped then died. turned out my maf sensor wasnt plugged in all the way.

[Red]

Starts, revs, then slows down and quits. Hmmm. Fuel, loss of airflow signal, vacuum leak...vacuum leak should stop it from starting as well, i would think. I'm drawing a blank, other than thta it is something that is switched in/over after the engine goes from the start circuit to the run circuit.

[ae86guy]

I'm assuming you have factory fuel management on a US model. I had this same problem after swapping an engine. It turned out to be the fuel pump main relay. The AFM sends a signal to switch on the fuel pump. If the AFM does not detect air flow it shuts off the fuel pump.

You can try bypassing the relay just to see if that's the problem. If the car runs with the relay bypassed then it's either a bad AFM or the relay itself. I wouldn't suggest this as a permanent fix as it's unsafe.

This might or might not be your problem but it worked for me.

[DJManila]

I'm assuming you have factory fuel management on a US model. I had this same problem after swapping an engine. It turned out to be the fuel pump main relay. The AFM sends a signal to switch on the fuel pump. If the AFM does not detect air flow it shuts off the fuel pump.

You can try bypassing the relay just to see if that's the problem. If the car runs with the relay bypassed then it's either a bad AFM or the relay itself. I wouldn't suggest this as a permanent fix as it's unsafe.

This might or might not be your problem but it worked for me.

That is what others suggested. I am going to try that this week

[Latino Hibino]

There is a ground wire on the exhaust side of the engine. It comes from the chassis and splits. One side goes to the block, the other to a plug that goes into the engine wiring harness. If you follow the wire in the harness, it will lead to the MAF. If this isn't properly grounded, your fuel pump will prime before starting, but it will not pump fuel while the engine in on.

[Red]

DJ-
1985 = AFM up front
1986/86 = MAF

same problem, different system, depending on what year engine you have.

[DJManila]

There is a ground wire on the exhaust side of the engine. It comes from the chassis and splits. One side goes to the block, the other to a plug that goes into the engine wiring harness. If you follow the wire in the harness, it will lead to the MAF. If this isn't properly grounded, your fuel pump will prime before starting, but it will not pump fuel while the engine in on.

do you remember which part of the chassis exhaust side its on? i.e. close to the battery, etc.

[Latino Hibino]

The side the exhaust exits out of the engine? lol. When I can get a pic, I will post it up here.

[DJManila]

I figured it out, turns out it was the MAF. Its running now but I think I still need a new TPS as it "jerks and bucks" at low RPMs and that goes away if the TPS is unplug (actually runs better).

Does anyone know the TPS part number for an 86?

[Red]

The TPS can be adjusted, there's a specific procedure for that and after you have done it once, the best thing is to do it again since that may tune it even more closely to the right spot. Not hard, just needs a lot of hands, a helper is a good idea. Also scribe the case before you tighten the cover down, it tends to shift as you tighten it, which throws it back off again.

WIth your year and possibly the VIN, anyplace that can sell you a TPS should be able to run the part number. This is something I'd say to buy new, not used, as you don't know how worn a used one is.

The MAF also ages and does not last forever, I'm told sometimes they may need replacing at 100k miles if they pick up contamination from the normal airflow.

And of course while you're doing those two, you may want to pick up a new O2 sensor. Those degrade and really should be replaced every 100k miles if not sooner. A brand name (like Bosch) with the correct wire fitting on it may be as little as $50, no need to buy OEM on that kind of part.

[MisterJerk]

I might have an extra one.

In the meantime, DL the manual and test the one you have and adjust it.
Links in my sig.

[DJManila]

Red I replaced the 02 Sensor thanks for the heads up. The connection on the MAF was just loose, might need to ziptie as the metal wire clips are no longer there.

Misterjerk, I will look into that and maybe mess with it later on.

[DJManila]

Red I replaced the 02 Sensor thanks for the heads up. The connection on the MAF was just loose, might need to ziptie as the metal wire clips are no longer there.

Misterjerk, I will look into that and maybe mess with it later on.

I adjusted the TPS, I think it fixed it.

[MisterJerk]

w000t! Congrats!

[DJManila]

w000t! Congrats!

thanks now just need some $$$ for wheels/tires and alignment