A friend of mine just rebuilt the engine on a S5 TII he picked up. He got it running and asked me to come over to help because it wouldn't idle right, and would randomly not be able to rev if you gave it over 10-15% throttle.

These things had been done prior to me trying to help:

• Completely drain fuel system of old fuel and replace with new
• Install new fuel filter
• Get all four injectors supersonicly cleaned/flow tested
• Replace battery
• Install new plugs and verify leading and trailing spark

When I came over, I checked and the TPS setting was off as was the timing just a bit. He had only stabbed the CAS and not verified with a timing light at this point. We set both of these to the correct specs after the car is warm. Everything seemed to work just fine.

Here is the kicker. After running for no set amount of time (anywhere from 5-20 minutes I've seen so far) the car will go from being able to accept any amount of throttle input and responding normally to completely cutting out if you press the throttle down more than maybe 15%. If you shut off the key and turn it back on, this symptom goes away, but if you don't turn the car off, the symptom never stops.

If anyone has a clue as to what we should check, that would be helpful. It seems odd that it is doing this with no real trend in time, temp, etc. Its very random.

-Josh

 

It's a bad spot in the low range tps. An intermittent bad spot.

Disconnect the tps completly and then see how it acts. Or, depending on how adept you are, just remove the low range tps wire at the ECU so you don't disrupt the upper/high range tps signal to the oil metering pump and see how things work out.

You might check for *codes* prior to doing the above. You will get codes when you disconnect the tps, so count on that. But see if there are any tps codes before doing the above.

 

Which plugs on the ecu do you diconnect for the low range tps?

 

not sure if this is the issue but when an electric S5 OMP starts to die it sends the ECU into a "limp" mode that have that exact symptom after about 20 minutes of running.

the only reason I know this is I had to deal with it.

good luck.

 

What happen if the omp is block off?

 

ttt

 

on a stock S5 ECU, turbo or not, if you unplug the OMP or it's going bad it will throw a code and go into that limp mode ......period.

it's a shitty part about having an S5 but many have had to deal with it. I think one of the electric gurus found a way around once but I can't be certain.

like I say, it may not be the root of the problem but I know for a FACT that issue exists.

I'f someboady found a way around it then I would love to hear about it.

Also, if you don't fix it quick it can ruin yer OMP AND yer ECU..........yep, I had to replace BOTH on mine once I found out what the issue was.

 

So if I install the omp back on and plug it's connection than the ecu wouldn't go on a limp mode? For some reason the car would rev all the way like it used to? I changed another tps and it got worst. I blocked the LIM,UIM, OMP, and cap out all the nipple on the manifold and yes I'm running this on a stock ECU.

 

I meant the car wouldn't rev like it used to after I installed a different tps.

 

I did a search about 89 TII and up MOP. I'm going to put it back and see how goes.

Thanks

 

before going through all of the trouble of reinstalling the OMP simply plug it back into the harness and let it sit off to the side of the engine bay, then run it for a bit and see if the issue continues. that should tell you if it is the lack of an OMP.

good luck man, hope you figure it out

 

my S4 has the same issue. if i crank it up and its running like *** all i have to do is turn it off and start it back up, then it runs like a dream.

 

The car runs great with the MOP plugged, it accelerate without any hesitation.

Thanks alot for your help.

 

no prob, glad you can enjoy it now

 

Thanks for the help guys.

 

Wait, what happened? Mine does the same thing, but I'm really tired so please put all that beefy input in my redneck lamens terms.

 

Wait, what happened? Mine does the same thing, but I'm really tired so please put all that beefy input in my redneck lamens terms. Please