Concern: FD dies after high RPM driving.
 

Good Morning,

Here are the facts:

1. bought my car 8 months ago

2. Has a street ported engine with 3k or so on it

3. 550cc primary, 1200cc secondary injectors

4. Starts fine and idles fine after it is warmed up

5. It takes at least 5 mins after I start the car for the rpm to get down to 1k. The start up process seems to be much different than my previous rx7s. My previous rx7s started up and it was high rpm for about 10 to 15 seconds before it came down.

5. runs super rich. basically it backfires after after getting up to 5k rpm or so when I let off the gas

6. I have a Odyssey PC680 battery

Here is the concern:

If I drive the car and keep it under 4k rpm I can drive it without issues
As soon as I get over 5k rmp or so (not sure exactly) and kind of step on it where the boost kicks in, the car starts to act funny at a red light or at stop and go traffic. The idle begins to jump and then the car dies.
The only way I found to counter that is to rev the engine at idle to keep the rpm from dropping and the car turning off. It feels as if the car is chocking and then just turns off.


Can it be:

The battery is to strong enough to power the car?
It needs a tune?
The injectors need to be cleaned?
Sensor?

Any suggestions? Thanks

My 1st guess would be compression. Someone turned up the idle so it idles smooth etc.....

Hopefully I'm wrong.

Wow. I was not expecting that. I hope that is not the case as well.

Engine was rebuilt by Ricks Rotary Performance about 6 years ago. The previous owner got back surgery and he couldn't drive it after that so the car sat in his garage for years. He started it from time to time. Rick also put the tune on it but it seems like it is a generic tune because it is running super rich.

When I bought one of the things that sealed the deal was the fact that it was rebuilt by a reputable shop and the PO provided all the receipts for the rebuilt.

The PO was not car savvy at all so I know he wouldn't know to turn up the idle to smooth out the idle but who knows, someone else might have done it for him...

what kind of ECU do you have?

Power FC

It could be many things so hopefully it's not compression that was just my 1st thought

Any codes?

ISC
Map senor
air temp senor
blah blah

Well, this weekend I took started my dual oil cooler installation so when I get my car back up and running, I will check for codes and do a compression test. Thanks for your input

You're not going to have codes with a power fc. I would look in the sensor/switch menu and see if everything is in spec. Post a pic or video of the screen with the car running.

Thank you for your feedback. I will do that as soon as the car is up and running again. Just need to finish installing the new oil coolers and I decided to get the injectors cleaned (I might have a leaky injector) and do a silicone vacuum hose job.

Although, I am having a hard time getting the damn rats nest out. I need to do a little more research on the forum to get some info on what the easiest way to take out the rats nest is.

Map sensor problem. Bad hose or not connected hose. Wrong Settings. t

Just got my injectors cleaned.

Could this have been the issue?

Attachment 617841
Attachment 617842

I would suggest you check all ground wire contacts. What you describe is happening after heat soak and with heat soak you get expansion. The expansion, in turn, may be compromising your ground wire connections if they are loose or corroded.

Its funny that you mentioned that. While I was doing my vacuum hoses I notice that a wire was easily coming off ( I have circled it in red). It was not staying on the little pointed piece that it snaps onto.

I pinched it with some pliers and it is grabbing very good now. I have to pull on it before it comes off where before I can literally lift it off.


Attachment 617634

I'm not sure just what that wire is as the "red" circle somewhat obscures where it connects, but that is not a ground wire. Probably a sensor wire of some sort. You won't know if that solved anything until you run the engine again. As for the principal ground wires, you have a ground wire running to the firewall from the UIM and you have one down at the bottom, left-side of the engine near the coolant drain plug. Check to be sure they are scuffed free of corrosion and crud, and seated tight against bare metal.

That's just a signal for the PS, it bumps the idle when the pump add more load to the engine.

I am learning a lot here guys. Thank you for the input. I will check on those grounds.

Double check the vacuum hose going to the MAP sensor is sound. It would also be quick and easy to try another MAP sensor if you have one to see if the problem follows the part.

I base this suggestion on the description of your problem going from high pressure to vacuum.
With a faulty MAP sensor or vac,/pres. source it could cause some issues you're having.

Plus it's an easy and inexpensive part to swap. (I hate to just swap parts... Always troubleshoot based on reason. :) )

Thank you for your suggestion. I will also look into that.

Mine had a similar problem. My mechanic found that on the dyno and monitoring the temperature sensor that it was reading erratically -20 to 90c. Something worth checking, does power fc have logging capability?

Yes, it does but I will need to purchase a datalogit. I assume you are referring to the water temp sensor. I have a water temp gauge and it seems to keep a stable normal temp, no erratic jumps. However, I will keep my eyes open in case I missed something. Thanks for the suggestion.

^ I'd assume he's talking about the iat sensor , which will add / remove fuel based on the temp of the the intake air. If it's faulty it will compensate with the incorrect amount of fuel

I got the car running now but I have not had a chance to take it for a drive. If it happens again I will look at the iat sensor first and start from there. I will keep you updated.

wrong thread