elwood

iTrader: (1)

Over the last few days, my car hasn't been running quite right. During a relatively easy drive today (only a few seconds at 10 psi max boost), the car began hesitating at part throttle. The throttle response has typically been awesome.

After I parked it and raised the hood, the turbine housing was glowing, which is very unusual, since I took it very easy during the last few minutes of driving.

AFRs were slightly leaner than target, but nothing that out of the ordinary or that should have affected drivability.

Plugged exhaust? Other guesses?

94touringFD

iTrader: (30)

Are you able to monitor your EGT's? Have you made any changes at all since the last time it was running good? I'm interested what caused your excessive EGT's. You should log some driving or check your current map against the last map you were tuned to and see if your tune got set off somehow if you haven't made any changes recently and the car is runs ok otherwise.

cewrx7r1

iTrader: (2)

Is your exhaust open/straight through or does it have any cats?
A broken cat will clogged and do similar things.

If open with no cats, then timing and fuel can cause that.

bumpstart

check leading spark is still all there too

elwood

iTrader: (1)

Thanks for the tips:

I haven't changed my MAP, and I don't have EGT monitoring capability.

I don't have cats, but I do have a pair of Magnaflow mufflers -- one in the middle of the car and another at the rear. I know they can be marginal, but I suppose it's unlikely the internal perforated tube would collapse or allow enough blockage to cause this problem.

I'll check spark. It's probably time for new plugs anyway.

RENESISFD

iTrader: (13)

My vote is an ignition/timing issue.

Mazda RX-7 EFINI TYPE

Sometimes little critters climb into exhausts, definitely still worth a check.

elwood

iTrader: (1)

I swapped the plugs; no difference. I beginning to think I cooked one or more of my coils. It seems to run OK at first, then begins hesitating after the engine warms up. I'm running the IGN-1As. My base dwell was 4.0ms, which may be too much.

dguy

iTrader: (8)

Probably correct regarding your dwell. As your underhood (read: coil) temps increase you'll probably need to decrease dwell as well. To give an example a poorly configured GT3 car I tuned with an M2R and Renesis coils had to have its dwell reduced to about .9 MS to combat really odd hesitation as soon as the engine had been running on the dyno for more than 4 or 5 pulls. Gross.

elwood

iTrader: (1)

Interesting. Was that to .9 ms or by .9 ms. I'm not familiar with Renesis coils, but .9 ms doesn't sound like much dwell.

I was told a long time ago that I should "throttle" my coils by using a table so that I didn't run them at high dwell when it wasn't necessary. Well, I didn't get around to doing that. When I increased the dwell to 4.0 ms, the car ran great, and I stopped messing with it.

In their defense, the coils lasted more than 3 years, and probably 12K - 15K hard miles like this.

My plan is to replace them all (not sure of the latent damage to the ones that are still working) and set up a dwell table.

RENESISFD

iTrader: (13)

It is my understanding that 4ms dewll is safe for those coils. You may have another issue. How did you wire them up? Are you sure you have good strong electrical connections and properly sized wiring. Those coils draw a ton of amperage.

also check your plug wires for damage.

elwood

iTrader: (1)

I talked with a few "experts" back when I did the wiring, and they "signed off" on a couple of deviations regarding grounding. There are three separate ground connections:
B. ECU sensor ground
C. Cyl head ground
D. Battery Ground

The coils are mounted directly on top of the engine. I ganged all the grounds together and attached them to the engine at the front iron. I then ran a ground strap from the front iron to the trans, trans to body, front iron to alternator, and alternator to body. Every connection is corrosion free and loaded with dielectric grease to keep it that way.

My battery's behind the pass seat, and the only negative wire goes directly to the body structure.

Both Lance Nist and 034 Motorsport thought this grounding arrangement was more than adequate.

The power is a separate feed from the battery via a 12ga wire with dedicated relay and 30amp fuse.

If I did have a wiring issue, I think it's odd that it would manifest 3 years later.

I'll check the plug wires.

dguy

iTrader: (8)

I had to drop them down to .9 ms. It isn't a lot (the renesis coils are trash), and really don't have anything to do with your coils except to illustrate that temperature under the hood definitely affects your coils efficiency.

BurntOrangeT2

iTrader: (30)

I had this problem before and it was caused by killing the leading coil pack (stock T2 coils) so I'd definitely start there, was running a LT10S at the time.

cewrx7r1

iTrader: (2)

8 days and no results of what the problem is.

elwood

iTrader: (1)

I've been working with Chris Ludwig, and he suspects wiring (like RENESISFD does). He specifically mentioned that the ECU sensor ground should be wired as specified, and that the battery ground should, in fact, go all the way back to the battery negative terminal (behind the pass seat in my case).

It'll take me a while to get around to it, but this seems like a fairly cheap solution if it works.

Neutron

iTrader: (10)

Subscribed. I am experiencing a similar issue. I am also on the IGN-1As coils but I am using a Ludwig harness. Ran great before the ECU and turbo change. In my case the front rotor EGT run about 200 degrees warmer. Adding fuel to the front primary injector got them very close. They used to be just about even with out any fuel manipulation. I am also experiencing what seems to be compressor surge. Not sure how this is possible on a S366.

elwood

iTrader: (1)

Chris is checking on resistance specs for primary and secondary windings. I figure I'll measure those to see if there's any obvious damage. He also mentioned that failed coils typically have a swollen case. I can't see mine very well until I remove the UIM (they're mounted beneath it).

rofuz

Have you found out what's up yet?

elwood

iTrader: (1)

Not yet. Hopefully I'll be able to tear into it next week.

Alpha-7

iTrader: (1)

map sensor pig tail?

elwood

iTrader: (1)

Are you asking if my MAP sensor is disconnected?

I'm sure it's connected and functioning. I drove the car once after I had forgotten to connect it, and it would barely run. My ECU defaulted to pig rich, and it was definitely an unforgettable experience.

Alpha-7

iTrader: (1)

I had a problem similar it was my map sensor pig tail wiring .. had a short..

elwood

iTrader: (1)

I finally got around to updating / fixing everything and the good news is the car runs great:

1. Rewired my coils per the manufacturer recommendations:

A - Ignition Signal, from ECU
B - Logic Ground, from ECU
C - Spark Wire Ground, to Rotor Housing
D - Power Ground (8AWG wire direct to battery Neg, behind pass seat)
E - 12V Power

2. Replaced all four coils

3. Changed from 4 X ID1000 injectors to 4 X ID1300

4. Installed the latest version of my Internal Surge Tank setup

The bad news is I don'd know what was wrong. My coils are mounted on top of the engine, and my alternator is side-mounted. With my 13B-RE intake setup, they should get a reasonable amount of air down the alley beneath the intake (at least that was the idea when I moved the alternator).

I checked coil secondary resistances, and all four measured about 18MOhm from pin "C" to the plug wire terminal, which is very different from the 8.5 kOhm that DIY AutoTune has listed in their specs. Since I'm sure all four coils aren't bad, I must be measuring this incorrectly.

Regardless, since all four measured the same, I'm guessing the problem, if there is one, is in the primary winding or the ignitor. There is discoloration of the casing on both the rotor 1 coils (both leading and trailing look like the picture), but not on the rotor 2 coils. This is counter-intuitive, since the rotor 1 coils are exposed to more air flow.

arghx

iTrader: (3)

Glad to hear you fixed it though