About to run my '87 Carrera off a cliff - still surging and backfiring

[Tippy]

So, I replaced the Idle Microswitch and now an Ariflow Meter. The car still backfires, hesitates, surges around 2000RPM or lower - especially when taking off from a stop.

Idle switch test - wasn't getting continuity at the DME harness plug pin, but was on the WOT switch

Airflow Meter was not gaining voltage in the first 5-10 degrees, then about a .3 or .4 jump in voltage.

Both I obviously thought were the problem.

My multi-meter testing was not fruitful!

Results though, at the DME harness is that every sensor is testing within ohm range or continuity.

My car has a Protomotive chip for the turbo, the only mod done to the DME.

So, ischmitz, Loren, Wong, or anyone else, is it time to tear into the DME?






CR

[Tippy]

The ignition box (CDI?) and coil are original from what I can tell.

If this helps......

The distributor came from Craig Garrett "cgarr" and worked just fine after I rebuilt the engine.

[Tippy]

Can someone point me to the thread on the DME test and repair?

I need get "knowed up".

[skulp]

Brother u find a good cliff let me know. I've been at my 84 for 2 months trying to fix same issues.

[r_towle]

Do you have an O2 sensor or some way to monitor your mixture?
If its backfiring alot just off idle, it may be flooding.
How are your fuel pressures on both rails?
Can you monitor the fuel pressure at different load conditions and different RPM's?
Rich

[ivangene]

I have a big curb out front...if that works you both can drop those cars over it and I will be glad to catch them at the bottom for you to "help out"

[Tippy]

Originally Posted by skulp

Brother u find a good cliff let me know. I've been at my 84 for 2 months trying to fix same issues.

Sorry to hear brother! It is frustrating. It is really bad for me since I just rebuilt the engine! I got to the 500 mile mark and this crap started happening.

Originally Posted by r_towle

Do you have an O2 sensor or some way to monitor your mixture?
If its backfiring alot just off idle, it may be flooding.
How are your fuel pressures on both rails?
Can you monitor the fuel pressure at different load conditions and different RPM's?
Rich

Rich, the O2 is not hooked up. It doesnt backfire too much, but when it does, it is very loud. I have a 12" long 3.5" inlet/outlet single muffler off the turbo. Fuel pressure is good and raises real quick with throttle movement. I have Defi gauges.

Originally Posted by ivangene

I have a big curb out front...if that works you both can drop those cars over it and I will be glad to catch them at the bottom for you to "help out"

Ed, you already have a fine example. You don't need my money pit!

[papajetta]

2nd that on the fuel pressure check.... Had a bmw e30, similar motronic and similar symptoms, was chasing everything u were chasing.. Afm, tps.... Checked the fuel pressure... 25psi. Changed the pump, 90 psi.... Return fuel line was clogged at the tank.....

[Joe Bob]

ingo at 3.6@cox.net can help on the DME.

[Tippy]

Originally Posted by papajetta

2nd that on the fuel pressure check.... Had a bmw e30, similar motronic and similar symptoms, was chasing everything u were chasing.. Afm, tps.... Checked the fuel pressure... 25psi. Changed the pump, 90 psi.... Return fuel line was clogged at the tank.....

Fuel pressures are good as monitored by Defi gauges in the car.

Originally Posted by Joe Bob

ingo at 3.6@cox.net can help on the DME.

What does ingo provide? Schematics, troubleshooting diagrams, repairs, parts?

[Joe Bob]

He rebuilds and repairs DMEs and CDI boxes. Located in Santa Barbara CA.

[Tippy]

Originally Posted by Joe Bob

He rebuilds and repairs DMEs and CDI boxes. Located in Santa Barbara CA.

Will he cough up technical data like schematics and troubleshooting stuff?

I would like to repair myself, just need the data.

[Joe Bob]

He has in the past.....do a search on his name, ischmitz, as well as Lorenfb and earlysman. They have posted schematics.

[Tippy]

Originally Posted by Joe Bob

He has in the past.....do a search on his name, ischmitz, as well as Lorenfb and earlysman. They have posted schematics.

Ah, thanks!

[chuckr]

IF all else fails.... Charlie Jones@Jones Autowerks

[Tippy]

Originally Posted by chuckr

IF all else fails.... Charlie Jones@Jones Autowerks

Do you mean Bob, or is that his dad?

I have spoke to Bob about this and he's ready to put it on the AFR monitor to start testing but I'm trying to fix it myself. Have to save a little money since I just rebuilt the engine.

[MotoSook]

Did you try checking the idle air valve?

[Tippy]

Originally Posted by Soukus

Did you try checking the idle air valve?

Yes. If I pinch the hose, the cars starts to die.

[Lorenfb]

"My car has a Protomotive chip for the turbo, the only mod done to the DME."

That's the problem! Your DME ECM/engine is/are NOT stock.
Does the engine really have a turbo? Is so, another problem.
You're wasting time AND money by not focusing on all the mods.
Had a ECM sent in that had the same problem. Once the chip (junk)
was replaced, the engine ran fine. The turbo mods I've seen use
a MAP sensor too.

You also mention a CDI. Did you install an additional ignition system
with the stock ECM.

Bottom line: If really a turbo mod AND a CDI mod, get it back to stock!

[Tippy]

Originally Posted by Lorenfb

"My car has a Protomotive chip for the turbo, the only mod done to the DME."

That's the problem! Your DME ECM/engine is/are NOT stock.
Does the engine really have a turbo? Is so, another problem.
You're wasting time AND money by not focusing on all the mods.
Had a ECM sent in that had the same problem. Once the chip (junk)
was replaced, the engine ran fine. The turbo mods I've seen use
a MAP sensor too.

You also mention a CDI. Did you install and additional ignition system
with the stock ECM.

Yes, the engine has a turbo (1-bar). No MAP is used.

I put a ? behind the CDI as I wasn't sure if that is proper? The ignition box is stock along with the coil.