Possible problem with Speed-Pro

[99redsnake]

I've got a bank to bank system on my Mustang. 83 lb/hr injectors, wide band, the usual.

Anyway, the idle quality and drivability of the car was fine tonight when I started the car and drove it for about 15 minutes. Then, the A:F ration all of the sudden went to 15.94 and it refused to idle. I tried restarting the car several times but it would fire and and then die. I pulled all of the plugs and all were lean - extremely lean. I was also noticing that I can't adjust the idle with the IAC, it simply has no effect on the idle no matter where I set it in the idle vs. water temp table.

I'm very confused. I need advice from the gurus. Do I have a bad IAC, a bad O2, or am I just stupid? Why did this happen after the car got warmed up and ran fine for 15 or 20 minutes?

BTW, great site! I've looked around awhile and just now decided I needed the advice of the pros. Thanks in advance.

 

[Chuck Leeper]

NO GO??

What's the fuel pressure w/ key on, engine off? [obviously!!]
Are you running an aftermkt pump? What about the regulator? Pull the vac line off and see if it has gas in it..If so, the diaphram has gone south and there's no fuel control.
Does the system have a FMU to control the pump??
Is the gas gauge working??

 

[99redsnake]

Fuel pressure is 44psi with the key on. It's a Weldon 2025 pump and there is no FMU. The regulator is a new Aeromotive unit.

 

[Craig Smith]

Does it idle too high? It almost sounds like you sprung a vacuum leak.

 

[bobc455]

When a problem develops "suddenly" like that, I tend to think ignition- coil, etc.

It's not your O2, you don't need that to run, and it doesn't kick in immediately after startup anyhow.

It's probably not IAC, although you could easily test that visually. Are you saying that the target IAC position was moving around, but the IAC motor wasn't actually following?

Doesn't sound like you're stupid, either...

You said this happened when the engine was hot- when it cools down, does the car run fine again? (Still thinking coil on this one)

Also, check fuses etc.

On some motors I would think that the cam might have jumped a tooth, but I don't know enough about Mustangs to know if this is a possibility for you.

-Bob Cunningham
bobc@gnttype.org

 

[99redsnake]

First off, thank you guys so much for the quick replies and the help!

The idle quality is horrible, it surges like crazy between 700 and 1500 rpm....but it was doing that before it died on me last night. It would stop the crazy idle if I adjusted the VE numbers just a bit, but then it started again...leaned out at idle...and just died.

But, this morning I reinstalled the plugs and fired the car up. It started this time and ran but the idle was still surging. I guess I'll try to hunt down any possible vacuum leak but I've checked all the lines (only 4: brake booster, FPR, blowoff, and MAP sensor). I'm truly baffled?!

 

[ijames]

Did you make any boost during that 15 minute drive? Maybe you blew out part of the intake manifold or plenum gasket somewhere - vacuum leaks aren't all on hoses, and if it blew into the lifter valley it's going to be hard to find.

 

[99redsnake]

Man you guys are fast! This is awesome!

Let me see if I can answer all of these questions.

ijames - I did make around 15-16 lb of boost on the 15 minute drive, but the idle quality and the lean condition (at idle) had already begun before I gave it boost. And I agree about the vacuum leak, I'm going to check out the intake when I get home.

bobc455 - I can move the IAC target but the motor does not follow. This has been true since I installed the system. On the hot vs. cold issue....last night it completely died on me when hot but this morning it ran while cold (still surging and searching for idle though). I wouldn't think the cam jumped...all hell would've broke loose then. I'm going to check all the timing, fuses, etc tonight.

Anymore ideas?

 

[99redsnake]

UPDATE!

Alright, I went home at lunch and played with the car. Reset the timing (it was dead on), looked for vacuum leaks and retightened the intake, and played with the VE table(added more fuel at idle due to lean condition) and reset the TPS to about 14(down from 17), and took the idle timing down from 34-35 down to 32.

Results: Car is idling perfect and will restart fine when hot. I guess I'll drive the car some tonight to see if the problem returns.

 

[bobc455]

You said that you change the IAC target, but the IAC motor doesn't follow? Do you need to repair your IAC?

One other thing- is your ECM mounted in a dry location? The units are pretty water tight, but not perfect.

-Bob Cunningham
bobc@gnttype.org

 

[99redsnake]

Bob,

I don't know about the IAC. It's been that way since I installed the system...and it was brand new then.

The unit is mounted under my passenger seat, no moisture anywhere near it.

Do you think I should just guy another IAC and try it? All the wiring is soldered and loomed, I checked the install several times. It's just funny that everything else works but no response from the IAC.

 

[TurboTR]

You may just have the throttle blade relationship with the IAC out of wack.

TurboTR

 

[bobc455]

If the IAC has never worked, then I guess that couldn't have been the thing to change to create this new problem (unless it just started to work). How do you know it's not working - have you confirmed visually? I wonder if it's wired backwards or something.

32 sounds like a lot of timing for idle! I would think that might be too much. Turning up the idle timing is tempting because the idle speed increases and vacuum goes up, but it can cause other problems at idle (surging). You'll have to be the judge of that.

It sounds like this problem has gone away- or has it come back sporadically?

-Bob Cunningham
bobc@gnttype.org