331 SEFI Stroker...still not running right!

[marjama]

Ok guys,

This is a copy of my post to a couple of the mailing lists. Be prepared...this is long!

After running out of ideas and sensors to check, I went ahead and bought a set of 24lb injectors and a matching MAF for my 331 stroker. For those of you who haven't been paying attention...the setup is as follows:

331 Stroker, approx 10.2:1 compression, AFR 185 heads, GT-40 intake, 65mm throttle body, 24lb/hr injectors, 76mm C&L MAF, A9P ECU, active EGR and PCV (no other smog stuff), all sensors hooked up and showing a-ok. Timing set at 12 degrees. FoMoCo shorty headers with 2 into 1 exhaust. TPS is set to ~.97v and max's at ~4.7v. Base idle was set to ~600 with IAC unplugged.

Previously I was running 30lb/hr injectors, and the engine would just plan not rev under load. Felt as though the brakes were on. Idle stabiility was very good and I wasn't throwing any codes at all. I ran this setup with a Pro-M MAF and also with the C&L (both calibrated for the 30's) and it was the exact same with both setups. Swapped in the 24lb/hr injectors and a new sample tube (yes, I know C&L sucks)...same basic thing. Now when I put my foot into it, it has the same "bog", but if I back out just slightly it revs. I think it did this with the 30's as well...just less pronounced.

It almost feels as though it's a vacuum leak - but I've had no luck finding anything. The ECU or one of the sensors is apparently giving a signal to dump a lot of fuel in when it's not necessary. I've also tried a couple of different MAP sensors and get the exact same thing. The 24lb/hr setup acutally idles worse than the 30's did...but there's other things going on as well...

I'm still getting no codes other than the standard deleted smog stuff. Runs & revs totally fine when not under load...but still won't rev under power.

Here's a new find as well: Last night I pulled the distributor cap and the terminals all look 'burned'. Any idea what would cause this? Stock ignition system not up to higher compression engine? (My dynamic compression numbers are not particularily high.) It's been running rougher lately and this could be part of it. I pulled a couple of plugs and they look dark / black...the very edges of the electrode are tan-ish, but they don't look like healthy plugs. Could I have a TFI issue? Weak coil? Uhh...???

Any ideas? Anyone out there running a reasonbly built stroker running stock Ford EFI and running well? My next step is to install a Tweecer and start tuning on my own...and get rid of the C&L and get an LMAF. And a wideband O2. That sounds really expensive. Anyone want to buy a kidney or something? HA!

I was thinking about possible vacuum leak sources on my way into work, and I'm wondering about the modulator on the trans. I seem to have really strong vacuum at idle though...and like I said, I've checked everything for vac leaks.

As always...any help / advice is appreciated! I'm just looking for ideas now...starting to run out of my own. I'll be posting this same message to the CB.com board as well...

Marcus

 

[mountainview68]

I am running a 5.0 EFI setup on my 427 stroker. I am not really sure what to tell you on your problems above. It sounds like you have checked everything EFI related, other than your distrubutor problem. FWIW I am running and MSD Ready to run TFI Dist. I am running everything very similar to you except 42 lb injectors and a 80mm throttle body and meter. I had Idle problems with mine, only when cold, no WOT issues.I took it to Blood Enterprises in Auburn, WA and had them Burn a chip for the computer. Night and day difference. I would highly recommend that you give them a call and schedule a time for them to work on it. What is your fuel pressure set at??

www.bloodenterprises.com
Talk to Mark. Tell him Chad said to call him.

 

[Broncobowsher]

Couple of things.

You mentions MAF and MAP sensor. You should only have one or the other. With a MAF the other sensor is a Baro sensor and is left open to the atmoshere.

Have you put a fuel pressure gauge on it yet? have you tried loading it with the fuel pressure gauge?

By chance do you have a stock A9 MAF and 19lb injectors? While it may not be proper for full power it may at least prove out some of you issues.

 

[marjama]

Hmm...

Idle problems seem to be a pretty common thing when dealing with larger than stock injectors. I was hoping for someone to come in and say "yes, that's exactly what I saw too...until I got a chip/tweecer".

How was the drivability before you were chipped? I have a feeling there is something else wrong that I'm missing, a bad sensor, ECU issues...something besides just the tuning! Based on what I've seen and read most guys don't have major issues like I'm having with stock Ford EFI on a non-stock application, but I could certainly be wrong there...

Thanks!
Marcus

 

[marjama]

Couple of things.

You mentions MAF and MAP sensor. You should only have one or the other. With a MAF the other sensor is a Baro sensor and is left open to the atmoshere.

Have you put a fuel pressure gauge on it yet? have you tried loading it with the fuel pressure gauge?

By chance do you have a stock A9 MAF and 19lb injectors? While it may not be proper for full power it may at least prove out some of you issues.

Sorry...I mean BARO - I'm just stuck on calling it a MAP sensor from my old Lightning days!

I have a Kirban AFPR, and the fuel is set at 38psi currently. I tried it at many different settings with the 30s and it was slightly better at lower pressures, but not a huge amount.

The ECU is a stock A9p, but I don't have a set of 19lb injectors or the stock MAF to try that out. Sorta wish I had installed a stock SEFI 5.0 BEFORE going to the 331 just to make sure everything was working before I installed the new motor. I was running a Q-Jetted 351W previously.

 

[mountainview68]

Hmm...

How was the drivability before you were chipped? I have a feeling there is something else wrong that I'm missing, a bad sensor, ECU issues...something besides just the tuning!

Basic drivability was good. Idle was OK. I got a bunch more power, a better cold start, and idle from the chip. What cam, Who put it in??? Have you checked cam timing? I am not an engine expert, maybe valves are not opening and closing properly in relation to crank timing? Chime in if I am wrong.

 

[justinoshea]

The Tweecer's data logging capability is a great debug tool. Even though it is expensive ($500), so is throwing parts at problems, plus the beers & swearing that go with them. I have a similar setup and have satisfactory results with a stock A9P , a C&L meter and no chip/or custom tune.

Could be ignition/timing related. Check that the timing advances under load. You may need a crazy buddy to help with this, or the Tweecer. The stock ignition is probably enough for a NA motor, but a MSD coil can’t hurt.

 

[iwlbcnu]

331 has nothing to do with it, and a completly stock EFI would run it ecept for max hp. What did you do to bypass the EGR? I think there is a resistor trick you have to do.
A tad different system, but I had a 94 GT that would free rev great but not under load. Something in the EGR system was flipped out and even a Ford tech couldn't figure it out. We replaced everything except the ECU and gave up. We finally rigged the EGR to a set setting and it ran great.

 

[Broncobowsher]

Is that 38 PSI fuel pressure still there under load or does it go away?

 

[marjama]

Wow...lots of comments to respond to! Here we go:

The cam is a Comp Cams 35-310-8, installed straight up and degreed by yours truely. I'm basically positive that the installation is correct (not the first cam I've installed/engine I've built, and I quadruple checked everything during the build up). I selected it because it gave me a power curve similar to what I was looking for (based on desktop dyno, and compared to many other cams), and gave me the proper dynamic CR and cylinder pressures. (On that note...my statement of static CR in my initial comments really isn't worth much...that goes against my belief that dynamic CR is much more important!)

I obvioiusly need to check timing and fuel pressure under load. While I'm spending all this money, I should probably also get a vacuum gauge. My C4 trans definitely shifts way harder than it used to. Does that mean the vacuum signal at the modulator is greater or lower? Still sort of wondering if there is a vacuum leak down there somewhere.

iwlbcnu - my EGR is functioning, so it's not bypassed. I don't see any EGR codes when I run self diagnosis.

I think I have a line on a used Tweecer R/T...may pick that up regardless. I'm still pretty convinced that it has to be something totally basic that is wrong...and it has to be timing / ignition or engine load signal / vacuum related. Keep the suggestions coming guys - I definitely appreciate the help!! (When I finally have the "DOH!" moment, I'll be sure to share so you can all laugh "with" me...HA!)

Thanks!

 

[mountainview68]

I had the vacuum line come off once. Shifted way late and super hard

 

[bsaunder]

couple of thoughts not mentioned yet-
vacuum hooked to fuel pressure regulator?
exhaust leak before O2 sensors?
correct heat range and gap of spark plugs?

 

[marjama]

I had the vacuum line come off once. Shifted way late and super hard

I need to get a vacuum gauge! I'll have to take a look at my connection and the modulator on the transmission. I'm not sure how they act if they 'fail', but it's definitely not the same as it was with my old engine (stock-ish 351w).

 

[marjama]

couple of thoughts not mentioned yet-
vacuum hooked to fuel pressure regulator?
exhaust leak before O2 sensors?
correct heat range and gap of spark plugs?

Vacuum is hooked to the FPR (but not when setting base pressure).

I don't *think* I have any exhaust leaks before the O2's, but I'll check.

The plugs I'm using are uhh...whatever AFR recommends for their heads. Autolite 3924's per my records. I gapped them to the 'stock' gap. I do have a high performance TFI coil I purchased used, but haven't installed it yet. When it showed up the coil was loose on the metal core and I haven't decided if that matters yet. I'm guessing not, but I wanted to call up the manufacturer first and find out.

I've got a ton of things to check now based on everyones suggestions here and on the lists. Some I know I've checked, but hopefully I'll either find it or stumble on something that should have been obvious. It may be that I just plan need to get it tuned to get it dialed in right...on that note, I just bought a used Tweecer R/T so step one of that process is now in the works if I end up needing it.

Thanks again to everyone for all your suggestions so far! I just need to quit my job so I have time to sort this stuff out! HA!

Marcus

 

[localrich]

I have a stock cobra MAF and ECU both of witch are calibrated for 24LB inj from ford if you are intrested in borrowing them email me at richardstrope at gmail dot com i would need them back by the 8th as i plan to fire up my 331 / 4r70w combo that weekend;D

 

[iwlbcnu]

I think the way i figured the GT out was i yanked the EGR plug and let it throw a code but it would run better.

 

[marjama]

I have a stock cobra MAF and ECU both of witch are calibrated for 24LB inj from ford if you are intrested in borrowing them email me at richardstrope at gmail dot com i would need them back by the 8th as i plan to fire up my 331 / 4r70w combo that weekend;D

Man, I sure appreciate the offer! I think I will be able to manage without borrowing it though. I've got a Tweecer RT on the way, so that should help diagnose any problems (assuming I don't find the issues before it arrives).

This is what I've always loved about the EB group...everyone is ready to lend a part/hand/etc anytime if you need it!

Thanks much,
Marcus

 

[AKwheeler]

I don't think I would be jumping into swapping injectors, PCMs and MAFs until I had all the basics checked. Backpressure checked (while problem is present, not at idle or by putting a finger on the O2 sensor hole). Intake restrictions, timing not advancing, Fuel pressure while problem is present and timing (not advancing-base timing only?). Then I would be looking at the O2 sensor and injectors. When the load is increased and the vehicle hesitates what are the injector on-times doing? Are they increasing to add fuel or decreasing/staying the same? Is the O2 sensor showing a rich mixture or lean? This information will get you going in the right direction. A scan tool helps as does a scope. If you have a high injection duration then the computer is trying to richen it up. If the O2 sensor is saying it's running lean (and the sensors actually work) then you have a fuel delivery problem (pressure, volume, plugged injectors or such). If the injector duration is staying low, then there is an input problem to the pcm or a defective pcm. The important thing is to watch it when it's running good and compare as it runs worse. What is changing, or maybe more importantly, what isn't changing. Good luck.

Just my .02...