Drivability of my Roadster - Solution Found

[GWL]

Help me out here as I don’t really know what to expect from my build.

I’ve spent the last few days go-karting around our community. I've got about 20 miles on the odometer. I’m licensed, tagged and insured and I live in a private community.

The cars starts well, runs well and although I haven’t pushed it yet, I can tell it is fast. Pulls very smoothly from first though forth, which is as far as I can get in the neighborhood. On one empty section of road, I can get it easily to 50 mph.

What I want to know is its low rpm drivability. While in second gear cruising at around 1500 rpm it bucks a little requiring a little clutch control or more throttle to eliminate the slight bucking. Is this normal with my present setup?

If this is normal my guess is to change the gearing in the rear end to make it more drivable in traffic or within a community where the speed limit is 20 to 30 mph. I’ve now got the old IRS set up with 3.27 gearing. I’ve read that many prefer the 3.55 ratio.

What are your thoughts?

Here is my engine and drive setup:

’89 Ford 302 - Bored to 306 - Balanced
Trickflow Top End Kit including
• Twisted Wedge 170 Aluminum Heads
• Mild Stage 1 cam
Intake
Duration @ .050” 221°
Valve Lift 0.499”
Exhaust
Duration @ .050” 279°
Valve Lift 0.510”
• Valve spring upgrade kit
• Roller Rockers - 1.6 Ratio
• Street Heat Upper Intake Manifold
• Throttle Body

Present idle set at 900 rpm with TPS at .975 volts – I am still working to get the throttle spring tension just right. I’ve added an extra spring, because I wanted more tension but then set it with too much tension. So, I’m working that out and will lower the idle when I’ve found that sweet spot with tension.

Stock A9L Mustang computer

24 lb. Ford Racing Injectors

’89 T-5 transmission from ’89 Mustang, rebuilt
1st- 3.35, 2nd-1.93, 3rd-1.29, 4th 1.00, and 5th-.68

IRS rear center section ratio 3:27

Thanks for you thoughts, George

[Mike N]

Do you have a mass air meter (MAF) calibrated for your 24 lb injectors? If not you will need one. Also with the kind of power increase / volumetric efficiency improvement that you have got with that top end package a tune is going to be a must.

I have twisted wedge heads and the TFS stage 1 cam in mine and it will drive nicely at 1500 rpm. I am using a MS2 (Mega Squirt) computer.

[rich grsc]

Man, I hate when an engine runs like that. 8 -10 Yrs ago I had almost the same setup that ran like that, got so disgusted, I swapped in a different engine. Do you have the IAC motor on that intake? If so I would start there, make sure it's clean and working, and as a last resort, go back to the stock 5.0 injectors.
My 331 never bucks, no matter what gear or speed I'm in. I am able to drive 45 mph in 5th gear, engine rpm's around 1300.

[j.miller]

Don't change the gears. 327's are great ratio. Get the engine sorted out (should run no prob at 1500 rpm) just hold your shift points higher till then. I've had a couple cars try to buck me out.....not that I didn't deserve it !...da bat

[GWL]

Do you have a mass air meter (MAF) calibrated for your 24 lb injectors? If not you will need one. Also with the kind of power increase / volumetric efficiency improvement that you have got with that top end package a tune is going to be a must.

I have twisted wedge heads and the TFS stage 1 cam in mine and it will drive nicely at 1500 rpm. I am using a MS2 (Mega Squirt) computer.


Man, I hate when an engine runs like that. 8 -10 Yrs ago I had almost the same setup that ran like that, got so disgusted, I swapped in a different engine. Do you have the IAC motor on that intake? If so I would start there, make sure it's clean and working, and as a last resort, go back to the stock 5.0 injectors.
My 331 never bucks, no matter what gear or speed I'm in. I am able to drive 45 mph in 5th gear, engine rpm's around 1300.

Mass Air Flow meter is calibrated for the 24 lb. injectors.

The IAC is a brand new Ford part.

So, I take it, from your replies to go back to the 19 lb. injectors or get a tune for the computer. Should I be worried about fuel starvation with the smaller injectors? I do still have the original set.

I do know the computer is not designed for the 24 lb. Injectors but have read that it should still be ok. I guess maybe it's not but still, will the 19 lb. injectors deliver enough fuel for my set up?

Thanks guys I feel better already because like da bat said keep working at it till you get it sorted out, George

[David Hodgkins]

What flywheel and clutch are you running? I had a quartermaster clutch and lightweight flywheel when I built mine. Changing out to a smoother clutch and steel (OEM) flywheel got rid of the bucking I was experiencing. BTW I have 3:55 ratio.

:)

[rich grsc]

Surging and bucking is almost always caused by issues with the IAC not responding correctly. I remember seeing a long time ago about drilling a small bypass hole in the throttle plate? I don't remember the specifics.
Try unplugging the IAC and do a short drive, also be sure you have good O2 sensors.

[Just puttering]

You need a tune for the computer. Changing half the components on the engine and hoping the stock tune will learn and run correctly is not going to get you there in my opinion!

Im am still working with someone on the tune for mine and it has been adjusted several times to get close.

Do you have a card to pull the data from the computer to see what it is doing?

[FFR 3099]

I had almost the same injection system with the Mass Air system (different throttle body but the Ford computer). I ran it for years, it ran Ok but never like I thought it should. I think the Ford computer didn't work well with even slightly bigger camshafts, they were made for emissions. There were no easy adjusments, anything that was changed messed up something else, even a simple idle increase. Recently I got fed up, pulled it all off and installed a PRO-Flo 4 system from Edelbrock. AMAZING difference! I wish I had done the change sooner. The only change was the EFI system and the car is more drivable, runs better in all RPM ranges and cold start drive offs are amazing. Also, the slow drop off to idle was gone ( I never did get used to that!) Pro- Flo 4 is an easy change over and is FULLY adjustable with the wireless pad. It self learns after a few easy input questions are answered. I have only had to change the fan control perimeters to later on and off, done on the control pad. The old 30 year old tech is outdated, this is a good replacement for the old 5.0 stuff I highly recommend.

[Bob Cowan]

There's a long list of things that can cause this; light weight flywheel and clutch, IAC, TPS, incorrect timing, poor tune, etc. It's a long list.

Don't just start changing parts. You're more than likely going to make it worse instead of better. Take a measured, scientific approach to the diagnosis.
- Check to be sure TPS and IAC are working correctly, and that the computer is reading the information correctly.
- Check timing. Be conservative.
- Get a good dyno tune

Don't change the injectors until you get it on the dyno. You'll probably find that they're just fine.

[GWL]

What flywheel and clutch are you running? I had a quartermaster clutch and lightweight flywheel when I built mine. Changing out to a smoother clutch and steel (OEM) flywheel got rid of the bucking I was experiencing. BTW I have 3:55 ratio.

:)

Dave, Stock Ford flywheel, Fidanza pressure plate and clutch from Breeze. Front damper is a Trickflow part but not undersized and standard weight.


Surging and bucking is almost always caused by issues with the IAC not responding correctly. I remember seeing a long time ago about drilling a small bypass hole in the throttle plate? I don't remember the specifics.
Try unplugging the IAC and do a short drive, also be sure you have good O2 sensors.

Rich, Not sure about that hole in the throttle plate idea. That air would bypass the TPS. I think that may have solved a malfunctioning IAC due to carbon build up or not functioning properly. Note the harness is removed from the IAC when setting idle. Like I said, I do have a brand new Ford IAC but maybe I can swap in the old one I still have. Actually, I've got two more older ones I can try.


You need a tune for the computer. Changing half the components on the engine and hoping the stock tune will learn and run correctly is not going to get you there in my opinion!

Im am still working with someone on the tune for mine and it has been adjusted several times to get close.

Do you have a card to pull the data from the computer to see what it is doing?

Just puttering, I'm starting to lean toward the computer upgrade. Yes, I've done a lot of mods that maybe the stock computer is just not able to work with. However, above 1500 rpm it runs great, pulls well from that 1500 and cruses well above that 1500 rpm. So, it only down low that I don't like and you guys are telling me it should run better. Has anyone had experience with the BAMA chip that are self installed and come with three tunes that base on your engine configuration and are switchable on the fly?


I had almost the same injection system with the Mass Air system (different throttle body but the Ford computer). I ran it for years, it ran Ok but never like I thought it should. I think the Ford computer didn't work well with even slightly bigger camshafts, they were made for emissions. There were no easy adjusments, anything that was changed messed up something else, even a simple idle increase. Recently I got fed up, pulled it all off and installed a PRO-Flo 4 system from Edelbrock. AMAZING difference! I wish I had done the change sooner. The only change was the EFI system and the car is more drivable, runs better in all RPM ranges and cold start drive offs are amazing. Also, the slow drop off to idle was gone ( I never did get used to that!) Pro- Flo 4 is an easy change over and is FULLY adjustable with the wireless pad. It self learns after a few easy input questions are answered. I have only had to change the fan control perimeters to later on and off, done on the control pad. The old 30 year old tech is outdated, this is a good replacement for the old 5.0 stuff I highly recommend.

You are saying the same thing Just puttering is saying and I'm leaning that way. I guess I'm hoping I can correct it with not too much of a change in the computer and intake system that I'm already invested in.

Thanks guys, George

[GWL]

There's a long list of things that can cause this; light weight flywheel and clutch, IAC, TPS, incorrect timing, poor tune, etc. It's a long list.

Don't just start changing parts. You're more than likely going to make it worse instead of better. Take a measured, scientific approach to the diagnosis.
- Check to be sure TPS and IAC are working correctly, and that the computer is reading the information correctly.
- Check timing. Be conservative.
- Get a good dyno tune

Don't change the injectors until you get it on the dyno. You'll probably find that they're just fine.

Bob, I have been conservative with the timing at 10° BTDC and I plan to leave it there. Have you heard about the BAMA chip? I will go over tuning it again to check my settings.

Thanks, George

[davekp]

Can someone explain what dyno tuning will do with the A9L ecu? I've read the BAMA chip is a waste of money. Probably needs further investigation to decide.
My previous Cobra had a setup very similar to the OP's. Similar characteristics. I think it's just a case of trying to use the 90's ecu technology with motor upgrades.
Anectdotally I had a Trick Flow Track Heat upper and it was quite "bucky" below 1500 RPMs. Changed to a Street Burner upper and it was much more driveable, although still somewhat "bucky".

[Old Timer]

I would check IAC first, maybe change to the spare. If you change to your original injectors,
you will have to change to a stock computer.

Before you spend money on a BAMA chip that might work, I would move up to a computer
that is easily programmable like the MS. I am running the MS3pro on my 347 and love it.
It's basically the same as the plug and play, but does not have the ford connector.
You can change so much stuff and make it all just the way your engine combo need to be.

Mega Squirt has a plug and play setup you can plug into the same connector your A9 is plugged into.
http://www.megasquirtpnp.com/mspnp2_features.php
https://www.diyautotune.com/

Then you have several stock programs you can load. They are all very conservative and a bit rich.
At this point you can drive around, but I would advise tuning it, either self tune, or better dyno tune.
The software will tune with your input as you drive, and get a lot of the maps pretty close, but the
dyno tune will get all the power available.

[Mike N]

The volumetric efficiency of your combination is going to be significantly better than what is programmed into the stock A9L. The A9L has the ability to adjust fuel trim (a little) but not timing and it could be your timing that is causing the bucking.

As you have a bolt on package I would suggest calling Trick Flow and asking if they know of a tuning or chip company that already has a 'canned' tune for your set up.

[RBachman]

Not sure if this will help, but an informative read.
https://www.autoblog.com/2019/06/12/symptoms-of-a-bad-or-failing-idle-control-valve/

[BradCraig]

Not sure if applicable, but my Gen3 Coyote had the bucking until I got Lund to tune.

[Railroad]

Advance your base timing to 14*. If you do not like it, put it back to your 10*.

[rich grsc]

Advance your base timing to 14*. If you do not like it, put it back to your 10*.
Agree, 10* too little timing. SBF's like more timing.

[Gumball]

I didn't see this in the comments so far, so just going to throw it out there for consideration. When I first started driving my car as a go-kart, it bucked quite a bit sometimes. What made it worse was that as it did so, it would throw me forward and back in the seat and my foot on the throttle would make things worse. I'm running a mechanical throttle linkage, so was able to dial out some of the responsiveness in order to make it more usable, without sacrificing full-throttle opening..... basically gave it more throw at the pedal.

My car has 3.27 gears, a carb'd (650 Holley DP blueprinted by ProSystems) 347 with a Ford "F" cam, and a T5Z transmission. I run a '64 Ford dual point distributor with a Pertronix, but no other electronics on the car. It now has just about 16k miles on it and is a joy to drive at lower cruising RPMs, regardless of the gear - although I'm careful not to tip into the throttle when running low RPM in a high gear, so as to avoid lugging the engine.

[Hoooper]

Tune Tune Tune. You can tune bucking out of engines with way bigger cams and way lighter flywheels than what you are running. Aside from being able to fix the bucking, there just is no possible scenario in which you should run different headers, injectors, heads, cam, intake, and throttle body on a stock tune any longer than it takes to get from your house to where you get the tune. 80s/90s ECUs didnt have the capabilities of todays computers, your computer will never learn your setup to the extent needed to keep the engine safe and running right.

[Jeff Kleiner]

All this custom tune talk has me thinking that I must be doing something wrong...mine has a Trick flow top end with Twisted Wedge heads, intake and stage 1 cam along with 24# injectors, matching Pro-M MAF, 75MM throttle body, resistors in place to spoof the EGR and TAD/TAB which has been running for the last 12 years and 25,000 miles an untouched/untuned A9L. I can pull away from a dead standstill in second gear without bucks, wheezes or any sort of protest. It runs "pretty good" ;)

Jeff

[rich grsc]

All this custom tune talk has me thinking that I must be doing something wrong...mine has a Trick flow top end with Twisted Wedge heads, intake and stage 1 cam along with 24# injectors, matching Pro-M MAF, 75MM throttle body, resistors in place to spoof the EGR and TAD/TAB which has been running for the last 12 years and 25,000 miles an untouched/untuned A9L. I can pull away from a dead standstill in second gear without bucks, wheezes or any sort of protest. It runs "pretty good" ;)

Jeff
It's a mystery how that happens. I had one just like George's, never was happy how it ran, this was my fix-------:D Now it pulls like a banshee
135176

[Jeff Kleiner]

What brand is your MAF George?

Jeff

[GWL]

I've got to say my car really runs well except at that lower rpm. I've included a few videos that will show how well it sounds and runs and then the slight bucking. I knew the slight bucking might happen so I was careful with the throttle. In the first video, I also held back a bit because of the bikers and 'my wife'. I've got a total of 28 miles on the odometer plus time for timing and tuning at idle.

The slight bucking takes place at around 2:50+ in the first video.

https://www.youtube.com/watch?v=YznZwU1ctFk&t=81s

This second video with the car under a bit more throttle from start.

https://www.youtube.com/watch?v=9AgW9o7ydYA

I'm not going to be able to work on any of the easy solutions for a couple of weeks now because I just sent my alternator back to Powermaster to get fixed. While setting the timing I shorted the positive terminal from the power output of the alternator to its case.

I may have the body on by the time the alternator gets back. Then during my testing I can go out on other roads.

When I do get the engine going again I'll work on the following:

Timing - I will advance timing to 12° then 14° BTDC and see how it runs at low rpm. My thought would be negative on that because I don't think I need any advancing at idle, that at idle it would make it worse with the cam overlap, although it is mild. My worry, too, is that as I advance the timing, when it may be lugging can you hear the engine 'knock' if it occurs as the exhaust is really loud. I've put the cats I have on to tone it down a bit but it didn't help much. I'm not worried about the last bit of HP at WOT but engine longevity. That's what old age will do to you.

Go through my tuning again. I may work to bring the TPS voltage down a bit to the lower .90 to .95 volts per Trickflow instructions and Jeff K, who has recommended, in the past, .92 - .95 volts. I had settled with .975 volt which was recommended by Ford Racing because as setting it, the voltage would jump from .975 to below .90 volts, so I stuck with the .975. I will play around with that setting and give it a test ride after every change.

IAC - If I don't get any satisfaction from the above setting changes I'll change this out as I have several older ones.

If anything, I now know that I can work this out.

I promise to check back in when I'm working on this again. Thanks to everyone, George

[GWL]

What brand is your MAF George?

Jeff

Pro-M calibrated for the 24 lb. injectors. I forgot which size, 70 or 75mm. I'll try to find that answer.

George

[bobl]

If your alternator was not charging during these events that could be the cause. EFI is really designed to work at a charge voltage. Lower voltage can cause some poor performance. I wouldn't mess with things until it is charging properly.

Bob

[GWL]

If your alternator was not charging during these events that could be the cause. EFI is really designed to work at a charge voltage. Lower voltage can cause some poor performance. I wouldn't mess with things until it is charging properly.

Bob

Good point Bob. Every time I went out for a test drive, which was probably five times, the battery was fully charged. I could feel the slight bucking right from the beginning of each drive. Then the battery never got under 12 volts during the drives. Note, in the first video, the voltage gauge at 2:12 is just above 12 volts. I wouldn't be able to run the car until I get the alternator back anyway.

Thanks, George

[Joel Hauser]

I didn't install the BAMA chip, but I did buy an SCT tuner from BAMA, which comes with unlimited free tunes. I found the BAMA techs to be really knowledgeable and good at what they do. However, it is a labor intensive process for the customer. You have to do a data log, which means downloading their program onto your laptop, selecting your tuning parameters, driving the car for 15 minutes in all the speed ranges with the laptop plugged into the OBD port, emailing the data log to BAMA, wait a few days for them to write the tune, down load the tune into the car...then do it all over again until you/they get it to where you are happy. It can takes well over a month with these cars. I'm guessing that the BAMA tuning process works much more efficiently with ordinary mustangs that have just a few mods.
Also, I always needed help from one of my sons, to help with the computer stuff, and to hold the laptop while driving around to do the datalog.

In my case, after months of struggling with replacing the less expensive parts (always a bad idea - I changed the 02 sensors twice, MAF, IAC, AIT, TPS, cam and crank position sensors - none of which was recommended by BAMA) and installing 6 different tunes from BAMA, the BAMA techs decided (correctly) that my PCM was bad. I ordered a new rebuild from Flagship One. BAMA wrote a tune for that one (which included the PATS delete) and the car runs near perfectly. Unfortunately, I think something has gone bad in the new PCM. The car still runs fine, but it is no longer able to interface with the SCT tuner so I can't download any more tunes. If and when I buy a new PCM BAMA will continue to write tunes, but I'm kind of over it.

So, if you have a local tuner you can use, I'm sure you'll be more satisfied going there. If that's not an option, BAMA may be worth a try.

[GWL]

Well, it looks like I’m headed for some smooth cruising in the near future.

After reading all the responses here and doing a lot of searching and reading on the internet I came to the conclusion that something was wrong with my ignition system. Just a hunch. But I was afraid to take action because if it was not the ignition one of the possible issues involved pulling the intake manifold and valve covers to check my valve lash.

So, after thinking about this for the past two weeks or more and doing some other work on the car and in the house, I returned to the drivability issue today. I had the original Ford stock parts of the ignition system. A while back before this issue, I had already changed out what I thought was a good Mallory distributor, for an older Ford stock distributor and it cleared up a back firing issue. So, today, I moved on to replace some other parts. The first was the ignition coil. No change, same issues. I then changed the coil ignition wire to the distributor and wow......... I can now cruise, in second gear, at 1100 rpm almost smoothly. No clutch needed just playing with the throttle. So, tomorrow I’m changing all the spark plug wires too but I am now feeling a lot better. Especially, after Rich said to make his drivable he had changed his engine.

Happy George

[CraigS]

It's great to have a fix for a vexing problem. Thanks for checking back on and letting us know. I haven't read your whole thread so may be a little off here but anyway...I'd look over the entire engine wiring and replace anything that you can w/ reasonable effort. We can't get mad at 20+ yr old wires for giving us problems but sure is nice to avoid them if possible.