Help Me Brainstorm...

Benboi92GT

Member
Dec 28, 2011
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So, since I built the top end of the 5.0 in my truck, I have had a random engin. shimmy/shudder/shake/whatever. Ive been trying to track down the cause but have been unsuccessful. Here is a video of another engine that looks to have the same "shudder" mine does:


View: https://m.youtube.com/watch?v=tktt4EHNCGM


Have any of you ever seen anything like this? It is completely random and inconsistent. Some shakes are more violent than other. Whenever the engine shudders the rpms dont seem to change nor does the exhaust note change.

Engine mods: tfs 170 61cc track heat heads (thermactor air function turned off in tune), custom ground ed curtis cam, 1.6 probe roller rockers, moss ported lower intake, jba shorty headers, magnaflow y-pipe, dronemaster 40, 3:73 frpp gears. Also turned off in tune: knock sensor function, and egr function. Truck put down 225/267 to the wheels. Poopy numbers if you ask me but when you consider the 205/275 they came with from the factory (to the flywheel) I guess its not terrible.

Some more details and things that have been suggested on other forums:

Fuel pump/fuel trims: This would have shown up in the A/F on the dyno, no?

Spark/miss: New plugs (gapped at .050) and wires, new tfi and coil, original distributor.

Motor mounts: Maybe?

Bad balancer: Not likely?

EGR: Still leaking exhaust gases into upper, despite being turned off in computer. Thoughts?

Anyway, trying to eradicate this engine shudder but havent been able to. Ideas please? No codes, cylinder balance test passes on first go.

If I dont have it figured out by mid-May then its going back to the tuner, and maybe he can uncover something with his data logs. In the mean time, Im bored and like tinkering, so lets figure this out =).

Thanks fellas.
 
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Dump the codes: Codes may be present even if the Check Engine Light (CEL) isn't on.

Dumping the computer diagnostic codes on 86-95 Mustangs

Revised 26-July-2011. Added need to make sure the clutch is pressed when dumping codes.

Codes may be present even if the check engine light hasn’t come on, so be sure to check for them.

Here's the way to dump the computer codes with only a jumper wire or paper clip and the check engine light, or test light or voltmeter. I’ve used it for years, and it works great. You watch the flashing test lamp or Check Engine Light and count the flashes.

Post the codes you get and I will post 86-93 model 5.0 Mustang specific code definitions and fixes. I do not have a complete listing for 94-95 model 5.0 Mustangs at this time.

Be sure to turn off the A/C, and put the transmission in neutral when dumping the codes. On a manual transmission car, be sure to press the clutch to the floor.
Fail to do this and you will generate a code 67 and not be able to dump the Engine Running codes.

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If your car is an 86-88 stang, you'll have to use the test lamp or voltmeter method. There is no functional check engine light on the 86-88's except possibly the Cali Mass Air cars.

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The STI has a gray connector shell and a white/red wire. It comes from the same bundle of wires as the self test connector.

89 through 95 cars have a working Check Engine light. Watch it instead of using a test lamp.

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The STI has a gray connector shell and a white/red wire. It comes from the same bundle of wires as the self test connector.


WARNING!!! There is a single dark brown connector with a black/orange wire. It is the 12 volt power to the under the hood light. Do not jumper it to the computer test connector. If you do, you will damage the computer.

What to expect:
You should get a code 11 (two single flashes in succession). This says that the computer's internal workings are OK, and that the wiring to put the computer into diagnostic mode is good. No code 11 and you have some wiring problems. This is crucial: the same wire that provides the ground to dump the codes provides signal ground for the TPS, EGR, ACT and Map/Baro sensors. If it fails, you will have poor performance, economy and driveablity problems

Some codes have different answers if the engine is running from the answers that it has when the engine isn't running. It helps a lot to know if you had the engine running when you ran the test.

Dumping the Engine Running codes: The procedure is the same, you start the engine with the test jumper in place. Be sure the A/C is off, and clutch (if present) is pressed to the floor, and the transmission is in neutral. You'll get an 11, then a 4 and the engine will speed up to do the EGR test. After the engine speed decreases back to idle, it will dump the engine running codes.

Trouble codes are either 2 digit or 3 digit, there are no cars that use both 2 digit codes and 3 digit codes.

Your 86-88 5.0 won't have a working Check Engine Light, so you'll need a test light.
See AutoZone Part Number: 25886 , $10
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Alternate methods:
For those who are intimidated by all the wires & connections, see Actron® for what a typical hand scanner looks like. Normal retail price is about $30 or so at AutoZone or Wal-Mart.

Or for a nicer scanner see Equus Digital Ford Code Reader (3145) Equus - Digital Ford Code Reader (3145It has a 3 digit LCD display so that you don’t have to count flashes or beeps.. Cost is $22-$36.
 
Thanks for the reply. No codes are present, however =/

No code 11 (two flashes when the computer dumps the codes)? A perfectly functioning system will always get a code 11, it is the everything is OK code. The 11 code is computer passed its internal self test.
If you don't get an 11, you have computer or wiring problems.
Please check and repost.
 
Sorry, I misspoke. KOEO shows a 511, which I read is because there is a chip on my PCM from the tuner. KOER shows a 111, pass.

When I said no codes, I meant there were none to point me towards a possible problem.
 
3 digit codes? The 94 and later computers gave 3 digit codes, the 93 and older used 2 digit codes. Did I miss reading something?
 
Let me give the whole backstory.

Bought the truck with nothing done to the engine except jba shorty headers. It was slow as balls and I had just gotten out of a 92 Mustang GT so I decided to build the top end.

Fast forward to build time. Ordered the assembled heads from summit (http://m.summitracing.com/parts/tfs-51410010-m61/overview/make/ford), got the lower intake ported by TMoss, ordered a direct-fit magnaflow y with high flow cat (****tiest fitting product Ive ever had the pleasure of dealing with), 1 inch phenolic spacer to clear the tall valve covers, 1.6 probe roller rockers, camshaft from FTI (Ed Curtis) with below mentioned specs, and all other associated gaskets and required hardware.

Cam Specs (this was ground for my specific combo, stock converter):

SB FORD – StreetBeast14L-HR12 +3*

Intake Exhaust

Valve Adjustment: .000” .000”

Lobe Lift: .358” .353”

Gross Valve Lift 1.60 Ratio: .573” .565”

Duration @ .050” Tappet Lift: 215* 227*

Lobe Separation: 112*

Recommended Intake Centerline: 109*

Specs at 109 Degree Intake Centerline:

Valve Timing at Open Close

.050” Tappet Lift: Intake: (-1.5*) BTDC 36.5* ABDC

Exhaust: 48.5* BBDC (-1.5*) ATDC

Took our time and immaculately cleaned any and all gaskets surfaces, measured PTV clearance, set valve lash, and degreed the cam (I think correctly). It was outside my scope and I left those details to my uncle (yes we used a degree wheel). However, it could have been done wrong and I'd be none the wiser.

Get it all buttoned up, set the initial to 14*, and the truck runs great (no tune yet). At this point I was not paying attention or really analyzing, as I had no reason to. I couldnt tell you if there was a shudder or not.

Weeks later, my knock sensor goes fruity. Terrible throttle response, no power anywhere in the band, just drove like ****. Took me weeks to track down the problem. Reset idle several times, cleaned sensors, replaced sensors, tried different MAF sensors, dumped codes, compression tests, etc. etc.. This is when I NOTICED the shudder. Finally tracked down the knock sensor, removed it, reset eec, and voila. Everything is back to normal, power is back, runs fine, BUT; engine shudder.

Take it to get tuned, truck put down 231/271 in MO. Thermactor air and EGR functions turned off in tune. Still a shudder. If I remember correctly, I want to say my tuner said hp/tq stopped rising at 28* total WOT on the dyno.

Just because, I replace all visible vacuum lines with high heat silicone, no change. I upgrade all engine grounds with 4ga wires and gold plated connectors as well.

Anyway, some more details =P
 
Why did you have the thermactor and EGR turned off?

Have you actually had a vacuum gauge on it? What's it pulling at idle?

Are we certain the rocker arms are correctly adjusted?

Does it run the same way warm and cold?
 
Why did you have the thermactor and EGR turned off?

Have you actually had a vacuum gauge on it? What's it pulling at idle?

Are we certain the rocker arms are correctly adjusted?

Does it run the same way warm and cold?

Track heat heads have no provision for the crossover tube. EGR is turned off because he turned it off, not sure.

Going to put a vacuum gauge on it today. Will be back with my findings.

Rockers were adjusted per Ed's instructions on the back of the cam card.

When first started during enrichment the shudders are either absent or not noticeable. When the truck idles down they appear, so yes, happens when cold and warm.
 
Idling at about 950 it is showing a very slow, but maybe random fluctuation between 13-14". (Greeley CO Elevation: 4658 ft)

Found this online:

Inches of Altitude Vacuum

Sea level-1000 ft. 18-22

1000-2000 ft. 17-21

2000-3000 ft. 16-20

3000-4000 ft. 15-19

4000-5000 ft. 14-18

5000-6000 ft. 13-17

I'm just about in that range, if not an inch or two short.

Throttle snap drops her down to 0, shoots up to 20" or so, and settles back at the 13-14".

Holding 3000 rpm, vacuum stays steady at an increased value, no drop off, so no exhaust blockage.

Maybe IT IS just the cam characteristics at idle? Ed didn't seem to think so, though.
 
How does your TPS check out?

I'm having a similar issue with my 331 and have tried just about everything. (set and reset rocker arms, check for vacuum leaks, new plugs, plug wires, confirmed distributor position, had the injectors cleaned, sent my MAF meter back to Pro-M for inspection and calibration, installed new O2 sensorts, confirmed EGR and FPR were functioning properly, tested both the ACT and Coolant Temp sensors, cleaned the salt and pepper shakers, etc). Not tripping any codes, but the random "shake" is still present.

I'm running a Comp XE274HR, straight up (Comp grinds about 4-deg advance into their cams), which is a pretty similar to yours, but still supposed to be quite streetable?

I too am now at a bit of a loss. I refuse to believe it's just "the nature of the beast". I've seen larger cams than mind running on smaller displacement engines that seems to have cleaner idles? I've got mine set up to idle at about 850RPM right now. Any lower and I'll get idle surge and much higher and I get a hanging idle when coming up to traffic stops.

My next suspicion is the TPS. I did a quick test with the volt meter, which showed a smooth arc as the throttle opened, but I often wonder if my Volt Meter is accurate enough to pick one up that's just on the verge of healthy.

I ordered another one today and am gonna give it a go when it gets in. For $60 it's at the very least piece of mind. I'll let you know how it turns out.
 
How does your TPS check out?

I'm having a similar issue with my 331 and have tried just about everything. (set and reset rocker arms, check for vacuum leaks, new plugs, plug wires, confirmed distributor position, had the injectors cleaned, sent my MAF meter back to Pro-M for inspection and calibration, installed new O2 sensorts, confirmed EGR and FPR were functioning properly, tested both the ACT and Coolant Temp sensors, cleaned the salt and pepper shakers, etc). Not tripping any codes, but the random "shake" is still present.

I'm running a Comp XE274HR, straight up (Comp grinds about 4-deg advance into their cams), which is pretty similar to yours, but still supposed to be quite streetable?

I too am now at a bit of a loss. I refuse to believe it's just "the nature of the beast". I've seen larger cams than mind running on smaller displacement engines that seems to have cleaner idles? I've got mine set up to idle at about 850RPM right now. Any lower and I'll get idle surge and much higher and I get a hanging idle when coming up to traffic stops.

My next suspicion is the TPS. I did a quick test with the volt meter, which showed a smooth arc as the throttle opened, but I often wonder if my Volt Meter is accurate enough to pick one up that's just on the verge of healthy.

I ordered another one today and am gonna give it a go when it gets in. For $60 it's at the very least piece of mind. I'll let you know how it turns out.

TPS at .94v.

I dont suspect my tps, and I doubt it will fix my (or your) problem. I replaced my tps not too long ago because it was bad. Funny thing is that it was reading a fine .97v key on, and increased and decreased smoothly. However, when coasting in idle off the throttle, I would pick up speed and rpm, hinting at a bad tps lol. Replaced it and voila, no more of that BS. I learned that day that voltage isnt everything with those. But this funky ass idle shudder? I dont see how that could be tps related.

Since my manifold vacuum seems to be at an acceptable value, I suppose Im thinking it fuel or timing related. Who knows. Mid-May cant get here soon enough, need this thing back to the tuner!!!
 
Run the cylinder balance test.

I had a random shudder that occurred on my Fox 5.0 that I attributed to the flywheel/clutch I just put in after my AOD-to-T5 swap. Drove this way for a year.

One day I did the cylinder balance test and discovered a fuel injector was completely dead. I drove on 7 cylinders for a year and didn't know it.
 
Figured I'd provide a bit of closure to this thread. Got it to my tuner, he looked at me and said "Seriously dude? You drove here from CO for that? That's normal for a cammed engine."

=)
 
Figured I'd provide a bit of closure to this thread. Got it to my tuner, he looked at me and said "Seriously dude? You drove here from CO for that? That's normal for a cammed engine."

=)


So did he tune it at all? Did the idle improve?

I changed my TPS and it didn't seem to make a difference. I'm sure my issue stems around the injectors. They're just too big for the parameters of the stock ECU's calibration to keep up with.

The theory of a Mass Air car being more capable of handling mods is a double edged sword IMO. Bolt on parts like H/C/I don't seem to be an issue for most, but once you start fooling with the fuel system, it all goes downhill. I believe once you get into the 30lb/hr range and up, reprogramming the fuel trim and curve levels of the ECU is probably mandatory. The stock ECU is only capable of compensating for fuel changes in the 10-15% range. Beyond that, you've run out of adjustability. Tricking it with a calibrated MAF sensor can help, which is why most can get away with running the 24lb/hr injectors, but it seems after that, you're gonna need to spend some money.

Time for me to place a call to Dirty Dirty Racing and throw some cash down on a Moats Quarterhorse.