Symptoms of "off" fuel sync

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Yeret

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Okay guys, this is something that I really should have posted long ago but, eh, anyway, I'm posting it now.

Here's the deal, some of you may remember the whole kerfuffle that I had with a mechanic friend of my dad involving tearing my engine apart, freshening it up and putting it back together again. A ridiculous process that spanned over several months.

In the end, as things went, screwups and misunderstandings on both ends were ultimately resolved and we have happily gone our own ways. In other words, no hard feelings. In my end, the engine as far as I've owned it has never been happier, especially with a tune courtesy of Flyin' Ryan.

Anyway, my main man was well on pace with me and had noted that when the distributors on these engines have been pulled and then reset with base timing, they have to be fine-tuned via DRBIII scanner due to the exacting relationship between the cam and crank sensors and their impact on injector firing. Unfortunately, neither he or I had access to this multi thousand dollar tool and we never had the chance to see how the engine would respond to this fine-tuning before, well, the roof collapsed, figuratively speaking.

Here's the deal now. Ever since the freshening, I've done some basic bolt-on stuff to the engine and of course had it SCT-tuned. However, no matter what I've done, the engine hesitates for a split-second or even more when taking off from a sit-still, especially when cold.

Basically, while sitting still, I step on the gas and there's this split-second hesitation before the engine "grabs" and goes. I can clearly hear the engine drawing in air when I step on the gas but the truck just doesn't jump and go right away as I expect that it would. It seems to me like there's a delay in fuel delivery with throttle input.

This is an issue that was not present before the dizzy was pulled...

Under low throttle/light load at less than 2,000 RPM, the engine has this weird oscillation which can very clearly be heard courtesy of my nice, open exhaust, LOL.

My question is since I've never had my fuel syncing fine-tuned, would that be causing my "hesitation" and aforementioned "oscillation" issues? I will say that when the RPM passes the 2,000 mark or if I just gun it, these issues disappear and the engine pulls like an SOB, way more than it ever did prior to my tune.

I'm not denying that my fuel syncing needs to be fine-tuned but I'm just wondering if this is what's causing my aforementioned issues.
 

dapepper9

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Possible. Local dealer can do it for like $50. Ask for +2 to +4 advance.

Oscillation is likely tps or torque converter related
 
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Yeret

Yeret

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Just a little update on this annoyance. I replaced the TPS and reset the computer. The problem did seem to be totally fixed but after a couple days, the problem showed up again. The other day, I replaced the MAP sensor, not because I needed to but because it was basically the last engine sensor that I haven't replaced. I once again reset the computer and the problem was once again resolved. Sure enough, after a couple days it came back.

So, it seems when I reset the computer, the problem goes away but as the computer "re-learns," the problem comes back. Any ideas? I'm honestly stumped at this point.

Also maybe worth noting. This "surging" only occurs when I'm not in overdrive. As soon as the tranny shifts into overdrive, the problem disappears irregardless of speed or throttle input.
 
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crazykid1994

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Symptoms of "off" fuel sync

Could be something tc related. OD is also lockup which if internally the tc is messed up and surging when it locks it can't surge any more because in and out are now 1:1. I'm not an expert. Just an idea I'm throwing out there.


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Yeret

Yeret

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Man, I'd **** a brick if it was an issue with the tranny. Granted, I didn't pay for the rebuild but it was rebuilt by a reputable shop a few years back. It's got 30,000 miles on it now and had a few extras thrown in including a TransGo shift kit and heavy duty torque converter. Of course, I'm well past the warranty so I guess I should expect anything at this point.

Are there any "tests" one can do to verify the health of a torque converter? I know far more about engines than I do about transmissions so I'm pretty much in the dark on this one.

I'm not yet going to jump to conclusions and start targeting the tranny but I'm all for easy tests on anything at this point. Plus, I'm pretty sure there are others here that have noted a similar problem so this could be some good reference for them as well.
 

crazykid1994

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Man, I'd **** a brick if it was an issue with the tranny. Granted, I didn't pay for the rebuild but it was rebuilt by a reputable shop a few years back. It's got 30,000 miles on it now and had a few extras thrown in including a TransGo shift kit and heavy duty torque converter. Of course, I'm well past the warranty so I guess I should expect anything at this point.

Are there any "tests" one can do to verify the health of a torque converter? I know far more about engines than I do about transmissions so I'm pretty much in the dark on this one.

I'm not yet going to jump to conclusions and start targeting the tranny but I'm all for easy tests on anything at this point. Plus, I'm pretty sure there are others here that have noted a similar problem so this could be some good reference for them as well.



The only one I can think of is hold the brake down and slowly press the gas while in drive. Not enough to burn the tires. Just until the motor stops revving higher. See if it keeps surging even though your not moving.


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Yeret

Yeret

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Just performed that test. RPM held steady the whole time even just under 2,000 RPM. At that point, the tires were just itching to tear a couple inches into the gravel, LOL.

Another question. Do our distributors have a shaft bushing? I'm thinking if that sucker ovals out or even just wears out, it might cause issues. While under the hood, I noticed that the engine seems particularly shaky with slight throttle input and doesn't smooth out until I give considerable throttle. This translates almost perfectly to when I am driving the truck.

It's been a few years since the cap/rotor/wires have been done. I might replace them anyway since they're not very expensive for decent stuff.
 
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crazykid1994

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I think if the distributor was wobbling you would know. If you do change the cap you should be able to see wear marks on the tabs inside


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Yeret

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I almost forgot about my intake temperature sensor. Replaced it yesterday with a Mopar one. The old one was pretty fouled with oil from my plenum leak back in the day. We'll see what effect this has.
 

Shadow_Death

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What do you mean oscillation? Is it like the vehicle lurches forward as you drive under 2k?
 
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Yeret

Yeret

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Basically, while accelerating under light throttle and sometimes even when holding speed, the RPMs bounce up and down under 2,000 RPM. Once I'm north of 2,000 RPM or the transmission shifts into overdrive, the issue disappears. The issue is much more prominent when the engine is cold.
 

Shadow_Death

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Mine does this same thing but with one slight twist. While driving down the highway with OD on the TC will constantly lock and unlock. It will stay in overdrive though. I can tell this because the RPMs will only go up 100-300. I haven't figured it out either. I have noticed that the problem does seem to go away once you unplug the battery and let the ECM reset but then comes back later.

That kind of makes me wonder if it isn't the ECM itself. Although on my truck you can hear it "oscillate" sort of. It sounds like my truck is idling like one of the older Ford 7.3l PSD but without the diesel clatter. I'll see if I can get a video of it tomorrow after work when it's hot outside.
 
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Yeah, I don't have lock/unlock issues with the overdrive. Actually, once OD engages, it takes a bit of persuasion to kick it off, unless of course I just click the OD switch on the shifter.

The main reason this issue irritates me so is because other than it, my engine runs very smooth, and my off-the-line torque is such that I gotta mind the throttle on the gravel because the rear tires will spin out quite handily. Hell, going to town today on the tarmac, I stopped at an intersection and gave her some go to pull in front of and pace an approaching car and the passenger side wheel spun briefly on just a few rocks spread across the road.

I've noticed that my low-end torque has noticeably improved after replacing the TPS sensor. I then replaced the MAP sensor but it didn't make any noticeable difference. I then replaced the IAT sensor the other day and everything seems good but I'll wait and see how things change as the computer "re-learns." At this point, the only engine sensor that I haven't replaced is the cam sensor/pickup in the distributor.

Also, for what it's worth, after searching the depths of my booze-soaked memory, I recall that this issue first surfaced after I swapped the OEM throttle body with my current modified one. My current TB has the air horns shaved off, the inlets are chamfered and the necked-down venturis bored so it's a true and straight 50mm. The plug that covers the idle-adjust screw has been removed. Don't know if it's been screwed with or not but my truck never had any idle issues after swapping on this throttle body.
 
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Shadow_Death

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https://goo.gl/photos/GhUhTYhmTSkEDaBo9

There you go, that is what I meant when I said I can hear it in the engine. When I put it in drive the whole truck lurches to that rhythm.

Also I decided to throw the codereader back on the truck and see what it pulls up for RPM stats. Then I decided to check for codes for giggles. Came up with this one despite the fact that the CEL wasn't lit and I know it works still. Funny thing is this is my 3rd TPS but my second BWD TPS. I can swap it out and I won't get this CEL. I suspect Orileys is selling crap TPS.
 
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Yeret

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After doing some reading and thinking about it, I'm thinking I'm gonna test the idle via this procedure and see if the throttle linkage is where it's supposed to be. I know that the throttle valve for the transmission is hooked up the throttle and if that's off then the transmission will be off as well. I noticed that my throttle body has had the plug for the idle adjust screw removed so it's not impossible to say that it hasn't been screwed with.

Not sure if a maladjustment here would be causing my problems but it couldn't hurt to check. Well, unless I somehow manage to place the adjuster screw in such a way that I can't recover my current setup, LOL.
 
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Yeret

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Okay, I just finished up with the idle adjust procedure. Unfortunately, by following the procedure and increasing the idle to 800 RPM, my RPM sat at 1,200 RPM with absolutely no intention of dropping. As such, I backed off the adjuster until the RPM dropped to an acceptable level. In the end, I don't think that I did much. However, I compared the RPM with the IAC open and with the IAC plugged before and after the procedure. I will say that right now, the idle is less affected (ie, doesn't drop as much) when the IAC is plugged than it did before. Also, the idle doesn't seem to drop as much when I put the tranny in gear or when I turn the wheels. The idle is still what it was before, which is ~650 RPM.

Also, when I snapped the throttle but only opening it a small amount, the idle used to stutter a smidge before recovering. Now, the idle returns much smoother. The idle itself doesn't seem to fluctuate quite as much. It seems to fluctuate by an average of 20 RPM whereas before it would fluctuate around 50 RPM.

What is this going to do to my target issues? Perhaps nothing but there's only one way to find out. Reckon we'll have to wait a little because I'm well too intoxicated to hit the public roads at the moment, LOL.
 
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Yeret

Yeret

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Just as I submitted the last post, I remembered that I needed to change the cats' litter box. I needed to cart the load up to the gravel for garbage pick up so obviously this seemed a good time to test whatever changes I made.

First of all, the engine fired and idled no problem. Then, I noticed that the accelerator felt much firmer than before. Obviously, I must have settled on an incrased input to the throttle which at least tightened the cable. Stepping on the gas, I noticed my off-the-line acceleration is virtually instant. Like you punch it and she punches right back. Furthermore, I noticed that the air cleaner was much quieter than before. Hell, the exhaust even sounded different. The engine seemed more relaxed than before yet seemed peppier.

Now the fun part. I goosed the throttle turning onto the gravel and holy crap! The rear tires broke loose instantly and actually spun through the gravel whereas before they would kind of hop and jump a little. Reaching the end, I turned around and gave her a hearty helping of throttle. I was caught off-guard as the truck instantly spun around and I just kept her from flat out spinning into a doughnut. ****, now that's what I call low-end torque!

Interestingly, the transmission seems to be shifting sooner than before, yet the acceleration seems unaffected by this.

As far as my "gravel" test goes, the truck's throttle response and low-end torque seems to have improved significantly. Perhaps I didn't increase the throttle blade opening at all but instead took some slack out of the throttle cable?

Gonna give her a proper road test tomorrow. Hopefully my drunk ass isn't just making stuff up but then, I've driven the old ******* the gravel while drunk before and this time, she's different...
 
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Yeret

Yeret

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Okay, just got back from a "sober" road test in which I travelled for some more beer. I am on vacation all week after all, LOL.

Anyway, I can still confirm that off-idle throttle response has definitely improved. The air cleaner is much quieter now, especially if I snap the throttle in gear. Cruising and uphill power seem improved but I'm gonna go a few days before I say one thing or the other.

Perhaps most notably, the surging issue seems to have disappeared. Once again, I'm gonna give it a few days before coming to a final conclusion as this issue seemed to be present in varying degrees of effect.

Well, my conclusions at this point are improved off-idle throttle response and a much quieter air cleaner. Oh, and I didn't screw anything up, so that's always a plus, LOL.
 
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Yeret

Yeret

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After driving for a couple days, the surging is still present. It honestly seems worst overall when I'm cruising in third gear around 50 MPH. My overdrive engages quite late as a result of my tune, typically only engaging at 60 MPH (vs 40 MPH with the original "death flash" programming).

It's not as bad as it was but it seems the improvement was more the result of replacing the TPS.

However, there were still a couple of improvements from fiddling with the idle screw on the throttle body. As a result of the increased tension on the throttle cable, the truck is much snappier off the line. Also, it seems to be cruising a bit stronger, maintaining 75 about as easy as I would cruise 70. I'm not sure how the cable adjustment would be a factor here but maybe for the same accelerator input, I'm getting more throttle input.

I'm gonna take a look at the throttle valve cable and lever on the transmission at some point this week to make sure everything is in sync with the throttle. Mom's Dakota is currently stranded 12 miles away because of a starter "bug" that I was just today made aware of from my uncle who insisted that the truck had "nothin' wrong with it." Pretty sure it's a toasted solenoid. Gotta head in tomorrow in an attempt to get the bugger to go just one more time so we don't have to pay $100 to have it towed back. Man, I just spent most of yesterday putting everything back together from the cooling system work and now this. SOB...
 
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