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Discussion Starter · #1 ·
I have not been able to diagnose a significant stumbling on tip-in. This is regardless of what RPM the peddle is depressed. Engine idles fine, the engine cruises fine. It has new ID1050 injectors, new plugs, new coils, AEM-EMS Series II,, new BOV, throttle body removed - cleaned - new gasket. Many items were looked at: tested for system leaks - all fixed, smoke test good, compression/leak down, TPS, air temp sensor, O2 sensor. Everything looks ok by the AEM. I was going to have it dyno'd but that's out till this is fixed.

This should be a no-brainer, right? Any ideas are greatly appreciated.

Thanks in advance for any help.
 

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The one thing that stuck out to me Dennis is "new BOV".
Is it possible it is opening just slightly during accel? (I'm assuming that's what TIP IN is?)
What type of BOV and what spring?

Could be WAY off base, but you were asking for suggestions...

Bob.
 

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Do you have a datalog? What do AFRs do when it "stumbles"? Happens if you roll into it or only if you go WOT quickly?
 

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Discussion Starter · #4 ·
The stumbling happens rolling into it or, of course, from a standing start. The second part of your question is interesting and I wish I could answer it. I've been too aorried about going WOT for fear of some kind of damage. The initial tune was done by the dyno tech who found the problem and was going to do the final tune until he found the stumbling problem. They have the datalogs. I can ask. Thanks for your input!
 

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Discussion Starter · #5 ·
The one thing that stuck out to me Dennis is "new BOV".
Is it possible it is opening just slightly during accel? (I'm assuming that's what TIP IN is?)
What type of BOV and what spring?

Could be WAY off base, but you were asking for suggestions...

Bob.
Yup, Bob. Tip-in is anytime the accelerator is depressed slightly from any steady RPM, in other words part-throttle. If depressed slightly the stumbling disappears somewhere in higher RPMs. The dyno place thinks it is a fuel issue but pressures are fine. I honestly don't know about the BOV. It was never brought up in conversation. It is a Turbosmart BOV. I'll ask and about the spring, too.
 

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I don't see how it could be a fuel (supply?) issue if the stumbling disappears in higher RPM, especially if your pressures are fine so you dont have some strange transient response from the FPR on vacuum to boost crossover. If your datalogs have a wideband in them that should provide some useful info. When you say tip in are you talking about that crossover point when you first go into boost? I would assume they are tuning at minimum boost (gate pressure) to start with? You didnt specify your turbos either.
 

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Discussion Starter · #7 ·
I don't see how it could be a fuel (supply?) issue if the stumbling disappears in higher RPM, especially if your pressures are fine so you dont have some strange transient response from the FPR on vacuum to boost crossover. If your datalogs have a wideband in them that should provide some useful info. When you say tip in are you talking about that crossover point when you first go into boost? I would assume they are tuning at minimum boost (gate pressure) to start with? You didnt specify your turbos either.
My definition of Tip-in is application of accelerator lightly. Stumbling begins immediately. Steady acceleration will reach a RPM where stumbling ends. This happens from any steady RPM when throttle is applied. No crossover to boost. Steady routine acceleration. If you back-off the throttle when stumbling, stumbling stops immediately. Turbos are 3SXecutioners 1st gen. Actually installed 10 years ago. Supposedly able to hold 24PSI to redline. You're correct about gate pressure tuning. I will ask again for Datalogs.
 

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I think my concern with the BOV may be squashed by the fact that you have a widely used (high quality) one.
Since I know absolutely ZERO about the AEM 2 and how it's tuned, and the fact that you are using what I'm assuming (by the name) are 1050cc injectors?
3SXExecutioners are the equivalent of DR650's? 750's?
I know you wanted plenty of injector for the turbo size, but maybe the AEM map is wrong down low?

I'm sorry if my suggestions SUCK, but I am just throwing out thoughts....

Bob. ;)
 

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My definition of Tip-in is application of accelerator lightly. Stumbling begins immediately. Steady acceleration will reach a RPM where stumbling ends. This happens from any steady RPM when throttle is applied. No crossover to boost. Steady routine acceleration. If you back-off the throttle when stumbling, stumbling stops immediately. Turbos are 3SXecutioners 1st gen. Actually installed 10 years ago. Supposedly able to hold 24PSI to redline. You're correct about gate pressure tuning. I will ask again for Datalogs.
Did you install the injectors 10 years ago as well, lol? If they are really old, they could have flow issues (inconsistent across injectors, bad spray pattern, etc). Although, one would expect those issues would be more consistent than just at tip in. I finally pulled my 550s after 12 years and had them flow tested and cleaned, and some were only flowing 260cc, so that shows how bad they can get, and the flow pattern was described as "dripping"
 

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Discussion Starter · #10 ·
I think my concern with the BOV may be squashed by the fact that you have a widely used (high quality) one.
Since I know absolutely ZERO about the AEM 2 and how it's tuned, and the fact that you are using what I'm assuming (by the name) are 1050cc injectors?
3SXExecutioners are the equivalent of DR650's? 750's?
I know you wanted plenty of injector for the turbo size, but maybe the AEM map is wrong down low?

I'm sorry if my suggestions SUCK, but I am just throwing out thoughts....

Bob. ;)
Bob, you and I are pretty similar in our experience with these types of engines, engine fuel systems and how they work and this is only my second turbo car, the first one being the '93 VR4 kept till I learned of the 2nd Gen VR4's bought the current one, a '97. I'm old and an old school guy. I did a boat load of upgrades 10years ago. Turbos, 550cc injectors, larger SMIC-CMOC-Radiator. And everything ran great for about 8yrs when I could feel a lack of power. When I took it in for maintenance they found system leaks all over .... couplings, gaskets, BOV. All were fixed, smoke test was fine, the shop recommend a move to the AEM-EMS II to remove all the add-on fuel management items. Ultimately, I knew that was the better way of handling engine management but always balked at the price. So I went with it, sold one of my kidneys (you only need one, you know) and had it put on. They recommended the ID injectors saying the Precision 550's were old tech. There went a couple of lobes of my right lung. After all of the work was completed the tip-in problems started. They swapped the AEM out for another one, no change. I doubt it is the injectors. I believe the turbo's are close to the DR650's. Ray P looked at them when he tuned it last (10Yrs Ago) and said they could be similar to 16T's
 

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Old eh? I got underwear that are your age ;)

All I am trying to say is "maybe" the settings for the AEM are not set correctly for the size injectors you have.
Maybe you should try to contact @familyMAN or @bboyalan for some help and possible remote tuning....
I would trust my car with either of these guys every day of the week and twice on Sunday...

Just sayin....

Bob.

Eric and Alan, forgive me for offering your services. I know you both have pretty full plates.
I wouldn't do it if I didn't believe that you honestly could help...
 
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Discussion Starter · #12 ·
Did you install the injectors 10 years ago as well, lol? If they are really old, they could have flow issues (inconsistent across injectors, bad spray pattern, etc). Although, one would expect those issues would be more consistent than just at tip in. I finally pulled my 550s after 12 years and had them flow tested and cleaned, and some were only flowing 260cc, so that shows how bad they can get, and the flow pattern was described as "dripping"
Yes, the Precision 550cc's were installed 10 yrs ago ....... no joke. So are you saying they were old school like me? LOL. Guilty as charged:) So the ID1050X injectors were installed in this latest round of work on the car. After12yrs for yours? I don't feel so bad now. I should have known they would decrease in flow after years of use. How much did it cost to have the injectors worked on? With the current injectors, are there potential generic injector issues that could pop up only during tip-in? I didn't think so, but what the heck do I know!

What I need is an experienced diagnostician with the necessary equipment.

Dennis
 

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Thanks, Bob! 😄

All of the suggestions mentioned are good, and if everything else supposedly "tests fine" then it is only a number of things. Difficult to say without a datalog and/or calibration though.

It could be the FPR responding slowly or just the tune itself, as already stated. Injectors are a possibility and usually tuned out until more serious symptoms or preventative measures require them to be serviced and tested. The twist is that you believe it cruises well, but how about everything else? Accel? Part-throttle into positive?

-sent from my Galaxy Note 9
 
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Discussion Starter · #14 ·
Thanks, Bob! 😄

All of the suggestions mentioned are good, and if everything else supposedly "tests fine" then it is only a number of things. Difficult to say without a datalog and/or calibration though.

It could be the FPR responding slowly or just the tune itself, as already stated. Injectors are a possibility and usually tuned out until more serious symptoms or preventative measures require them to be serviced and tested. The twist is that you believe it cruises well, but how about everything else? Accel? Part-throttle into positive?

-sent from my Galaxy Note 9
The stumbling happens during at least part throttle acceleration. It stops immediately when the peddle is lifted even just a small amount. I haven't attempted WOT as I don't know how that might effect the engine. The problem with the cruising is maintaining speed ... not slowly decreasing speed because you can't keep a rock solid peddle. Slightest Tip-in and the stumbling begins. The small amount of time I was able maintain steady/cruising speed it seemed fine. I tried attaching a .cal file that I have but your system doesn't accept those. Can it be sent any other way? I'll ask for a datalog file on Monday.

Thanks for taking time on your busy weekend.

Dennis
 

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It could be a sensor error needing replacement or recalibration especially TPS. FPR is still a suspect too. If the car is in your possession, then just start a datalog on your own while in the tuning tab.

For any files that are not supported, just change the file extension to upload; anyone can change it back to the correct one upon downloading.

Cheers,
-Alan

-sent from my Galaxy Note 9
 

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Yes, the Precision 550cc's were installed 10 yrs ago ....... no joke. So are you saying they were old school like me? LOL. Guilty as charged:) So the ID1050X injectors were installed in this latest round of work on the car. After12yrs for yours? I don't feel so bad now. I should have known they would decrease in flow after years of use. How much did it cost to have the injectors worked on? With the current injectors, are there potential generic injector issues that could pop up only during tip-in? I didn't think so, but what the heck do I know!

What I need is an experienced diagnostician with the necessary equipment.

Dennis
Injector flow test and cleaning is pretty cheap. I have RC injectors and RC is local to me in SoCal so i just dropped them off. Flow test is 10-15$, test and clean is usually 20-25$ per injector. Includes all new seals and orings and screen. They come out brand new basically.
 

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Discussion Starter · #17 ·
It could be a sensor error needing replacement or recalibration especially TPS. FPR is still a suspect too. If the car is in your possession, then just start a datalog on your own while in the tuning tab.

For any files that are not supported, just change the file extension to upload; anyone can change it back to the correct one upon downloading.

Cheers,
-Alan

-sent from my Galaxy Note 9
Hi Alan,

I had already tried a extension change to .jpg. Your system is locked down pretty tight..... said it wasn't an image file. I'll try with another extension.

Have you run anything a M1 yet?? Last year I took some laps with our son's M3. Not bad for a short track in the middle of the burbs. I'm hoping when this tip-in issue is solved I can run the VR4 there. Then there's my ProTouring RestoMod of my '70 Firebird! That car will see plenty of track time;):)
 
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