Need some help on this one... Drove the car two weeks ago with zero issues; it drove fantastic. Took it out yesterday and it had a massive hesitation at 3.5k+ rpms and any positive boost. I checked the coils (look very clean and within spec resistance), wires (connected and good resistance) and plugs (look great) last night and took her out again today and it's still there. What's so perplexing is that nothing has changed, it just sat for two weeks.

Relevant info:

1). Rel Mods: GT4088R, HKS twin power (new), 1680 secondaries (flow tested 200 miles ago), 550 primaries, supra fuel pump

2). Fresh street port rebuild 200 miles, idles perfectly smooth, pulls great vacuum, etc.

3). Runs smooth and clean with no boost and below ~3.3k RPMs, completely bogs down above that, drives just awful.

4). Boost seems to be fine, but I'm not comfortable taking it above 5psi or so

Any ideas?

thanks.

 

Sounds like a secondary injection issue. Check your secondaries. I realize they were just flow tested but it's a good place to start.

 

do you have an air fuel ratio meter?

 

check your wideband if you see a major AFR change, some times this happens due to injector transition.

 

Thaks guys. But, I thought the secondaries came on later than 3500 RPMs. Either way I'll get my hands on a wideband and see what is happening. It's still kind of strange that all of a sudden there would be a problem with the secondaries.

Would a clogged fuel filter cause this behavior?

 

I'd still do a compression check, I've seen side seal failure's that ran and idled fine until they hit a moderate amount of boost. Can you even rev the engine past 3.5K without boost or in neutral?

Did you move the plug wires around when you checked resistance? I've seen internal breaks on plug wires that do this. Maybe do the 9V battery test on the secondaries and see if they're clicking. Fuel filter would defiantly do this if it's clogged.

Also, for someone running a gt4088, you should defiantly have a wideband installed.

 

^ The engine pulls great vacuum and idles perfectly. I can rev easily and smoothly in neutral to 6k (didn't go any higher today sine it made it easily past the problem area). First gear goes to 5k RPMs without any noticeable breakup. I'd be absolutely shocked if its the engine... Never seen an engine work so good in every other way and be blown. It seems to be correlated to boost, secondaries or increased fuel load in general.

What's the 9v test for the injectors, is it litterally just connecting a 9v battery to see of the injectors open?

 

my car used to do this during colder weather early in the morning or late night, never during the day and i was going insane trying to figure out what was happening!! But that just speculation on your issue, u deff need that wideband or take it to JPR for a quick dyno pull to make sure its all good insted of dropping $300 on a wideband!! $100 bucks well worth it!!

 

The last engine I saw with a broken side seal idled perfectly, revved freely to redline, and pulled great vacuum. Problems from side seal failures are usually apparent when boost is applied. Not saying your engine definitely has a broken side seal but I've seen engines that have the exact problem you're describing that have a broken side seal. Takes little time to do a compression check, if anything do it for peace of mind instead of wasting time on other potential problems.

The 9v test is simply wiring a 9v battery to the injector and tapping one of the leads to the injector to see if it's clicking. If the injector is stuck you won't hear the injector click when you place the leads on the injector.

 

Provide data logs

 

Check the vacuum line to your MAP, if it craps out as soon as you hit positive boost it could be blowing of one of the ends or damage to the line itself.

 

Well that's depressing. Thanks for the help.

I don't have a datalogit, is that the only way?


Just pulled the line to make sure, but it looked good good, air filter flows, and everything is ziptied. Only 200 miles on the 3 bar sensor, so I believe it's good too.

 

subscribing, because I'm having the EXACT same problems.

Gt35r, 1680 second/850prim supra pump

Boosts fine to 3.5/4k then it sounds like i have a two step and bogs down. massive sputtering etc.

 

You didn't accidentally change map sensor settings in the commander did you? Maybe try switching to the default setting and put the stock map sensor back on. Oh, and as others have said you absolutely should have a wide-band with a 4088r and enough boost to require running a 3bar sensor, probably a datalogit too.

 

Interesting, did these symptoms come from nowhere, or did they start after a specific event?


Not a bad idea, I'll give it a try. I just need to set my PIM option to Normal, right? I still can't get over that everything worked two weeks ago and nothing with the setup has changed. Even the gas is the same.

...It's funny, my last FD had a cabin fuel pressure gauge and a wideband and I hardly ever needed them over three years. Now, both could be very helpful.

 

Came out of nowhere. Boosted fine after I got it tuned for about a week. Then bam nothing. The only thing I changed was reinstalling my boost controller.

 

Can anyone please elaborate on the 9V test for the secondaries? I searched and a few people mention testing them by applying 9V b/W the ECU pin and the injector relay. I like this approach since it's tests the full loop to the ECU, not simply the injector itself.

Which pin and relay do I connect to perform this test?

 

I figured out the secondary injector test and both secondaries click when I connect a 9 battery from the PCM connector (4z and 4x) to the EGI relay port. I have a fuel filter to install, but with only around 4500 miles on my current filter, I don't expect that to be the issue.

I then went ahead and tried the fuel pressure tests in section F in the manual; specifically on page F-101 in the 94 manual, "Fuel Pump Maximum Pressure". This test asks that I ground two points in the data link control box and turn the key to the On position. It says that I should see 70-107 PSI. I saw about 40 PSI from my FPR off the secondary rail. Is this because of where I'm measuring the pressure from, or is it indicative of a fuel pump problem?

Anther thing I checd was the voltage at the fuel pump connector and I got 5.89 v. Should it have been 12, or is that expected?

Thanks for the help!

 

I think you found the problem. Have you tested the voltage under load??? as voltage varies between idle and full load.

From what I read the supra pumps are know to draw more amps then stock and tax the stock wiring. Maybe try to run a heavy gauge wire to the pump and see if the stumble goes away...

 

http://www.norotors.com/index.php?topic=572.0

Diagram of the fuel pump control system from norotors.com

 

I did a few more tests since my last post... I was testing the voltage wrong at the fuel pump, it's 11.9 volts and I re-read the FSM and noticed that the test on F100 requires one side of the pressure gauge to be capped, so 40 psi is good (I wrote that post to fast )

That being said, one thing I did find is that my fuel system is not holding pressure. When doing the FSM pressure test, my pressure drops from 40 psi to 0 in about 45 seconds. There's no sign of an external leak, and I think, given all the issues, that it may be at the pump. Given that all 4 injectors click open and close nicely with the 9v battery test, if one injector was leaking minorly, I would expect the effects would be minor at 3.5k+ RPMs. I also smell zero gas. Maybe a leak in the pump hardware would cause the FP drop for the FSM test and under load too.

 

^I actually had a similar issue with my car. Poor sealing where the pump outlet mates to the hard line on the in-tank fixture. New o-ring fixed the issue. Though, the issue was much less severe for me, I just could not richen the AFR below ~12.0 at medium-high load. Pressure would not drop for me until at medium load under boost (so probably 50psi at the regulator). Could still be your issue, or one of multiple issues.

Freshly tested and cleaned injectors are known to sometimes stick if they have been sitting for a while. Do the injector test again, but correctly this time: VERIFY that the injectors are not leaking VISUALLY. Effects of a leaky injector are not minor at any RPM point. The amount of fuel combusted is relatively miniscule.

Not being able to access datalogs and your map will make diagnosis more difficult.

"But, I thought the secondaries came on later than 3500 RPMs."
- You do not understand how the PFC controls fuel delivery, which is another reason that logs and your map would be so helpful. The PFC will turn on the secondaries when a certain injector duty cycle is reached. This could happen well before 3500rpm, especially with 550cc/min primaries. Secondary transition is more related to load than RPM.

Finally, once you have this issue figured out, you will need to rewire the fuel pump to get more voltage. Search for a thread about rewiring the fuel pump. You basically add a ground to the pump (~.5V increase), add a parallel positive wire to the pump from the fuel pump relay output (>1V increase), and add a positive wire from the battery to the circuit opening relay (~.5V increase, don't forget a fusible link). The last wire can be neglected, but you should at least add the new ground and new live wire to the pump. They are easy mods for greatly increased flow. That's the basics, reference the thread for the specifics before you do this modification. These Supra pumps respond very well to increases in voltage.

Read up on MAP sensor calibration.

Finally, why are you boosting with 200 miles on your rebuild?! Don't be in such a hurry, wait for the engine to be broken in and making better compression, then get it tuned. Just go easy on her for now...

 

I have also experienced a bad O-ring on the top of the fuel pump, in my case pressure would drop to 0 almost instantly after **** down, new O-ring fixed it.

 

Do you have the stock FPR?

 

No, I have an aromotive FPR connected at the back of a KG parts rail.

Thanks for the help Enthalpy. I'm pretty sure the injectors are not the issue. I ran about 15 pressure tests yesterday and smelled no fuel and had no flooding issues. Given that the idle is so clean and neutral and low load reving is crisp, I don't think that the dramatic hesitation is from a leaking injector. However, if the FP O-ring is bad, I can see how that would cause issues when more pressure at the pump is needed. So I'm going to start there at this point.

As far as engine breakin period, 200 miles is plenty for my rebuild (only soft parts and apex seals were replaced). Car was tuned and drove great for 2 or 3 drives, then this issue arose.