Boost and no go

[MA71_Static]

So earlier this week I was driving up hwy 17 and I came to a steep part of the freeway and I accelerate to keep my speed steady (80mph) and after I started up the incline I lost momentum so I had to press the pedal alittle harder and built up about 4psi but my car stopped accelerating, it was slowing down so I pressed the pedal further down and by then I was at 9psi and still not moving just getting slower so as I let off the gas and my psi got around 0 the sjumped like it wanted to go so I got on it again and it accelerated but as soon as boost is built it stops accelerating. It drives fine on the road until I spool past 2 psi or so so I just keep under vacuum as much as possible. If I go WOT it will accelerate slowly and hit many flat spots but accelerating while maintaining vacuum is faster. Any ideas?? Car info: 1989 Supra Turbo Automagic

BTW I went from 80mph to 35-40 when I reached the top, I have a code 52 but that one is intermittent so it comes and goes as it pleases and the other is a 71 (I have no EGR but ran fine for a month)

 

[RazoE]

resistance builds boost, so if you're keeping her steady, eventually she'll stop boosting..

I noticed on my aftermarket boost gauge that I hit 4-5 psi when gassing it, as soon as I keep her steady it slowly drops to 0psi and then goes to a -20 vacuum...

 

[dumbo]

I would say your going pig rich with code 52, do the rewire.

And put your egr back on, what you described is the PERFECT way to detonate with no EGR, your prolly very lucky you got the code 52...

 

[DBN]

Even if the CEL isn't on the code 52 is still present and it wont allow you to boost until you fix it AKA rewire or clear the codes. But i'd recommend the rewire.

 

[shaeff]

Knock sensor rewire: http://supras.com/06/techcenter/display.php?QID=69

 

[mkiii222]

Even if the CEL isn't on the code 52 is still present and it wont allow you to boost until you fix it AKA rewire or clear the codes. But i'd recommend the rewire.

Where did you hear this?

The ECU goes into 'safe' mode which runs rich and has a failsafe timing pattern, but does not stop you from boosting. I know this first hand as I had a 52 forever (ended up being the sensor itself) and could still push 6 psi all day long. It just ran pig rich and the rise and fall of rpms was choppy.

This problem sounds like a boost leak coupled with a 52. Check the IC pipes and fix the 52 (shaeff sells a very nice rewire kit which will fix it unless you're one of the unlucky few with a bad sensor).

 

[shaeff]

Where did you hear this?

The ECU goes into 'safe' mode which runs rich and has a failsafe timing pattern, but does not stop you from boosting. I know this first hand as I had a 52 forever (ended up being the sensor itself) and could still push 6 psi all day long. It just ran pig rich and the rise and fall of rpms was choppy.

This problem sounds like a boost leak coupled with a 52. Check the IC pipes and fix the 52 (shaeff sells a very nice rewire kit which will fix it unless you're one of the unlucky few with a bad sensor).

While it doesn't prevent you from boosting, when Code 52 is registered in the ECU, timing is retarded (severe lack of power), and fuel mixture is enriched. That combination kills power, regardless of how much boost you're pushing.

 

[mkiii222]

That combination kills power, regardless of how much boost you're pushing.

I can also vouch for that first hand as I got my first ticket in 5+ yrs two days after I fixed my code 52. The car just ran so smooth I had to open it up a little.

I did mention the richness and timing though (lack of power being the end result). DBN just flat out said 'it won't allow you to boost'.

I'm saying boost leak because regardless of the power loss from a 52, he still should be able to go up a hill without losing 40+ mph and he said when he got out of boost it seemed like it wanted to go.

 

[kamikazemkiii]

sounds like mine when i had the boost leak
felt like i hit something when i started building boost

 

[DBN]

While it doesn't prevent you from boosting, when Code 52 is registered in the ECU, timing is retarded (severe lack of power), and fuel mixture is enriched. That combination kills power, regardless of how much boost you're pushing.

Exactly what i meant. I've had experience with code 52.

 

[Mk3runner]

lol

 

[paradox616]

i have no idea about EGR because they didn't fit it to Australian Spec 7m's sounds like 2 things ive experianced,

as mentioned before boost leak but i didnt loose boost just blew clouds of smoke and once i had the wire on a knock sensor ground, cant remember the code but any more than 1-2 psi and you'd loose all power and slow down.

 

[MA71_Static]

I did the rewire a few months ago and the code went away but after I did the headgasket recently it came back but did not affect the acceleration in any way other than my MPG was as good as a Cummins turbo diesel lol. Then I got the 71 recently and this happened a few days later, I experienced this issue once when my MAF went bad but when it was on its way out it did not throw a code till it died. I can build and hold boost steady at 8 no problem but as described a few posts earlier it feels like I hit somethng, better yet like I am pulling a parachute behind me. Only while boosting though, under vacuum the car accelerates perfectly, and my idle is steady at 750rpms.

 

[mkiii222]

Is the 71 resolved?

If the 52 code came back after doing a HG job then you may want to recheck the wiring. Lots of stuff coming in and out under the hood could have knocked something loose or possibly cracked a knock sensor.

Either code will put the ECU in 'fail safe' IIRC. 52 for sure, not sure about 71. This will give you the bad MPG, make acceleration/deceleration choppy, and cause power loss.

As for the issue with the engine running fine except when positive boost kicks in that really does sound like a boost leak. I went months thinking it was something else only to find out my lower IC pipe was cracked.

 

[MA71_Static]

I finally got my internet back on lol, k so I'm putting my EGR back on to fix the 71 and am checking the 52 out at the moment. One of the wires was probly pulled so I think I know what area to check. I averaged out my MPG to 16 so this needs to get fixed ASAP lol