Barwick

Is it POSSIBLE (and how likely) that my boost problem (5.5psi max, goes down as approach redline) is caused by my ignition being off?

When I'm sitting at idle, it SOUNDS like the engine is missing just a little bit, BUT the RPM doesn't change at all when it makes that sound. It just shakes the engine a little bit. Kinda like a "doof" sound going through the exhaust.

I've got a '90 TurboII with a j-spec motor. I've checked the Duty Solenoid Valve, I've checked the pressure sensor (at the sensor, not the ECU), I've checked the TPS, etc.. etc..

I've got a FULL custom 2.5" exhaust on it.. no cats (they were clogged, thought that was the problem, apparently not).

Oh yeah, I ran a 14.4 @ 96 mph in the 1/4 mile on Friday, but it doesn't seem to build more and more power as it approaches like 6500 or 7000.. the torque just seems to come on @ like 3000 or something when 5.5psi boost hits, then power seems to go up for a little, but then just kinda stay there. I'm not sure, but it seems like there SHOULD be more. Then again, I've driven a '90 Accord, '96 GS-R, and '92 Civic all my life, where the torque peak is up in the RPM range.

So, do you think it could be the ignition missing maybe a little, or something? Just not sure. And if so, how to check/change it. I looked for the timing marks on the pulley and don't see them.

NZConvertible

If it's the stock pulley, they'll be there. The paint may have come off though. Definitively check the base timing. If it’s retarded from the stock setting, you’ll loose power everywhere.
I can’t remember your history (sorry), but have you checked the state of the turbo? I’ve heard of people with your symptoms removing turbos and finding things like chewed up compressor and turbine blades, which will kill boost and power.

Barwick

I checked the turbo before I put the engine in. It seemed to be in good shape. Only thing that MIGHT have happened to the turbo was the BOV wasn't hooked up right on my first drive (from Detroit to Cleveland), and I ran it up to around 5500-6000, maybe it surged on that one drive and something messed up? I doubt it would happen THAT quick though.

I guess I'll just degrease my pulley somehow and see if the marks are still there. If not, what would I do to time it then? That's gonna be tough.

Piranha

I couldn't find mine, and one thing I did was just turn the pulleys over by hand until I saw the notch where the mark should be. It was suggested to take some crayon when the engine is hot and melt it into the hole; and that worked great.

Barwick

okay, so is it possible that this is the problem, the ignition timing?

Does it sound like it's missing, or do TurboII's always sound like that? The little "doof" in the exhaust from time to time at idle. I don't think I hear it when it's going or under load, but it might just be masked by the exhaust. And I'm not even sure if it IS missing in the first place.

Barwick

ok, so is it possible that an ignition problem could be causing the boost problem?

jimmyv13

Barwick,
I have the same problem, now. I was chasing an idle problem and swapped TPS's(making sure mine is good) with my friends TII. My idle started hunting from 1400-1500 RPM and my boost moved quickly up to 5 PSI and stopped. I did the TB mod and swapped back to my original TPS, and now my car idles at a very steady 900, but my boost problem is still there. I tried using a boost controller to increase boost, but it stays at 5 PSI even with three turns on an XS MBC. I am pretty sure it's a vac leak somewhere or a misadjusted TPS. I used my MM to set it at 1K OHMS at idle and it goes to 6K OHMS at WOT. I've read that the light method is a better method of adjusting the TPS.

I never touched the timing, but I did play around with the idle mix screw, the BAC, and the TPS, along with removing the UIM and TB.

I'll let you know what I find out.

Barwick

I've played with the BAC (that's on the intake manifold, the screw thing, correct? I've adjusted the TPS with a multimeter, and checked the tension and everything on the throttle. When I pulled the wastegate bleed line wide open and just had the precat, it went to 6 psi, then when I plugged it, it went back down to normal.

I got a letter back from Dave @ fc3s.org and he said that it could be a cracked manifold (I hope not.. it looked to be in good shape) or a bad gasket between the UIM and lower IM, or the IM and block. I hope it's none of those. The gasket I had was like STUCK on the lower, and I don't want to screw with it. I already have an extra gasket sitting around though, but the stock one looked fine.

He said to pull the wastegate line now & plug it, and see if it boosts higher than it does now. If so, it's sensor/ECU related. Which is what I'm guessing it is, the ECU isn't seeing the correct amount of boost, and therefore not opening the Duty Solenoid Valve.

BlackRx7

I had the same prob you where having and I just installed my RB downpipe and now I see a nice 8-9 psi, alot more power past 5k...........only $90 the best mod I've done so far

Barwick

yeah that's what I thought the problem was too, but the exhaust hasn't fixed the problem. I'm pretty sure it's a sensor problem.

Matter of fact, I just pulled the wastegate lines, and it boosts to about 7 or 8 psi on the freeway now. I plugged them back in, gonna rewire the pressure sensor to ECU and possibly DSV to ECU.

jimmyv13

I shoulda done this earlier!!!!!!!!!

I'm gonna try this with my MBC on my way home from work. I can turn it all the way closed to completely cut off any vac or boost going to the wastegate.

Barwick

doesn't the MBC bleed off air? Or does it just shut it down a little bit? I would think it'd bleed it off.. because if it didn't, it'd basically be a restrictor, wouldn't it?

jimmyv13

It bleeds air when the boost gets to the point to push the ball and spring out of the way and get to the wastegate. If I close it completely, no air will get to the wastegate, thus keeping it closed.

NZConvertible

That doesn’t prove the boost control system is at fault, in fact it proves it’s not.
The S5 boost control system works just like any other bleeder system; bleeding air from the wastegate actuator line to lower the pressure seen by the wastegate actuator. If the solenoid wasn’t opening, boost would only be ~6psi on a stock car. Yours has intake and exhaust mods so it should be higher than that (I have a pod filter and 3” cat-back and get 8psi).
Pulling the wastegate lines meant the turbo was completely uncontrolled and should have massively overboosted. That you only got 7-8psi means you have a big problem somewhere else, and I still suspect it’s the turbo itself.

Barwick

sonofarussianwhore.. I don't want to replace the turbo.. I mean.. I have one sitting around, but I don't want to do the work.

Barwick

OR is it possible that the person before me ported the wastegate, or clipped the turbines?

jimmyv13

My boost didn't go any higher than 5 PSI when I turned my MBC up all the way. The boost came on earlier and shot up to 5 quickly, but stayed there all the way up to 6K RPM.