Mazda99Nikon

I've noticed a rare problem as of late along with a slight performance issue. Coming out of boost on the freeway and coasting to idle, my RPMs will drop from 750 to 200 and sometimes even rarer, stall. The same thing will happen if I'm doing a lot of short trips around town. It's very rare, but annoying. Also, my car seems to hesitate on developing full boost. I have a perfect 10-8-10 boost pattern, but the momentary hesitation is annoying.

Well, based on a search of similar threads, a boost leak seemed likely. Had some time today so I started checking hoses. It probabaly shouldn't have surprised me, but the two hoses going to the pressure chamber were very loose. The rubber hoses seemed to be too large for the nipple on the chamber. I fixed the problem by wrapping electrical tape around the nipples. The hoses were now very snug.

Is it my imagination that I've fixed both problems? Car doesn't drop idle RPMs and the hesitation to full boost is fixed. By the way, the hoses weren't brittle, they just seem to have mysteriously grown in diameter.

Any thoughts?

dubulup

good work

DaleClark

iTrader: (55)

Get some silicone hoses in there - electrical tape is a hack. Fix it right.

The stalling after pushing the clutch in can sometimes be a bad or misadjusted dashpot on the throttle body. Search for more info on it if the problem reappears. The loose hoses shouldn't have fixed the problems you're mentioning, except maybe the stutter in boost. Those loose hoses probably weren't keeping pressure in the tank.

Dale

Mazda99Nikon

Thanks Dale. I'll look for some silicon hose. The idle problem is so rare, it may not have had enough time to show itself with a 20 minute test drive. The dashpot suggestion seems to be the third most common culprit for idle issues, based on searches for idle problems. I'll check that out. There's no doubt however that that the hesitation to full boost is fixed. The car now accelerates like a rocket before the accelerator pedal reaches one-half full depression. Your description of flutter seems to be a more accurate portrait of the problem before the hoses were tightened. How does that pressure chamber interact with everyhting else in the rats nest?

DaveW

At one point, I had one of the pressure-chamber hoses blow off (before I did my hose job - Viton from Hi-Temp Silicone). The only symptom of the dislodged hose was slow or non-existant transition to the secondary turbo. There were no idle problems as a result of the dislodged hose.

recon fd

I had the really low idle drop/ sometimes stall issue at one point, but I thought it was my TPS. I adjusted that sucker and have had no problems since.

goodlcuk,
-josh

Mazda99Nikon

Thanks Dave and recon, as well.

I drove it to work and back home today, 44 miles round trip, and oddly, no significant problems. Boost out of first and second gear definitely comes on much faster, actually any gear. It's like when I first bought it two years ago (Thanks Tim, by the way). The idle appeared to falter only once after I slowed to a stop and depressed the clutch at a stoplight, where it dropped maybe 300 RPMs and simultaneously lost 3-4 pounds of vacuum on the stutter and then instantly came back (I've already checked clutch switches, they are fine). It was actually in heavy traffic on a city street. Dashpot sounds like a good bet, yet, but that TPS keeps cropping up in similar discussions I keep finding on idle issues. Both are simple issues to check - I'll get back over the weekend with the answer when I have some time to do it right.

whitet777

Glad you're still enjoying her. I miss her once in a while, but the Evo keeps me happy too. I'd be tempted to get back into a FD if it had a LS1 conversion.

Now back to the topic. Good luck. I never had that problem before.

FallenCho

iTrader: (1)

I don't understand how the dashpot can be a problem at idle since it's not an electrical unit or anything that is connected to the car in a manner to tell the ECU "hey you are stupid!". Honestly I just don't see how the dashpot can do this cause I've never seen that throttle part that it touches move during idle. Or am I just a n00b?

DaleClark

iTrader: (55)

If the dashpot is totally stuck in (ie, it's broken) then you won't see it touch the throttle linkage.

The dashpot eases the throttle body shut when you take your foot off the gas. Without it, revs can drop too quickly for the idle speed motor to compensate for, and you get a very low idle or stall. Do some searching on the topic - I've written more on the subject.

Dale