Stuttering problem

[Steve_N]

My 89T is having a intermittent stuttering issue that I think is fuel related but I would like to get your opinions. The problem occurs occasionally during normal driving under 3K rpms & occasionally during idle at stop lights. Example of whats going on; as I'm driving 45-50 mph the car will start to stutter (very slightly buck like a minute form of fuel cut). It will do this for 5-10 sec then clear up as fast a it started. It has does this with me doing 35-65 mph under 3K RPMs. When this happens on the highway I accelerate & get into boost slightly & it goes away. I have not had any problems while in boost, at 3/4 to full throttle, just in the lower normal driving modes. Also driving on the side roads going 35-45 when I stop at a light the rpms rapidly bounce from 600 to 1000 rpms & the car stutters as I'm accelerating from the light then clears up. For the next several miles & several lights I stop at the idle is a smooth 650 rpms & acceleration is smooth & normal.

Im Only at BPU+ Mods Are: Lexus AFM, K&N FIPK Custom IC, IC Hardpipes, 3" Exhaust, Blitz Spec S, Greddy Boost, A/F, & EGT Gauges. Deleted the FPD

I checked & there aren't any codes. Ths ISC is working (it clicks when engine is turned off) The wiring & connections at the TPS, ISC, CPS, & AFM are tight & in good shape. All the grounds on the wire harness are clean & tight, didn't see any vacuum leaks & vacuum is at -19 to -20 on the boost gauge at normal idle but it does jump around when the rpms bounce. I cleaned the air Filter & replaced the plug wires with new NGK's. I'm leaning toward the stock fuel system but not sure where to start. Pump, FPR, Inj, filter, ???

Your input is appreciated

 

[e90suprat]

Have you checked your timing? My 90t did basically the same thing and I thought it was fuel system related, and it turned out to be my timing.

 

[Nick M]

The fuel pump relay or circuit opening relay could be causing trouble. Ive seen it on many Toyotas. The customer ignored it until the car wouldnt run at all.

Or a loose ground wire, seen that too.

 

[Steve_N]

Thanks guys.. I'll see what the timming is doing & replace that relay.

 

[Nick M]

You can test the relays before replacing them. There is also the control side of the relay.

 

[Steve_N]

Yea I know but i can easily get a used one.

 

[ross1]

steve,
what did you find out, my 89t has been doing the same thing, always off the line under normal driving and right around 2250-3000 rpm's, i thought i might've had a clogged fuel filter since i doubt it's been changed, i'm going to do this next week no matter what, but if you find anything out let me know...

much appreciated,
ross

 

[Steve_N]

Well problems fixed. Turns out it was a vacuum leak after all but from a most suprising source. The oil filler cap. I never would have thought to check it if it hadn't been listed do so in the TSRM. About a year ago I traded the stock filler cap for nice shiny alum. one. Turnes out the O-ring gasket got loose & deformed. That was causing intermitten vacum leak that played havoc with my car & mind. I replaced it with the STOCK cap & the problem went away immedietly. I did this a cpl days ago & thought this was too good to be true & must be a fluke. So after driving it around for a cpl days w/o any issues I thought i would post the news.

 

[ross1]

i checked vaccuum on my car and it was normal -19 at idle, but would that reading change if i did the check at a different vaccuum tube on the car? and should the factory oil cap have an o-ring on it? b/c mine doesn't and i guess that could be causing it, anyway, great to hear that it's not fuel related cuz i didn't want to have to drop that kind of money yet. but a few cents for an o-ring is ok...


thanx
ross

 

[Steve_N]

The stock cap dosen't have an O ring. It has more like a self sealing material underneath the cap. Hard to explain but you will see what I mean. I'm suer it can go bad but its Much better then an O ring in my opinion. If you replace the cap get one from toyota.

 

[dbsupra90]

or a trd

glad you got the prob sorted steve.