BayAreaZT Posted August 17, 2003 Share Posted August 17, 2003 I thought I had fixed my stumbling problem a while back but it came back a few days later. A few days ago it was worse than it has ever been. Not just stumbling at the top end but I was hitting a brick wall under any hard acceleration. I've been putting off working on it cause I've been kinda busy with other stuff but the final straw happened the other day when I had a chance to run a 911 and a C4 vette at the same time but as soon as I got on it I bogged badly. That pissed me off So last night tore apart the whole intake sytem from the throttle body to the turbo. Checked the AFM and TPS with a multimeter and everything checked out. Cleaned all the connectors, AFM, and TB. Opened up the TPS and cleaned the contacts. Cleaned the ECU connectors again. On my grainger boost controller, I shortened the signal line and turned the boost down a little. I wanted to run it at less than 10psi until I got things straightened out. Took it out for a run after I was done and imediately the car pulled very strong under WOT. I was like holy s**t this pulls harder than it's ever pulled. How can this be if I turned the boost down? Did another run and watched the boost gauge. No wonder it pulled harder. Boost was at 14psi . Could just shortening the signal line increase boost like that or is it just cause the car is running better now (this was at 12:30am BTW so the air was cool)? It doesn't really matter though cause this car ROCKS at 14psi so I'm gonna leave like that for a while Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted August 18, 2003 Share Posted August 18, 2003 the grainger boost controller will give higher boost when it's cold out, I talked about this on another post. I dont know about that much increase though mine only gives about 1 more psi of boost at night over what it gives in the daytime (avg 100 degs in the day, 70ish at night). Funny how our cars mimmick each other even in their problems. I thought my stumble had gone away completely, then a couple days ago it came back. I did the 'routine' cleaning everything, disconnecting and reconnecting everything, and the car ran great again afterwards. Now it's getting stumbly again, especially in cold air when the motor is not fully up to temp but even after warmed up... odd thing is now it's stumbly when puttzing around, but when I get on it it seems fine. my car decided to do it right at the wrong time too... this guy in a mustang GT convertible... I KNOW I coulda took him, but as soon as I hit boost in first it cut out bad.... pissed me off! Quote Link to comment Share on other sites More sharing options...
BayAreaZT Posted August 18, 2003 Author Share Posted August 18, 2003 I know the boost control may vary depending on temperature outside or under the hood but I drove it plenty of times at night before and it only varied 1-2psi if at all. After thinking aout it, I may have introduced a leak in the signal line. I was kinda rough on it when I shortened it (it was late and I wanted to finish up ). Mine also seemed to stumble the worst when not fully warmed up. I think I narrowed down my problem to a bad AFM signal. It must have been bad enough to send the computer into "safe mode" and cause it to run bad. Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted August 18, 2003 Share Posted August 18, 2003 yeah most difference I get after I shortened the hoses to and from the MBC is about 1psi. Used to be worse and would spike more like 2psi. Now the thing is so close to the turbo.. pain in the butt to adjust it if the car is warm... I'm thinking of trying a different AFM altogether. I'm really getting tired of this car running differently every day. Also I think it is missing a lot at idle and cruising, i'm not sure if that's what i"m hearing, kind of like really light backfiring, and it happens a LOT, several times in any 10 second period. This problem is also worse when the car is cold but doesn't improve by much when it warms up. Sometimes it can make the car very jerky when I'm just cruising around, like surging. Maybe the AFM is just mis-adjusted? That might make sense why the car runs badly at low rpms, but seems to pull fine (usually). As soon as I get some more $$$ I'm just gonna start replacing sensors and see what happens. Quote Link to comment Share on other sites More sharing options...
fl327 Posted August 19, 2003 Share Posted August 19, 2003 I thought I had fixed my stumbling problem a while back but it came back a few days later. A few days ago it was worse than it has ever been. Not just stumbling at the top end but I was hitting a brick wall under any hard acceleration. I've been putting off working on it cause I've been kinda busy with other stuff but the final straw happened the other day when I had a chance to run a 911 and a C4 vette at the same time but as soon as I got on it I bogged badly. That pissed me off So last night tore apart the whole intake sytem from the throttle body to the turbo. Checked the AFM and TPS with a multimeter and everything checked out. Cleaned all the connectors' date=' AFM, and TB. Opened up the TPS and cleaned the contacts. Cleaned the ECU connectors again. On my grainger boost controller, I shortened the signal line and turned the boost down a little. I wanted to run it at less than 10psi until I got things straightened out. Took it out for a run after I was done and imediately the car pulled very strong under WOT. I was like holy s**t this pulls harder than it's ever pulled. How can this be if I turned the boost down? Did another run and watched the boost gauge. No wonder it pulled harder. Boost was at 14psi . Could just shortening the signal line increase boost like that or is it just cause the car is running better now (this was at 12:30am BTW so the air was cool)? It doesn't really matter though cause this car ROCKS at 14psi so I'm gonna leave like that for a while [/quote'] The corrosion of the connectors and badconnection has been the only prevailing issue of mine since I went with turbo. Keeping them clean makes a huge diference sometimes, I think somebody called it "Sudden Turbo Death" Quote Link to comment Share on other sites More sharing options...
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