Is there someone here that I can email my TTS DataMaster log file to that can tell me why my car is stalling and hesitating in open loop? I don't really know what to look out for yet in the stats. The links below are to other threads that will further describe my problem. It's been several weeks now and it's driving my crazy.

http://forums.corvetteforum.com/show....php?t=1366460

http://forums.corvetteforum.com/show....php?t=1343675

http://forums.corvetteforum.com/show....php?t=1351435




Thanks

 

That was an aweful lot of posts! Let me ask you, how many of the tests did you perform that you were advised to. Secondly, do you have the FSMs, because they have a certain amount of scan data, typical data values, in the Driveability and Emissions section. As far as your question now-you might try the scan and tune section.

 

Sorry about the posts. I'll try to keep it to one only in the future. I do not have a factory service manual yet. I am looking into buying one now. I tried some of the tests / possible fixes recomended. I cleaned the throttle body. I replaced the fuel filter. I replaced the fuel injectors. I checked the MAF sensor for a blockage. I have a haynes repair manual bit it's hard to understand some of the tests because it jumps around so much and covers several different years. One paragraph it's TBI the next it's TPI. etc.. I was hoping that with a log someone could read it and identify the problem or at least a problem with one of the sensors based on the stats.

Thanks again

 

Problem is I can't compare your scan data to an 87-if I did I may be giving you false information. I got my FSMs off ebay-less than 100 for both books. The other thing is that scan data may not even point you to the problem, and an 02 sensor jumps around alot-so it's hard to tell,on an 87 IAC counts (steps) are 1-40, BLM counts 118-138, TPS
volts .46-.62, MAF Gm/Sec 4-7, air flow same, Mat temp Cdegrees 10-90. BUT, I have no idea as to your year, I'm not even certain you have MAF. I thought I heard Helms was having a sale-you can go to their web site. But it's imperative for you to have-basically a scan tool is worthless without them.

 

Thanks for the advice. HELMS has the FSM for $130 I'm still checking ebay. In the meantime I may burrow one from a friend for a 94. I reviewed the log several times last night. I noticed two things but not sure if it means something. The first is that when I floored it from a dead stop up to 50mph the highest the TPS ever went was 89.8% and a max of 3.20v. I checked other parts of the log and that is the highest it ever went. Should this go to 100%? Maybe a bad tps sensor? But that was in the closed loop mode where the stall is not occuring. The second thing is that in open loop right where it bogged down at I noticed the EGR DC reading jumped to 100%. Could that be something usefull or is that maybe just a reaction to whatever is really wrong? If someone has a late model C4 and know how to read these logs with TTS I'd like to email it to you.

Thanks

 

Your TPS reading is a bit low, but not bad. Should be around 4.0v at WOT. I know mine has to be just about perfect for a smooth idle. I also have a 95 vette also but it has low miles and I haven't had to do any real work on it so far. As for the FSM I would only go by a year specific manual. The 94 manual might be close to what you need but there were some changes in year to year. Since it would be free while you wait on yours, I would give it a shot. I don't live far from you and would be willing to take a look at your vette. I'm not a certified mechanic but have delt with C4's for 8 years now.

 

I think the Problem with the hesitation in open loop is finally solved!!
Thanks to all for helping! This weekend I put on a powercoupler/smooth intake. At the same time I also cleaned and re-oiled my K&N airfilter, changed my pcv valve, and cleaned the MAF sensor. I believe it was the MAF sensor being dirty that was causing the problem. I used some some spray on it I bought from PepBoys that cleaned it up pretty good. There was one little black spot on the inside of one of the sensor wires that wouldnt come off. I have started it 3 times since, when cold and in open loop, and no stall.
Still more questions. My TPS still seems to be maxing out at 89.8% and 3.20v and not going to 100% on the TTS datalog. Should I change it out or can this be fixed or adjusted. It just doesnt seem normal that it would not go to 100% Does that mean I'm loosing 11.2% power at WOT?? I'm having my N2O kit installed this week. The ZEX is designed to only work at WOT does that mean it will not engage if the throttle is not signaling 100%? One other thing I noticed is a rattling that seems to be coming from the inside of my passanger Catalytic converter. (Louder that the driver side) Is that normal? I have about 70k miles on the car. Maybe time to replace? Also on the same side I noticed a clicking noise that seems to be coming from the intake manifold. It is loud only on the passanger side. I just replaced the injectors. Do they make this noise or is it the lifters, rr, or something else and it just sounds like it's coming form the intake manifold. I just thought it was unusual or could mean something that I'm hearing noises only on the passanger side of the car. (Cat and Intake) I hope I'm not being a bit of a hypercondriac over little meaningless things. I'm just trying to get it running as perfect as possible before I move on.

 

have someone push the gas pedal while you watch the throttle blades. check to see that the throttle fully opens when the gas pedal is all the way down. put a digital multitester on the TPS leads and open the throttle, watch to see if it goes to max volts (I don't remember what max voltage is off the top of my head). Also check base voltage (throttle body closed) is in spec.

It may be that the sensor is bad, fully opened throttle reads low voltage, or that you're not getting 100% open throttle blades with the gas pedal (cable needs adjuting).

you can also adjust the TPS by loosening the mounting screws and turning the TPS. this will adjust both ends of the scale (throttle closed, low voltage; throttle open, high voltage) You can elongate the mounting holes on the TPS to get a little more adjustment, but make sure you double check the base (throttle closed) voltage is in spec when you're finished.

 

Thanks a lot I'll try that this weekend. Does the engine have to be running or just the key on. Well, nevermind I'll figure that out when I go to test it. I don't have my fsm in yet so if anyone knows the correct TPS voltages for a 95 I could use em. The hesitation/stall definately had to be the MAF because it's now completely gone. What about the noises am I just being too picky? They don't sound normal.

Thanks

 

Longshot here, but do you think maybe your floormat is getting between the pedal and the floor?

 

lol, I sure hope I'm not that dumb. Well now that you mention it maybe I should check that next time.

 

Come to think of it, maybe it's the clutch pedal that's worn the hole on my floormat. Not even sure the back of the accelerator touches the floor or if the stop is in the lever higher up the firewall. Worth a quick look though.

Heck I had a fan belt break once and stood there staring under the hood of the truck wondering why it was overheating...and the fan wasnt even spinning.

 

Problem with stall is definitely fixed. Got the N2O kit installed. Wow what a difference!!! I'm still hearing a really bad rattling from the passanger cat. It's in the shop right now getting the TPS and throttle cable checked. The mechanic said the knocking noise sounds like a bad catalytic converter and should probably be replaced. Before I through more money at it by buying high performance cats does that sound right or could it be a bad O2 sensor or something else? If the cat is bad I may just delete them. Should I not do that, maybe to little back pressure? Eventually in the future I'll put headers on also, but not right now. I've spent enough on it for a few months.

Thanks