hi everyone, I am having lots of trouble with my car
its been having the 2k rpm stumble for a little while, I replaced the plugs and wires, it ran better, but the stumble was still there. last time that happened, I replaced the Optispark and it ran perfect after that. I just replaced the opti again, along with a new stock MAF (old one was ported and descreened) new percy's dead soft header gaskets, egr delete, tb bypass, and some sensors like low coolant, knock sensor (old one looked all broken and moved around inside itself) O2 sensors, and the coolant temp sensor for the pcm.

the car is a full bolt on car, here is a link where you can download the Datamaster file:
http://www.freefileupload.net/file.p...utoLog_002.uni

I dont want to drive it like this, the highest it will rev to is 3275rpm, for some reason the knock counts are 13000-18606 and fairly static. i was just idling and slightly reving in the driveway to record the sparatic way it is running, and how it bogs down over 3k and then stalls if you take your foot off the throttle. then it is hard to get started up again.
any help would be greatly appreciated.
Could this all be fixed with a tune from MadZ28 ?
95 lt1 obd1 bolt on car, never been tuned before

from the datalog would I be able to tell if i needed new fuel injectors?

 

anybody?

 

Sort of hard to review a log with such limited time span. Basically, you cold started it, it only ran fo about 71 seconds, never warming up enough or running long enough to go into closed loop. Appears the PCM may have been reset, since the long terms in the two cells that show up in the log are "128".

You have a DTC 48 for the MAF.... if you've changed the MAF out, you might want to clear that code. If its still active, you might want to find out why. The air flow AFGS looks fairly rational.

Because its still not in closed loop, the AFGS looks a little high, IAC looks high and MAP looks high (assuming you have a stock cam). Your system voltage falls off badly, down into the 11.x V range.

There appears to be some sort of electrical interference, affecting the knock retard and the VSS signal. I'm assuming the car never actually moved, but there are a couple points in the log where the MPG starts spiking.... ex - 12MPH in frame #205, yet MPH = 0 in the frame beofre and after that. Knock retard is ocurring at the same time you get the MPH/VSS glitches. Both the upsets in MPH and knock retard occur just as you appear to have hit the upper limit of the revs. It almost like you start getting some sort of electrical interference at about 2000-2200rpm, the knock retard goes to 0.1 degree, then the VSS starts to jump around

I see where it stalls, and it takes you from #316 to #400 to get it restarted. The MAF sensor doesn't appear to be indicating any air flow when you are trying to start it.

Is it possible to get a log after its been running long enough to go into closed loop?

 

Injuneer thank you so much for the input.
that was not the first try to get it scanned, it was not all the way up to operating temps, but it had been running.

you are right, stock cam, the car never moved,
and yes, around 2000-2200 rpm it starts shaking and bogs down.

It does have a new MAF, I'll clear that then.
Could my MSD box be causing interference? any ideas where I should look to find that electrical disturbance?
also, I got a fuel pressure test gauge; with the vaccum hose on the regulator, its only at 38psi, with the hose off the regulator, it drops like 1 or 2 psi. the fuel pump is less than a year old, never been run out of gas, and has a new fuel filter.
I have a new laptop battery on order, as soon as I get it, I will try to get a better datalog for you.
Thanks again for the help.

 

At idle, with the vacuum line connected, 38psi is normal. When you remove teh vacuum line, the fuel pressure should RISE to 43.5psi. GM accepts anything from 41-47psi with no vacuum. If your pressure DROPS when you pull the vacuum line off, there's something wrong.

 

Try saving the file as a .csv file also, so us that don't have access to Datamaster (I do, but I do most of my 'browsing' while at work), can check out the log.

 

I installed my new tune from Ion (madwolf/madz28.com), and I also replaced my collector gaskets which were leaking. I got the percy's seal 4 good gaskets. but the loose flange thing on the Y-pipe is bowed and wont let the y-pipe and headers seal up, so they like whistle. I think that If i pulled the y-pipe apart and fliped those rings over, I would be able to get them to seal up. however, I dont think I can get it apart, it isnt welded, but I couldnt get the clamp off last time I tried..... But I didnt try hitting it after loosening the nut on the clamp. Once that is off, it should slip out of the actual Y part, right? seems like it would be really tight and hard to manuver. I wish I had done this the first time, so it would have been done right!

With the new tune and the new, slightly less leaky collector gaskets, it seems to run much better in the driveway. I will try to get the collector trouble figured out this weekend. then I will testdrive it and see what is what.

and as soon as I get a new laptop battery(backordered, but ordered), I will get another datalog, and post a *.csv

any ideas about the collectors? are there any 3 peice collector rings? that I can put on with out dissassembling the Y-pipe. If it turns out that the flange on the collector is what is bent/bowed is there a brand/type of silicone that can take the heat? the high temp permatex gasket maker stuff I used for the EGR blockoff kit said not for use on headers. worth a try?

Thanks for the help everyone!

 

Alright guys, I got sick of waiting, so I got a power inverter to power the laptop in the car, and went for a drive around the neighborhood. I barely made it home, and had to push it in the driveway. the car does go into closed loop this time. Also I have the MSD 6A box bypassed for this datalog.

datamaster file: http://www5.upload2.net/download/vgf...utoLog_003.uni
if that does not work try here:
http://www.upload2.net/page/download...g_003.uni.html

I tried to expoert a *.csv file, but I'm not sure that I did it correctly, here is what I got when I exported:
http://www5.upload2.net/download/RO5...SlX/waylow.csv
if that does not work try here:
http://www.upload2.net/page/download...aylow.csv.html

I think that I can still hear an exhaust leak on the driver's side. I have another new set of header gaskets ordered, the collectors are sealed up now, and I will be sure to clean the surfaces as best as I can when I install the new header gasket.(only drivers side leaks) But I can't imagine an exhaust leak causing this much trouble. if I were to guess, I would say that there is 85-90% less leaking than there was 2 months ago, when the car ran fine. it runs much much quieter under tha hood now.

any ideas?

 

I've picked up on one item. Your MAP values when you're at 1200-1600 rpm are WAY to high (80's, 90's, etc) almost no vacuum at all (100 Map = 0 in. of vacuum)

I've looked at my logs and my MAP values in those rpm ranges are in the high 30's to high 40's.

Couple things can cause this:

1) a really bad vacuum leak- check all of the vacuum lines that lead to the intake manifold. Unhook each one at a time and put a plug on the inlet fitting (you can get a set of all the sizes at Autozone, etc. for about a buck). If the car runs better, replace the whole line.
2) Bad EGR valve - stuck open - check with vacuum pump to see if it opens or sticks open
2) leaking intake gasket
3) bad MAP sensor
4) mechanical reasons (leaking valves, bad rings, etc)

Note: the leaking headers will draw clean air in and pass over the O2 sensors causing a "false lean" condition and cause the injectors to dump fuel into the system causing it to run richer on the leaking side. You have a little of that, but not much. You can see this in the diff between the pulsewidths left and right ( on the average, the left has longer pulsewidths).

Start with the vacuum lines - I ended up replacing all of mine.

 

elisowski thanks a lot for the input.
I think my egr valve was working fine, but I eliminated it with the block off plates and put on a vacuum cap to complete the egr delete.

I have still have a set of vacuum caps, when the rain stops, I will take some time to do what you said, one bye one; cap off each vacuum line comming off the intake manifold. figure out which lines are messed up, and replace them as necessary... or probably all of them as you did haha.
Were you able to just use universal hoses for everything? or did you get the actual specially sized/shapped lines with the 90 degree angled boots and stuff?

 

I bought the gm ones. After I found out which one was leaking, I ended up replacing each a week or so at a time.

I was looking at the log again and I noticed a couple of other things:

1) There were no DTC codes - so the MAP may not be the problem

2) Your O2 readings drop down into the single digits, that's too low. They should move around real quickly, but they shouldn't go below 200 very often.
I don't think they're bad, it just shows how lean the mixture is.

3)Try to see if you can switch the MAF sensor with someone. I wiped mine out with a power washer once and it caused all kinds of problems for me. A quick switch with my buddy and I was good to go, and spend $255 to fix it.

One last thing, when you're looking for the vacuum leaks, make sure all of the elbows and clamps on your intake are tight. Look especially after the MAF and before the TB.

Good luck

 

I'm pretty sure you only get a DTC code for the MAP showing a value equal to or greater than 68 kPa at idle. I don't think driving it around with a higher than normal MAP value will throw a code, but it will make the car run worse; it would be referencing the wrong parts of the timing tables.

 

In OBD-I, you only get codes for going under 14kPa above 15-20% TPP and over 68kPa at less than 4% TPP, as noted in the post above. Its not going to set a code for 90kPA under any circumstances, even if it is an irrational value. The rationality check was added with OBD-II, and requires that a sudden change in MAP must be preceded by a corresponding change in throttle position, change in the EGR status, or change in IAC counts. And when the MAP increases in the data log, he is opening the throttle.

From my experience, and reviewing hundred of data logs for people, its not unusual at all for the closed loop O2 values to cover the full range of 0xx-9xx mV.

 

I had a MAF code before, from my descreened and ported MAF. I recently got a brand new MAF from BlackScreaminMachine and its not throwing MAF codes now. I dont think that any of my vacuum hoses have ever been replaced, other than for the EGR valve when I still had it installed. So that is a great place to go from here!

elisowski, out of curiosity, about how much did all the new GM Vacuum hoses/tubes/elbows cost?

 

Dude really knows his stuff!!