My 95 LT1 has been hesitating signifigantly. I cleaned off my MAF and that seemed to help my idle, but the acceleration up top is still hurting. Down low it still pulls very strong, but accelerating on the highway, say from 80-100 is very much slower than it should be. I had my friend ride with me to copy down scanmaster reading for various things while I was driving.

L02/R02 (WOT): Between 850-900, like Ive read it should be
MAF (WOT): 170... Ive read that 255 is the max. Is that a big discrepency?
MAP (WOT): 30. BAR is also 30, so this would seem to be correct
SP (WOT): 34
SP (CRUISE): 46

The numbers that seem the most off are these:

LP (WOT): 9
RP (WOT): 8.4

I read that for a stock LT1, this should be around 15 ms at WOT. I realize that mine isnt exaclty stock, but I do have stock injectors and a stock computer. It would make sense that this problem is possibly fuel related, so the low injector pulse width numebrs coincide with that.

Any ideas on what is causing this or how to hunt down the culprit?

Also, every so often when I get in the car I can smell gas, like gas leak. I replaced the fuel filter yesterday, no change. And last night I went from like a 50-90 run, and it wasnt hesitating at all...so its only part of the time.

Thanks for any help.

PS: Last tank I got 13.5 mpg (mostly city). It is usually 14.5mpg or so. I drive fairly conservatively.

Here's a link to a good page on the scanmaster and its readings

 

those readings are nice but what you need to find out are the BLMs in the 128 range and are they the same on both sides. also, are you getting any knock retard? that might cause hesitation you described.

 

Ok I got some knock readings the other night...at WOT the most I recorded was 5.5...jes crusing its in the 0.~ range.

The BLMs we looked at and noticed they were the same, but i cant remember what the numbers were. Ill get those readings asap...but ill wait for antoher reply or two. If the BLMS are necessary, ill go get those real quick.

 

Should I get anymore readings while out...or jes the BLMs?

 

OK I just got my BLM readings....the L was 160 at idle and 136 at WOT. The r was 135 at WOT.

I also go tthe CLE(CEL) and I got 01 at idle and 15 at WOT.

 

I had the same problem...mine was the o2s...the right side was getting loaded with fuel trying to even the motor out but it was very hesitent.

matt

 

Well Matt...my name is Matt too, so that would make sense if we have the same problem

But according to my scanmaster, it says my O2's are in the operational range...and they both are equal. So im not sure. I know some of you guys know all about these readings...

 

If noone in here can help me, where should I post this?

 

I would check the fuel pressure through the rpm range. See if you loose pressure anywhere. Since your BLM is at 160 then it may be running lean because that is as far as it can ajust to try and add more fuel. So this could definitily be a fuel issue.

 

Some of your readings look questionable.

MAF = 170gps @ WOT?????
PW = 9/8.4 @ WOT

You can't just look at it at "WOT"... it has to be at some RPM to be meaningful. As I indicate in my guidelines, you should be over 200gps at or near redline.

Same with pulse width... should be closer to 15mS at redline.

Looks like you just took the data with your foot on the floor, but not at max rpm.... maybe at 4,000rpm.

MAP = 30 = BAR????

Odd, you usually see some sort of pressure loss through the air intake track..... but you are getting "0".... again, either you took the reading with no air flow, right after you opened the throttle wide, or you have some sort of a vacuum leak.

With the data not making any sense, its sort of hard to figure what is wrong.

255 is not the max value out of the MAF. Max is 470gps... if you can max that # out, you are making huge HP. Something over 200gps is typical for WOT/max rpm.

Stock O2 sensors are not an accurate way to judge A/F ratio. I give examples in my writeup, but point out that they are not reliable. The sensors are too sensitive to operating temperature at rich A/F ratios.

 

Hmm ok. So i need to get the MAF and PW readings at redline not jes WOT....I guess I missed that part, I was reading too fast.
My bad..ill get some new readings asap.

Also, are the BLM readings supposed to be at WOT or redline?

 

MAF = "mass air flow". Air flow is roughly proportional to RPM. 6-10gps at idle, 240gps at 5,800rpm. Varies sort of linearly in between.

Since pulse width is a "ratio" vs. mass air flow, the pulse width will also vary linearly from 2-3mS at idle to 15-16mS at 5,800rpm.

All these are "rough" numbers... but you get the idea.

 

Ok I just went out and got some new numbers..i got the MAF and PW at redline this time(~5800rpm)

My MAF read around 220~
I only got the LP at redline, but the RP is around the same at idle and cruising so..
LP=9.3 (Redline)

'These are still low...Also I noticed my BLM's are now off ..I was getting

BLM(L) 146
BLM(R) 139 These were from a cruising at about 1300RPM

and then

BLM(L) 155
BLM(R) 149 This was idling in park after i drove so it was warm.

So they are off, which I read could be a leaky injector? I still think its injector due to the fact that I smell gas every now and again

Thanks for any help

 

If you had a leaky injector the PCM would be pulling fuel, BLM's below 128. The high BLM's you show indicate an air leak ahead of the O2's. The O2's are reading extra oxygen, think that there is a lean condition and are adding more fuel. That's why you smell gas.

 

If it smells rich, and you have the huge BLM's, you need to find out why it is adding fuel it probably doesn't need. Looks like maybe the O2 sensors are not reading right. Is it mostly stock? No headers?

You've got worse BLM's at low loads, so it points to the possibility of a big air leak somewhere in the system, or O2 sensors that aren't getting hot enough. There appears to be a small "split" from left to right, but whatever is screwing things up is screwing up both side.

List any mods.