Stumbling Problem in Great Detail
#136
I didn't read the WHOLE thread this time, but I've been keeping track of your problem over @ speeddensity.org.
I have a 93 also and to me it seems your TPS voltage is above normal @ .92v.
Mine @ idle is only .55-.57volts....
Hope you figure it out.
I have a 93 also and to me it seems your TPS voltage is above normal @ .92v.
Mine @ idle is only .55-.57volts....
Hope you figure it out.
#138
Thanks. Hopefully I'll be running again by the end of April with any luck. Should be pretty nasty.
I just have to ask, of all the reasons for a stumble, WHY did it have to be the worst??
I just have to ask, of all the reasons for a stumble, WHY did it have to be the worst??
#139
Originally posted by Fastbird93
Guess I should update this. On Monday 1 March I get a call from the shop. Dropped compression on #3 and #5. Leakdown was 45% on #5 and 35% on #3. A new 355/custom cam setup is in the works right now from AP Engineering.
Guess I should update this. On Monday 1 March I get a call from the shop. Dropped compression on #3 and #5. Leakdown was 45% on #5 and 35% on #3. A new 355/custom cam setup is in the works right now from AP Engineering.
Great post!!
Quick question, did they identify what they suspect in causing the drop? i.e. rings, head gasket, valves etc...
#140
We're suspecting ring lands, as the block had 108K miles on it, with the last 24K being under be and driven very hard.
I'll give AP a call in another day and try to see where they are at. They're the one disassembling the engine.
If it helps at all, the shop that did the leakdown test could hear the air escaping through the pushrod passages it was so bad.
I'll give AP a call in another day and try to see where they are at. They're the one disassembling the engine.
If it helps at all, the shop that did the leakdown test could hear the air escaping through the pushrod passages it was so bad.
#143
Re: Stumbling Problem in Great Detail
Originally Posted by blown383
Any updates?
-B
-B
#145
Re: Stumbling Problem in Great Detail
Originally Posted by blown383
So you're waiting for the new opti, o2 conversion and new bottom end?
-B
-B
I'm STILL getting that fuel load up condition though. Next thing to try on my list is unplugging one injector at a time.
I just replaced the fuel pump last week with a Racetronix and it didn't help.
#147
Re: Stumbling Problem in Great Detail
Update!!
I just read this entire thread, my eyes hurt, but I'm intrigued...even though your motor wasn't the cause of the stumble, at least you got a 355 out of it
I have a slight stumble as well...haven't attempted to track it down yet...but it doesn't affect my driving, I'm the only one in the car who can notice it, passengers can't even tell if I tell them to pay attention right when it's about to do it.
I just read this entire thread, my eyes hurt, but I'm intrigued...even though your motor wasn't the cause of the stumble, at least you got a 355 out of it
I have a slight stumble as well...haven't attempted to track it down yet...but it doesn't affect my driving, I'm the only one in the car who can notice it, passengers can't even tell if I tell them to pay attention right when it's about to do it.
#148
Re: Stumbling Problem in Great Detail
Well, I think this is what everyone was waiting for. I do believe that I have found and relieved the culprit parts of their duties.
A recap of what my issues were: Car was fine on a cold start up. After things started heating up, usually within 45 seconds, the car would mysteriously start running rich. Rich to the point of a fast deep neutral rev would cause the car to stall out at times. Under load while driving, the car was obviously surging, and whenever I got into the gas fast and deep, the car would misfire/stumble/hesitate for a second before picking up. On the dyno a once near perfect 13.0 A/F turned into a 10.5 at the low end and leaned out to a 13.0 at 6K RPM.
Parts that I had replaced or verified to be good:
Replaced: Opti, Coil, Plugs, Wires, Fuel Filter, Fuel Pump, Fuel Pressure Regulator, EGR, Oxygen Sensors, several revised tunes, and the SHORTBLOCK.
Verified to be operating within limits: Injectors, IAC, TPS, MAP, Evap System, IAT, ICM (off my other car), ECM (again off my other car).
Nothing did the trick.
So, back in July, while trying to set my valve lash, I was having a hell of a time getting it right. What I noticed at the time was that a bunch of my Comp R lifters were "spongy" at best, when warm. I could very easily compress the lifter by pushing on the back side of the rocker. I blew it off on the advice of some people who played it off as the Comp R's had a larger oiling port and thus bled down easier. I thought nothing more of it until after I replaced the fuel pump and the problem was still there. At that point, I only had a couple more options. Either there was an injector getting a fautly signal and sticking open (but I verified that I was NOT having a leaky injector), the lifters had something to do with it, or I had another fried shortblock. The most obvious choice was the lifters.
Thanks to TQdrivenWS6, I acquired a set of stock lifters about a month and a half ago. Having been frustrated with the car, and due to a minor setback while swapping the O2 system to the 4 Wire Heated units, work on the car was almost nil. So, a couple weeks ago, in went the new lifters, and finally last weekend I got to start working with Alvin, the Pcmforless chip guy, to get the car figured out and tuned in.
I IMMEDIATELY noticed a change in the cars idling behaviour with the stock lifters. On the same tune as previous with the Comp R's, the car was actualy surging at idle. Funny.....it never did that before. A testing idle rev where it used to stumble almost to the point of dying yeilded a tiny hesitation, which I am playing off to the plugs being fouled out. So today I took the car for it's first taste of the glorious asphalt since July. Driving it around, I noticed that my O2's were doing the rich-lean-rich-lean bounce instead of being pegged on the rich end. The car was surging, but it's still in the early stages of tuning. Then the time came, I was sitting in fourth gear at about 1500 RPM. Stab the gas, and the car just settled down and went. No stumble, no backfire, nothing but pulling from the start. Seems that my woes may be coming to an end.
So, it seems that the lifters were at fault. While cold, they were fine, I couldn't compress them at all. Aparrently what was happening was that as certain lifters warmed up, they were becoming "spongy" and not allowing the valves to open up far enough, causing all of my issues. Comp has already confirmed that if the stock lifters worked they'd work with me on getting a brand new set, even those that I currently have are over 1 1/2 year old (but with less than 900 miles on them).
Once we get the tune dialed in some more I will be without a doubt able to say that the lifters were the problem, but after the past weeks findings I am 99% sure that they were the problem. Many thanks go out to all the people that offered help along the way, and especially to TQdrivenWS6 who offered me the stock lifters in the first place. Thanks guys.
A recap of what my issues were: Car was fine on a cold start up. After things started heating up, usually within 45 seconds, the car would mysteriously start running rich. Rich to the point of a fast deep neutral rev would cause the car to stall out at times. Under load while driving, the car was obviously surging, and whenever I got into the gas fast and deep, the car would misfire/stumble/hesitate for a second before picking up. On the dyno a once near perfect 13.0 A/F turned into a 10.5 at the low end and leaned out to a 13.0 at 6K RPM.
Parts that I had replaced or verified to be good:
Replaced: Opti, Coil, Plugs, Wires, Fuel Filter, Fuel Pump, Fuel Pressure Regulator, EGR, Oxygen Sensors, several revised tunes, and the SHORTBLOCK.
Verified to be operating within limits: Injectors, IAC, TPS, MAP, Evap System, IAT, ICM (off my other car), ECM (again off my other car).
Nothing did the trick.
So, back in July, while trying to set my valve lash, I was having a hell of a time getting it right. What I noticed at the time was that a bunch of my Comp R lifters were "spongy" at best, when warm. I could very easily compress the lifter by pushing on the back side of the rocker. I blew it off on the advice of some people who played it off as the Comp R's had a larger oiling port and thus bled down easier. I thought nothing more of it until after I replaced the fuel pump and the problem was still there. At that point, I only had a couple more options. Either there was an injector getting a fautly signal and sticking open (but I verified that I was NOT having a leaky injector), the lifters had something to do with it, or I had another fried shortblock. The most obvious choice was the lifters.
Thanks to TQdrivenWS6, I acquired a set of stock lifters about a month and a half ago. Having been frustrated with the car, and due to a minor setback while swapping the O2 system to the 4 Wire Heated units, work on the car was almost nil. So, a couple weeks ago, in went the new lifters, and finally last weekend I got to start working with Alvin, the Pcmforless chip guy, to get the car figured out and tuned in.
I IMMEDIATELY noticed a change in the cars idling behaviour with the stock lifters. On the same tune as previous with the Comp R's, the car was actualy surging at idle. Funny.....it never did that before. A testing idle rev where it used to stumble almost to the point of dying yeilded a tiny hesitation, which I am playing off to the plugs being fouled out. So today I took the car for it's first taste of the glorious asphalt since July. Driving it around, I noticed that my O2's were doing the rich-lean-rich-lean bounce instead of being pegged on the rich end. The car was surging, but it's still in the early stages of tuning. Then the time came, I was sitting in fourth gear at about 1500 RPM. Stab the gas, and the car just settled down and went. No stumble, no backfire, nothing but pulling from the start. Seems that my woes may be coming to an end.
So, it seems that the lifters were at fault. While cold, they were fine, I couldn't compress them at all. Aparrently what was happening was that as certain lifters warmed up, they were becoming "spongy" and not allowing the valves to open up far enough, causing all of my issues. Comp has already confirmed that if the stock lifters worked they'd work with me on getting a brand new set, even those that I currently have are over 1 1/2 year old (but with less than 900 miles on them).
Once we get the tune dialed in some more I will be without a doubt able to say that the lifters were the problem, but after the past weeks findings I am 99% sure that they were the problem. Many thanks go out to all the people that offered help along the way, and especially to TQdrivenWS6 who offered me the stock lifters in the first place. Thanks guys.
#150
Re: Stumbling Problem in Great Detail
Originally Posted by TQdrivenws6
Now you gotta get that thing tuned up, dyno it and get to the track!
Chris
Chris