Hey
1988 305 TPI, everything stock
Car is running pretty bad, every time you start, it'll be one of two possible ways;
-Will run a bit rich in Open or Closed loop, if you give it more than about 10% throttle it will stutter and revs will drop
or
-Will run like a complete dog in Open or Closed loop, can't idle, can barely move, will throw a code 34 (low voltage at MAF) when it stalls and will eventually go into Soft Fail (SES light stuck on). After this it runs almost perfect?
Is there a way to tell which sensor is being ignored in Soft Fail? I guess I could pull the connectors one by one with the engine running. Looking at the ALDL output, it will only list what the ECM sees, not if it's moved to a default for one particular sensor.
Anyway, I replaced the plugs, leads, distributor cap/rotor a while ago, problem has been around since before that, but used to be a lot more intermittent.
What I've tried so far;
Replaced both the MAF relays
Checked injectors, all 16.5 ohms cold, 17.5 ohms hot (think they were replaced last year)
Cold start injector is 4.7 ohms, but I think that's normal
Adjusted TPS to .57V, 4.53V WOT
MAF flow rate engine off = 15.00gm/s, idle = 8gm/s, part throttle gets up to 30gm/s (pretty sure the engine off flow rate is normal)
CTS = 500 ohms, getting 5V, right temp showing in tunerpro (when using 6E mask)
I've checked for vacuum leaks, but possibly not well enough. Pulling smaller hoses off makes little difference to the engine (when it's running mostly fine).
The wiring on the MAF isn't the best (had a bent pin, one side of the connector is cracked), but the ECM seems to be reading it ok.
The other night I was poking around with it, started it up, it ran absolutely perfect. Turned it off, back on again in 5 mins and it was back to running rich (although not stall-rich).
I'm running out of ideas... I thought it was the CTS, as it was reading -40, but that was only when using a $32B datastream with a calculation wrong. I also thought it was the CSI when it came in at 4.7ohms, but I think that's "normal". I'm getting a gauge to test the fuel pressure, but it won't be here for another week. I've looked at a lot of the data I'm getting from Tunerpro, but can't see anything seriously out of the ordinary, I could post a log up though if it anyone might have more experience with these.
I'm guessing I can rule out the 02, as it's bad in Open and Closed loop, the IAT as it doesn't affect fueling.
Any help would be seriously appreciated, I'm not sure what else I can check until the fuel gauge gets here.
edit- If I disconnect the MAF, it goes into Soft Fail and runs fine. I'm going to have to have a second look for vacuum leaks and look at the EGR valve.
1988 305 TPI, everything stock
Car is running pretty bad, every time you start, it'll be one of two possible ways;
-Will run a bit rich in Open or Closed loop, if you give it more than about 10% throttle it will stutter and revs will drop
or
-Will run like a complete dog in Open or Closed loop, can't idle, can barely move, will throw a code 34 (low voltage at MAF) when it stalls and will eventually go into Soft Fail (SES light stuck on). After this it runs almost perfect?
Is there a way to tell which sensor is being ignored in Soft Fail? I guess I could pull the connectors one by one with the engine running. Looking at the ALDL output, it will only list what the ECM sees, not if it's moved to a default for one particular sensor.
Anyway, I replaced the plugs, leads, distributor cap/rotor a while ago, problem has been around since before that, but used to be a lot more intermittent.
What I've tried so far;
Replaced both the MAF relays
Checked injectors, all 16.5 ohms cold, 17.5 ohms hot (think they were replaced last year)
Cold start injector is 4.7 ohms, but I think that's normal
Adjusted TPS to .57V, 4.53V WOT
MAF flow rate engine off = 15.00gm/s, idle = 8gm/s, part throttle gets up to 30gm/s (pretty sure the engine off flow rate is normal)
CTS = 500 ohms, getting 5V, right temp showing in tunerpro (when using 6E mask)
I've checked for vacuum leaks, but possibly not well enough. Pulling smaller hoses off makes little difference to the engine (when it's running mostly fine).
The wiring on the MAF isn't the best (had a bent pin, one side of the connector is cracked), but the ECM seems to be reading it ok.
The other night I was poking around with it, started it up, it ran absolutely perfect. Turned it off, back on again in 5 mins and it was back to running rich (although not stall-rich).
I'm running out of ideas... I thought it was the CTS, as it was reading -40, but that was only when using a $32B datastream with a calculation wrong. I also thought it was the CSI when it came in at 4.7ohms, but I think that's "normal". I'm getting a gauge to test the fuel pressure, but it won't be here for another week. I've looked at a lot of the data I'm getting from Tunerpro, but can't see anything seriously out of the ordinary, I could post a log up though if it anyone might have more experience with these.
I'm guessing I can rule out the 02, as it's bad in Open and Closed loop, the IAT as it doesn't affect fueling.
Any help would be seriously appreciated, I'm not sure what else I can check until the fuel gauge gets here.
edit- If I disconnect the MAF, it goes into Soft Fail and runs fine. I'm going to have to have a second look for vacuum leaks and look at the EGR valve.
Try starting the car with the MAF disconnected.
thanks Viprklr
Yeah I've been driving it with the MAF disconnected, bit rough at first till it figures out there's no MAF (3 secs or so), then it's pretty much fine. Can feel it's not quite driving right, but heaps better than usual.
I thought it might be the EGR, so I pulled the plenum. It's a negative pressure EGR valve, I couldn't get it off the manifold (1 broken spanner and 2 ouchy fingers), but if anything the diaphragm seemed to be stuck down when I first tried to move it. Moved a bit better after that, but still pretty stiff (needs fingers on both sides to move it up), diaphagm wasn't ripped and it seemed to be fully closing down. I'll probably have a shot at pulling it up tommorrow, see if it causes RPM to drop, but I'm not sure I'll be able to get my fingers under the plenum. Aside from being stiff, and possibly stuck closed, it didn't seem to be the cause of my problem.
I was thinking it might be a vacuum leak, but I think I'd need a vacuum leak the size of a tennis ball to cause the problem I'm having. The TB intake piping has to be partially disconnected to cause anything like the drivability issues I'm having.
Guess it's back to checking the MAF circuitry, some other old posts mentioned the ECM cradle and main engine ground as also being culprits in the past, so will have to look at those as well. A lot of this might seem obvious, but 2 months ago I knew pretty much nothing about TPI engines.
Yeah I've been driving it with the MAF disconnected, bit rough at first till it figures out there's no MAF (3 secs or so), then it's pretty much fine. Can feel it's not quite driving right, but heaps better than usual.
I thought it might be the EGR, so I pulled the plenum. It's a negative pressure EGR valve, I couldn't get it off the manifold (1 broken spanner and 2 ouchy fingers), but if anything the diaphragm seemed to be stuck down when I first tried to move it. Moved a bit better after that, but still pretty stiff (needs fingers on both sides to move it up), diaphagm wasn't ripped and it seemed to be fully closing down. I'll probably have a shot at pulling it up tommorrow, see if it causes RPM to drop, but I'm not sure I'll be able to get my fingers under the plenum. Aside from being stiff, and possibly stuck closed, it didn't seem to be the cause of my problem.
I was thinking it might be a vacuum leak, but I think I'd need a vacuum leak the size of a tennis ball to cause the problem I'm having. The TB intake piping has to be partially disconnected to cause anything like the drivability issues I'm having.
Guess it's back to checking the MAF circuitry, some other old posts mentioned the ECM cradle and main engine ground as also being culprits in the past, so will have to look at those as well. A lot of this might seem obvious, but 2 months ago I knew pretty much nothing about TPI engines.
From my research here, I haven't had any MAF issues on my car, "If you disconnect the MAF and it runs better then the MAF needs to be replaced."
Again, that's just what I gathered from my research here. I've had no personal issues with mine.
You say it drives better without the MAF connected............
Again, that's just what I gathered from my research here. I've had no personal issues with mine.
You say it drives better without the MAF connected............
Actually, from checking the MAF, both the grounds are good, there isn't any voltage over the output wire, the input signal voltage is 5.03V, howerver on E (red wire) I'm getting 13.6V power. Probably a really dumb question, but should this be battery voltage? Or is it meant to be regulated to 12V somewhere along the line?
All the circuit diagrams I've looked at put it as 12V, and from searching through a half-dozen old TGO posts they all mention finding 12V on this wire
All the circuit diagrams I've looked at put it as 12V, and from searching through a half-dozen old TGO posts they all mention finding 12V on this wire
For anyone who's interested, or finds this in a search in years to come.. the problem was the MAF, swapped another one in temporarily and it ran fine.