SlaughtrHousJak

Not sure if I worded my search correctly, but I haven't seen anything. I'm still looking. The fuel economy dash data is not showing and running poorly. This is currently happening with no DTC's on the ALDL dash light. My 87 4+3 car has all the typical mods from the 90s. Test pipe, air foil, Hypertech chip. I dont know the history so its been fun figuring this all out. Chasing vacuum leaks and getting the air pump working, then finding out the cat was gutted and smog pipe was welded closed.. Ive replaced most if not all valves, sensors, relays ect. Its always seemed to have a slight miss or run rough at low rpms, but has run fine otherwise as Ive been working on it. This new problem is a problem tho. Smells rich and stalls some times. Occasionally has a warm hard start. About 5 or 6 second crank time. I'm hoping I can get this one figured out sooner than later with some help. I'll try to have a video linked or posted here if I have permission. I do believe this is my first post. Thank you for taking the time to look, and thank you for keeping a great forum.

bjankuski

We need more information. The instant MPG will always read zero when the can is not moving, does it still read zero when the car is moving?

As far as stalling have you done a tune-up by replacing or at least inspecting the plugs, wires, and rotor? If not start there. the hard staring when hot may be related to an injector leak down issue but first make sure the plugs, wires, and cap are good, along with timing.

SlaughtrHousJak

Range and instant always zero during this problem. I meant to mention it seems intermittent. Ground was unplugged for a week while gone, but problem came back a day or so later. I haven't nailed it down quite yet. Plugs, wires, cap, rotor, distributor, coil, mass airflow, fuel pump/filter, IAC, alternator, intake gaskets, thermostat, water pump. Almost every serviceable part has been serviced or replaced since I bought it as my daily. 68K miles. Thanks for your time.

SlaughtrHousJak

bjankuski

Take a look at the vacuum line going from the fuel pressure to the plenum to make sure there is no fuel in it. It is possible that the regulator diaphragm ruptured and is dumping raw fuel in at idle, causing a rough idle and hard starting. Also check the grounds behind the where they attach to the cylinder head to make sure they are tight and not missing. This could be the problem with your dash readouts.

SlaughtrHousJak

I'll let ya know what I come up with. Thank you.

'78CorvetteS.A.

Great advice above, and it wouldn't hurt to put a fuel pressure gauge on it....observe pressures starting, idling and driving...."rent" (borrow with deposit)a good kit (if you don't have one) that has a long enough hose to tape/pin the gauge against the windshield to read pressures under driving conditions. Are your injectors the stock originals? I will post some info for the instant/average mpg gauge today, to help you troubleshoot that (not by my manuals at the moment)! Good luck👍

SlaughtrHousJak

Not seeing any fuel in vacuum lines at regulator. Here's a couple short clips from this morning.

I may have a ground issue like mentioned. ALDL won't put codes out but will display milage till empty number. Not sure if it's related to my rough idle and stall issue. Milage number flashes here, then car dies after a short blip. ALDL is not grounded in video. Or while running. =)

SlaughtrHousJak

I do have a fuel pressure guage. I just put a pump in last fall. I'll hook it up and see what it looks like this weekend.

SlaughtrHousJak

It was running while I made last post, then it cleared up and started running great. It did this recently and it's never run better, but it doesn't last. Was more power and way more smooth. Idk. Weird.

SlaughtrHousJak

I finished a rebuild and install of the oem distributor last night. No change in my current problem, not that it would have been. But ignition system is in good shape. I believe I have a Thermomaster chip, but I put an oem 190 thermostat befor I knew I had it. I think I'll try pullin the chip out and see what happens.

My mistake. I had thought the Thermomaster chip was piggy backed along with oem for some reason...

SlaughtrHousJak

I should have some down time soon so I'll be looking for somewhere to send out for a re-tune. Should I look to buy a second prom, or can the hypertech be rewritten? Is there a preferred vendor to support here on the forum?

Thanks.

2011KLR

Subscribing. Mine does exactly the same except mine is intermittent. Ive noticed that mine will run fine, instant and avg mpg show realistic numbers. Then with no perceivable change anywhere... the idle will start fluctuating, stumbling , avg goes to 12.8 and instant goes to 0.

VikingTrad3r

i may have missed it, but did you get a fuel pressure reading key on and while running?

historically has the car ever ran properly? you mention installing a new fuel pump, did it run fine prior to this?

SlaughtrHousJak

Its ran ok since Ive got it, but not great. Its had a low RPM miss, rough idle at times, but never stalled. Its starting to get worse with one stall per warm up.(kinda weird) Ill see if I can get a better video today.
iirc fuel pressure was about 42psi in driveway a week or two ago. Sorry for not posting. My guage isnt quite long enough to tape to windshield to drive with it. Easy to recheck today and Ill update soon

VikingTrad3r

so then grab an aldl cable and a laptop, tunerpro rt, dl ur 87 definitions file, load it into the program, and observe what the car is doing.

SlaughtrHousJak

35-41psi or so. PS pump is squeeking. Already on my to-dos.


During warm up it starts running rough, and if it gets any throttle it'll die. But only once. On occasion it'll do it once while driving. I dont think its ever happened more than once tho. Emissions have been tuned out im assuming. Ive removed quite a bit hoping is a vacuum leak issue and not getting any DTCs as I go.

2011KLR

As we know, your Instant MPG is gong to be 0 sitting still. No help there.

Flip over to AVG MPG. I noticed that your Range was 0 for most of the video but began to jump around near the end. Id expect your AVG to be going up and down hand in hand with the Range but when your Range is at 0, your AVG shows 12.8. If, so, it is eerily similiar to what mine does.... things are fine then suddenly it starts idling poorly, and these numbers dance.

Even if it is the same as mine, im stuck on the fix. I need to get a scanner. But thats not in the cards right now.

SlaughtrHousJak

Got myself a laptop this week and TunerPro RT. Waiting on serial to usb that should be here tomorrow. Do these look like the right files to get for an 87 4+3 car?



I also see these.




Thanks for your time. Its much appreciated.

SlaughtrHousJak

This is what Ive gotten so far. I know im on the right track, but still no idea what i'm doin'.


I got a serial to USB. I think I got the right one.:





I made my self a cable with a switched 10k resistor. Short pin A and B with resistor, and pin E. - I could have skipped using a switch, yea?







And this is what Ive gotten with $32B.ads and $32B.xdf. I'm still not sure if this is right, or something is messed up. Is there something different I should do with having a Hypertech thermomaster?