So, i picked up an 87 Turbo last december, and finally got some time to troubleshoot. It wasn't running, just cranked and cranks, misfired every once in awhile. now, the story is that the PO had bought it a year ago, drove for a month and... BHG :: angry ::
So he ported and polished the head and had new valve seals installed, as verified by the race shop that did it, with receipts as well.
I have done the following:
compression test: All cylinders have compression at 125psi, cold, except cylinder #2. After putting alittle bit of oil in #2 compression was up to 125 as well, so it's probably a bad ring. my leakdown tester has a bad fitting, so I'm waiting to get a new one to check the leakdown results.
CPS: CPS has resistance values within the right range, as specified by the TSRM, air gaps are in spec as well. However, tach doesn't move when cranking, so not sure if that's good or bad. I just remember reading something about that on the boards a week or two ago. CPS is also timed correctly, as stated in the timing article here.
Coil Packs: The coil packs were in bad shape, so I purchased another set with wires and harness from a fellow member on here. I have spark on all wires, bright and blue. I assume this means igniter works as well.
Fuel pump and injectors: Fuel pump pressurizes when jumping B+ and Fp in the diagnostic box, injectors click like they shoould when cranking. Interesting note: Plugs were black but not fouled.
Timing: Stroke timing is correct, When timing mark is at 0, piston is in fact, at TDC, cams line up correctly as well.
AFM: Here's where I got confused, I tested the terminals as mentioned in TSRM, however, something is off. Is there a typo in the TSRM? Is asks to check for resistance values between two terminals, a terminal VS to E1, however, there is no VS in the diagram, so i jusst tested VC to E1. Values are all over the place.
KS to E1 does not show infinite resistance, but something like 700k ohms.
E1 to KS shows 12k ohms, Spec is 5-10k
VS to E1 shows 17k ohms, Spec is 10-15k
E1 to VC : i forgot what it showed but it was above spec, which is 5-12k
THA to E2: Temp at the time was 85 degrees F, and the spec was 1.6k ohms. there is no range close to that, just 68 degrees and 104f degrees. spec at 68 is 2-3k and spec at 104 is 0.9 to 1.3k. I assume that that test is ok, because it falls right in between the spec values for both temperatures.
My speculation: Bad AFM? Everything checks out, although injectors might not be firing correctly. however, since the plugs are new, and fouled from the constant cranking as misfires (not backfiring, just stumbles) I think that the AFM is not sending correct signals to the ECU, and subsequently, wrong amounts of fuel? that's just my speculation though.
Can a bad afm do this?
Sorry for the long read, but I just tried to get as much info as I can.
So he ported and polished the head and had new valve seals installed, as verified by the race shop that did it, with receipts as well.
I have done the following:
compression test: All cylinders have compression at 125psi, cold, except cylinder #2. After putting alittle bit of oil in #2 compression was up to 125 as well, so it's probably a bad ring. my leakdown tester has a bad fitting, so I'm waiting to get a new one to check the leakdown results.
CPS: CPS has resistance values within the right range, as specified by the TSRM, air gaps are in spec as well. However, tach doesn't move when cranking, so not sure if that's good or bad. I just remember reading something about that on the boards a week or two ago. CPS is also timed correctly, as stated in the timing article here.
Coil Packs: The coil packs were in bad shape, so I purchased another set with wires and harness from a fellow member on here. I have spark on all wires, bright and blue. I assume this means igniter works as well.
Fuel pump and injectors: Fuel pump pressurizes when jumping B+ and Fp in the diagnostic box, injectors click like they shoould when cranking. Interesting note: Plugs were black but not fouled.
Timing: Stroke timing is correct, When timing mark is at 0, piston is in fact, at TDC, cams line up correctly as well.
AFM: Here's where I got confused, I tested the terminals as mentioned in TSRM, however, something is off. Is there a typo in the TSRM? Is asks to check for resistance values between two terminals, a terminal VS to E1, however, there is no VS in the diagram, so i jusst tested VC to E1. Values are all over the place.
KS to E1 does not show infinite resistance, but something like 700k ohms.
E1 to KS shows 12k ohms, Spec is 5-10k
VS to E1 shows 17k ohms, Spec is 10-15k
E1 to VC : i forgot what it showed but it was above spec, which is 5-12k
THA to E2: Temp at the time was 85 degrees F, and the spec was 1.6k ohms. there is no range close to that, just 68 degrees and 104f degrees. spec at 68 is 2-3k and spec at 104 is 0.9 to 1.3k. I assume that that test is ok, because it falls right in between the spec values for both temperatures.
My speculation: Bad AFM? Everything checks out, although injectors might not be firing correctly. however, since the plugs are new, and fouled from the constant cranking as misfires (not backfiring, just stumbles) I think that the AFM is not sending correct signals to the ECU, and subsequently, wrong amounts of fuel? that's just my speculation though.
Can a bad afm do this?
Sorry for the long read, but I just tried to get as much info as I can.
