Misfire help.

[GOskidmark]

I have 1990 Ranger 2.9L with 140,000 miles on it, and I can't stop it from
misfiring.

New MAP sensor.

New Plugs, wires, and cap.

New Coil.

Cleaned IAC valve.

New " Thing that goes behind the dizzy." Forgive me I'm tired.

It idles at 1,200 Rpm and the timing was done by hand with the jumper
out of the harness. When I put the jumper in it just dies. The motor does not
smoke. There is no oil on the spark plugs. Intake is not leaking. Vacuum seems to be in range. It has power, but it's just misfiring bad throughout
the rev range. I'm getting a buddy to come over with his timing light Friday.
What am I doing wrong? Thanks guys.

 

[kimcrwbr1]

Have your buddie bring a code reader also or maybe you can pull the codes at the part store or buy one. did you check the fuel pressure change the fuel filter. Are all the plugs the same color. Put the timing light on the coil wire and see if it misses. Are you talking about the spout wire connector going to the dizzy. Unplug it when you time it make sure the dizzy is tight and check it then plug the spout in. Erase the memory on the computer then disconnect the battery for 30 minutes while you check all the connectors and grounds then take it for a drive at medium speeds till it gets hot then run the codes. KOEO while it is still hot and address the codes in the order received. Don`t keep throwing parts at it fix the faults one at a time and reset the computer whenever you change or clean a sensor and retest always with a hot engine. Hopefully it is just the timing but it sounds like it needs a good diagnostic anyway to eliminate variables. One bad sensor can give multiple codes so write them down and fix the lowest number first.

 

[low_five]

I have 1990 Ranger 2.9L with 140,000 miles on it, and I can't stop it from
misfiring.

New MAP sensor.

New Plugs, wires, and cap.

New Coil.

Cleaned IAC valve.

New " Thing that goes behind the dizzy." Forgive me I'm tired.

It idles at 1,200 Rpm and the timing was done by hand with the jumper
out of the harness. When I put the jumper in it just dies. The motor does not
smoke. There is no oil on the spark plugs. Intake is not leaking. Vacuum seems to be in range. It has power, but it's just misfiring bad throughout
the rev range. I'm getting a buddy to come over with his timing light Friday.
What am I doing wrong? Thanks guys.

dont take this the wrong way, but I have probably gone behind 20 guys who have changed the spark plug wires and put them back in the wrong firing order. Ive done it myself once or twice. Id check that first. then I would have my buddy check each wire with the light and make sure its firing. then, I would pull each wire one at a time and see which one or ones causes the least difference to the engine running. if that doesnt isolate the problem cylinder, I would carefully feel the exhaust and see which one or ones arent getting as hot as the others.

 

[Hotrodlincoln]

Have you checked the resistance of the fuel injectors?
Done a compression test?

 

[GOskidmark]

I've rechecked the firing order and wires. That's all correct. I'll let it warm up
after a reset, and touch the headers/Pulling the plug wires one by one, to
see if I have a dead cylinder.

Fuel pump was changed when I first bought the truck a few weeks ago.
The pump that was in it was dead. New fuel filter was installed also.

The FPR was checked, and no gas is coming out of the vacuum hose.
I know they can fail and not leak fuel, so I might just replace that part
since it's twenty years old anyways. I didn't think to reset the ECC after I
installed the new parts.

Thanks so much you guys for the information. I'll go try this stuff out
in the morning after I slay the cat that keeps jumping on my hood a night.

 

[GOskidmark]

Okay, today I reset the ECC or the ECU, whatever you want to call it.
Idles allot better, but still missing a bit. I find it odd that when I gently ease the gas while driving she rev's up just fine. If I just hammer it, the truck stumbles and accelerates slowly. Is that timing?

 

[IMenriched]

Okay, today I reset the ECC or the ECU, whatever you want to call it.
Idles allot better, but still missing a bit. I find it odd that when I gently ease the gas while driving she rev's up just fine. If I just hammer it, the truck stumbles and accelerates slowly. Is that timing?

Might be time to check the Throttle Position Sensor (TPS)
info for doing so is in the Tech Library

Have you done a vacuum pressure test yet? what were the numbers?

what about the fuel pressure?