88 2.9L Misfireing/backfireing issue

[Spott]

For the price, the best test for a relay is to replace it with a new one, unless it's only a couple years old.

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[Mark_88]

This sounds like something new...codes!

Is this the first time they've shown up or the first time they were pulled? It sounds like something worth fixing either way!

 

[88 XLT Ranger]

This sounds like something new...codes!

Is this the first time they've shown up or the first time they were pulled? It sounds like something worth fixing either way!

Thanks again Spott & Mark

I am still trying to figure out how to reply to two people on one post. I bought a new fuel pump relay from Napa. I just don't know the right one to change? one is green the other brown bottom?

On the scanner test when it was popping before I always stopped plugged it in and started it before testing. Now this last time it was popping running crappy when I got home I waited 10 min than just plugged the scanner in turned the key on I got at first 11 than twice 69 did it again twice 69 the third time code 11 system pass. I though what is going on here? Maybe this is why the on and off popping missing a short in the fuse. If not the next step is to replace the computer Oreilly auto parts is the only one that can get one. I see there is also a computer relay could this be bad as well? I do appreciate all the help if it wasn't for you folks I would be lost I mean lost in this on going issue

 

[alwaysFlOoReD]

Green is gas.

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[Spott]

I would think that if the computer relay was intermittent, your engine would not merely misfire. However, testing that relay is even simpler than testing the fuel pump relay, once you've done that.

The relays are exactly the same, except for color. Buy one new relay, and use it to replace the fuel pump relay, but hang onto the old fuel pump relay. If that doesn't affect the problem, then put the old fuel pump relay back in and use the new relay to replace the EEC relay instead, and see if that helps. If nothing improves, then hang onto the extra relay for a future spare.

 

[88 XLT Ranger]

I would think that if the computer relay was intermittent, your engine would not merely misfire. However, testing that relay is even simpler than testing the fuel pump relay, once you've done that.

The relays are exactly the same, except for color. Buy one new relay, and use it to replace the fuel pump relay, but hang onto the old fuel pump relay. If that doesn't affect the problem, then put the old fuel pump relay back in and use the new relay to replace the EEC relay instead, and see if that helps. If nothing improves, then hang onto the extra relay for a future spare.

Thanks Spott

I will try that the fuel relay has never been changed in the whole life of the truck. I hope it helps will work on it this evening give it a shot

 

[88 XLT Ranger]

"Guy's still no go on fixing this truck"

I put the new fuel pump relay in it stated popping as soon as I started it. I drove it same results popping missing. I took and put the original relay back on and changed the EEC relay fired it popping missing. I did a scanner test key on engine off code 11 pass. I did the run test got code 42 again exhaust gas oxygen sensor always rich low value wont switch and code 12 idle wont come up on test. I did it a second time no code 42 just 12 and 77 and 74. I did give it some throttle when scanner was hooked up and on hold. It popped a lot more real bad now again after testing its back to running normal

When I did the temp sensor test un-plugged it started for a couple seconds and died. The second time turned the key on all the lights inside where real dim it started and died in a couple seconds. Now the third try I just tuned the key on lights real dim inside turned to start all power went off in the truck. I checked the battery over 12 volts I disconnected the battery to re-set computer in a panic. I hooked the battery back still no power I think within 10 seconds or more after that the power came back up to normal. Has anyone had this happen before? can an auto store test a computer if taken out of the truck? I hate to spend $120+ dollars on a rebuilt one and nothing changes

 

[Mark_88]

The complete dimming and loss of power indicates a short or faulty ground somewhere. My suspicion would fall on the starter circuit and I'd be almost willing to bet (no gambling...) that it is either the starter relay on the fender needs attention or the ground wire to the starter itself.

It could also be a frayed wire shorting out but it seems more like the starter circuit needs attention.

I was about to ask if you'd reset the computer after swapping the relay but it appears you did after removing the new relay from the fuel pump feed...I would suggest reset the computer...replace the fuel pump relay with the new one...and check the wires to the starter relay and the starter itself.

Did you at any time replace the wires from the battery to the starter relay/starter motor?

 

[88 XLT Ranger]

The complete dimming and loss of power indicates a short or faulty ground somewhere. My suspicion would fall on the starter circuit and I'd be almost willing to bet (no gambling...) that it is either the starter relay on the fender needs attention or the ground wire to the starter itself.

It could also be a frayed wire shorting out but it seems more like the starter circuit needs attention.

I was about to ask if you'd reset the computer after swapping the relay but it appears you did after removing the new relay from the fuel pump feed...I would suggest reset the computer...replace the fuel pump relay with the new one...and check the wires to the starter relay and the starter itself.

Did you at any time replace the wires from the battery to the starter relay/starter motor?

Mark thanks again for helping I always take the negative battery cable off before changing relays or sensors. Re-stetting the computer you just disconnect the battery for 5-10 min? what does the starter relay look like? I will check the ground wire to starter. Maybe this is why the battery light comes on and off when it does I no drop in voltage. Only disconnecting the temp sensor killed all power and diming of the lights when starting. I never changed the wires from battery to starter relay or starter motor. The starter relay is the one with the positive and negative battery cables going to it? there is a green wire someone replaced it goes from there where the positive cable goes into the small wire harness going forward to the headlights

 

[Pauls 4x4]

I would interject to unplug the air temp sensor so it falls completely into limp mode and see if it persist.
With OBD1 it'll also rich up if misfiring/ or the exhaust is cracked, or your valves/headgasket are dead. The symptom is then only so useful. Whats the regular exhaust note?

With all the swapping i have lost track...Did you do the fuel filter (could lean out intermittently and cause a flood when free)?

Since you did so much ignition work, unless the coil isn't giving a nice shock it's either fuel trim or compression.

Fuel trim is controlled by the ect (rich cold/lean hot), air temp, 88 I think has an egr so it leans by effecting stoiometrics, the tps controls firing rate, and the injector nossels stop drip down. MAP sees load and ECU calculates it all. One bad field in an alternator won't take it out at 35mph as 2 fields are up, and the system catches dropped reference voltages and tosses codes for that two.

Grounds cause little stumbles but I've not seen them cause miricale fixes unless tottaly missing.

If limp mode fixes it, than that's the breakdown of culprits. If it doesn't than compression, injectors leaking, pump, valves, and mechanical.

While a lot of this is good advice, its not methodical. Fuel pump and plugs and temp sensors are all on different system trees, so jumping one to the other doesn't narrow down your scope. Its best to go spark, fuel, etc. like the old advice to trace systems not diverse parts.

My own wild speculation? Throttle position sensor allowing air ratio to get off or the egr is stuck.

 

[88 XLT Ranger]

I would interject to unplug the air temp sensor so it falls completely into limp mode and see if it persist.
With OBD1 it'll also rich up if misfiring/ or the exhaust is cracked, or your valves/headgasket are dead. The symptom is then only so useful. Whats the regular exhaust note?

With all the swapping i have lost track...Did you do the fuel filter (could lean out intermittently and cause a flood when free)?

Since you did so much ignition work, unless the coil isn't giving a nice shock it's either fuel trim or compression.

Fuel trim is controlled by the ect (rich cold/lean hot), air temp, 88 I think has an egr so it leans by effecting stoiometrics, the tps controls firing rate, and the injector nossels stop drip down. MAP sees load and ECU calculates it all. One bad field in an alternator won't take it out at 35mph as 2 fields are up, and the system catches dropped reference voltages and tosses codes for that two.

Grounds cause little stumbles but I've not seen them cause miricale fixes unless tottaly missing.

If limp mode fixes it, than that's the breakdown of culprits. If it doesn't than compression, injectors leaking, pump, valves, and mechanical.

While a lot of this is good advice, its not methodical. Fuel pump and plugs and temp sensors are all on different system trees, so jumping one to the other doesn't narrow down your scope. Its best to go spark, fuel, etc. like the old advice to trace systems not diverse parts.

My own wild speculation? Throttle position sensor allowing air ratio to get off or the egr is stuck.

Paul thanks for helping the exhaust is good no leaks and free flowing. I did change the fuel filter and pump and tested fuel pressure. The TPS has never been changed the Idle Air control valve seams to have issues keeping idle up on start up. I will try and disconnect the air temp sensor its the one on the side of the Intake manifold? there is no EGR on this truck

 

[Mark_88]

I would interject to unplug the air temp sensor so it falls completely into limp mode and see if it persist.
With OBD1 it'll also rich up if misfiring/ or the exhaust is cracked, or your valves/headgasket are dead. The symptom is then only so useful. Whats the regular exhaust note?

With all the swapping i have lost track...Did you do the fuel filter (could lean out intermittently and cause a flood when free)?

Since you did so much ignition work, unless the coil isn't giving a nice shock it's either fuel trim or compression.

Fuel trim is controlled by the ect (rich cold/lean hot), air temp, 88 I think has an egr so it leans by effecting stoiometrics, the tps controls firing rate, and the injector nossels stop drip down. MAP sees load and ECU calculates it all. One bad field in an alternator won't take it out at 35mph as 2 fields are up, and the system catches dropped reference voltages and tosses codes for that two.

Grounds cause little stumbles but I've not seen them cause miricale fixes unless tottaly missing.

If limp mode fixes it, than that's the breakdown of culprits. If it doesn't than compression, injectors leaking, pump, valves, and mechanical.

While a lot of this is good advice, its not methodical. Fuel pump and plugs and temp sensors are all on different system trees, so jumping one to the other doesn't narrow down your scope. Its best to go spark, fuel, etc. like the old advice to trace systems not diverse parts.

My own wild speculation? Throttle position sensor allowing air ratio to get off or the egr is stuck.

What you are saying is all good and may help with the stumble, but what is happening is he is losing all power..which is probably totally unrelated to his initial problem of stumbling...

Problems with starter not cranking and lights dimming are all related to ground issues or problems with connections on the relay...

The relay is the connection point on the fender where the battery power is connected before it goes to the starter...sounds like you may have left something loose or, perhaps, too tight. I've had those connections break on an old relay so be careful if this is the original parts...and might be worthwhile to swap that out just in case.

I have three of them sitting in a box outside that I'd offer to send you if you were closer...but they are not expensive if yours is damaged...

 

[88 XLT Ranger]

What you are saying is all good and may help with the stumble, but what is happening is he is losing all power..which is probably totally unrelated to his initial problem of stumbling...

Problems with starter not cranking and lights dimming are all related to ground issues or problems with connections on the relay...

The relay is the connection point on the fender where the battery power is connected before it goes to the starter...sounds like you may have left something loose or, perhaps, too tight. I've had those connections break on an old relay so be careful if this is the original parts...and might be worthwhile to swap that out just in case.

I have three of them sitting in a box outside that I'd offer to send you if you were closer...but they are not expensive if yours is damaged...

Mark

I found the problem it was the positive battery cable when I disconnected the air temp sensor. I fired it up it died tried it again it died the third time all power went off. I took and checked each wire the positive wire the crimp on the end where it bolts to the relay I moved and all came back on. I took it off crimped both ends tight

 

[88 XLT Ranger]

I would interject to unplug the air temp sensor so it falls completely into limp mode and see if it persist.
With OBD1 it'll also rich up if misfiring/ or the exhaust is cracked, or your valves/headgasket are dead. The symptom is then only so useful. Whats the regular exhaust note?

With all the swapping i have lost track...Did you do the fuel filter (could lean out intermittently and cause a flood when free)?

Since you did so much ignition work, unless the coil isn't giving a nice shock it's either fuel trim or compression.

Fuel trim is controlled by the ect (rich cold/lean hot), air temp, 88 I think has an egr so it leans by effecting stoiometrics, the tps controls firing rate, and the injector nossels stop drip down. MAP sees load and ECU calculates it all. One bad field in an alternator won't take it out at 35mph as 2 fields are up, and the system catches dropped reference voltages and tosses codes for that two.

Grounds cause little stumbles but I've not seen them cause miricale fixes unless tottaly missing.

If limp mode fixes it, than that's the breakdown of culprits. If it doesn't than compression, injectors leaking, pump, valves, and mechanical.

While a lot of this is good advice, its not methodical. Fuel pump and plugs and temp sensors are all on different system trees, so jumping one to the other doesn't narrow down your scope. Its best to go spark, fuel, etc. like the old advice to trace systems not diverse parts.

My own wild speculation? Throttle position sensor allowing air ratio to get off or the egr is stuck.

Paul

I drove the truck until it started popping missing I got home and un-plugged the air temp sensor the popping went away. I have to give it a little throttle to keep it running if I let it idle it dies. Is it ok to drive it like that to test it there is an idle adjustment screw on the throttle body. I got some carb cleaner to clean the idle air control valve hope that helps it don't want to high idle on cold start up than come down to 800rpm's

 

[Spott]

There is not an idle adjustment screw on the throttle body, this is not like a carbureted engine. Do not adjust that screw to try and fix idle problems.

That screw is to calibrate the TPS and set the "throttle closed" point; the computer uses the IAC valve to regulate idle instead of using a screw to hold the throttle plate open a certain amount.