OHV “exhaust popcorn”/ no burn cyl, 3/5

[lancasterpunk29]

1999 (edit this POS phone put 1990 and i didn’t proof read like a J.A. ) 4.0 OHV. so I know this is weird, but i’m getting popcorn sound only under high load (and a massive drop in power) (in the exhaust). Did the spark plug check and I’m not getting a burn or incomplete burn on three and five which tells me it’s not necessarily the coil pack with this wasted spark system. Coil pack was changed, spark plugs, and wires were changed same thing. Ignition timing won’t go past 22° ever since I disconnected the four-wheel-drive motor. the stupid thing isn’t popping any codes. i was getting lean codes but i swapped the O2 sensors for the correct ones. it’s not burning coolant or oil. Any clue what could be happening ? I can try to take a video another day.

 

[SenorNoob]

Broken honeycomb in the cat? Can you pull it to have a look? Maybe even drive it that way as a test.

 

[Shran]

Pinging? That would be my first guess.

4.0's were fairly well known for carbon knock, which is caused by buildup of carbon on the head/piston/or both which increases the compression ratio and causes pinging under load. Ford had a TSB on it, basically you use something similar to Seafoam to remove the buildup... could be other causes as well but I'd rule that out first since it's easy.

 

[lancasterpunk29]

Broken honeycomb in the cat? Can you pull it to have a look? Maybe even drive it that way as a test.

that’s all squared . it’s missing, can tell 100% based on plug read. already decarbonized to get that out of the way, hence the new O2’s, spark plugs, wires.

Pinging? That would be my first guess.

4.0's were fairly well known for carbon knock, which is caused by buildup of carbon on the head/piston/or both which increases the compression ratio and causes pinging under load. Ford had a TSB on it, basically you use something similar to Seafoam to remove the buildup... could be other causes as well but I'd rule that out first since it's easy.

done , that was my gathering from the forums here .

 

[Shran]

Hmmmmm... any history of major engine/head work? Are you sure the injectors are firing on those cylinders? Plug wires aren't in the wrong order (easy to do on that side of the engine, they don't match the coil pack.)

There is a deal with 4 cylinder heads where the valves can wear or the seats can be cut too far back during a valve job which results in a valve stem that is too long and under load/high oil pressure situations the valves won't close completely. Never heard of that happening on a 4.0 but I suppose it could.

If you have newer heads on an older block with old style pistons it could ping because the compression ratio is increased a fair bit with that particular combination.

Have you cleaned the MAF sensor?

Have you run a fuel pressure test? A lean condition from low fuel pressure will definitely make it pop & miss.

 

[lancasterpunk29]

Hmmmmm... any history of major engine/head work? Are you sure the injectors are firing on those cylinders? Plug wires aren't in the wrong order (easy to do on that side of the engine, they don't match the coil pack.)

There is a deal with 4 cylinder heads where the valves can wear or the seats can be cut too far back during a valve job which results in a valve stem that is too long and under load/high oil pressure situations the valves won't close completely. Never heard of that happening on a 4.0 but I suppose it could.

If you have newer heads on an older block with old style pistons it could ping because the compression ratio is increased a fair bit with that particular combination.

Have you cleaned the MAF sensor?

Have you run a fuel pressure test? A lean condition from low fuel pressure will definitely make it pop & miss.

I mean the plugs look kinda dirty and fouled , I am dreading pulling injectors. I can see in my SCT my fuel pump is only pushing 1 and .5 on the duty cycle and it used to do up to two occasionally. I could try to do a fuel pressure test , i’m having a bad feeling about it being lifters sticking , or blown rings. my other engine didn’t do this and had a coolant leak I didn’t want to deal with. But I also did the injectors on that. MAF is brand new. was thinking maybe CPS , or CKP whatever you wanna call it . my other engine was doing this until i threw parts at it , and pulled rich codes after doing injectors and every once in a while pulled lean. you got me thinking I should throw a fuel pump at it .

 

[lancasterpunk29]

I mean the plugs look kinda dirty and fouled , I am dreading pulling injectors. I can see in my SCT my fuel pump is only pushing 1 and .5 on the duty cycle and it used to do up to two occasionally. I could try to do a fuel pressure test , i’m having a bad feeling about it being lifters sticking , or blown rings. my other engine didn’t do this and had a coolant leak I didn’t want to deal with. But I also did the injectors on that. MAF is brand new. was thinking maybe CPS , or CKP whatever you wanna call it . my other engine was doing this until i threw parts at it , and pulled rich codes after doing injectors and every once in a while pulled lean. you got me thinking I should throw a fuel pump at it .

I was getting lean codes right before I swapped the O2 sensors . would make sense if it double misses and then ignites the minimal fuel off hot exhaust. but i’ll tell you right now it’s not pinging , i know that sound all to well from messing with old dizzy systems and milking the 73 2.6 for all it’s worth. Carbs and dizzys FTW.

 

[Shran]

I think you should run a fuel pressure test and report back.

 

[lancasterpunk29]

I think you should run a fuel pressure test and report back.

So KOEO 55 or there about

KOER 63 on the money , full rev same. 100% not fuel pressure.

so I’m waiting for my compression tester to show. ( figured i’d buy one since apparently i’m into rebuilding engines now.)

Changed IACV for the hell of it , the other one was crusty. going for a test drive and gonna read plugs . not in the mood to change injectors , but if it compression tests ok I will.

 

[Shran]

So KOEO 55 or there about

KOER 63 on the money , full rev same. 100% not fuel pressure.

so I’m waiting for my compression tester to show. ( figured i’d buy one since apparently i’m into rebuilding engines now.)

Changed IACV for the hell of it , the other one was crusty. going for a test drive and gonna read plugs . not in the mood to change injectors , but if it compression tests ok I will.

OK...hold up... your original post said this is for a 1990. Is that correct? Not the '99 that shows in your profile?

1990 had zero electronic monitoring of fuel pressure - none - those EEC-IV test codes mean nothing. You need actual pressure readings from a gauge hooked up to the fuel rail. You should be getting about 35psi at idle and up to 40psi briefly if you blip the throttle. Anything way outside of that will cause problems.

My kid's '95 has a weak pump at the moment and he was complaining about it not running well, it pops & sputters and is basically not drivable. It is NOT throwing any codes... and that is OBD-2.... there is no monitoring there. My fuel pressure gauge shows that the pump is not even making 20psi - obviously the problem but my point is that you cannot rely on code readers to fix stuff like this.

 

[lancasterpunk29]

got one that might mess with your head , i know it is mine . hooked up a timing light for gigs . the if i keep the inductor open it lights at half the speed of the engine (both banks), expected. if i put it on driver side bank , all good . full flash engine rpm. i put it on passenger side bank, intermittent/ nothing . please tell me it’s not the PCM and i’m gonna have to go to a dealer to get it flashed. any chance it’s the CPS /CKP ?

 

[lancasterpunk29]

OK...hold up... your original post said this is for a 1990. Is that correct? Not the '99 that shows in your profile?

1990 had zero electronic monitoring of fuel pressure - none - those EEC-IV test codes mean nothing. You need actual pressure readings from a gauge hooked up to the fuel rail. You should be getting about 35psi at idle and up to 40psi briefly if you blip the throttle. Anything way outside of that will cause problems.

My kid's '95 has a weak pump at the moment and he was complaining about it not running well, it pops & sputters and is basically not drivable. It is NOT throwing any codes... and that is OBD-2.... there is no monitoring there. My fuel pressure gauge shows that the pump is not even making 20psi - obviously the problem but my point is that you cannot rely on code readers to fix stuff like this.

if it said 1990 then autocorrect screwed me hard . this is for the 99 . F-this Iphone

 

[lancasterpunk29]

if it said 1990 then autocorrect screwed me hard . this is for the 99 . F-this Iphone

it’s an analog guage my guy… on the fuel rail

 

[Shran]

got one that might mess with your head , i know it is mine . hooked up a timing light for gigs . the if i keep the inductor open it lights at half the speed of the engine (both banks), expected. if i put it on driver side bank , all good . full flash engine rpm. i put it on passenger side bank, intermittent/ nothing . please tell me it’s not the PCM and i’m gonna have to go to a dealer to get it flashed. any chance it’s the CPS /CKP ?

A timing light is really only useful on the #1 plug wire, to see where that spark plug is firing in relation to the timing marks on the crank pulley... what is this "banks" thing you're talking about? Fuel injectors? There is not really a correlation between those parts, a timing light will not tell you if the injectors are firing........

it’s an analog guage my guy… on the fuel rail

So KOEO 55 or there about

KOER 63 on the money , full rev same. 100% not fuel pressure.

So what were your fuel pressure readings on the analog gauge? I don't see where you posted those. Just those EEC-IV codes. 63 is a low voltage @ the throttle position sensor code... could indicate a broken wire or bad ground, if the TPS isn't working, you will see weird symptoms happen.

 

[lancasterpunk29]

OK...hold up... your original post said this is for a 1990. Is that correct? Not the '99 that shows in your profile?

1990 had zero electronic monitoring of fuel pressure - none - those EEC-IV test codes mean nothing. You need actual pressure readings from a gauge hooked up to the fuel rail. You should be getting about 35psi at idle and up to 40psi briefly if you blip the throttle. Anything way outside of that will cause problems.

My kid's '95 has a weak pump at the moment and he was complaining about it not running well, it pops & sputters and is basically not drivable. It is NOT throwing any codes... and that is OBD-2.... there is no monitoring there. My fuel pressure gauge shows that the pump is not even making 20psi - obviously the problem but my point is that you cannot rely on code readers to fix stuff like this.

Also double check your specs for pressure, i’m going by book readings

35 is way too low for a 99 4.0